diff --git a/docs/manual/basics.ipynb b/docs/manual/basics.ipynb
index c75b22d225..05d218396d 100644
--- a/docs/manual/basics.ipynb
+++ b/docs/manual/basics.ipynb
@@ -272,7 +272,7 @@
     "    var first: Int\n",
     "    var second: Int\n",
     "\n",
-    "    fn __init__(inout self, first: Int, second: Int):\n",
+    "    fn __init__(out self, first: Int, second: Int):\n",
     "        self.first = first\n",
     "        self.second = second\n",
     "\n",
diff --git a/docs/manual/decorators/nonmaterializable.ipynb b/docs/manual/decorators/nonmaterializable.ipynb
index 494a9880a1..4e88c205ae 100644
--- a/docs/manual/decorators/nonmaterializable.ipynb
+++ b/docs/manual/decorators/nonmaterializable.ipynb
@@ -48,11 +48,11 @@
     "struct HasBool:\n",
     "    var x: Bool\n",
     "\n",
-    "    fn __init__(inout self, x: Bool):\n",
+    "    fn __init__(out self, x: Bool):\n",
     "        self.x = x\n",
     "\n",
     "    @always_inline(\"nodebug\")\n",
-    "    fn __init__(inout self, nms: NmStruct):\n",
+    "    fn __init__(out self, nms: NmStruct):\n",
     "        self.x = True if (nms.x == 77) else False\n",
     "\n",
     "@value\n",
diff --git a/docs/manual/decorators/register-passable.ipynb b/docs/manual/decorators/register-passable.ipynb
index 31c31d8e4d..174418abaa 100644
--- a/docs/manual/decorators/register-passable.ipynb
+++ b/docs/manual/decorators/register-passable.ipynb
@@ -42,11 +42,11 @@
                 "    var a: Int\n",
                 "    var b: Int\n",
                 "\n",
-                "    fn __init__(inout self, one: Int, two: Int):\n",
+                "    fn __init__(out self, one: Int, two: Int):\n",
                 "        self.a = one\n",
                 "        self.b = two\n",
                 "\n",
-                "    fn __copyinit__(inout self, existing: Self):\n",
+                "    fn __copyinit__(out self, existing: Self):\n",
                 "        self.a = existing.a\n",
                 "        self.b = existing.b\n",
                 "\n",
diff --git a/docs/manual/decorators/staticmethod.ipynb b/docs/manual/decorators/staticmethod.ipynb
index 84ff19d90d..bcd9a4d2e5 100644
--- a/docs/manual/decorators/staticmethod.ipynb
+++ b/docs/manual/decorators/staticmethod.ipynb
@@ -38,10 +38,10 @@
     "struct MyStruct:\n",
     "    var data: List[UInt8]\n",
     "\n",
-    "    fn __init__(inout self):\n",
+    "    fn __init__(out self):\n",
     "        self.data = List[UInt8]()\n",
     "\n",
-    "    fn __moveinit__(inout self, owned existing: Self):\n",
+    "    fn __moveinit__(out self, owned existing: Self):\n",
     "        self.data = existing.data ^\n",
     "\n",
     "    @staticmethod\n",
diff --git a/docs/manual/decorators/value.ipynb b/docs/manual/decorators/value.ipynb
index 807bd962cb..f82a54a21b 100644
--- a/docs/manual/decorators/value.ipynb
+++ b/docs/manual/decorators/value.ipynb
@@ -58,15 +58,15 @@
     "    var name: String\n",
     "    var age: Int\n",
     "\n",
-    "    fn __init__(inout self, owned name: String, age: Int):\n",
+    "    fn __init__(out self, owned name: String, age: Int):\n",
     "        self.name = name^\n",
     "        self.age = age\n",
     "\n",
-    "    fn __copyinit__(inout self, existing: Self):\n",
+    "    fn __copyinit__(out self, existing: Self):\n",
     "        self.name = existing.name\n",
     "        self.age = existing.age\n",
     "\n",
-    "    fn __moveinit__(inout self, owned existing: Self):\n",
+    "    fn __moveinit__(out self, owned existing: Self):\n",
     "        self.name = existing.name^\n",
     "        self.age = existing.age"
    ]
diff --git a/docs/manual/functions.ipynb b/docs/manual/functions.ipynb
index 420d13aa46..6f24f70e0d 100755
--- a/docs/manual/functions.ipynb
+++ b/docs/manual/functions.ipynb
@@ -794,7 +794,7 @@
    "source": [
     "@value\n",
     "struct MyString:\n",
-    "    fn __init__(inout self, string: StringLiteral):\n",
+    "    fn __init__(out self, string: StringLiteral):\n",
     "        pass\n",
     "\n",
     "fn foo(name: String):\n",
diff --git a/docs/manual/lifecycle/death.ipynb b/docs/manual/lifecycle/death.ipynb
index 74cfb1e86e..9329b7aebb 100644
--- a/docs/manual/lifecycle/death.ipynb
+++ b/docs/manual/lifecycle/death.ipynb
@@ -186,7 +186,7 @@
         "    var name: String\n",
         "    var age: Int\n",
         "\n",
-        "    fn __init__(inout self, name: String, age: Int):\n",
+        "    fn __init__(out self, name: String, age: Int):\n",
         "        self.name = name\n",
         "        self.age = age"
       ]
@@ -216,7 +216,7 @@
         "    var data: UnsafePointer[Int]\n",
         "    var size: Int\n",
         "\n",
-        "    fn __init__(inout self, size: Int, val: Int):\n",
+        "    fn __init__(out self, size: Int, val: Int):\n",
         "        self.size = size\n",
         "        self.data = UnsafePointer[Int].alloc(self.size)\n",
         "        for i in range(self.size):\n",
@@ -272,7 +272,7 @@
         "    var name: String\n",
         "    var age: Int\n",
         "\n",
-        "    fn __init__(inout self, name: String, age: Int):\n",
+        "    fn __init__(out self, name: String, age: Int):\n",
         "        self.name = name\n",
         "        self.age = age\n",
         "\n",
@@ -398,7 +398,7 @@
         "\n",
         "```mojo\n",
         "struct TwoStrings:\n",
-        "    fn __moveinit__(inout self, owned existing: Self):\n",
+        "    fn __moveinit__(out self, owned existing: Self):\n",
         "        # Initializes a new `self` by consuming the contents of `existing`\n",
         "    fn __del__(owned self):\n",
         "        # Destroys all resources in `self`\n",
@@ -448,11 +448,11 @@
         "    var str1: String\n",
         "    var str2: String\n",
         "\n",
-        "    fn __init__(inout self, one: String):\n",
+        "    fn __init__(out self, one: String):\n",
         "        self.str1 = one\n",
         "        self.str2 = String(\"bar\")\n",
         "\n",
-        "    fn __moveinit__(inout self, owned existing: Self):\n",
+        "    fn __moveinit__(out self, owned existing: Self):\n",
         "        self.str1 = existing.str1\n",
         "        self.str2 = existing.str2\n",
         "\n",
diff --git a/docs/manual/lifecycle/life.ipynb b/docs/manual/lifecycle/life.ipynb
index ef262ef54b..6c64745fdc 100644
--- a/docs/manual/lifecycle/life.ipynb
+++ b/docs/manual/lifecycle/life.ipynb
@@ -104,7 +104,7 @@
     "    var name: String\n",
     "    var age: Int\n",
     "\n",
-    "    fn __init__(inout self, name: String, age: Int):\n",
+    "    fn __init__(out self, name: String, age: Int):\n",
     "        self.name = name\n",
     "        self.age = age"
    ]
@@ -181,11 +181,11 @@
     "    var name: String\n",
     "    var age: Int\n",
     "\n",
-    "    fn __init__(inout self):\n",
+    "    fn __init__(out self):\n",
     "        self.name = \"\"\n",
     "        self.age = 0\n",
     "\n",
-    "    fn __init__(inout self, name: String):\n",
+    "    fn __init__(out self, name: String):\n",
     "        self = MyPet()\n",
     "        self.name = name"
    ]
@@ -218,7 +218,7 @@
     "    var name: String\n",
     "    var age: Int\n",
     "\n",
-    "    fn __init__(inout self, name: String, age: Int, cond: Bool):\n",
+    "    fn __init__(out self, name: String, age: Int, cond: Bool):\n",
     "        self.name = name\n",
     "        if cond:\n",
     "            self.age = age\n",
@@ -254,7 +254,7 @@
     "\n",
     "```mojo\n",
     "struct Target:\n",
-    "  fn __init__(inout self, s: Source): ...\n",
+    "  fn __init__(out self, s: Source): ...\n",
     "```\n",
     "\n",
     "With implicit conversion, the assignment above is essentially identical to:\n",
@@ -269,7 +269,7 @@
     "\n",
     "```mojo\n",
     "struct Target:\n",
-    "  fn __init__(inout self, s: Source, reverse: Bool = False): ...\n",
+    "  fn __init__(out self, s: Source, reverse: Bool = False): ...\n",
     "```\n",
     "\n",
     "Implicit conversion also occurs if the type doesn't declare its own constructor,\n",
@@ -293,14 +293,14 @@
     "\n",
     "```mojo\n",
     "struct A: \n",
-    "  fn __init__(inout self, s: Source): ...\n",
+    "  fn __init__(out self, s: Source): ...\n",
     "\n",
     "struct B: \n",
-    "  fn __init__(inout self, s: Source): ...\n",
+    "  fn __init__(out self, s: Source): ...\n",
     "\n",
     "struct Target:\n",
-    "  fn __init__(inout self, a: A): ...\n",
-    "  fn __init__(inout self, b: B): ...\n",
+    "  fn __init__(out self, a: A): ...\n",
+    "  fn __init__(out self, b: B): ...\n",
     "\n",
     "# Fails\n",
     "var t = Target(Source())\n",
@@ -316,7 +316,7 @@
     "```mojo\n",
     "struct Target:\n",
     "  # does not support implicit conversion\n",
-    "  fn __init__(inout self, *, source: Source): ...\n",
+    "  fn __init__(out self, *, source: Source): ...\n",
     "\n",
     "# the constructor must be called with a keyword\n",
     "var t = Target(source=a)\n",
@@ -363,11 +363,11 @@
     "    var name: String\n",
     "    var age: Int\n",
     "\n",
-    "    fn __init__(inout self, name: String, age: Int):\n",
+    "    fn __init__(out self, name: String, age: Int):\n",
     "        self.name = name\n",
     "        self.age = age\n",
     "\n",
-    "    fn __copyinit__(inout self, existing: Self):\n",
+    "    fn __copyinit__(out self, existing: Self):\n",
     "        self.name = existing.name\n",
     "        self.age = existing.age"
    ]
@@ -433,14 +433,14 @@
     "    var size: Int\n",
     "    var cap: Int\n",
     "\n",
-    "    fn __init__(inout self, size: Int, val: Int):\n",
+    "    fn __init__(out self, size: Int, val: Int):\n",
     "        self.size = size\n",
     "        self.cap = size * 2\n",
     "        self.data = UnsafePointer[Int].alloc(self.cap)\n",
     "        for i in range(self.size):\n",
     "            (self.data + i).init_pointee_copy(val)\n",
     "\n",
-    "    fn __copyinit__(inout self, existing: Self):\n",
+    "    fn __copyinit__(out self, existing: Self):\n",
     "        # Deep-copy the existing value\n",
     "        self.size = existing.size\n",
     "        self.cap = existing.cap\n",
@@ -600,14 +600,14 @@
     "    var cap: Int\n",
     "\n",
     "\n",
-    "    fn __init__(inout self, size: Int, val: Int):\n",
+    "    fn __init__(out self, size: Int, val: Int):\n",
     "        self.size = size\n",
     "        self.cap = size * 2\n",
     "        self.data = UnsafePointer[Int].alloc(self.size)\n",
     "        for i in range(self.size):\n",
     "            (self.data + i).init_pointee_copy(val)\n",
     "\n",
-    "    fn __copyinit__(inout self, existing: Self):\n",
+    "    fn __copyinit__(out self, existing: Self):\n",
     "        # Deep-copy the existing value\n",
     "        self.size = existing.size\n",
     "        self.cap = existing.cap\n",
@@ -616,7 +616,7 @@
     "            (self.data + i).init_pointee_copy(existing.data[i])\n",
     "        # The lifetime of `existing` continues unchanged\n",
     "\n",
-    "    fn __moveinit__(inout self, owned existing: Self):\n",
+    "    fn __moveinit__(out self, owned existing: Self):\n",
     "        print(\"move\")\n",
     "        # Shallow copy the existing value\n",
     "        self.size = existing.size\n",
@@ -771,15 +771,15 @@
     "    var name: String\n",
     "    var age: Int\n",
     "\n",
-    "    fn __init__(inout self, owned name: String, age: Int):\n",
+    "    fn __init__(out self, owned name: String, age: Int):\n",
     "        self.name = name^\n",
     "        self.age = age\n",
     "\n",
-    "    fn __copyinit__(inout self, existing: Self):\n",
+    "    fn __copyinit__(out self, existing: Self):\n",
     "        self.name = existing.name\n",
     "        self.age = existing.age\n",
     "\n",
-    "    fn __moveinit__(inout self, owned existing: Self):\n",
+    "    fn __moveinit__(out self, owned existing: Self):\n",
     "        self.name = existing.name^\n",
     "        self.age = existing.age"
    ]
@@ -809,7 +809,7 @@
     "    var name: String\n",
     "    var age: Int\n",
     "\n",
-    "    fn __init__(inout self, owned name: String):\n",
+    "    fn __init__(out self, owned name: String):\n",
     "        self.name = name^\n",
     "        self.age = 0\n"
    ]
diff --git a/docs/manual/parameters/index.ipynb b/docs/manual/parameters/index.ipynb
index cbf61f4f7f..358f846ff3 100644
--- a/docs/manual/parameters/index.ipynb
+++ b/docs/manual/parameters/index.ipynb
@@ -233,7 +233,7 @@
     "    var data: UnsafePointer[ElementType]\n",
     "    var size: Int\n",
     "\n",
-    "    fn __init__(inout self, *elements: ElementType):\n",
+    "    fn __init__(out self, *elements: ElementType):\n",
     "        self.size = len(elements)\n",
     "        self.data = UnsafePointer[ElementType].alloc(self.size)\n",
     "        for i in range(self.size):\n",
@@ -438,7 +438,7 @@
     "    var value: … # Some low-level MLIR stuff here\n",
     "\n",
     "    # Create a new SIMD from a number of scalars\n",
-    "    fn __init__(inout self, *elems: SIMD[type, 1]):  ...\n",
+    "    fn __init__(out self, *elems: SIMD[type, 1]):  ...\n",
     "\n",
     "    # Fill a SIMD with a duplicated scalar value.\n",
     "    @staticmethod\n",
@@ -536,7 +536,7 @@
     "    var value: Int\n",
     "\n",
     "    @always_inline(\"nodebug\")\n",
-    "    fn __init__(inout self, _a: Int):\n",
+    "    fn __init__(out self, _a: Int):\n",
     "        self.value = _a\n",
     "\n",
     "fn foo[x: MyInt, a: Int]():\n",
@@ -569,7 +569,7 @@
     "parameter_overloads[1, 2, MyInt(3)]()\n",
     "\n",
     "struct MyStruct:\n",
-    "    fn __init__(inout self):\n",
+    "    fn __init__(out self):\n",
     "        pass\n",
     "\n",
     "    fn foo(inout self):\n",
@@ -730,7 +730,7 @@
     "struct One[Type: StringableCollectionElement]:\n",
     "    var value: Type\n",
     "\n",
-    "    fn __init__(inout self, value: Type):\n",
+    "    fn __init__(out self, value: Type):\n",
     "        self.value = value\n",
     "\n",
     "def use_one():\n",
@@ -768,7 +768,7 @@
     "    var val1: Type\n",
     "    var val2: Type\n",
     "\n",
-    "    fn __init__(inout self, one: One[Type], another: One[Type]):\n",
+    "    fn __init__(out self, one: One[Type], another: One[Type]):\n",
     "        self.val1 = one.value\n",
     "        self.val2 = another.value\n",
     "        print(str(self.val1), str(self.val2))\n",
@@ -886,7 +886,7 @@
    "outputs": [],
    "source": [
     "struct KwParamStruct[greeting: String = \"Hello\", name: String = \"🔥mojo🔥\"]:\n",
-    "    fn __init__(inout self):\n",
+    "    fn __init__(out self):\n",
     "        print(greeting, name)\n",
     "\n",
     "fn use_kw_params():\n",
@@ -1193,7 +1193,7 @@
     "    var data: UnsafePointer[T]\n",
     "    var size: Int\n",
     "\n",
-    "    fn __init__(inout self, size: Int, value: T):\n",
+    "    fn __init__(out self, size: Int, value: T):\n",
     "        self.size = size\n",
     "        self.data = UnsafePointer[T].alloc(self.size)\n",
     "        for i in range(self.size):\n",
diff --git a/docs/manual/structs.ipynb b/docs/manual/structs.ipynb
index ba46521ccd..aff69827b1 100644
--- a/docs/manual/structs.ipynb
+++ b/docs/manual/structs.ipynb
@@ -81,7 +81,7 @@
     "    var first: Int\n",
     "    var second: Int\n",
     "\n",
-    "    fn __init__(inout self, first: Int, second: Int):\n",
+    "    fn __init__(out self, first: Int, second: Int):\n",
     "        self.first = first\n",
     "        self.second = second"
    ]
@@ -153,7 +153,7 @@
     "    var first: Int\n",
     "    var second: Int\n",
     "\n",
-    "    fn __init__(inout self, first: Int, second: Int):\n",
+    "    fn __init__(out self, first: Int, second: Int):\n",
     "        self.first = first\n",
     "        self.second = second\n",
     "\n",
@@ -223,7 +223,7 @@
    "source": [
     "struct Logger:\n",
     "\n",
-    "    fn __init__(inout self):\n",
+    "    fn __init__(out self):\n",
     "        pass\n",
     "\n",
     "    @staticmethod\n",
@@ -408,15 +408,15 @@
     "    var name: String\n",
     "    var age: Int\n",
     "\n",
-    "    fn __init__(inout self, owned name: String, age: Int):\n",
+    "    fn __init__(out self, owned name: String, age: Int):\n",
     "        self.name = name^\n",
     "        self.age = age\n",
     "\n",
-    "    fn __copyinit__(inout self, existing: Self):\n",
+    "    fn __copyinit__(out self, existing: Self):\n",
     "        self.name = existing.name\n",
     "        self.age = existing.age\n",
     "\n",
-    "    fn __moveinit__(inout self, owned existing: Self):\n",
+    "    fn __moveinit__(out self, owned existing: Self):\n",
     "        self.name = existing.name^\n",
     "        self.age = existing.age"
    ]
diff --git a/docs/manual/traits.ipynb b/docs/manual/traits.ipynb
index a0b665410f..ef9fbd824e 100755
--- a/docs/manual/traits.ipynb
+++ b/docs/manual/traits.ipynb
@@ -391,7 +391,7 @@
             "outputs": [],
             "source": [
                 "trait DefaultConstructible:\n",
-                "    fn __init__(inout self): ...\n",
+                "    fn __init__(out self): ...\n",
                 "\n",
                 "trait MassProducible(DefaultConstructible, Movable):\n",
                 "    pass\n",
@@ -402,10 +402,10 @@
                 "struct Thing(MassProducible):\n",
                 "    var id: Int\n",
                 "\n",
-                "    fn __init__(inout self):\n",
+                "    fn __init__(out self):\n",
                 "        self.id = 0\n",
                 "\n",
-                "    fn __moveinit__(inout self, owned existing: Self):\n",
+                "    fn __moveinit__(out self, owned existing: Self):\n",
                 "        self.id = existing.id\n",
                 "\n",
                 "var thing = factory[Thing]()"
@@ -504,7 +504,7 @@
                 "    var size: Int\n",
                 "    # ...\n",
                 "\n",
-                "    fn __init__(inout self):\n",
+                "    fn __init__(out self):\n",
                 "        self.size = 0\n",
                 "\n",
                 "    fn __len__(self) -> Int:\n",
diff --git a/docs/manual/values/lifetimes.ipynb b/docs/manual/values/lifetimes.ipynb
index 0c350dac66..314e186c81 100644
--- a/docs/manual/values/lifetimes.ipynb
+++ b/docs/manual/values/lifetimes.ipynb
@@ -229,7 +229,7 @@
     "struct BoxedString:\n",
     "    var box: OwnedPointer[String]\n",
     "\n",
-    "    fn __init__(inout self, value: String):\n",
+    "    fn __init__(out self, value: String):\n",
     "        self.box = OwnedPointer(value)\n",
     "\n",
     "    fn as_ptr(self) -> Pointer[String, __origin_of(self.box)]:\n",
@@ -259,7 +259,7 @@
     "its `origin` value from the list:\n",
     "\n",
     "```mojo\n",
-    "    fn __init__(inout self, ref [origin]list: List[T, *_]):\n",
+    "    fn __init__(out self, ref [origin]list: List[T, *_]):\n",
     "        \"\"\"Construct a Span from a List.\n",
     "\n",
     "        Args:\n",
@@ -422,7 +422,7 @@
     "struct NameList:\n",
     "    var names: List[String]\n",
     "\n",
-    "    def __init__(inout self, *names: String):\n",
+    "    def __init__(out self, *names: String):\n",
     "        self.names = List[String]()\n",
     "        for name in names:\n",
     "            self.names.append(name[])\n",
diff --git a/docs/manual/variables.ipynb b/docs/manual/variables.ipynb
index e4f676b0cd..68b87ce68e 100644
--- a/docs/manual/variables.ipynb
+++ b/docs/manual/variables.ipynb
@@ -312,7 +312,7 @@
     "As shown above, value assignment can be converted into a constructor call if the \n",
     "target type has a constructor that takes a single argument that matches the\n",
     "value being assigned. So, this code uses the `Float64` constructor that takes an\n",
-    "integer: `__init__(inout self, value: Int)`.\n",
+    "integer: `__init__(out self, value: Int)`.\n",
     "\n",
     "In general, implicit conversions should only be supported where the conversion\n",
     "is lossless.\n",
diff --git a/examples/mandelbrot.mojo b/examples/mandelbrot.mojo
index a2a7d12a43..9603e31c70 100644
--- a/examples/mandelbrot.mojo
+++ b/examples/mandelbrot.mojo
@@ -39,7 +39,7 @@ alias max_y = 1.5
 struct Matrix[type: DType, rows: Int, cols: Int]:
     var data: UnsafePointer[Scalar[type]]
 
-    fn __init__(inout self):
+    fn __init__(out self):
         self.data = UnsafePointer[Scalar[type]].alloc(rows * cols)
 
     fn store[nelts: Int](self, row: Int, col: Int, val: SIMD[type, nelts]):
diff --git a/examples/matmul.mojo b/examples/matmul.mojo
index 4b1a08e7cd..44cc91f097 100644
--- a/examples/matmul.mojo
+++ b/examples/matmul.mojo
@@ -52,12 +52,12 @@ struct Matrix[rows: Int, cols: Int]:
     var data: UnsafePointer[Scalar[type]]
 
     # Initialize zeroing all values
-    fn __init__(inout self):
+    fn __init__(out self):
         self.data = UnsafePointer[Scalar[type]].alloc(rows * cols)
         memset_zero(self.data, rows * cols)
 
     # Initialize taking a pointer, don't set any elements
-    fn __init__(inout self, data: UnsafePointer[Scalar[type]]):
+    fn __init__(out self, data: UnsafePointer[Scalar[type]]):
         self.data = data
 
     ## Initialize with random values
diff --git a/examples/notebooks/BoolMLIR.ipynb b/examples/notebooks/BoolMLIR.ipynb
index 2e4a6a09b3..355dc77909 100644
--- a/examples/notebooks/BoolMLIR.ipynb
+++ b/examples/notebooks/BoolMLIR.ipynb
@@ -133,7 +133,7 @@
     "struct OurBool:\n",
     "    var value: __mlir_type.i1\n",
     "\n",
-    "    fn __init__(inout self):\n",
+    "    fn __init__(out self):\n",
     "        self.value = __mlir_op.`index.bool.constant`[\n",
     "            value=__mlir_attr.false,\n",
     "        ]()"
@@ -191,7 +191,7 @@
     "struct OurBool:\n",
     "    var value: __mlir_type.i1\n",
     "\n",
-    "    fn __init__(inout self):\n",
+    "    fn __init__(out self):\n",
     "        self.value = __mlir_op.`index.bool.constant`[\n",
     "                value=__mlir_attr.false,\n",
     "            ]()"
@@ -239,7 +239,7 @@
     "\n",
     "    # ...\n",
     "\n",
-    "    fn __init__(inout self, value: __mlir_type.i1):\n",
+    "    fn __init__(out self, value: __mlir_type.i1):\n",
     "        self.value = value"
    ]
   },
@@ -303,10 +303,10 @@
     "    var value: __mlir_type.i1\n",
     "\n",
     "    # We can simplify our no-argument constructor:\n",
-    "    fn __init__(inout self):\n",
+    "    fn __init__(out self):\n",
     "        self = OurFalse\n",
     "\n",
-    "    fn __init__(inout self, value: __mlir_type.i1):\n",
+    "    fn __init__(out self, value: __mlir_type.i1):\n",
     "        self.value = value"
    ]
   },
@@ -369,7 +369,7 @@
     "\n",
     "    # ...\n",
     "\n",
-    "    fn __init__(inout self, value: __mlir_type.i1):\n",
+    "    fn __init__(out self, value: __mlir_type.i1):\n",
     "        self.value = value\n",
     "\n",
     "    # Our new method converts `OurBool` to `Bool`:\n",
@@ -441,7 +441,7 @@
     "struct OurBool:\n",
     "    var value: __mlir_type.i1\n",
     "\n",
-    "    fn __init__(inout self, value: __mlir_type.i1):\n",
+    "    fn __init__(out self, value: __mlir_type.i1):\n",
     "        self.value = value\n",
     "\n",
     "    # Our new method converts `OurBool` to `i1`:\n",
@@ -507,7 +507,7 @@
     "struct OurBool:\n",
     "    var value: __mlir_type.i1\n",
     "\n",
-    "    fn __init__(inout self, value: __mlir_type.i1):\n",
+    "    fn __init__(out self, value: __mlir_type.i1):\n",
     "        self.value = value\n",
     "\n",
     "    # ...\n",
diff --git a/examples/notebooks/Mandelbrot.ipynb b/examples/notebooks/Mandelbrot.ipynb
index ad269046ce..4dcec04c6a 100644
--- a/examples/notebooks/Mandelbrot.ipynb
+++ b/examples/notebooks/Mandelbrot.ipynb
@@ -100,7 +100,7 @@
                 "struct Matrix[type: DType, rows: Int, cols: Int]:\n",
                 "    var data: UnsafePointer[Scalar[type]]\n",
                 "\n",
-                "    fn __init__(inout self):\n",
+                "    fn __init__(out self):\n",
                 "        self.data = UnsafePointer[Scalar[type]].alloc(rows * cols)\n",
                 "\n",
                 "    fn __getitem__(self, row: Int, col: Int) -> Scalar[type]:\n",
diff --git a/examples/notebooks/Matmul.ipynb b/examples/notebooks/Matmul.ipynb
index f7a4a796a4..239654bf5e 100644
--- a/examples/notebooks/Matmul.ipynb
+++ b/examples/notebooks/Matmul.ipynb
@@ -416,12 +416,12 @@
         "    var data: UnsafePointer[Scalar[type]]\n",
         "\n",
         "    # Initialize zeroeing all values\n",
-        "    fn __init__(inout self):\n",
+        "    fn __init__(out self):\n",
         "        self.data = UnsafePointer[Scalar[type]].alloc(rows * cols)\n",
         "        memset_zero(self.data, rows * cols)\n",
         "\n",
         "    # Initialize taking a pointer, don't set any elements\n",
-        "    fn __init__(inout self, data: UnsafePointer[Scalar[type]]):\n",
+        "    fn __init__(out self, data: UnsafePointer[Scalar[type]]):\n",
         "        self.data = data\n",
         "\n",
         "    # Initialize with random values\n",
diff --git a/examples/notebooks/RayTracing.ipynb b/examples/notebooks/RayTracing.ipynb
index a6d9d221ba..1ce972b6b4 100644
--- a/examples/notebooks/RayTracing.ipynb
+++ b/examples/notebooks/RayTracing.ipynb
@@ -81,11 +81,11 @@
         "    var data: SIMD[DType.float32, 4]\n",
         "\n",
         "    @always_inline\n",
-        "    fn __init__(inout self, x: Float32, y: Float32, z: Float32):\n",
+        "    fn __init__(out self, x: Float32, y: Float32, z: Float32):\n",
         "        self.data = SIMD[DType.float32, 4](x, y, z, 0)\n",
         "\n",
         "    @always_inline\n",
-        "    fn __init__(inout self, data: SIMD[DType.float32, 4]):\n",
+        "    fn __init__(out self, data: SIMD[DType.float32, 4]):\n",
         "        self.data = data\n",
         "\n",
         "    @always_inline\n",
@@ -207,14 +207,14 @@
         "    var height: Int\n",
         "    var width: Int\n",
         "\n",
-        "    fn __init__(inout self, height: Int, width: Int):\n",
+        "    fn __init__(out self, height: Int, width: Int):\n",
         "        self.height = height\n",
         "        self.width = width\n",
         "        self.pixels = UnsafePointer[Vec3f].alloc(self.height * self.width)\n",
         "        self.rc = UnsafePointer[Int].alloc(1)\n",
         "        self.rc[] = 1\n",
         "\n",
-        "    fn __copyinit__(inout self, other: Self):\n",
+        "    fn __copyinit__(out self, other: Self):\n",
         "        other._inc_rc()\n",
         "        self.pixels = other.pixels\n",
         "        self.rc = other.rc\n",
@@ -401,7 +401,7 @@
         "    var albedo: Vec3f\n",
         "    var specular_component: Float32\n",
         "\n",
-        "    fn __init__(inout self, color: Vec3f, albedo: Vec3f = Vec3f(0, 0, 0),\n",
+        "    fn __init__(out self, color: Vec3f, albedo: Vec3f = Vec3f(0, 0, 0),\n",
         "                specular_component: Float32 = 0):\n",
         "        self.color = color\n",
         "        self.albedo = albedo\n",
diff --git a/stdlib/src/builtin/_closure.mojo b/stdlib/src/builtin/_closure.mojo
index b456d1405a..c5465bdf09 100644
--- a/stdlib/src/builtin/_closure.mojo
+++ b/stdlib/src/builtin/_closure.mojo
@@ -21,11 +21,11 @@ struct __ParameterClosureCaptureList[
     # Parameter closure invariant requires this function be marked 'capturing'.
     @parameter
     @always_inline
-    fn __init__(inout self):
+    fn __init__(out self):
         self.value = __mlir_op.`kgen.capture_list.create`[callee=fn_ref]()
 
     @always_inline
-    fn __copyinit__(inout self, existing: Self):
+    fn __copyinit__(out self, existing: Self):
         self.value = __mlir_op.`kgen.capture_list.copy`[callee=fn_ref](
             existing.value
         )
diff --git a/stdlib/src/builtin/_format_float.mojo b/stdlib/src/builtin/_format_float.mojo
index 31a48829d5..2686917119 100644
--- a/stdlib/src/builtin/_format_float.mojo
+++ b/stdlib/src/builtin/_format_float.mojo
@@ -50,7 +50,7 @@ struct _MulParity:
     var parity: Bool
     var is_integer: Bool
 
-    fn __init__(inout self, parity: Bool, is_integer: Bool):
+    fn __init__(out self, parity: Bool, is_integer: Bool):
         self.parity = parity
         self.is_integer = is_integer
 
diff --git a/stdlib/src/builtin/_location.mojo b/stdlib/src/builtin/_location.mojo
index a79adfc33d..0940e49f8e 100644
--- a/stdlib/src/builtin/_location.mojo
+++ b/stdlib/src/builtin/_location.mojo
@@ -23,7 +23,7 @@ struct _SourceLocation(Writable, Stringable):
     var col: Int
     var file_name: StringLiteral
 
-    fn __init__(inout self, *, other: Self):
+    fn __init__(out self, *, other: Self):
         self = other
 
     @no_inline
diff --git a/stdlib/src/builtin/_stubs.mojo b/stdlib/src/builtin/_stubs.mojo
index bdb830bece..92e661dc00 100644
--- a/stdlib/src/builtin/_stubs.mojo
+++ b/stdlib/src/builtin/_stubs.mojo
@@ -68,7 +68,7 @@ struct _ParamForIterator[IteratorT: Copyable]:
     var value: Int
     var stop: Bool
 
-    fn __init__(inout self, next_it: IteratorT, value: Int, stop: Bool):
+    fn __init__(out self, next_it: IteratorT, value: Int, stop: Bool):
         self.next_it = next_it
         self.value = value
         self.stop = stop
diff --git a/stdlib/src/builtin/anytype.mojo b/stdlib/src/builtin/anytype.mojo
index c54a4e1745..03da7a124d 100644
--- a/stdlib/src/builtin/anytype.mojo
+++ b/stdlib/src/builtin/anytype.mojo
@@ -46,7 +46,7 @@ trait AnyType:
         var p: UnsafePointer[Int]
         var size: Int
 
-        fn __init__(inout self, size: Int):
+        fn __init__(out self, size: Int):
             self.p = UnsafePointer[Int].alloc(size)
             self.size = size
 
diff --git a/stdlib/src/builtin/bool.mojo b/stdlib/src/builtin/bool.mojo
index aebc43a7a8..06ccff6578 100644
--- a/stdlib/src/builtin/bool.mojo
+++ b/stdlib/src/builtin/bool.mojo
@@ -116,12 +116,12 @@ struct Bool(
     """The underlying storage of the boolean value."""
 
     @always_inline("nodebug")
-    fn __init__(inout self):
+    fn __init__(out self):
         """Construct a default, `False` Bool."""
         self = False
 
     @always_inline("nodebug")
-    fn __init__(inout self, *, other: Self):
+    fn __init__(out self, *, other: Self):
         """Explicitly construct a deep copy of the provided value.
 
         Args:
@@ -131,7 +131,7 @@ struct Bool(
 
     @doc_private
     @always_inline("nodebug")
-    fn __init__(inout self, value: __mlir_type.i1):
+    fn __init__(out self, value: __mlir_type.i1):
         """Construct a Bool value given a __mlir_type.i1 value.
 
         Args:
@@ -141,7 +141,7 @@ struct Bool(
 
     @doc_private
     @always_inline("nodebug")
-    fn __init__(inout self, value: __mlir_type.`!pop.scalar<bool>`):
+    fn __init__(out self, value: __mlir_type.`!pop.scalar<bool>`):
         """Construct a Bool value given a `!pop.scalar<bool>` value.
 
         Args:
@@ -164,7 +164,7 @@ struct Bool(
         self = value.__bool__()
 
     @always_inline("nodebug")
-    fn __init__(inout self, value: SIMD[DType.bool, 1]):
+    fn __init__(out self, value: SIMD[DType.bool, 1]):
         """Convert a scalar SIMD value to a Bool.
 
         Args:
diff --git a/stdlib/src/builtin/builtin_list.mojo b/stdlib/src/builtin/builtin_list.mojo
index 9ea758583d..7541b4f9c4 100644
--- a/stdlib/src/builtin/builtin_list.mojo
+++ b/stdlib/src/builtin/builtin_list.mojo
@@ -40,7 +40,7 @@ struct ListLiteral[*Ts: CollectionElement](Sized, CollectionElement):
     # ===-------------------------------------------------------------------===#
 
     @always_inline
-    fn __init__(inout self, owned *args: *Ts):
+    fn __init__(out self, owned *args: *Ts):
         """Construct the list literal from the given values.
 
         Args:
@@ -49,7 +49,7 @@ struct ListLiteral[*Ts: CollectionElement](Sized, CollectionElement):
         self.storage = Tuple(storage=args^)
 
     @always_inline
-    fn __copyinit__(inout self, existing: Self):
+    fn __copyinit__(out self, existing: Self):
         """Copy construct the tuple.
 
         Args:
@@ -57,7 +57,7 @@ struct ListLiteral[*Ts: CollectionElement](Sized, CollectionElement):
         """
         self.storage = existing.storage
 
-    fn __moveinit__(inout self, owned existing: Self):
+    fn __moveinit__(out self, owned existing: Self):
         """Move construct the list.
 
         Args:
@@ -164,7 +164,7 @@ struct VariadicList[type: AnyTrivialRegType](Sized):
     alias IterType = _VariadicListIter[type]
 
     @always_inline
-    fn __init__(inout self, *value: type):
+    fn __init__(out self, *value: type):
         """Constructs a VariadicList from a variadic list of arguments.
 
         Args:
@@ -175,7 +175,7 @@ struct VariadicList[type: AnyTrivialRegType](Sized):
 
     @doc_private
     @always_inline
-    fn __init__(inout self, value: Self._mlir_type):
+    fn __init__(out self, value: Self._mlir_type):
         """Constructs a VariadicList from a variadic argument type.
 
         Args:
@@ -327,7 +327,7 @@ struct VariadicListMem[
     # Provide support for borrowed variadic arguments.
     @doc_private
     @always_inline
-    fn __init__(inout self, value: Self._mlir_type):
+    fn __init__(out self, value: Self._mlir_type):
         """Constructs a VariadicList from a variadic argument type.
 
         Args:
@@ -344,7 +344,7 @@ struct VariadicListMem[
     ]
 
     @always_inline
-    fn __init__(inout self, value: Self._inout_variadic_type):
+    fn __init__(out self, value: Self._inout_variadic_type):
         """Constructs a VariadicList from a variadic argument type.
 
         Args:
@@ -364,7 +364,7 @@ struct VariadicListMem[
     ]
 
     @always_inline
-    fn __init__(inout self, value: Self._owned_variadic_type):
+    fn __init__(out self, value: Self._owned_variadic_type):
         """Constructs a VariadicList from a variadic argument type.
 
         Args:
@@ -377,7 +377,7 @@ struct VariadicListMem[
         self._is_owned = True
 
     @always_inline
-    fn __moveinit__(inout self, owned existing: Self):
+    fn __moveinit__(out self, owned existing: Self):
         """Moves constructor.
 
         Args:
@@ -509,7 +509,7 @@ struct VariadicPack[
 
     @doc_private
     @always_inline("nodebug")
-    fn __init__(inout self, value: Self._mlir_type, is_owned: Bool):
+    fn __init__(out self, value: Self._mlir_type, is_owned: Bool):
         """Constructs a VariadicPack from the internal representation.
 
         Args:
diff --git a/stdlib/src/builtin/builtin_slice.mojo b/stdlib/src/builtin/builtin_slice.mojo
index 77d7811c01..cc5a6d2f1a 100644
--- a/stdlib/src/builtin/builtin_slice.mojo
+++ b/stdlib/src/builtin/builtin_slice.mojo
@@ -53,7 +53,7 @@ struct Slice(
     # ===-------------------------------------------------------------------===#
 
     @always_inline
-    fn __init__(inout self, start: Int, end: Int):
+    fn __init__(out self, start: Int, end: Int):
         """Construct slice given the start and end values.
 
         Args:
@@ -82,7 +82,7 @@ struct Slice(
         self.end = end
         self.step = step
 
-    fn __init__(inout self, *, other: Self):
+    fn __init__(out self, *, other: Self):
         """Creates a deep copy of the Slice.
 
         Args:
diff --git a/stdlib/src/builtin/coroutine.mojo b/stdlib/src/builtin/coroutine.mojo
index 1246e099fa..4c8517d687 100644
--- a/stdlib/src/builtin/coroutine.mojo
+++ b/stdlib/src/builtin/coroutine.mojo
@@ -120,7 +120,7 @@ struct Coroutine[type: AnyType, origins: OriginSet]:
         )
 
     @always_inline
-    fn __init__(inout self, handle: AnyCoroutine):
+    fn __init__(out self, handle: AnyCoroutine):
         """Construct a coroutine object from a handle.
 
         Args:
@@ -200,7 +200,7 @@ struct RaisingCoroutine[type: AnyType, origins: OriginSet]:
         )
 
     @always_inline
-    fn __init__(inout self, handle: AnyCoroutine):
+    fn __init__(out self, handle: AnyCoroutine):
         """Construct a coroutine object from a handle.
 
         Args:
diff --git a/stdlib/src/builtin/dtype.mojo b/stdlib/src/builtin/dtype.mojo
index 26ae8cd003..e0b81dadc7 100644
--- a/stdlib/src/builtin/dtype.mojo
+++ b/stdlib/src/builtin/dtype.mojo
@@ -93,7 +93,7 @@ struct DType(
     on the system."""
 
     @always_inline
-    fn __init__(inout self, *, other: Self):
+    fn __init__(out self, *, other: Self):
         """Copy this DType.
 
         Args:
diff --git a/stdlib/src/builtin/error.mojo b/stdlib/src/builtin/error.mojo
index a974d6a8c2..482f4aa454 100644
--- a/stdlib/src/builtin/error.mojo
+++ b/stdlib/src/builtin/error.mojo
@@ -59,13 +59,13 @@ struct Error(
     # ===-------------------------------------------------------------------===#
 
     @always_inline
-    fn __init__(inout self):
+    fn __init__(out self):
         """Default constructor."""
         self.data = UnsafePointer[UInt8]()
         self.loaded_length = 0
 
     @always_inline
-    fn __init__(inout self, value: StringLiteral):
+    fn __init__(out self, value: StringLiteral):
         """Construct an Error object with a given string literal.
 
         Args:
@@ -74,7 +74,7 @@ struct Error(
         self.data = value.unsafe_ptr()
         self.loaded_length = len(value)
 
-    fn __init__(inout self, src: String):
+    fn __init__(out self, src: String):
         """Construct an Error object with a given string.
 
         Args:
@@ -91,7 +91,7 @@ struct Error(
         self.data = dest
         self.loaded_length = -length
 
-    fn __init__(inout self, src: StringRef):
+    fn __init__(out self, src: StringRef):
         """Construct an Error object with a given string ref.
 
         Args:
@@ -108,7 +108,7 @@ struct Error(
         self.data = dest
         self.loaded_length = -length
 
-    fn __init__(inout self, *, other: Self):
+    fn __init__(out self, *, other: Self):
         """Copy the object.
 
         Args:
@@ -121,7 +121,7 @@ struct Error(
         if self.loaded_length < 0:
             self.data.free()
 
-    fn __copyinit__(inout self, existing: Self):
+    fn __copyinit__(out self, existing: Self):
         """Creates a deep copy of an existing error.
 
         Args:
diff --git a/stdlib/src/builtin/file.mojo b/stdlib/src/builtin/file.mojo
index 6fd4aac2c8..0803d4f3e0 100644
--- a/stdlib/src/builtin/file.mojo
+++ b/stdlib/src/builtin/file.mojo
@@ -44,7 +44,7 @@ struct _OwnedStringRef(Boolable):
     var data: UnsafePointer[UInt8]
     var length: Int
 
-    fn __init__(inout self):
+    fn __init__(out self):
         self.data = UnsafePointer[UInt8]()
         self.length = 0
 
@@ -73,11 +73,11 @@ struct FileHandle:
     var handle: OpaquePointer
     """The underlying pointer to the file handle."""
 
-    fn __init__(inout self):
+    fn __init__(out self):
         """Default constructor."""
         self.handle = OpaquePointer()
 
-    fn __init__(inout self, path: String, mode: String) raises:
+    fn __init__(out self, path: String, mode: String) raises:
         """Construct the FileHandle using the file path and mode.
 
         Args:
@@ -86,7 +86,7 @@ struct FileHandle:
         """
         self.__init__(path.as_string_slice(), mode.as_string_slice())
 
-    fn __init__(inout self, path: StringSlice, mode: StringSlice) raises:
+    fn __init__(out self, path: StringSlice, mode: StringSlice) raises:
         """Construct the FileHandle using the file path and string.
 
         Args:
@@ -126,7 +126,7 @@ struct FileHandle:
 
         self.handle = OpaquePointer()
 
-    fn __moveinit__(inout self, owned existing: Self):
+    fn __moveinit__(out self, owned existing: Self):
         """Moves constructor for the file handle.
 
         Args:
diff --git a/stdlib/src/builtin/file_descriptor.mojo b/stdlib/src/builtin/file_descriptor.mojo
index 0745273a9a..e4132603bc 100644
--- a/stdlib/src/builtin/file_descriptor.mojo
+++ b/stdlib/src/builtin/file_descriptor.mojo
@@ -38,7 +38,7 @@ struct FileDescriptor(Writer):
     var value: Int
     """The underlying value of the file descriptor."""
 
-    fn __init__(inout self, value: Int = 1):
+    fn __init__(out self, value: Int = 1):
         """Constructs the file descriptor from an integer.
 
         Args:
@@ -46,7 +46,7 @@ struct FileDescriptor(Writer):
         """
         self.value = value
 
-    fn __init__(inout self, f: FileHandle):
+    fn __init__(out self, f: FileHandle):
         """Constructs the file descriptor from a file handle.
 
         Args:
diff --git a/stdlib/src/builtin/float_literal.mojo b/stdlib/src/builtin/float_literal.mojo
index d6a19e9595..c3da23fcbc 100644
--- a/stdlib/src/builtin/float_literal.mojo
+++ b/stdlib/src/builtin/float_literal.mojo
@@ -49,7 +49,7 @@ struct FloatLiteral(
     # ===------------------------------------------------------------------===#
 
     @always_inline("nodebug")
-    fn __init__(inout self, value: Self.fp_type):
+    fn __init__(out self, value: Self.fp_type):
         """Create a FloatLiteral value from a kgen.float_literal value.
 
         Args:
@@ -58,7 +58,7 @@ struct FloatLiteral(
         self.value = value
 
     @always_inline("nodebug")
-    fn __init__(inout self, value: IntLiteral):
+    fn __init__(out self, value: IntLiteral):
         """Convert an IntLiteral to a FloatLiteral value.
 
         Args:
diff --git a/stdlib/src/builtin/int.mojo b/stdlib/src/builtin/int.mojo
index 9c97d71359..aa6bd7de8b 100644
--- a/stdlib/src/builtin/int.mojo
+++ b/stdlib/src/builtin/int.mojo
@@ -308,11 +308,11 @@ struct Int(
     # ===------------------------------------------------------------------=== #
 
     @always_inline("nodebug")
-    fn __init__(inout self):
+    fn __init__(out self):
         """Default constructor that produces zero."""
         self.value = __mlir_op.`index.constant`[value = __mlir_attr.`0:index`]()
 
-    fn __init__(inout self, *, other: Self):
+    fn __init__(out self, *, other: Self):
         """Explicitly copy the provided value.
 
         Args:
@@ -322,7 +322,7 @@ struct Int(
 
     @doc_private
     @always_inline("nodebug")
-    fn __init__(inout self, value: __mlir_type.index):
+    fn __init__(out self, value: __mlir_type.index):
         """Construct Int from the given index value.
 
         Args:
@@ -332,7 +332,7 @@ struct Int(
 
     @doc_private
     @always_inline("nodebug")
-    fn __init__(inout self, value: __mlir_type.`!pop.scalar<si16>`):
+    fn __init__(out self, value: __mlir_type.`!pop.scalar<si16>`):
         """Construct Int from the given Int16 value.
 
         Args:
@@ -346,7 +346,7 @@ struct Int(
 
     @doc_private
     @always_inline("nodebug")
-    fn __init__(inout self, value: __mlir_type.`!pop.scalar<si32>`):
+    fn __init__(out self, value: __mlir_type.`!pop.scalar<si32>`):
         """Construct Int from the given Int32 value.
 
         Args:
@@ -360,7 +360,7 @@ struct Int(
 
     @doc_private
     @always_inline("nodebug")
-    fn __init__(inout self, value: __mlir_type.`!pop.scalar<si64>`):
+    fn __init__(out self, value: __mlir_type.`!pop.scalar<si64>`):
         """Construct Int from the given Int64 value.
 
         Args:
@@ -374,7 +374,7 @@ struct Int(
 
     @doc_private
     @always_inline("nodebug")
-    fn __init__(inout self, value: __mlir_type.`!pop.scalar<index>`):
+    fn __init__(out self, value: __mlir_type.`!pop.scalar<index>`):
         """Construct Int from the given Index value.
 
         Args:
@@ -385,7 +385,7 @@ struct Int(
         )
 
     @always_inline("nodebug")
-    fn __init__(inout self, value: IntLiteral):
+    fn __init__(out self, value: IntLiteral):
         """Construct Int from the given IntLiteral value.
 
         Args:
@@ -406,7 +406,7 @@ struct Int(
         self = value.__index__()
 
     @always_inline("nodebug")
-    fn __init__(inout self, value: UInt):
+    fn __init__(out self, value: UInt):
         """Construct Int from the given UInt value.
 
         Args:
diff --git a/stdlib/src/builtin/int_literal.mojo b/stdlib/src/builtin/int_literal.mojo
index 90b3850ddb..326759e115 100644
--- a/stdlib/src/builtin/int_literal.mojo
+++ b/stdlib/src/builtin/int_literal.mojo
@@ -53,13 +53,13 @@ struct IntLiteral(
     # ===-------------------------------------------------------------------===#
 
     @always_inline("nodebug")
-    fn __init__(inout self):
+    fn __init__(out self):
         """Default constructor."""
         self.value = __mlir_attr.`#kgen.int_literal<0> : !kgen.int_literal`
 
     @doc_private
     @always_inline("nodebug")
-    fn __init__(inout self, value: __mlir_type.`!kgen.int_literal`):
+    fn __init__(out self, value: __mlir_type.`!kgen.int_literal`):
         """Construct IntLiteral from the given mlir !kgen.int_literal value.
 
         Args:
diff --git a/stdlib/src/builtin/io.mojo b/stdlib/src/builtin/io.mojo
index 696730e94d..d605324b1c 100644
--- a/stdlib/src/builtin/io.mojo
+++ b/stdlib/src/builtin/io.mojo
@@ -43,7 +43,7 @@ from utils import StringRef, StaticString, StringSlice
 struct _fdopen[mode: StringLiteral = "a"]:
     var handle: OpaquePointer
 
-    fn __init__(inout self, stream_id: FileDescriptor):
+    fn __init__(out self, stream_id: FileDescriptor):
         """Creates a file handle to the stdout/stderr stream.
 
         Args:
diff --git a/stdlib/src/builtin/math.mojo b/stdlib/src/builtin/math.mojo
index 2506699f9d..eb1b088242 100644
--- a/stdlib/src/builtin/math.mojo
+++ b/stdlib/src/builtin/math.mojo
@@ -269,7 +269,7 @@ trait Powable:
         var numerator: Float64
         var denominator: Float64
 
-        fn __init__(inout self, numerator: Float64, denominator: Float64):
+        fn __init__(out self, numerator: Float64, denominator: Float64):
             self.numerator = numerator
             self.denominator = denominator
 
diff --git a/stdlib/src/builtin/none.mojo b/stdlib/src/builtin/none.mojo
index a5e85d39a8..966525ef95 100644
--- a/stdlib/src/builtin/none.mojo
+++ b/stdlib/src/builtin/none.mojo
@@ -33,12 +33,12 @@ struct NoneType(
     var _value: Self._mlir_type
 
     @always_inline
-    fn __init__(inout self):
+    fn __init__(out self):
         """Construct an instance of the `None` type."""
         self._value = None
 
     @always_inline
-    fn __init__(inout self, *, other: Self):
+    fn __init__(out self, *, other: Self):
         """Explicit copy constructor.
 
         Args:
diff --git a/stdlib/src/builtin/object.mojo b/stdlib/src/builtin/object.mojo
index f7587a8ac6..2d0cef2c92 100644
--- a/stdlib/src/builtin/object.mojo
+++ b/stdlib/src/builtin/object.mojo
@@ -32,7 +32,7 @@ from utils import StringRef, Variant
 struct _NoneMarker(CollectionElementNew):
     """This is a trivial class to indicate that an object is `None`."""
 
-    fn __init__(inout self, *, other: Self):
+    fn __init__(out self, *, other: Self):
         pass
 
 
@@ -50,12 +50,12 @@ struct _ImmutableString(CollectionElement, CollectionElementNew):
     """The length of the string."""
 
     @always_inline
-    fn __init__(inout self, data: UnsafePointer[UInt8], length: Int):
+    fn __init__(out self, data: UnsafePointer[UInt8], length: Int):
         self.data = data
         self.length = length
 
     @always_inline
-    fn __init__(inout self, *, other: Self):
+    fn __init__(out self, *, other: Self):
         self = other
 
     @always_inline
@@ -78,7 +78,7 @@ struct _RefCountedList:
     var impl: Arc[List[_ObjectImpl]]
     """The list value."""
 
-    fn __init__(inout self):
+    fn __init__(out self):
         self.impl = Arc[List[_ObjectImpl]](List[_ObjectImpl]())
 
 
@@ -89,13 +89,13 @@ struct _RefCountedListRef(CollectionElement, CollectionElementNew):
     """The reference to the list."""
 
     @always_inline
-    fn __init__(inout self):
+    fn __init__(out self):
         var ptr = UnsafePointer[_RefCountedList].alloc(1)
         __get_address_as_uninit_lvalue(ptr.address) = _RefCountedList()
         self.lst = ptr.bitcast[NoneType]()
 
     @always_inline
-    fn __init__(inout self, *, other: Self):
+    fn __init__(out self, *, other: Self):
         self.lst = other.lst
 
     @always_inline
@@ -118,7 +118,7 @@ struct _RefCountedAttrsDict:
     var impl: Arc[Dict[StringLiteral, _ObjectImpl]]
     """The implementation of the map."""
 
-    fn __init__(inout self):
+    fn __init__(out self):
         self.impl = Arc[Dict[StringLiteral, _ObjectImpl]](
             Dict[StringLiteral, _ObjectImpl]()
         )
@@ -159,7 +159,7 @@ struct Attr:
     """The value of the attribute."""
 
     @always_inline
-    fn __init__(inout self, key: StringLiteral, owned value: object):
+    fn __init__(out self, key: StringLiteral, owned value: object):
         """Initializes the attribute with a key and value.
 
         Args:
@@ -178,7 +178,7 @@ struct _RefCountedAttrsDictRef(CollectionElement, CollectionElementNew):
     """The reference to the dictionary."""
 
     @always_inline
-    fn __init__(inout self, values: VariadicListMem[Attr, _]):
+    fn __init__(out self, values: VariadicListMem[Attr, _]):
         var ptr = UnsafePointer[_RefCountedAttrsDict].alloc(1)
         __get_address_as_uninit_lvalue(ptr.address) = _RefCountedAttrsDict()
         # Elements can only be added on construction.
@@ -188,7 +188,7 @@ struct _RefCountedAttrsDictRef(CollectionElement, CollectionElementNew):
         self.attrs = ptr.bitcast[Int8]()
 
     @always_inline
-    fn __init__(inout self, *, other: Self):
+    fn __init__(out self, *, other: Self):
         self = other
 
     @always_inline
@@ -216,7 +216,7 @@ struct _Function(CollectionElement, CollectionElementNew):
         self.value = f
 
     @always_inline
-    fn __init__(inout self, *, other: Self):
+    fn __init__(out self, *, other: Self):
         self.value = other.value
 
     alias fn0 = fn () raises -> object
@@ -305,15 +305,15 @@ struct _ObjectImpl(
     # ===------------------------------------------------------------------=== #
 
     @always_inline
-    fn __init__(inout self, value: Self.type):
+    fn __init__(out self, value: Self.type):
         self.value = value
 
     @always_inline
-    fn __init__(inout self):
+    fn __init__(out self):
         self.value = Self.type(_NoneMarker {})
 
     @always_inline
-    fn __init__(inout self, value: Bool):
+    fn __init__(out self, value: Bool):
         self.value = Self.type(value)
 
     @always_inline
@@ -325,23 +325,23 @@ struct _ObjectImpl(
             self.value = Self.type(value)
 
     @always_inline
-    fn __init__(inout self, value: _ImmutableString):
+    fn __init__(out self, value: _ImmutableString):
         self.value = Self.type(value)
 
     @always_inline
-    fn __init__(inout self, value: _RefCountedListRef):
+    fn __init__(out self, value: _RefCountedListRef):
         self.value = Self.type(value)
 
     @always_inline
-    fn __init__(inout self, value: _Function):
+    fn __init__(out self, value: _Function):
         self.value = Self.type(value)
 
     @always_inline
-    fn __init__(inout self, value: _RefCountedAttrsDictRef):
+    fn __init__(out self, value: _RefCountedAttrsDictRef):
         self.value = Self.type(value)
 
     @always_inline
-    fn __init__(inout self, *, other: Self):
+    fn __init__(out self, *, other: Self):
         """Copy the object.
 
         Args:
@@ -350,11 +350,11 @@ struct _ObjectImpl(
         self = other.value
 
     @always_inline
-    fn __copyinit__(inout self, existing: Self):
+    fn __copyinit__(out self, existing: Self):
         self = existing.value
 
     @always_inline
-    fn __moveinit__(inout self, owned other: Self):
+    fn __moveinit__(out self, owned other: Self):
         self = other.value^
 
     @always_inline
@@ -720,12 +720,12 @@ struct object(
     # ===------------------------------------------------------------------=== #
 
     @always_inline
-    fn __init__(inout self):
+    fn __init__(out self):
         """Initializes the object with a `None` value."""
         self._value = _ObjectImpl()
 
     @always_inline
-    fn __init__(inout self, impl: _ObjectImpl):
+    fn __init__(out self, impl: _ObjectImpl):
         """Initializes the object with an implementation value. This is meant for
         internal use only.
 
@@ -735,7 +735,7 @@ struct object(
         self._value = impl
 
     @always_inline
-    fn __init__(inout self, none: NoneType):
+    fn __init__(out self, none: NoneType):
         """Initializes a none value object from a `None` literal.
 
         Args:
@@ -744,7 +744,7 @@ struct object(
         self._value = _ObjectImpl()
 
     @always_inline
-    fn __init__(inout self, value: Int):
+    fn __init__(out self, value: Int):
         """Initializes the object with an integer value.
 
         Args:
@@ -753,7 +753,7 @@ struct object(
         self._value = Int64(value)
 
     @always_inline
-    fn __init__(inout self, value: Float64):
+    fn __init__(out self, value: Float64):
         """Initializes the object with an floating-point value.
 
         Args:
@@ -781,7 +781,7 @@ struct object(
             self._value = value
 
     @always_inline
-    fn __init__(inout self, value: Bool):
+    fn __init__(out self, value: Bool):
         """Initializes the object from a bool.
 
         Args:
@@ -790,7 +790,7 @@ struct object(
         self._value = value
 
     @always_inline
-    fn __init__(inout self, value: StringLiteral):
+    fn __init__(out self, value: StringLiteral):
         """Initializes the object from a string literal.
 
         Args:
@@ -799,7 +799,7 @@ struct object(
         self = object(StringRef(value))
 
     @always_inline
-    fn __init__(inout self, value: StringRef):
+    fn __init__(out self, value: StringRef):
         """Initializes the object from a string reference.
 
         Args:
@@ -850,7 +850,7 @@ struct object(
                 ]()
 
     @always_inline
-    fn __init__(inout self, func: Self.nullary_function):
+    fn __init__(out self, func: Self.nullary_function):
         """Initializes an object from a function that takes no arguments.
 
         Args:
@@ -859,7 +859,7 @@ struct object(
         self._value = _Function(func)
 
     @always_inline
-    fn __init__(inout self, func: Self.unary_function):
+    fn __init__(out self, func: Self.unary_function):
         """Initializes an object from a function that takes one argument.
 
         Args:
@@ -868,7 +868,7 @@ struct object(
         self._value = _Function(func)
 
     @always_inline
-    fn __init__(inout self, func: Self.binary_function):
+    fn __init__(out self, func: Self.binary_function):
         """Initializes an object from a function that takes two arguments.
 
         Args:
@@ -877,7 +877,7 @@ struct object(
         self._value = _Function(func)
 
     @always_inline
-    fn __init__(inout self, func: Self.ternary_function):
+    fn __init__(out self, func: Self.ternary_function):
         """Initializes an object from a function that takes three arguments.
 
         Args:
@@ -886,7 +886,7 @@ struct object(
         self._value = _Function(func)
 
     @always_inline
-    fn __init__(inout self, *attrs: Attr):
+    fn __init__(out self, *attrs: Attr):
         """Initializes the object with a sequence of zero or more attributes.
 
         Args:
@@ -895,7 +895,7 @@ struct object(
         self._value = _RefCountedAttrsDictRef(attrs)
 
     @always_inline
-    fn __moveinit__(inout self, owned existing: object):
+    fn __moveinit__(out self, owned existing: object):
         """Move the value of an object.
 
         Args:
@@ -905,7 +905,7 @@ struct object(
         existing._value = _ObjectImpl()
 
     @always_inline
-    fn __copyinit__(inout self, existing: object):
+    fn __copyinit__(out self, existing: object):
         """Copies the object. This clones the underlying string value and
         increases the refcount of lists or dictionaries.
 
diff --git a/stdlib/src/builtin/range.mojo b/stdlib/src/builtin/range.mojo
index ccc01436db..2b9e691e42 100644
--- a/stdlib/src/builtin/range.mojo
+++ b/stdlib/src/builtin/range.mojo
@@ -48,7 +48,7 @@ struct _ZeroStartingRange(Sized, ReversibleRange, _IntIterable):
     var end: Int
 
     @always_inline
-    fn __init__(inout self, end: Int):
+    fn __init__(out self, end: Int):
         self.curr = max(0, end)
         self.end = self.curr
 
@@ -149,7 +149,7 @@ struct _StridedRange(Sized, ReversibleRange, _StridedIterable):
     var step: Int
 
     @always_inline
-    fn __init__(inout self, start: Int, end: Int):
+    fn __init__(out self, start: Int, end: Int):
         self.start = start
         self.end = end
         self.step = 1
@@ -324,7 +324,7 @@ struct _UIntZeroStartingRange(UIntSized):
     var end: UInt
 
     @always_inline
-    fn __init__(inout self, end: UInt):
+    fn __init__(out self, end: UInt):
         self.curr = max(0, end)
         self.end = self.curr
 
@@ -382,7 +382,7 @@ struct _UIntStridedRange(UIntSized, _UIntStridedIterable):
     var step: UInt
 
     @always_inline
-    fn __init__(inout self, start: UInt, end: UInt, step: UInt):
+    fn __init__(out self, start: UInt, end: UInt, step: UInt):
         self.start = start
         self.end = end
         debug_assert(
@@ -464,7 +464,7 @@ struct _ZeroStartingScalarRange[type: DType]:
     var end: Scalar[type]
 
     @always_inline
-    fn __init__(inout self, end: Scalar[type]):
+    fn __init__(out self, end: Scalar[type]):
         self.curr = max(0, end)
         self.end = self.curr
 
diff --git a/stdlib/src/builtin/simd.mojo b/stdlib/src/builtin/simd.mojo
index fb4fc32fca..3ae36ad548 100644
--- a/stdlib/src/builtin/simd.mojo
+++ b/stdlib/src/builtin/simd.mojo
@@ -227,7 +227,7 @@ struct SIMD[type: DType, size: Int](
     # ===-------------------------------------------------------------------===#
 
     @always_inline("nodebug")
-    fn __init__(inout self):
+    fn __init__(out self):
         """Default initializer of the SIMD vector.
 
         By default the SIMD vectors are initialized to all zeros.
@@ -237,7 +237,7 @@ struct SIMD[type: DType, size: Int](
 
     # FIXME(MOCO-1291): Can't implement this due to ambiguity.
     # @always_inline("nodebug")
-    # fn __init__(inout self, *, other: SIMD[type, size]):
+    # fn __init__(out self, *, other: SIMD[type, size]):
     #    """Explicitly copy the provided value.
 
     #    Args:
@@ -246,7 +246,7 @@ struct SIMD[type: DType, size: Int](
     #    self.__copyinit__(other)
 
     @always_inline("nodebug")
-    fn __init__(inout self, value: UInt):
+    fn __init__(out self, value: UInt):
         """Initializes the SIMD vector with an unsigned integer.
 
         The unsigned integer value is splatted across all the elements of the SIMD
@@ -258,7 +258,7 @@ struct SIMD[type: DType, size: Int](
         self = Self(value.value)
 
     @always_inline("nodebug")
-    fn __init__(inout self, value: Int):
+    fn __init__(out self, value: Int):
         """Initializes the SIMD vector with a signed integer.
 
         The signed integer value is splatted across all the elements of the SIMD
@@ -271,7 +271,7 @@ struct SIMD[type: DType, size: Int](
 
     @doc_private
     @always_inline("nodebug")
-    fn __init__(inout self, value: __mlir_type.index):
+    fn __init__(out self, value: __mlir_type.index):
         _simd_construction_checks[type, size]()
 
         var t0 = __mlir_op.`pop.cast_from_builtin`[
@@ -285,7 +285,7 @@ struct SIMD[type: DType, size: Int](
         ](casted)
 
     @always_inline("nodebug")
-    fn __init__(inout self, value: IntLiteral):
+    fn __init__(out self, value: IntLiteral):
         """Initializes the SIMD vector with an integer.
 
         The integer value is splatted across all the elements of the SIMD
@@ -310,7 +310,7 @@ struct SIMD[type: DType, size: Int](
         ](casted)
 
     @always_inline("nodebug")
-    fn __init__(inout self: SIMD[DType.bool, size], value: Bool, /):
+    fn __init__(out self: SIMD[DType.bool, size], value: Bool, /):
         """Initializes the SIMD vector with a bool value.
 
         The bool value is splatted across all elements of the SIMD vector.
@@ -341,7 +341,7 @@ struct SIMD[type: DType, size: Int](
         self.value = value
 
     @always_inline("nodebug")
-    fn __init__(inout self, value: Scalar[type], /):
+    fn __init__(out self, value: Scalar[type], /):
         """Constructs a SIMD vector by splatting a scalar value.
 
         The input value is splatted across all elements of the SIMD vector.
@@ -357,7 +357,7 @@ struct SIMD[type: DType, size: Int](
         ](value.value)
 
     @always_inline("nodebug")
-    fn __init__(inout self, *elems: Scalar[type]):
+    fn __init__(out self, *elems: Scalar[type]):
         """Constructs a SIMD vector via a variadic list of elements.
 
         The input values are assigned to the corresponding elements of the SIMD
@@ -396,7 +396,7 @@ struct SIMD[type: DType, size: Int](
             self[i] = elems[i]
 
     @always_inline
-    fn __init__(inout self, value: FloatLiteral):
+    fn __init__(out self, value: FloatLiteral):
         """Initializes the SIMD vector with a float.
 
         The value is splatted across all the elements of the SIMD
diff --git a/stdlib/src/builtin/sort.mojo b/stdlib/src/builtin/sort.mojo
index df93331427..77d00ecc3e 100644
--- a/stdlib/src/builtin/sort.mojo
+++ b/stdlib/src/builtin/sort.mojo
@@ -34,7 +34,7 @@ alias insertion_sort_threshold = 32
 struct _SortWrapper[type: CollectionElement](CollectionElement):
     var data: type
 
-    fn __init__(inout self, *, other: Self):
+    fn __init__(out self, *, other: Self):
         self.data = other.data
 
 
diff --git a/stdlib/src/builtin/string_literal.mojo b/stdlib/src/builtin/string_literal.mojo
index 7f358cdd6c..2974eadbb7 100644
--- a/stdlib/src/builtin/string_literal.mojo
+++ b/stdlib/src/builtin/string_literal.mojo
@@ -70,7 +70,7 @@ struct StringLiteral(
     # ===-------------------------------------------------------------------===#
 
     @always_inline("nodebug")
-    fn __init__(inout self, value: Self.type):
+    fn __init__(out self, value: Self.type):
         """Create a string literal from a builtin string type.
 
         Args:
@@ -79,7 +79,7 @@ struct StringLiteral(
         self.value = value
 
     @always_inline("nodebug")
-    fn __init__(inout self, *, other: Self):
+    fn __init__(out self, *, other: Self):
         """Copy constructor.
 
         Args:
diff --git a/stdlib/src/builtin/tuple.mojo b/stdlib/src/builtin/tuple.mojo
index 963b605af4..8984289bb6 100644
--- a/stdlib/src/builtin/tuple.mojo
+++ b/stdlib/src/builtin/tuple.mojo
@@ -47,7 +47,7 @@ struct Tuple[*element_types: CollectionElement](Sized, CollectionElement):
     """The underlying storage for the tuple."""
 
     @always_inline("nodebug")
-    fn __init__(inout self, owned *args: *element_types):
+    fn __init__(out self, owned *args: *element_types):
         """Construct the tuple.
 
         Args:
@@ -92,7 +92,7 @@ struct Tuple[*element_types: CollectionElement](Sized, CollectionElement):
             UnsafePointer.address_of(self[i]).destroy_pointee()
 
     @always_inline("nodebug")
-    fn __copyinit__(inout self, existing: Self):
+    fn __copyinit__(out self, existing: Self):
         """Copy construct the tuple.
 
         Args:
@@ -108,7 +108,7 @@ struct Tuple[*element_types: CollectionElement](Sized, CollectionElement):
             UnsafePointer.address_of(self[i]).init_pointee_copy(existing[i])
 
     @always_inline("nodebug")
-    fn __moveinit__(inout self, owned existing: Self):
+    fn __moveinit__(out self, owned existing: Self):
         """Move construct the tuple.
 
         Args:
diff --git a/stdlib/src/builtin/uint.mojo b/stdlib/src/builtin/uint.mojo
index 9c744052df..cc9f9b8d22 100644
--- a/stdlib/src/builtin/uint.mojo
+++ b/stdlib/src/builtin/uint.mojo
@@ -54,13 +54,13 @@ struct UInt(IntLike, _HashableWithHasher):
     """
 
     @always_inline("nodebug")
-    fn __init__(inout self):
+    fn __init__(out self):
         """Default constructor that produces zero."""
         self.value = __mlir_op.`index.constant`[value = __mlir_attr.`0:index`]()
 
     @doc_private
     @always_inline("nodebug")
-    fn __init__(inout self, value: __mlir_type.index):
+    fn __init__(out self, value: __mlir_type.index):
         """Construct UInt from the given index value.
 
         Args:
@@ -70,7 +70,7 @@ struct UInt(IntLike, _HashableWithHasher):
 
     @doc_private
     @always_inline("nodebug")
-    fn __init__(inout self, value: __mlir_type.`!pop.scalar<index>`):
+    fn __init__(out self, value: __mlir_type.`!pop.scalar<index>`):
         """Construct UInt from the given Index value.
 
         Args:
@@ -81,7 +81,7 @@ struct UInt(IntLike, _HashableWithHasher):
         )
 
     @always_inline("nodebug")
-    fn __init__(inout self, value: Int):
+    fn __init__(out self, value: Int):
         """Construct UInt from the given index value.
 
         Args:
@@ -90,7 +90,7 @@ struct UInt(IntLike, _HashableWithHasher):
         self.value = value.value
 
     @always_inline("nodebug")
-    fn __init__(inout self, value: IntLiteral):
+    fn __init__(out self, value: IntLiteral):
         """Construct UInt from the given IntLiteral value.
 
         Args:
diff --git a/stdlib/src/builtin/value.mojo b/stdlib/src/builtin/value.mojo
index 74e033330b..d8e6d8e5ea 100644
--- a/stdlib/src/builtin/value.mojo
+++ b/stdlib/src/builtin/value.mojo
@@ -24,10 +24,10 @@ trait Movable:
 
     ```mojo
     struct Foo(Movable):
-        fn __init__(inout self):
+        fn __init__(out self):
             pass
 
-        fn __moveinit__(inout self, owned existing: Self):
+        fn __moveinit__(out self, owned existing: Self):
             print("moving")
     ```
 
@@ -47,7 +47,7 @@ trait Movable:
     ```
     """
 
-    fn __moveinit__(inout self, owned existing: Self, /):
+    fn __moveinit__(out self, owned existing: Self, /):
         """Create a new instance of the value by moving the value of another.
 
         Args:
@@ -66,10 +66,10 @@ trait Copyable:
     struct Foo(Copyable):
         var s: String
 
-        fn __init__(inout self, s: String):
+        fn __init__(out self, s: String):
             self.s = s
 
-        fn __copyinit__(inout self, other: Self):
+        fn __copyinit__(out self, other: Self):
             print("copying value")
             self.s = other.s
     ```
@@ -90,7 +90,7 @@ trait Copyable:
     ```
     """
 
-    fn __copyinit__(inout self, existing: Self, /):
+    fn __copyinit__(out self, existing: Self, /):
         """Create a new instance of the value by copying an existing one.
 
         Args:
@@ -117,10 +117,10 @@ trait ExplicitlyCopyable:
     struct Foo(ExplicitlyCopyable):
         var s: String
 
-        fn __init__(inout self, s: String):
+        fn __init__(out self, s: String):
             self.s = s
 
-        fn __init__(inout self, copy: Self):
+        fn __init__(out self, copy: Self):
             print("explicitly copying value")
             self.s = copy.s
     ```
@@ -145,7 +145,7 @@ trait ExplicitlyCopyable:
     #   `other` is a required named argument for the time being to minimize
     #   implicit conversion overload ambiguity errors, particularly
     #   with SIMD and Int.
-    fn __init__(inout self, *, other: Self):
+    fn __init__(out self, *, other: Self):
         """Explicitly construct a deep copy of the provided value.
 
         Args:
@@ -164,7 +164,7 @@ trait Defaultable:
     struct Foo(Defaultable):
         var s: String
 
-        fn __init__(inout self):
+        fn __init__(out self):
             self.s = "default"
     ```
 
@@ -183,7 +183,7 @@ trait Defaultable:
     ```
     """
 
-    fn __init__(inout self):
+    fn __init__(out self):
         """Create a default instance of the value."""
         ...
 
diff --git a/stdlib/src/collections/counter.mojo b/stdlib/src/collections/counter.mojo
index b65076d9e0..64db6a205a 100644
--- a/stdlib/src/collections/counter.mojo
+++ b/stdlib/src/collections/counter.mojo
@@ -51,12 +51,12 @@ struct Counter[V: KeyElement](Sized, CollectionElement, Boolable):
     # Life cycle methods
     # ===------------------------------------------------------------------=== #
 
-    fn __init__(inout self):
+    fn __init__(out self):
         """Create a new, empty Counter object."""
         self._data = Dict[V, Int]()
 
     # TODO: Change List to Iterable when it is supported in Mojo
-    fn __init__(inout self, items: List[V, *_]):
+    fn __init__(out self, items: List[V, *_]):
         """Create a from an input iterable.
 
         Args:
@@ -68,7 +68,7 @@ struct Counter[V: KeyElement](Sized, CollectionElement, Boolable):
             self._data[item] = self._data.get(item, 0) + 1
 
     @always_inline
-    fn __init__(inout self, *, other: Self):
+    fn __init__(out self, *, other: Self):
         """Create a new Counter by copying another Counter.
 
         Args:
@@ -616,7 +616,7 @@ struct CountTuple[V: KeyElement](
     # Life cycle methods
     # ===------------------------------------------------------------------=== #
 
-    fn __init__(inout self, value: V, count: Int):
+    fn __init__(out self, value: V, count: Int):
         """Create a new CountTuple.
 
         Args:
@@ -626,7 +626,7 @@ struct CountTuple[V: KeyElement](
         self._value = value
         self._count = count
 
-    fn __copyinit__(inout self, other: Self):
+    fn __copyinit__(out self, other: Self):
         """Create a new CountTuple by copying another CountTuple.
 
         Args:
@@ -635,7 +635,7 @@ struct CountTuple[V: KeyElement](
         self._value = other._value
         self._count = other._count
 
-    fn __moveinit__(inout self, owned other: Self):
+    fn __moveinit__(out self, owned other: Self):
         """Create a new CountTuple by moving another CountTuple.
 
         Args:
diff --git a/stdlib/src/collections/deque.mojo b/stdlib/src/collections/deque.mojo
index c52991fa85..b619c4bb5a 100644
--- a/stdlib/src/collections/deque.mojo
+++ b/stdlib/src/collections/deque.mojo
@@ -132,7 +132,7 @@ struct Deque[ElementType: CollectionElement](
         if elements is not None:
             self.extend(elements.value())
 
-    fn __init__(inout self, owned *values: ElementType):
+    fn __init__(out self, owned *values: ElementType):
         """Constructs a deque from the given values.
 
         Args:
@@ -167,7 +167,7 @@ struct Deque[ElementType: CollectionElement](
 
         self._tail = args_length
 
-    fn __init__(inout self, other: Self):
+    fn __init__(out self, other: Self):
         """Creates a deepcopy of the given deque.
 
         Args:
@@ -185,7 +185,7 @@ struct Deque[ElementType: CollectionElement](
 
         self._tail = len(other)
 
-    fn __moveinit__(inout self, owned existing: Self):
+    fn __moveinit__(out self, owned existing: Self):
         """Moves data of an existing deque into a new one.
 
         Args:
diff --git a/stdlib/src/collections/dict.mojo b/stdlib/src/collections/dict.mojo
index 8cbd4b6357..bd9cdb5687 100644
--- a/stdlib/src/collections/dict.mojo
+++ b/stdlib/src/collections/dict.mojo
@@ -220,7 +220,7 @@ struct DictEntry[K: KeyElement, V: CollectionElement](
     var value: V
     """The value associated with the key."""
 
-    fn __init__(inout self, owned key: K, owned value: V):
+    fn __init__(out self, owned key: K, owned value: V):
         """Create an entry from a key and value, computing the hash.
 
         Args:
@@ -231,7 +231,7 @@ struct DictEntry[K: KeyElement, V: CollectionElement](
         self.key = key^
         self.value = value^
 
-    fn __init__(inout self, *, other: Self):
+    fn __init__(out self, *, other: Self):
         """Copy an existing entry.
 
         Args:
@@ -270,7 +270,7 @@ struct _DictIndex:
     var data: OpaquePointer
 
     @always_inline
-    fn __init__(inout self, reserved: Int):
+    fn __init__(out self, reserved: Int):
         if reserved <= 128:
             var data = UnsafePointer[Int8].alloc(reserved)
             for i in range(reserved):
@@ -312,7 +312,7 @@ struct _DictIndex:
             memcpy(new_data, data, reserved)
         return index^
 
-    fn __moveinit__(inout self, owned existing: Self):
+    fn __moveinit__(out self, owned existing: Self):
         self.data = existing.data
 
     fn get_index(self, reserved: Int, slot: Int) -> Int:
@@ -472,7 +472,7 @@ struct Dict[K: KeyElement, V: CollectionElement](
     # ===-------------------------------------------------------------------===#
 
     @always_inline
-    fn __init__(inout self):
+    fn __init__(out self):
         """Initialize an empty dictiontary."""
         self.size = 0
         self._n_entries = 0
@@ -480,7 +480,7 @@ struct Dict[K: KeyElement, V: CollectionElement](
         self._index = _DictIndex(len(self._entries))
 
     @always_inline
-    fn __init__(inout self, *, power_of_two_initial_capacity: Int):
+    fn __init__(out self, *, power_of_two_initial_capacity: Int):
         """Initialize an empty dictiontary with a pre-reserved initial capacity.
 
         Args:
@@ -513,7 +513,7 @@ struct Dict[K: KeyElement, V: CollectionElement](
         return len(self._entries)
 
     @always_inline
-    fn __init__(inout self, *, other: Self):
+    fn __init__(out self, *, other: Self):
         """Copy an existing dictiontary.
 
         Args:
@@ -555,7 +555,7 @@ struct Dict[K: KeyElement, V: CollectionElement](
         """
         return Dict[K, Optional[V]].fromkeys(keys, value)
 
-    fn __copyinit__(inout self, existing: Self):
+    fn __copyinit__(out self, existing: Self):
         """Copy an existing dictiontary.
 
         Args:
@@ -566,7 +566,7 @@ struct Dict[K: KeyElement, V: CollectionElement](
         self._index = existing._index.copy(existing._reserved())
         self._entries = existing._entries
 
-    fn __moveinit__(inout self, owned existing: Self):
+    fn __moveinit__(out self, owned existing: Self):
         """Move data of an existing dict into a new one.
 
         Args:
@@ -1083,11 +1083,11 @@ struct OwnedKwargsDict[V: CollectionElement](
     # Life cycle methods
     # ===-------------------------------------------------------------------===#
 
-    fn __init__(inout self):
+    fn __init__(out self):
         """Initialize an empty keyword dictionary."""
         self._dict = Dict[Self.key_type, V]()
 
-    fn __init__(inout self, *, other: Self):
+    fn __init__(out self, *, other: Self):
         """Copy an existing keyword dictionary.
 
         Args:
@@ -1095,7 +1095,7 @@ struct OwnedKwargsDict[V: CollectionElement](
         """
         self._dict = other._dict
 
-    fn __copyinit__(inout self, existing: Self):
+    fn __copyinit__(out self, existing: Self):
         """Copy an existing keyword dictionary.
 
         Args:
@@ -1103,7 +1103,7 @@ struct OwnedKwargsDict[V: CollectionElement](
         """
         self._dict = existing._dict
 
-    fn __moveinit__(inout self, owned existing: Self):
+    fn __moveinit__(out self, owned existing: Self):
         """Move data of an existing keyword dictionary into a new one.
 
         Args:
diff --git a/stdlib/src/collections/inline_array.mojo b/stdlib/src/collections/inline_array.mojo
index 0721f33e6f..7aab9d4618 100644
--- a/stdlib/src/collections/inline_array.mojo
+++ b/stdlib/src/collections/inline_array.mojo
@@ -67,7 +67,7 @@ struct InlineArray[
     # ===------------------------------------------------------------------===#
 
     @always_inline
-    fn __init__(inout self):
+    fn __init__(out self):
         """This constructor will always cause a compile time error if used.
         It is used to steer users away from uninitialized memory.
         """
@@ -85,7 +85,7 @@ struct InlineArray[
         ]()
 
     @always_inline
-    fn __init__(inout self, *, unsafe_uninitialized: Bool):
+    fn __init__(out self, *, unsafe_uninitialized: Bool):
         """Create an InlineArray with uninitialized memory.
 
         Note that this is highly unsafe and should be used with caution.
@@ -139,7 +139,7 @@ struct InlineArray[
             )
 
     @always_inline
-    fn __init__(inout self, fill: Self.ElementType):
+    fn __init__(out self, fill: Self.ElementType):
         """Constructs an empty array where each element is the supplied `fill`.
 
         Args:
@@ -157,7 +157,7 @@ struct InlineArray[
             ptr.init_pointee_copy(fill)
 
     @always_inline
-    fn __init__(inout self, owned *elems: Self.ElementType):
+    fn __init__(out self, owned *elems: Self.ElementType):
         """Constructs an array given a set of arguments.
 
         Args:
@@ -194,7 +194,7 @@ struct InlineArray[
         # Mark the elements as already destroyed.
         storage._is_owned = False
 
-    fn __init__(inout self, *, other: Self):
+    fn __init__(out self, *, other: Self):
         """Explicitly copy the provided value.
 
         Args:
@@ -207,7 +207,7 @@ struct InlineArray[
             var ptr = self.unsafe_ptr() + idx
             ptr.init_pointee_copy(other[idx])
 
-    fn __copyinit__(inout self, other: Self):
+    fn __copyinit__(out self, other: Self):
         """Copy construct the array.
 
         Args:
diff --git a/stdlib/src/collections/inline_list.mojo b/stdlib/src/collections/inline_list.mojo
index 0922999700..792635f427 100644
--- a/stdlib/src/collections/inline_list.mojo
+++ b/stdlib/src/collections/inline_list.mojo
@@ -100,7 +100,7 @@ struct InlineList[ElementType: CollectionElementNew, capacity: Int = 16](Sized):
     # ===-------------------------------------------------------------------===#
 
     @always_inline
-    fn __init__(inout self):
+    fn __init__(out self):
         """This constructor creates an empty InlineList."""
         self._array = InlineArray[
             UnsafeMaybeUninitialized[ElementType], capacity
@@ -109,7 +109,7 @@ struct InlineList[ElementType: CollectionElementNew, capacity: Int = 16](Sized):
 
     # TODO: Avoid copying elements in once owned varargs
     # allow transfers.
-    fn __init__(inout self, *values: ElementType):
+    fn __init__(out self, *values: ElementType):
         """Constructs a list from the given values.
 
         Args:
diff --git a/stdlib/src/collections/list.mojo b/stdlib/src/collections/list.mojo
index 6fa162fd2e..301825d0a7 100644
--- a/stdlib/src/collections/list.mojo
+++ b/stdlib/src/collections/list.mojo
@@ -109,13 +109,13 @@ struct List[T: CollectionElement, hint_trivial_type: Bool = False](
     # Life cycle methods
     # ===-------------------------------------------------------------------===#
 
-    fn __init__(inout self):
+    fn __init__(out self):
         """Constructs an empty list."""
         self.data = UnsafePointer[T]()
         self.size = 0
         self.capacity = 0
 
-    fn __init__(inout self, *, other: Self):
+    fn __init__(out self, *, other: Self):
         """Creates a deep copy of the given list.
 
         Args:
@@ -125,7 +125,7 @@ struct List[T: CollectionElement, hint_trivial_type: Bool = False](
         for e in other:
             self.append(e[])
 
-    fn __init__(inout self, *, capacity: Int):
+    fn __init__(out self, *, capacity: Int):
         """Constructs a list with the given capacity.
 
         Args:
@@ -135,7 +135,7 @@ struct List[T: CollectionElement, hint_trivial_type: Bool = False](
         self.size = 0
         self.capacity = capacity
 
-    fn __init__(inout self, owned *values: T):
+    fn __init__(out self, owned *values: T):
         """Constructs a list from the given values.
 
         Args:
@@ -143,7 +143,7 @@ struct List[T: CollectionElement, hint_trivial_type: Bool = False](
         """
         self = Self(variadic_list=values^)
 
-    fn __init__(inout self, *, owned variadic_list: VariadicListMem[T, _]):
+    fn __init__(out self, *, owned variadic_list: VariadicListMem[T, _]):
         """Constructs a list from the given values.
 
         Args:
@@ -164,7 +164,7 @@ struct List[T: CollectionElement, hint_trivial_type: Bool = False](
 
         self.size = length
 
-    fn __init__(inout self, span: Span[T]):
+    fn __init__(out self, span: Span[T]):
         """Constructs a list from the a Span of values.
 
         Args:
@@ -188,7 +188,7 @@ struct List[T: CollectionElement, hint_trivial_type: Bool = False](
         self.size = length
         self.capacity = capacity
 
-    fn __moveinit__(inout self, owned existing: Self):
+    fn __moveinit__(out self, owned existing: Self):
         """Move data of an existing list into a new one.
 
         Args:
@@ -198,7 +198,7 @@ struct List[T: CollectionElement, hint_trivial_type: Bool = False](
         self.size = existing.size
         self.capacity = existing.capacity
 
-    fn __copyinit__(inout self, existing: Self):
+    fn __copyinit__(out self, existing: Self):
         """Creates a deepcopy of the given list.
 
         Args:
diff --git a/stdlib/src/collections/optional.mojo b/stdlib/src/collections/optional.mojo
index b4a1b00c74..d9326aa4cc 100644
--- a/stdlib/src/collections/optional.mojo
+++ b/stdlib/src/collections/optional.mojo
@@ -38,7 +38,7 @@ from utils import Variant
 # TODO(27780): NoneType can't currently conform to traits
 @value
 struct _NoneType(CollectionElement, CollectionElementNew):
-    fn __init__(inout self, *, other: Self):
+    fn __init__(out self, *, other: Self):
         pass
 
 
@@ -88,11 +88,11 @@ struct Optional[T: CollectionElement](
     # Life cycle methods
     # ===-------------------------------------------------------------------===#
 
-    fn __init__(inout self):
+    fn __init__(out self):
         """Construct an empty Optional."""
         self._value = Self._type(_NoneType())
 
-    fn __init__(inout self, owned value: T):
+    fn __init__(out self, owned value: T):
         """Construct an Optional containing a value.
 
         Args:
@@ -104,7 +104,7 @@ struct Optional[T: CollectionElement](
     #   This initializer should not be necessary, we should need
     #   only the initilaizer from a `NoneType`.
     @doc_private
-    fn __init__(inout self, value: NoneType._mlir_type):
+    fn __init__(out self, value: NoneType._mlir_type):
         """Construct an empty Optional.
 
         Args:
@@ -112,7 +112,7 @@ struct Optional[T: CollectionElement](
         """
         self = Self(value=NoneType(value))
 
-    fn __init__(inout self, value: NoneType):
+    fn __init__(out self, value: NoneType):
         """Construct an empty Optional.
 
         Args:
@@ -120,7 +120,7 @@ struct Optional[T: CollectionElement](
         """
         self = Self()
 
-    fn __init__(inout self, *, other: Self):
+    fn __init__(out self, *, other: Self):
         """Copy construct an Optional.
 
         Args:
@@ -403,11 +403,11 @@ struct OptionalReg[T: AnyTrivialRegType](Boolable):
     # Life cycle methods
     # ===-------------------------------------------------------------------===#
 
-    fn __init__(inout self):
+    fn __init__(out self):
         """Create an optional with a value of None."""
         self = Self(None)
 
-    fn __init__(inout self, value: T):
+    fn __init__(out self, value: T):
         """Create an optional with a value.
 
         Args:
@@ -421,7 +421,7 @@ struct OptionalReg[T: AnyTrivialRegType](Boolable):
     #   This initializer should not be necessary, we should need
     #   only the initilaizer from a `NoneType`.
     @doc_private
-    fn __init__(inout self, value: NoneType._mlir_type):
+    fn __init__(out self, value: NoneType._mlir_type):
         """Construct an empty Optional.
 
         Args:
@@ -429,7 +429,7 @@ struct OptionalReg[T: AnyTrivialRegType](Boolable):
         """
         self = Self(value=NoneType(value))
 
-    fn __init__(inout self, value: NoneType):
+    fn __init__(out self, value: NoneType):
         """Create an optional without a value from a None literal.
 
         Args:
diff --git a/stdlib/src/collections/set.mojo b/stdlib/src/collections/set.mojo
index 8d9f6d60f0..809d838a55 100644
--- a/stdlib/src/collections/set.mojo
+++ b/stdlib/src/collections/set.mojo
@@ -54,7 +54,7 @@ struct Set[T: KeyElement](Sized, Comparable, Hashable, Boolable):
     # Life cycle methods
     # ===-------------------------------------------------------------------===#
 
-    fn __init__(inout self, *ts: T):
+    fn __init__(out self, *ts: T):
         """Construct a set from initial elements.
 
         Args:
@@ -64,7 +64,7 @@ struct Set[T: KeyElement](Sized, Comparable, Hashable, Boolable):
         for t in ts:
             self.add(t[])
 
-    fn __init__(inout self, elements: Self):
+    fn __init__(out self, elements: Self):
         """Explicitly copy another Set instance.
 
         Args:
@@ -74,7 +74,7 @@ struct Set[T: KeyElement](Sized, Comparable, Hashable, Boolable):
         for e in elements:
             self.add(e[])
 
-    fn __init__(inout self, elements: List[T, *_]):
+    fn __init__(out self, elements: List[T, *_]):
         """Construct a set from a List of elements.
 
         Args:
@@ -84,7 +84,7 @@ struct Set[T: KeyElement](Sized, Comparable, Hashable, Boolable):
         for e in elements:
             self.add(e[])
 
-    fn __moveinit__(inout self, owned other: Self):
+    fn __moveinit__(out self, owned other: Self):
         """Move constructor.
 
         Args:
diff --git a/stdlib/src/collections/vector.mojo b/stdlib/src/collections/vector.mojo
index b371c7ec05..6fd87dd51e 100644
--- a/stdlib/src/collections/vector.mojo
+++ b/stdlib/src/collections/vector.mojo
@@ -114,7 +114,7 @@ struct InlinedFixedVector[
     """The maximum number of elements that can fit in the vector."""
 
     @always_inline
-    fn __init__(inout self, capacity: Int):
+    fn __init__(out self, capacity: Int):
         """Constructs `InlinedFixedVector` with the given capacity.
 
         The dynamically allocated portion is `capacity - size`.
@@ -130,7 +130,7 @@ struct InlinedFixedVector[
         self.capacity = capacity
 
     @always_inline
-    fn __init__(inout self, existing: Self):
+    fn __init__(out self, existing: Self):
         """
         Copy constructor.
 
@@ -148,7 +148,7 @@ struct InlinedFixedVector[
         self.capacity = existing.capacity
 
     @always_inline
-    fn __moveinit__(inout self, owned existing: Self):
+    fn __moveinit__(out self, owned existing: Self):
         """
         Move constructor.
 
diff --git a/stdlib/src/documentation/documentation.mojo b/stdlib/src/documentation/documentation.mojo
index 76892d3c6c..69ea07675c 100644
--- a/stdlib/src/documentation/documentation.mojo
+++ b/stdlib/src/documentation/documentation.mojo
@@ -34,7 +34,7 @@ fn doc_private():
     ```mojo
     struct Foo:
         @doc_private
-        fn __init__(inout self):
+        fn __init__(out self):
             "This should not be called directly, use `Foo.create` instead."
             return
 
diff --git a/stdlib/src/hashlib/_ahash.mojo b/stdlib/src/hashlib/_ahash.mojo
index d54036d0fe..7dccb4dd9d 100644
--- a/stdlib/src/hashlib/_ahash.mojo
+++ b/stdlib/src/hashlib/_ahash.mojo
@@ -93,7 +93,7 @@ struct AHasher[key: U256](_Hasher):
     var pad: UInt64
     var extra_keys: U128
 
-    fn __init__(inout self):
+    fn __init__(out self):
         """Initialize the hasher."""
         alias pi_key = key ^ U256(
             0x243F_6A88_85A3_08D3,
diff --git a/stdlib/src/hashlib/_hasher.mojo b/stdlib/src/hashlib/_hasher.mojo
index 505ae4fc0a..7bd278d5e9 100644
--- a/stdlib/src/hashlib/_hasher.mojo
+++ b/stdlib/src/hashlib/_hasher.mojo
@@ -21,7 +21,7 @@ trait _HashableWithHasher:
 
 
 trait _Hasher:
-    fn __init__(inout self):
+    fn __init__(out self):
         ...
 
     fn _update_with_bytes(inout self, data: UnsafePointer[UInt8], length: Int):
diff --git a/stdlib/src/memory/arc.mojo b/stdlib/src/memory/arc.mojo
index d07383f165..9863d700b0 100644
--- a/stdlib/src/memory/arc.mojo
+++ b/stdlib/src/memory/arc.mojo
@@ -54,7 +54,7 @@ struct _ArcInner[T: Movable]:
     var refcount: Atomic[DType.uint64]
     var payload: T
 
-    fn __init__(inout self, owned value: T):
+    fn __init__(out self, owned value: T):
         """Create an initialized instance of this with a refcount of 1."""
         self.refcount = 1
         self.payload = value^
@@ -88,7 +88,7 @@ struct Arc[T: Movable](CollectionElement, CollectionElementNew, Identifiable):
     alias _inner_type = _ArcInner[T]
     var _inner: UnsafePointer[Self._inner_type]
 
-    fn __init__(inout self, owned value: T):
+    fn __init__(out self, owned value: T):
         """Construct a new thread-safe, reference-counted smart pointer,
         and move the value into heap memory managed by the new pointer.
 
@@ -101,7 +101,7 @@ struct Arc[T: Movable](CollectionElement, CollectionElementNew, Identifiable):
             value^
         )
 
-    fn __init__(inout self, *, other: Self):
+    fn __init__(out self, *, other: Self):
         """Copy the object.
 
         Args:
@@ -110,7 +110,7 @@ struct Arc[T: Movable](CollectionElement, CollectionElementNew, Identifiable):
         other._inner[].add_ref()
         self._inner = other._inner
 
-    fn __copyinit__(inout self, existing: Self):
+    fn __copyinit__(out self, existing: Self):
         """Copy an existing reference. Increment the refcount to the object.
 
         Args:
diff --git a/stdlib/src/memory/maybe_uninitialized.mojo b/stdlib/src/memory/maybe_uninitialized.mojo
index 33689c6260..010822a602 100644
--- a/stdlib/src/memory/maybe_uninitialized.mojo
+++ b/stdlib/src/memory/maybe_uninitialized.mojo
@@ -34,7 +34,7 @@ struct UnsafeMaybeUninitialized[ElementType: AnyType](CollectionElementNew):
     var _array: Self.type
 
     @always_inline
-    fn __init__(inout self):
+    fn __init__(out self):
         """The memory is now considered uninitialized."""
         self._array = __mlir_op.`kgen.param.constant`[
             _type = Self.type,
@@ -43,7 +43,7 @@ struct UnsafeMaybeUninitialized[ElementType: AnyType](CollectionElementNew):
 
     @doc_private
     @always_inline
-    fn __init__(inout self, *, other: Self):
+    fn __init__(out self, *, other: Self):
         """It is not possible to call this method.
 
         Trying to call this method will abort.
@@ -77,7 +77,7 @@ struct UnsafeMaybeUninitialized[ElementType: AnyType](CollectionElementNew):
         self.write(value^)
 
     @always_inline
-    fn __copyinit__(inout self, other: Self):
+    fn __copyinit__(out self, other: Self):
         """Copy another object.
 
         This method should never be called as implicit copy should not
@@ -131,7 +131,7 @@ struct UnsafeMaybeUninitialized[ElementType: AnyType](CollectionElementNew):
         self.unsafe_ptr().init_pointee_explicit_copy(other)
 
     @always_inline
-    fn __moveinit__(inout self, owned other: Self):
+    fn __moveinit__(out self, owned other: Self):
         """Move another object.
 
         This method should never be called as implicit moves should not
diff --git a/stdlib/src/memory/owned_pointer.mojo b/stdlib/src/memory/owned_pointer.mojo
index 3976fc8c6d..4f00050e89 100644
--- a/stdlib/src/memory/owned_pointer.mojo
+++ b/stdlib/src/memory/owned_pointer.mojo
@@ -85,7 +85,7 @@ struct OwnedPointer[T: AnyType]:
         """
         self.__init__(copy_value=other[])
 
-    fn __moveinit__(inout self, owned existing: Self):
+    fn __moveinit__(out self, owned existing: Self):
         """Move this OwnedPointer[].
 
         Args:
diff --git a/stdlib/src/memory/unsafe_pointer.mojo b/stdlib/src/memory/unsafe_pointer.mojo
index 4b128170bd..772199ed5f 100644
--- a/stdlib/src/memory/unsafe_pointer.mojo
+++ b/stdlib/src/memory/unsafe_pointer.mojo
@@ -98,13 +98,13 @@ struct UnsafePointer[
     # ===-------------------------------------------------------------------===#
 
     @always_inline
-    fn __init__(inout self):
+    fn __init__(out self):
         """Create a null pointer."""
         self.address = __mlir_attr[`#interp.pointer<0> : `, Self._mlir_type]
 
     @doc_private
     @always_inline
-    fn __init__(inout self, value: Self._mlir_type):
+    fn __init__(out self, value: Self._mlir_type):
         """Create a pointer with the input value.
 
         Args:
@@ -113,7 +113,7 @@ struct UnsafePointer[
         self.address = value
 
     @always_inline
-    fn __init__(inout self, other: UnsafePointer[type, address_space, *_, **_]):
+    fn __init__(out self, other: UnsafePointer[type, address_space, *_, **_]):
         """Exclusivity parameter cast a pointer.
 
         Args:
@@ -124,7 +124,7 @@ struct UnsafePointer[
         )
 
     @always_inline
-    fn __init__(inout self, *, other: Self):
+    fn __init__(out self, *, other: Self):
         """Copy the object.
 
         Args:
diff --git a/stdlib/src/os/_linux_aarch64.mojo b/stdlib/src/os/_linux_aarch64.mojo
index b8e8740068..9647be1218 100644
--- a/stdlib/src/os/_linux_aarch64.mojo
+++ b/stdlib/src/os/_linux_aarch64.mojo
@@ -48,7 +48,7 @@ struct _c_stat(Stringable):
     var st_birthtimespec: _CTimeSpec  # time of file creation(birth)
     var unused: InlineArray[Int64, 2]  # RESERVED: DO NOT USE!
 
-    fn __init__(inout self):
+    fn __init__(out self):
         self.st_dev = 0
         self.st_mode = 0
         self.st_nlink = 0
diff --git a/stdlib/src/os/_linux_x86.mojo b/stdlib/src/os/_linux_x86.mojo
index 472e16c61d..d2872d8a1a 100644
--- a/stdlib/src/os/_linux_x86.mojo
+++ b/stdlib/src/os/_linux_x86.mojo
@@ -47,7 +47,7 @@ struct _c_stat(Stringable):
     var st_birthtimespec: _CTimeSpec  # time of file creation(birth)
     var unused: InlineArray[Int64, 3]  # RESERVED: DO NOT USE!
 
-    fn __init__(inout self):
+    fn __init__(out self):
         self.st_dev = 0
         self.st_mode = 0
         self.st_nlink = 0
diff --git a/stdlib/src/os/_macos.mojo b/stdlib/src/os/_macos.mojo
index faeb23f686..1d1a7d11d3 100644
--- a/stdlib/src/os/_macos.mojo
+++ b/stdlib/src/os/_macos.mojo
@@ -50,7 +50,7 @@ struct _c_stat(Stringable):
     var st_lspare: Int32  # RESERVED: DO NOT USE!
     var st_qspare: InlineArray[Int64, 2]  # RESERVED: DO NOT USE!
 
-    fn __init__(inout self):
+    fn __init__(out self):
         self.st_dev = 0
         self.st_mode = 0
         self.st_nlink = 0
diff --git a/stdlib/src/os/atomic.mojo b/stdlib/src/os/atomic.mojo
index 6b7bd43d90..f7902c1cf4 100644
--- a/stdlib/src/os/atomic.mojo
+++ b/stdlib/src/os/atomic.mojo
@@ -41,7 +41,7 @@ struct Atomic[type: DType]:
     """
 
     @always_inline
-    fn __init__(inout self, value: Scalar[type]):
+    fn __init__(out self, value: Scalar[type]):
         """Constructs a new atomic value.
 
         Args:
diff --git a/stdlib/src/os/os.mojo b/stdlib/src/os/os.mojo
index ba00c1b447..c00532ff9a 100644
--- a/stdlib/src/os/os.mojo
+++ b/stdlib/src/os/os.mojo
@@ -95,7 +95,7 @@ struct _DirHandle:
 
     var _handle: OpaquePointer
 
-    fn __init__(inout self, path: String) raises:
+    fn __init__(out self, path: String) raises:
         """Construct the _DirHandle using the path provided.
 
         Args:
diff --git a/stdlib/src/pathlib/path.mojo b/stdlib/src/pathlib/path.mojo
index 45a8c9aacf..e77c305081 100644
--- a/stdlib/src/pathlib/path.mojo
+++ b/stdlib/src/pathlib/path.mojo
@@ -80,11 +80,11 @@ struct Path(
     var path: String
     """The underlying path string representation."""
 
-    fn __init__(inout self) raises:
+    fn __init__(out self) raises:
         """Initializes a path with the current directory."""
         self = cwd()
 
-    fn __init__(inout self, path: String):
+    fn __init__(out self, path: String):
         """Initializes a path with the provided path.
 
         Args:
@@ -92,7 +92,7 @@ struct Path(
         """
         self.path = path
 
-    fn __init__(inout self, *, other: Self):
+    fn __init__(out self, *, other: Self):
         """Copy the object.
 
         Args:
diff --git a/stdlib/src/python/_cpython.mojo b/stdlib/src/python/_cpython.mojo
index b908306ddf..9e7983cfbe 100644
--- a/stdlib/src/python/_cpython.mojo
+++ b/stdlib/src/python/_cpython.mojo
@@ -160,7 +160,7 @@ struct PyObjectPtr:
     # ===-------------------------------------------------------------------===#
 
     @always_inline
-    fn __init__(inout self):
+    fn __init__(out self):
         """Initialize a null PyObjectPtr."""
         self.unsized_obj_ptr = UnsafePointer[PyObject]()
 
@@ -259,7 +259,7 @@ struct PythonVersion:
     var patch: Int
     """The patch version number."""
 
-    fn __init__(inout self, version: StringRef):
+    fn __init__(out self, version: StringRef):
         """Initialize a PythonVersion object from a version string.
 
         Args:
@@ -333,7 +333,7 @@ struct PyMethodDef:
     # Life cycle methods
     # ===-------------------------------------------------------------------===#
 
-    fn __init__(inout self):
+    fn __init__(out self):
         """Constructs a zero initialized PyModuleDef.
 
         This is suitable for use terminating an array of PyMethodDef values.
@@ -343,7 +343,7 @@ struct PyMethodDef:
         self.method_flags = 0
         self.method_docstring = UnsafePointer[c_char]()
 
-    fn __init__(inout self, *, other: Self):
+    fn __init__(out self, *, other: Self):
         """Explicitly construct a deep copy of the provided value.
 
         Args:
@@ -465,7 +465,7 @@ struct PyObject(Stringable, Representable, Writable):
     var object_ref_count: Int
     var object_type: UnsafePointer[PyTypeObject]
 
-    fn __init__(inout self):
+    fn __init__(out self):
         self.object_ref_count = 0
         self.object_type = UnsafePointer[PyTypeObject]()
 
@@ -541,13 +541,13 @@ struct PyModuleDef_Base(Stringable, Representable, Writable):
     # Life cycle methods
     # ===------------------------------------------------------------------=== #
 
-    fn __init__(inout self):
+    fn __init__(out self):
         self.object_base = PyObject()
         self.init_fn = _null_fn_ptr[Self._init_fn_type]()
         self.index = 0
         self.dict_copy = UnsafePointer[PyObject]()
 
-    fn __moveinit__(inout self, owned existing: Self):
+    fn __moveinit__(out self, owned existing: Self):
         self.object_base = existing.object_base
         self.init_fn = existing.init_fn
         self.index = existing.index
@@ -647,7 +647,7 @@ struct PyModuleDef(Stringable, Representable, Writable):
     alias _free_fn_type = fn (OpaquePointer) -> OpaquePointer
     var free_fn: Self._free_fn_type
 
-    fn __init__(inout self, name: String):
+    fn __init__(out self, name: String):
         self.base = PyModuleDef_Base()
         self.name = name.unsafe_cstr_ptr()
         self.docstring = UnsafePointer[c_char]()
@@ -661,7 +661,7 @@ struct PyModuleDef(Stringable, Representable, Writable):
         self.clear_fn = _null_fn_ptr[Self._clear_fn_type]()
         self.free_fn = _null_fn_ptr[Self._free_fn_type]()
 
-    fn __moveinit__(inout self, owned existing: Self):
+    fn __moveinit__(out self, owned existing: Self):
         self.base = existing.base^
         self.name = existing.name
         self.docstring = existing.docstring
@@ -748,7 +748,7 @@ struct CPython:
     # Life cycle methods
     # ===-------------------------------------------------------------------===#
 
-    fn __init__(inout self):
+    fn __init__(out self):
         var logging_enabled = getenv("MODULAR_CPYTHON_LOGGING") == "ON"
         if logging_enabled:
             print("CPython init")
diff --git a/stdlib/src/python/python.mojo b/stdlib/src/python/python.mojo
index a0c0878228..f2fb0237b9 100644
--- a/stdlib/src/python/python.mojo
+++ b/stdlib/src/python/python.mojo
@@ -59,10 +59,10 @@ fn _get_global_python_itf() -> _PythonInterfaceImpl:
 struct _PythonInterfaceImpl:
     var _cpython: UnsafePointer[CPython]
 
-    fn __init__(inout self, cpython: UnsafePointer[CPython]):
+    fn __init__(out self, cpython: UnsafePointer[CPython]):
         self._cpython = cpython
 
-    fn __copyinit__(inout self, existing: Self):
+    fn __copyinit__(out self, existing: Self):
         self._cpython = existing._cpython
 
     fn cpython(self) -> CPython:
@@ -79,11 +79,11 @@ struct Python:
     # Life cycle methods
     # ===-------------------------------------------------------------------===#
 
-    fn __init__(inout self):
+    fn __init__(out self):
         """Default constructor."""
         self.impl = _get_global_python_itf()
 
-    fn __copyinit__(inout self, existing: Self):
+    fn __copyinit__(out self, existing: Self):
         """Copy constructor.
 
         Args:
diff --git a/stdlib/src/python/python_object.mojo b/stdlib/src/python/python_object.mojo
index 05397a1c75..a7089fc8f5 100644
--- a/stdlib/src/python/python_object.mojo
+++ b/stdlib/src/python/python_object.mojo
@@ -50,7 +50,7 @@ struct _PyIter(Sized):
     # Life cycle methods
     # ===-------------------------------------------------------------------===#
 
-    fn __copyinit__(inout self, existing: Self):
+    fn __copyinit__(out self, existing: Self):
         """Copy another iterator.
 
         Args:
@@ -60,7 +60,7 @@ struct _PyIter(Sized):
         self.preparedNextItem = existing.preparedNextItem
         self.isDone = existing.isDone
 
-    fn __init__(inout self, iter: PythonObject):
+    fn __init__(out self, iter: PythonObject):
         """Initialize an iterator.
 
         Args:
@@ -76,7 +76,7 @@ struct _PyIter(Sized):
             self.preparedNextItem = PythonObject(maybeNextItem)
             self.isDone = False
 
-    fn __init__(inout self):
+    fn __init__(out self):
         """Initialize an empty iterator."""
         self.iterator = PythonObject(PyObjectPtr())
         self.isDone = True
@@ -145,7 +145,7 @@ struct TypedPythonObject[type_hint: StringLiteral](
     # Life cycle methods
     # ===-------------------------------------------------------------------===#
 
-    fn __init__(inout self, *, owned unsafe_unchecked_from: PythonObject):
+    fn __init__(out self, *, owned unsafe_unchecked_from: PythonObject):
         """Construct a TypedPythonObject without any validation that the given
         object is of the specified hinted type.
 
@@ -155,7 +155,7 @@ struct TypedPythonObject[type_hint: StringLiteral](
         """
         self._obj = unsafe_unchecked_from^
 
-    fn __copyinit__(inout self, other: Self):
+    fn __copyinit__(out self, other: Self):
         """Copy an instance of this type.
 
         Args:
@@ -249,11 +249,11 @@ struct PythonObject(
     # Life cycle methods
     # ===-------------------------------------------------------------------===#
 
-    fn __init__(inout self):
+    fn __init__(out self):
         """Initialize the object with a `None` value."""
         self.__init__(None)
 
-    fn __init__(inout self, *, other: Self):
+    fn __init__(out self, *, other: Self):
         """Copy the object.
 
         Args:
@@ -261,7 +261,7 @@ struct PythonObject(
         """
         self = other
 
-    fn __init__(inout self, ptr: PyObjectPtr):
+    fn __init__(out self, ptr: PyObjectPtr):
         """Initialize this object from an owned reference-counted Python object
         pointer.
 
@@ -308,7 +308,7 @@ struct PythonObject(
 
         return PythonObject(borrowed_ptr)
 
-    fn __init__(inout self, owned typed_obj: TypedPythonObject[_]):
+    fn __init__(out self, owned typed_obj: TypedPythonObject[_]):
         """Construct a PythonObject from a typed object, dropping the type hint
         information.
 
@@ -330,7 +330,7 @@ struct PythonObject(
     #   This initializer should not be necessary, we should need
     #   only the initilaizer from a `NoneType`.
     @doc_private
-    fn __init__(inout self, none: NoneType._mlir_type):
+    fn __init__(out self, none: NoneType._mlir_type):
         """Initialize a none value object from a `None` literal.
 
         Args:
@@ -338,7 +338,7 @@ struct PythonObject(
         """
         self = Self(none=NoneType())
 
-    fn __init__(inout self, none: NoneType):
+    fn __init__(out self, none: NoneType):
         """Initialize a none value object from a `None` literal.
 
         Args:
@@ -348,7 +348,7 @@ struct PythonObject(
         self.py_object = cpython.Py_None()
         cpython.Py_IncRef(self.py_object)
 
-    fn __init__(inout self, value: Bool):
+    fn __init__(out self, value: Bool):
         """Initialize the object from a bool.
 
         Args:
@@ -357,7 +357,7 @@ struct PythonObject(
         cpython = _get_global_python_itf().cpython()
         self.py_object = cpython.PyBool_FromLong(int(value))
 
-    fn __init__(inout self, integer: Int):
+    fn __init__(out self, integer: Int):
         """Initialize the object with an integer value.
 
         Args:
@@ -389,7 +389,7 @@ struct PythonObject(
             fp_val = value.cast[DType.float64]()
             self.py_object = cpython.PyFloat_FromDouble(fp_val)
 
-    fn __init__(inout self, value: StringLiteral):
+    fn __init__(out self, value: StringLiteral):
         """Initialize the object from a string literal.
 
         Args:
@@ -397,7 +397,7 @@ struct PythonObject(
         """
         self = PythonObject(str(value))
 
-    fn __init__(inout self, strref: StringRef):
+    fn __init__(out self, strref: StringRef):
         """Initialize the object from a string reference.
 
         Args:
@@ -406,7 +406,7 @@ struct PythonObject(
         cpython = _get_global_python_itf().cpython()
         self.py_object = cpython.PyUnicode_DecodeUTF8(strref)
 
-    fn __init__(inout self, string: String):
+    fn __init__(out self, string: String):
         """Initialize the object from a string.
 
         Args:
@@ -500,7 +500,7 @@ struct PythonObject(
             cpython.Py_IncRef(obj.py_object)
             _ = cpython.PyTuple_SetItem(self.py_object, i, obj.py_object)
 
-    fn __init__(inout self, slice: Slice):
+    fn __init__(out self, slice: Slice):
         """Initialize the object from a Mojo Slice.
 
         Args:
@@ -508,7 +508,7 @@ struct PythonObject(
         """
         self.py_object = _slice_to_py_object_ptr(slice)
 
-    fn __init__(inout self, value: Dict[Self, Self]):
+    fn __init__(out self, value: Dict[Self, Self]):
         """Initialize the object from a dictionary of PythonObjects.
 
         Args:
@@ -521,7 +521,7 @@ struct PythonObject(
                 self.py_object, entry[].key.py_object, entry[].value.py_object
             )
 
-    fn __copyinit__(inout self, existing: Self):
+    fn __copyinit__(out self, existing: Self):
         """Copy the object.
 
         This increments the underlying refcount of the existing object.
diff --git a/stdlib/src/sys/ffi.mojo b/stdlib/src/sys/ffi.mojo
index ad4058b1e5..b3c86e6373 100644
--- a/stdlib/src/sys/ffi.mojo
+++ b/stdlib/src/sys/ffi.mojo
@@ -117,7 +117,7 @@ struct DLHandle(CollectionElement, CollectionElementNew, Boolable):
 
     # TODO(#15590): Implement support for windows and remove the always_inline.
     @always_inline
-    fn __init__(inout self, path: String, flags: Int = DEFAULT_RTLD):
+    fn __init__(out self, path: String, flags: Int = DEFAULT_RTLD):
         """Initialize a DLHandle object by loading the dynamic library at the
         given path.
 
@@ -136,7 +136,7 @@ struct DLHandle(CollectionElement, CollectionElementNew, Boolable):
         else:
             self.handle = OpaquePointer()
 
-    fn __init__(inout self, *, other: Self):
+    fn __init__(out self, *, other: Self):
         """Copy the object.
 
         Args:
diff --git a/stdlib/src/sys/intrinsics.mojo b/stdlib/src/sys/intrinsics.mojo
index d5ceafdfb0..b60eecbbc5 100644
--- a/stdlib/src/sys/intrinsics.mojo
+++ b/stdlib/src/sys/intrinsics.mojo
@@ -279,7 +279,7 @@ struct PrefetchLocality:
     """Extremely local locality (keep in cache)."""
 
     @always_inline("nodebug")
-    fn __init__(inout self, value: Int):
+    fn __init__(out self, value: Int):
         """Constructs a prefetch locality option.
 
         Args:
@@ -301,7 +301,7 @@ struct PrefetchRW:
     """Write prefetch."""
 
     @always_inline("nodebug")
-    fn __init__(inout self, value: Int):
+    fn __init__(out self, value: Int):
         """Constructs a prefetch read-write option.
 
         Args:
@@ -324,7 +324,7 @@ struct PrefetchCache:
     """The data prefetching option."""
 
     @always_inline("nodebug")
-    fn __init__(inout self, value: Int):
+    fn __init__(out self, value: Int):
         """Constructs a prefetch option.
 
         Args:
@@ -359,7 +359,7 @@ struct PrefetchOptions:
     """Indicates i-cache or d-cache prefetching."""
 
     @always_inline("nodebug")
-    fn __init__(inout self):
+    fn __init__(out self):
         """Constructs an instance of PrefetchOptions with default params."""
         self.rw = PrefetchRW.READ
         self.locality = PrefetchLocality.HIGH
diff --git a/stdlib/src/tempfile/tempfile.mojo b/stdlib/src/tempfile/tempfile.mojo
index d33c41f867..7f3c2dd09d 100644
--- a/stdlib/src/tempfile/tempfile.mojo
+++ b/stdlib/src/tempfile/tempfile.mojo
@@ -350,7 +350,7 @@ struct NamedTemporaryFile:
         if self._delete:
             os.remove(self.name)
 
-    fn __moveinit__(inout self, owned existing: Self):
+    fn __moveinit__(out self, owned existing: Self):
         """Moves constructor for the file handle.
 
         Args:
diff --git a/stdlib/src/testing/testing.mojo b/stdlib/src/testing/testing.mojo
index 79369bea7c..5dff04c458 100644
--- a/stdlib/src/testing/testing.mojo
+++ b/stdlib/src/testing/testing.mojo
@@ -526,7 +526,7 @@ struct assert_raises:
     """Assigned the value returned by __call_locations() at Self.__init__."""
 
     @always_inline
-    fn __init__(inout self, *, location: Optional[_SourceLocation] = None):
+    fn __init__(out self, *, location: Optional[_SourceLocation] = None):
         """Construct a context manager with no message pattern.
 
         Args:
diff --git a/stdlib/src/time/time.mojo b/stdlib/src/time/time.mojo
index 39cca3aff6..b964a3f85c 100644
--- a/stdlib/src/time/time.mojo
+++ b/stdlib/src/time/time.mojo
@@ -63,7 +63,7 @@ struct _CTimeSpec(Stringable):
     var tv_sec: Int  # Seconds
     var tv_subsec: Int  # subsecond (nanoseconds on linux and usec on mac)
 
-    fn __init__(inout self):
+    fn __init__(out self):
         self.tv_sec = 0
         self.tv_subsec = 0
 
@@ -85,7 +85,7 @@ struct _FILETIME:
     var dwLowDateTime: UInt32
     var dwHighDateTime: UInt32
 
-    fn __init__(inout self):
+    fn __init__(out self):
         self.dwLowDateTime = 0
         self.dwHighDateTime = 0
 
diff --git a/stdlib/src/utils/index.mojo b/stdlib/src/utils/index.mojo
index 93eb5dbc8d..26c8620f26 100644
--- a/stdlib/src/utils/index.mojo
+++ b/stdlib/src/utils/index.mojo
@@ -194,13 +194,13 @@ struct IndexList[
     """The underlying storage of the tuple value."""
 
     @always_inline
-    fn __init__(inout self):
+    fn __init__(out self):
         """Constructs a static int tuple of the given size."""
         self = 0
 
     @doc_private
     @always_inline
-    fn __init__(inout self, value: __mlir_type.index):
+    fn __init__(out self, value: __mlir_type.index):
         """Constructs a sized 1 static int tuple of given the element value.
 
         Args:
@@ -210,7 +210,7 @@ struct IndexList[
         self = Int(value)
 
     @always_inline
-    fn __init__(inout self, elems: (Int, Int)):
+    fn __init__(out self, elems: (Int, Int)):
         """Constructs a static int tuple given a tuple of integers.
 
         Args:
@@ -235,7 +235,7 @@ struct IndexList[
         self = tup
 
     @always_inline
-    fn __init__(inout self, elems: (Int, Int, Int)):
+    fn __init__(out self, elems: (Int, Int, Int)):
         """Constructs a static int tuple given a tuple of integers.
 
         Args:
@@ -260,7 +260,7 @@ struct IndexList[
         self = tup
 
     @always_inline
-    fn __init__(inout self, elems: (Int, Int, Int, Int)):
+    fn __init__(out self, elems: (Int, Int, Int, Int)):
         """Constructs a static int tuple given a tuple of integers.
 
         Args:
@@ -285,7 +285,7 @@ struct IndexList[
         self = tup
 
     @always_inline
-    fn __init__(inout self, *elems: Int):
+    fn __init__(out self, *elems: Int):
         """Constructs a static int tuple given a set of arguments.
 
         Args:
@@ -308,7 +308,7 @@ struct IndexList[
         self = tup
 
     @always_inline
-    fn __init__(inout self, elem: Int):
+    fn __init__(out self, elem: Int):
         """Constructs a static int tuple given a set of arguments.
 
         Args:
@@ -321,7 +321,7 @@ struct IndexList[
             ]
         ](Self._int_type(elem))
 
-    fn __init__(inout self, *, other: Self):
+    fn __init__(out self, *, other: Self):
         """Copy constructor.
 
         Args:
@@ -330,7 +330,7 @@ struct IndexList[
         self.data = other.data
 
     @always_inline
-    fn __init__(inout self, values: VariadicList[Int]):
+    fn __init__(out self, values: VariadicList[Int]):
         """Creates a tuple constant using the specified values.
 
         Args:
diff --git a/stdlib/src/utils/inline_string.mojo b/stdlib/src/utils/inline_string.mojo
index 42d04f19d4..e163727f51 100644
--- a/stdlib/src/utils/inline_string.mojo
+++ b/stdlib/src/utils/inline_string.mojo
@@ -53,12 +53,12 @@ struct InlineString(Sized, Stringable, CollectionElement, CollectionElementNew):
     # Life cycle methods
     # ===------------------------------------------------------------------===#
 
-    fn __init__(inout self):
+    fn __init__(out self):
         """Constructs a new empty string."""
         var fixed = _FixedString[Self.SMALL_CAP]()
         self._storage = Self.Layout(fixed^)
 
-    fn __init__(inout self, literal: StringLiteral):
+    fn __init__(out self, literal: StringLiteral):
         """Constructs a InlineString value given a string literal.
 
         Args:
@@ -82,7 +82,7 @@ struct InlineString(Sized, Stringable, CollectionElement, CollectionElementNew):
             var heap = String(literal)
             self._storage = Self.Layout(heap^)
 
-    fn __init__(inout self, owned heap_string: String):
+    fn __init__(out self, owned heap_string: String):
         """Construct a new small string by taking ownership of an existing
         heap-allocated String.
 
@@ -91,7 +91,7 @@ struct InlineString(Sized, Stringable, CollectionElement, CollectionElementNew):
         """
         self._storage = Self.Layout(heap_string^)
 
-    fn __init__(inout self, *, other: Self):
+    fn __init__(out self, *, other: Self):
         """Copy the object.
 
         Args:
@@ -328,12 +328,12 @@ struct _FixedString[CAP: Int](
     # Life cycle methods
     # ===------------------------------------------------------------------===#
 
-    fn __init__(inout self):
+    fn __init__(out self):
         """Constructs a new empty string."""
         self.buffer = InlineArray[UInt8, CAP](unsafe_uninitialized=True)
         self.size = 0
 
-    fn __init__(inout self, *, other: Self):
+    fn __init__(out self, *, other: Self):
         """Copy the object.
 
         Args:
@@ -341,7 +341,7 @@ struct _FixedString[CAP: Int](
         """
         self = other
 
-    fn __init__(inout self, literal: StringLiteral) raises:
+    fn __init__(out self, literal: StringLiteral) raises:
         """Constructs a FixedString value given a string literal.
 
         Args:
diff --git a/stdlib/src/utils/lock.mojo b/stdlib/src/utils/lock.mojo
index 18cdeef46b..e7529401d7 100644
--- a/stdlib/src/utils/lock.mojo
+++ b/stdlib/src/utils/lock.mojo
@@ -29,7 +29,7 @@ struct SpinWaiter:
     var storage: OpaquePointer
     """Pointer to the underlying SpinWaiter instance."""
 
-    fn __init__(inout self: Self):
+    fn __init__(out self: Self):
         """Initializes a SpinWaiter instance."""
         self.storage = external_call[
             "KGEN_CompilerRT_AsyncRT_InitializeSpinWaiter",
@@ -60,7 +60,7 @@ struct BlockingSpinLock:
     var counter: Atomic[DType.int64]
     """The atomic counter implementing the spin lock."""
 
-    fn __init__(inout self: Self):
+    fn __init__(out self: Self):
         """Default constructor."""
 
         self.counter = Atomic[DType.int64](Self.UNLOCKED)
diff --git a/stdlib/src/utils/numerics.mojo b/stdlib/src/utils/numerics.mojo
index b5c006aef4..72dea362b3 100644
--- a/stdlib/src/utils/numerics.mojo
+++ b/stdlib/src/utils/numerics.mojo
@@ -421,7 +421,7 @@ struct FlushDenormals:
     """The current state."""
 
     @always_inline
-    fn __init__(inout self):
+    fn __init__(out self):
         """Initializes the FlushDenormals."""
         self.state = Self._current_state()
 
diff --git a/stdlib/src/utils/span.mojo b/stdlib/src/utils/span.mojo
index e413dc4e42..c2a5fee6c0 100644
--- a/stdlib/src/utils/span.mojo
+++ b/stdlib/src/utils/span.mojo
@@ -114,7 +114,7 @@ struct Span[
     # ===------------------------------------------------------------------===#
 
     @always_inline
-    fn __init__(inout self, *, ptr: UnsafePointer[T], length: Int):
+    fn __init__(out self, *, ptr: UnsafePointer[T], length: Int):
         """Unsafe construction from a pointer and length.
 
         Args:
@@ -125,7 +125,7 @@ struct Span[
         self._len = length
 
     @always_inline
-    fn __init__(inout self, *, other: Self):
+    fn __init__(out self, *, other: Self):
         """Explicitly construct a deep copy of the provided Span.
 
         Args:
@@ -135,7 +135,7 @@ struct Span[
         self._len = other._len
 
     @always_inline
-    fn __init__(inout self, ref [origin]list: List[T, *_]):
+    fn __init__(out self, ref [origin]list: List[T, *_]):
         """Construct a Span from a List.
 
         Args:
diff --git a/stdlib/src/utils/static_tuple.mojo b/stdlib/src/utils/static_tuple.mojo
index 3f009988f7..f4066c9a4e 100644
--- a/stdlib/src/utils/static_tuple.mojo
+++ b/stdlib/src/utils/static_tuple.mojo
@@ -126,7 +126,7 @@ struct StaticTuple[element_type: AnyTrivialRegType, size: Int](Sized):
     """The underlying storage for the static tuple."""
 
     @always_inline
-    fn __init__(inout self):
+    fn __init__(out self):
         """Constructs an empty (undefined) tuple."""
         _static_tuple_construction_checks[size]()
         self.array = __mlir_op.`kgen.param.constant`[
@@ -135,7 +135,7 @@ struct StaticTuple[element_type: AnyTrivialRegType, size: Int](Sized):
         ]()
 
     @always_inline
-    fn __init__(inout self, *elems: Self.element_type):
+    fn __init__(out self, *elems: Self.element_type):
         """Constructs a static tuple given a set of arguments.
 
         Args:
@@ -145,7 +145,7 @@ struct StaticTuple[element_type: AnyTrivialRegType, size: Int](Sized):
         self.array = _create_array[size](elems)
 
     @always_inline
-    fn __init__(inout self, values: VariadicList[Self.element_type]):
+    fn __init__(out self, values: VariadicList[Self.element_type]):
         """Creates a tuple constant using the specified values.
 
         Args:
@@ -154,7 +154,7 @@ struct StaticTuple[element_type: AnyTrivialRegType, size: Int](Sized):
         _static_tuple_construction_checks[size]()
         self.array = _create_array[size, Self.element_type](values)
 
-    fn __init__(inout self, *, other: Self):
+    fn __init__(out self, *, other: Self):
         """Explicitly copy the provided StaticTuple.
 
         Args:
diff --git a/stdlib/src/utils/string_slice.mojo b/stdlib/src/utils/string_slice.mojo
index 1c270d6983..c0e38d5f42 100644
--- a/stdlib/src/utils/string_slice.mojo
+++ b/stdlib/src/utils/string_slice.mojo
@@ -267,7 +267,7 @@ struct StringSlice[is_mutable: Bool, //, origin: Origin[is_mutable].type,](
     # ===------------------------------------------------------------------===#
 
     @always_inline
-    fn __init__(inout self: StaticString, lit: StringLiteral):
+    fn __init__(out self: StaticString, lit: StringLiteral):
         """Construct a new `StringSlice` from a `StringLiteral`.
 
         Args:
@@ -288,7 +288,7 @@ struct StringSlice[is_mutable: Bool, //, origin: Origin[is_mutable].type,](
         self = StaticString(unsafe_from_utf8=lit.as_bytes())
 
     @always_inline
-    fn __init__(inout self, *, owned unsafe_from_utf8: Span[Byte, origin]):
+    fn __init__(out self, *, owned unsafe_from_utf8: Span[Byte, origin]):
         """Construct a new `StringSlice` from a sequence of UTF-8 encoded bytes.
 
         Args:
@@ -300,7 +300,7 @@ struct StringSlice[is_mutable: Bool, //, origin: Origin[is_mutable].type,](
 
         self._slice = unsafe_from_utf8^
 
-    fn __init__(inout self, *, unsafe_from_utf8_strref: StringRef):
+    fn __init__(out self, *, unsafe_from_utf8_strref: StringRef):
         """Construct a new StringSlice from a `StringRef` pointing to UTF-8
         encoded bytes.
 
@@ -323,7 +323,7 @@ struct StringSlice[is_mutable: Bool, //, origin: Origin[is_mutable].type,](
         self = Self(unsafe_from_utf8=byte_slice)
 
     @always_inline
-    fn __init__(inout self, *, ptr: UnsafePointer[Byte], length: Int):
+    fn __init__(out self, *, ptr: UnsafePointer[Byte], length: Int):
         """Construct a `StringSlice` from a pointer to a sequence of UTF-8
         encoded bytes and a length.
 
@@ -340,7 +340,7 @@ struct StringSlice[is_mutable: Bool, //, origin: Origin[is_mutable].type,](
         self._slice = Span[Byte, origin](ptr=ptr, length=length)
 
     @always_inline
-    fn __init__(inout self, *, other: Self):
+    fn __init__(out self, *, other: Self):
         """Explicitly construct a deep copy of the provided `StringSlice`.
 
         Args:
@@ -1162,7 +1162,7 @@ struct _FormatCurlyEntry(CollectionElement, CollectionElementNew):
     alias _args_t = VariadicPack[element_trait=_CurlyEntryFormattable, *_]
     """Args types that are formattable by curly entry."""
 
-    fn __init__(inout self, *, other: Self):
+    fn __init__(out self, *, other: Self):
         self.first_curly = other.first_curly
         self.last_curly = other.last_curly
         self.conversion_flag = other.conversion_flag
diff --git a/stdlib/src/utils/stringref.mojo b/stdlib/src/utils/stringref.mojo
index 4d9e427580..8406c7451e 100644
--- a/stdlib/src/utils/stringref.mojo
+++ b/stdlib/src/utils/stringref.mojo
@@ -69,12 +69,12 @@ struct StringRef(
     # ===-------------------------------------------------------------------===#
 
     @always_inline
-    fn __init__(inout self):
+    fn __init__(out self):
         """Construct a StringRef value with length zero."""
         self = StringRef(UnsafePointer[UInt8](), 0)
 
     @always_inline
-    fn __init__(inout self, *, other: Self):
+    fn __init__(out self, *, other: Self):
         """Copy the object.
 
         Args:
@@ -84,7 +84,7 @@ struct StringRef(
         self.length = other.length
 
     @always_inline
-    fn __init__(inout self, str: StringLiteral):
+    fn __init__(out self, str: StringLiteral):
         """Construct a StringRef value given a constant string.
 
         Args:
@@ -93,7 +93,7 @@ struct StringRef(
         self = StringRef(str.unsafe_ptr(), len(str))
 
     @always_inline
-    fn __init__(inout self, ptr: UnsafePointer[c_char], len: Int):
+    fn __init__(out self, ptr: UnsafePointer[c_char], len: Int):
         """Construct a StringRef value given a (potentially non-0 terminated
         string).
 
@@ -112,7 +112,7 @@ struct StringRef(
         self.length = len
 
     @always_inline
-    fn __init__(inout self, *, ptr: UnsafePointer[UInt8]):
+    fn __init__(out self, *, ptr: UnsafePointer[UInt8]):
         """Construct a StringRef value given a null-terminated string.
 
         Args:
@@ -126,7 +126,7 @@ struct StringRef(
         self = StringRef(ptr, len)
 
     @always_inline
-    fn __init__(inout self, ptr: UnsafePointer[c_char]):
+    fn __init__(out self, ptr: UnsafePointer[c_char]):
         """Construct a StringRef value given a null-terminated string.
 
         Note that you should use the constructor from `UnsafePointer[UInt8]` instead
diff --git a/stdlib/src/utils/variant.mojo b/stdlib/src/utils/variant.mojo
index 34546cba4b..e26cd537fc 100644
--- a/stdlib/src/utils/variant.mojo
+++ b/stdlib/src/utils/variant.mojo
@@ -115,7 +115,7 @@ struct Variant[*Ts: CollectionElement](
     # Life cycle methods
     # ===-------------------------------------------------------------------===#
 
-    fn __init__(inout self, *, unsafe_uninitialized: ()):
+    fn __init__(out self, *, unsafe_uninitialized: ()):
         """Unsafely create an uninitialized Variant.
 
         Args:
@@ -138,7 +138,7 @@ struct Variant[*Ts: CollectionElement](
         self._get_discr() = idx
         self._get_ptr[T]().init_pointee_move(value^)
 
-    fn __init__(inout self, *, other: Self):
+    fn __init__(out self, *, other: Self):
         """Explicitly creates a deep copy of an existing variant.
 
         Args:
@@ -154,7 +154,7 @@ struct Variant[*Ts: CollectionElement](
                 self._get_ptr[T]().init_pointee_move(other._get_ptr[T]()[])
                 return
 
-    fn __copyinit__(inout self, other: Self):
+    fn __copyinit__(out self, other: Self):
         """Creates a deep copy of an existing variant.
 
         Args:
@@ -164,7 +164,7 @@ struct Variant[*Ts: CollectionElement](
         # Delegate to explicit copy initializer.
         self = Self(other=other)
 
-    fn __moveinit__(inout self, owned other: Self):
+    fn __moveinit__(out self, owned other: Self):
         """Move initializer for the variant.
 
         Args:
diff --git a/stdlib/src/utils/write.mojo b/stdlib/src/utils/write.mojo
index 5329ab296e..8e3e55579d 100644
--- a/stdlib/src/utils/write.mojo
+++ b/stdlib/src/utils/write.mojo
@@ -228,7 +228,7 @@ struct _WriteBufferHeap[W: MovableWriter, //, capacity: Int](Writer):
     var pos: Int
     var writer: W
 
-    fn __init__(inout self, owned writer: W):
+    fn __init__(out self, owned writer: W):
         self.data = UnsafePointer[
             UInt8,
             address_space = AddressSpace.GENERIC,
@@ -275,7 +275,7 @@ struct _WriteBufferStack[W: MovableWriter, //, capacity: Int](Writer):
     var pos: Int
     var writer: W
 
-    fn __init__(inout self, owned writer: W):
+    fn __init__(out self, owned writer: W):
         self.data = InlineArray[UInt8, capacity](unsafe_uninitialized=True)
         self.pos = 0
         self.writer = writer^
diff --git a/stdlib/test/builtin/test_none.mojo b/stdlib/test/builtin/test_none.mojo
index 028471881c..9d588bb7d4 100644
--- a/stdlib/test/builtin/test_none.mojo
+++ b/stdlib/test/builtin/test_none.mojo
@@ -37,10 +37,10 @@ def test_format_to():
 struct FromNone:
     var value: Int
 
-    fn __init__(inout self, none: NoneType):
+    fn __init__(out self, none: NoneType):
         self.value = -1
 
-    fn __init__(inout self, value: Int):
+    fn __init__(out self, value: Int):
         self.value = value
 
 
diff --git a/stdlib/test/builtin/test_print.mojo b/stdlib/test/builtin/test_print.mojo
index d17765bf88..ca3b03afcc 100644
--- a/stdlib/test/builtin/test_print.mojo
+++ b/stdlib/test/builtin/test_print.mojo
@@ -47,7 +47,7 @@ struct PrintChecker:
     var call_location: _SourceLocation
 
     @always_inline
-    fn __init__(inout self) raises:
+    fn __init__(out self) raises:
         self.tmp = NamedTemporaryFile("rw")
         self.call_location = __call_location()
         self.cursor = 0
@@ -55,7 +55,7 @@ struct PrintChecker:
     fn __enter__(owned self) -> Self:
         return self^
 
-    fn __moveinit__(inout self, owned existing: Self):
+    fn __moveinit__(out self, owned existing: Self):
         self.tmp = existing.tmp^
         self.cursor = existing.cursor
         self.call_location = existing.call_location
diff --git a/stdlib/test/builtin/test_rebind.mojo b/stdlib/test/builtin/test_rebind.mojo
index f23ae595e4..0d73aee2af 100644
--- a/stdlib/test/builtin/test_rebind.mojo
+++ b/stdlib/test/builtin/test_rebind.mojo
@@ -51,7 +51,7 @@ def test_rebind_register():
 struct MyMemStruct[size: Int]:
     var value: Int
 
-    fn __copyinit__(inout self, existing: Self):
+    fn __copyinit__(out self, existing: Self):
         # Make sure no copy is made due to the rebind.
         print("Should not copy this!")
         self.value = existing.value
diff --git a/stdlib/test/builtin/test_slice.mojo b/stdlib/test/builtin/test_slice.mojo
index b552d13f0b..2208a5bf3a 100644
--- a/stdlib/test/builtin/test_slice.mojo
+++ b/stdlib/test/builtin/test_slice.mojo
@@ -38,7 +38,7 @@ struct BoringSlice:
 
 
 struct Sliceable:
-    fn __init__(inout self):
+    fn __init__(out self):
         pass
 
     fn __getitem__(self, a: FunnySlice) -> FunnySlice:
@@ -63,7 +63,7 @@ def test_slicable():
 
 
 struct SliceStringable:
-    fn __init__(inout self):
+    fn __init__(out self):
         pass
 
     fn __getitem__(self, a: Slice) -> String:
diff --git a/stdlib/test/builtin/test_sort.mojo b/stdlib/test/builtin/test_sort.mojo
index 987dbda3ec..7ff2834d46 100644
--- a/stdlib/test/builtin/test_sort.mojo
+++ b/stdlib/test/builtin/test_sort.mojo
@@ -497,7 +497,7 @@ fn test_sort_stress() raises:
 struct MyStruct(CollectionElement):
     var val: Int
 
-    fn __init__(inout self, *, other: Self):
+    fn __init__(out self, *, other: Self):
         self.val = other.val
 
 
@@ -550,7 +550,7 @@ struct Person(ComparableCollectionElement):
     var name: String
     var age: Int
 
-    fn __init__(inout self, *, other: Self):
+    fn __init__(out self, *, other: Self):
         self.name = String(other=other.name)
         self.age = other.age
 
diff --git a/stdlib/test/collections/test_dict.mojo b/stdlib/test/collections/test_dict.mojo
index 44a7a04d5b..d9807ea83b 100644
--- a/stdlib/test/collections/test_dict.mojo
+++ b/stdlib/test/collections/test_dict.mojo
@@ -391,7 +391,7 @@ def test_dict_update_empty_new():
 struct DummyKey(KeyElement):
     var value: Int
 
-    fn __init__(inout self, *, other: Self):
+    fn __init__(out self, *, other: Self):
         self = other
 
     fn __hash__(self) -> UInt:
diff --git a/stdlib/test/collections/test_list.mojo b/stdlib/test/collections/test_list.mojo
index 35365af488..49bd72a1bb 100644
--- a/stdlib/test/collections/test_list.mojo
+++ b/stdlib/test/collections/test_list.mojo
@@ -551,11 +551,11 @@ struct CopyCountedStruct(CollectionElement):
     var counter: CopyCounter
     var value: String
 
-    fn __init__(inout self, *, other: Self):
+    fn __init__(out self, *, other: Self):
         self.counter = CopyCounter(other=other.counter)
         self.value = String(other=other.value)
 
-    fn __init__(inout self, value: String):
+    fn __init__(out self, value: String):
         self.counter = CopyCounter()
         self.value = value
 
@@ -876,16 +876,16 @@ struct DtorCounter(CollectionElement):
     # NOTE: payload is required because List does not support zero sized structs.
     var payload: Int
 
-    fn __init__(inout self):
+    fn __init__(out self):
         self.payload = 0
 
-    fn __init__(inout self, *, other: Self):
+    fn __init__(out self, *, other: Self):
         self.payload = other.payload
 
-    fn __copyinit__(inout self, existing: Self, /):
+    fn __copyinit__(out self, existing: Self, /):
         self.payload = existing.payload
 
-    fn __moveinit__(inout self, owned existing: Self, /):
+    fn __moveinit__(out self, owned existing: Self, /):
         self.payload = existing.payload
         existing.payload = 0
 
diff --git a/stdlib/test/hashlib/test_hasher.mojo b/stdlib/test/hashlib/test_hasher.mojo
index 44bf5eed15..f41685b553 100644
--- a/stdlib/test/hashlib/test_hasher.mojo
+++ b/stdlib/test/hashlib/test_hasher.mojo
@@ -25,7 +25,7 @@ from utils import StringRef
 struct DummyHasher(_Hasher):
     var _dummy_value: UInt64
 
-    fn __init__(inout self):
+    fn __init__(out self):
         self._dummy_value = 0
 
     fn _update_with_bytes(inout self, data: UnsafePointer[UInt8], length: Int):
diff --git a/stdlib/test/memory/test_unsafepointer.mojo b/stdlib/test/memory/test_unsafepointer.mojo
index f7573c1941..657fc02b81 100644
--- a/stdlib/test/memory/test_unsafepointer.mojo
+++ b/stdlib/test/memory/test_unsafepointer.mojo
@@ -23,12 +23,12 @@ struct MoveOnlyType(Movable):
     var actions: UnsafePointer[List[String]]
     var value: Int
 
-    fn __init__(inout self, value: Int, actions: UnsafePointer[List[String]]):
+    fn __init__(out self, value: Int, actions: UnsafePointer[List[String]]):
         self.actions = actions
         self.value = value
         self.actions[0].append("__init__")
 
-    fn __moveinit__(inout self, owned existing: Self):
+    fn __moveinit__(out self, owned existing: Self):
         self.actions = existing.actions
         self.value = existing.value
         self.actions[0].append("__moveinit__")
diff --git a/stdlib/test/os/path/test_expandvars.mojo b/stdlib/test/os/path/test_expandvars.mojo
index 662558bbfb..d81746d88c 100644
--- a/stdlib/test/os/path/test_expandvars.mojo
+++ b/stdlib/test/os/path/test_expandvars.mojo
@@ -21,7 +21,7 @@ from testing import assert_equal
 struct EnvVar:
     var name: String
 
-    fn __init__(inout self, name: String, value: String) -> None:
+    fn __init__(out self, name: String, value: String) -> None:
         self.name = name
         _ = os.setenv(name, value)
 
diff --git a/stdlib/test/test_utils/types.mojo b/stdlib/test/test_utils/types.mojo
index ade9d8c809..b9dd9cd91a 100644
--- a/stdlib/test/test_utils/types.mojo
+++ b/stdlib/test/test_utils/types.mojo
@@ -27,7 +27,7 @@ struct MoveOnly[T: Movable](Movable):
     var data: T
     """Test data payload."""
 
-    fn __init__(inout self, owned i: T):
+    fn __init__(out self, owned i: T):
         """Construct a MoveOnly providing the payload data.
 
         Args:
@@ -35,7 +35,7 @@ struct MoveOnly[T: Movable](Movable):
         """
         self.data = i^
 
-    fn __moveinit__(inout self, owned other: Self):
+    fn __moveinit__(out self, owned other: Self):
         """Move construct a MoveOnly from an existing variable.
 
         Args:
@@ -53,11 +53,11 @@ struct ExplicitCopyOnly(ExplicitlyCopyable):
     var value: Int
     var copy_count: Int
 
-    fn __init__(inout self, value: Int):
+    fn __init__(out self, value: Int):
         self.value = value
         self.copy_count = 0
 
-    fn __init__(inout self, *, other: Self):
+    fn __init__(out self, *, other: Self):
         self.value = other.value
         self.copy_count = other.copy_count + 1
 
@@ -71,11 +71,11 @@ struct ImplicitCopyOnly(Copyable):
     var value: Int
     var copy_count: Int
 
-    fn __init__(inout self, value: Int):
+    fn __init__(out self, value: Int):
         self.value = value
         self.copy_count = 0
 
-    fn __copyinit__(inout self, *, other: Self):
+    fn __copyinit__(out self, *, other: Self):
         self.value = other.value
         self.copy_count = other.copy_count + 1
 
@@ -90,16 +90,16 @@ struct CopyCounter(CollectionElement, ExplicitlyCopyable):
 
     var copy_count: Int
 
-    fn __init__(inout self):
+    fn __init__(out self):
         self.copy_count = 0
 
-    fn __init__(inout self, *, other: Self):
+    fn __init__(out self, *, other: Self):
         self.copy_count = other.copy_count + 1
 
-    fn __moveinit__(inout self, owned existing: Self):
+    fn __moveinit__(out self, owned existing: Self):
         self.copy_count = existing.copy_count
 
-    fn __copyinit__(inout self, existing: Self):
+    fn __copyinit__(out self, existing: Self):
         self.copy_count = existing.copy_count + 1
 
 
@@ -117,7 +117,7 @@ struct MoveCounter[T: CollectionElementNew](
     var value: T
     var move_count: Int
 
-    fn __init__(inout self, owned value: T):
+    fn __init__(out self, owned value: T):
         """Construct a new instance of this type. This initial move is not counted.
         """
         self.value = value^
@@ -125,7 +125,7 @@ struct MoveCounter[T: CollectionElementNew](
 
     # TODO: This type should not be ExplicitlyCopyable, but has to be to satisfy
     #       CollectionElementNew at the moment.
-    fn __init__(inout self, *, other: Self):
+    fn __init__(out self, *, other: Self):
         """Explicitly copy the provided value.
 
         Args:
@@ -134,13 +134,13 @@ struct MoveCounter[T: CollectionElementNew](
         self.value = T(other=other.value)
         self.move_count = other.move_count
 
-    fn __moveinit__(inout self, owned existing: Self):
+    fn __moveinit__(out self, owned existing: Self):
         self.value = existing.value^
         self.move_count = existing.move_count + 1
 
     # TODO: This type should not be Copyable, but has to be to satisfy
     #       CollectionElement at the moment.
-    fn __copyinit__(inout self, existing: Self):
+    fn __copyinit__(out self, existing: Self):
         # print("ERROR: _MoveCounter copy constructor called unexpectedly!")
         self.value = T(other=existing.value)
         self.move_count = existing.move_count
@@ -156,7 +156,7 @@ struct ValueDestructorRecorder(ExplicitlyCopyable):
     var value: Int
     var destructor_counter: UnsafePointer[List[Int]]
 
-    fn __init__(inout self, *, other: Self):
+    fn __init__(out self, *, other: Self):
         self.value = other.value
         self.destructor_counter = other.destructor_counter
 
@@ -173,7 +173,7 @@ struct ValueDestructorRecorder(ExplicitlyCopyable):
 struct ObservableDel(CollectionElement):
     var target: UnsafePointer[Bool]
 
-    fn __init__(inout self, *, other: Self):
+    fn __init__(out self, *, other: Self):
         self = other
 
     fn __del__(owned self):
diff --git a/stdlib/test/utils/test_variant.mojo b/stdlib/test/utils/test_variant.mojo
index f517433183..bafac3221f 100644
--- a/stdlib/test/utils/test_variant.mojo
+++ b/stdlib/test/utils/test_variant.mojo
@@ -25,18 +25,18 @@ struct TestCounter(CollectionElement):
     var copied: Int
     var moved: Int
 
-    fn __init__(inout self):
+    fn __init__(out self):
         self.copied = 0
         self.moved = 0
 
-    fn __init__(inout self, *, other: Self):
+    fn __init__(out self, *, other: Self):
         self = other
 
-    fn __copyinit__(inout self, other: Self):
+    fn __copyinit__(out self, other: Self):
         self.copied = other.copied + 1
         self.moved = other.moved
 
-    fn __moveinit__(inout self, owned other: Self):
+    fn __moveinit__(out self, owned other: Self):
         self.copied = other.copied
         self.moved = other.moved + 1
 
@@ -65,16 +65,16 @@ fn _destroy_poison(p: OpaquePointer):
 
 
 struct Poison(CollectionElement):
-    fn __init__(inout self):
+    fn __init__(out self):
         pass
 
-    fn __init__(inout self, *, other: Self):
+    fn __init__(out self, *, other: Self):
         _poison_ptr().init_pointee_move(True)
 
-    fn __copyinit__(inout self, other: Self):
+    fn __copyinit__(out self, other: Self):
         _poison_ptr().init_pointee_move(True)
 
-    fn __moveinit__(inout self, owned other: Self):
+    fn __moveinit__(out self, owned other: Self):
         _poison_ptr().init_pointee_move(True)
 
     fn __del__(owned self):