diff --git a/crates/erg_compiler/context/compare.rs b/crates/erg_compiler/context/compare.rs
index cc9526d20..d5ebb611e 100644
--- a/crates/erg_compiler/context/compare.rs
+++ b/crates/erg_compiler/context/compare.rs
@@ -1715,6 +1715,7 @@ impl Context {
     /// intersection(Int, Str) == Never
     /// intersection(Obj, Int) == Int
     /// intersection(Never, Int) == Never
+    /// intersection(Iterable(Int), List(Int)) == List(Int)
     /// ```
     pub(crate) fn intersection(&self, lhs: &Type, rhs: &Type) -> Type {
         if lhs == rhs {
diff --git a/crates/erg_compiler/context/eval.rs b/crates/erg_compiler/context/eval.rs
index fb9a9bc37..1b1ee5737 100644
--- a/crates/erg_compiler/context/eval.rs
+++ b/crates/erg_compiler/context/eval.rs
@@ -3038,7 +3038,7 @@ impl Context {
                 self.convert_type_to_dict_type(t)
             }
             Type::Refinement(refine) => self.convert_type_to_dict_type(*refine.t),
-            Type::Poly { name, params } if &name[..] == "Dict" => {
+            Type::Poly { name, params } if &name[..] == "Dict" || &name[..] == "Dict!" => {
                 let dict = Dict::try_from(params[0].clone())?;
                 let mut new_dict = dict! {};
                 for (k, v) in dict.into_iter() {
@@ -3076,6 +3076,29 @@ impl Context {
         }
     }
 
+    pub(crate) fn convert_value_to_dict(
+        &self,
+        val: &ValueObj,
+    ) -> Result<Dict<ValueObj, ValueObj>, ()> {
+        match val {
+            ValueObj::Dict(dic) => Ok(dic.clone()),
+            ValueObj::Type(ty) if ty.typ().is_dict() || ty.typ().is_dict_mut() => {
+                let Ok(dict) = self
+                    .convert_type_to_dict_type(ty.typ().clone())
+                    .map(|dict| {
+                        dict.into_iter()
+                            .map(|(k, v)| (ValueObj::builtin_type(k), ValueObj::builtin_type(v)))
+                            .collect()
+                    })
+                else {
+                    return Err(());
+                };
+                Ok(dict)
+            }
+            _ => Err(()),
+        }
+    }
+
     pub(crate) fn convert_type_to_tuple_type(&self, ty: Type) -> Result<Vec<Type>, ()> {
         match ty {
             Type::FreeVar(fv) if fv.is_linked() => {
diff --git a/crates/erg_compiler/context/initialize/const_func.rs b/crates/erg_compiler/context/initialize/const_func.rs
index eec8979ee..c670e5e03 100644
--- a/crates/erg_compiler/context/initialize/const_func.rs
+++ b/crates/erg_compiler/context/initialize/const_func.rs
@@ -339,7 +339,7 @@ pub(crate) fn __dict_getitem__(mut args: ValueArgs, ctx: &Context) -> EvalValueR
     let slf = args
         .remove_left_or_key("Self")
         .ok_or_else(|| not_passed("Self"))?;
-    let ValueObj::Dict(slf) = slf else {
+    let Ok(slf) = ctx.convert_value_to_dict(&slf) else {
         return Err(type_mismatch("Dict", slf, "Self"));
     };
     let index = args
@@ -367,7 +367,7 @@ pub(crate) fn dict_keys(mut args: ValueArgs, ctx: &Context) -> EvalValueResult<T
     let slf = args
         .remove_left_or_key("Self")
         .ok_or_else(|| not_passed("Self"))?;
-    let ValueObj::Dict(slf) = slf else {
+    let Ok(slf) = ctx.convert_value_to_dict(&slf) else {
         return Err(type_mismatch("Dict", slf, "Self"));
     };
     let dict_type = slf
@@ -394,7 +394,7 @@ pub(crate) fn dict_values(mut args: ValueArgs, ctx: &Context) -> EvalValueResult
     let slf = args
         .remove_left_or_key("Self")
         .ok_or_else(|| not_passed("Self"))?;
-    let ValueObj::Dict(slf) = slf else {
+    let Ok(slf) = ctx.convert_value_to_dict(&slf) else {
         return Err(type_mismatch("Dict", slf, "Self"));
     };
     let dict_type = slf
@@ -421,7 +421,7 @@ pub(crate) fn dict_items(mut args: ValueArgs, ctx: &Context) -> EvalValueResult<
     let slf = args
         .remove_left_or_key("Self")
         .ok_or_else(|| not_passed("Self"))?;
-    let ValueObj::Dict(slf) = slf else {
+    let Ok(slf) = ctx.convert_value_to_dict(&slf) else {
         return Err(type_mismatch("Dict", slf, "Self"));
     };
     let dict_type = slf
@@ -451,11 +451,11 @@ pub(crate) fn dict_items(mut args: ValueArgs, ctx: &Context) -> EvalValueResult<
 
 /// If the key is duplicated, the value of the right dict is used.
 /// `{Str: Int, Int: Float}.concat({Int: Str, Float: Bool}) == {Str: Int, Int: Str, Float: Bool}`
-pub(crate) fn dict_concat(mut args: ValueArgs, _ctx: &Context) -> EvalValueResult<TyParam> {
+pub(crate) fn dict_concat(mut args: ValueArgs, ctx: &Context) -> EvalValueResult<TyParam> {
     let slf = args
         .remove_left_or_key("Self")
         .ok_or_else(|| not_passed("Self"))?;
-    let ValueObj::Dict(slf) = slf else {
+    let Ok(slf) = ctx.convert_value_to_dict(&slf) else {
         return Err(type_mismatch("Dict", slf, "Self"));
     };
     let other = args
@@ -467,11 +467,11 @@ pub(crate) fn dict_concat(mut args: ValueArgs, _ctx: &Context) -> EvalValueResul
     Ok(ValueObj::Dict(slf.concat(other)).into())
 }
 
-pub(crate) fn dict_diff(mut args: ValueArgs, _ctx: &Context) -> EvalValueResult<TyParam> {
+pub(crate) fn dict_diff(mut args: ValueArgs, ctx: &Context) -> EvalValueResult<TyParam> {
     let slf = args
         .remove_left_or_key("Self")
         .ok_or_else(|| not_passed("Self"))?;
-    let ValueObj::Dict(slf) = slf else {
+    let Ok(slf) = ctx.convert_value_to_dict(&slf) else {
         return Err(type_mismatch("Dict", slf, "Self"));
     };
     let other = args
diff --git a/crates/erg_compiler/context/inquire.rs b/crates/erg_compiler/context/inquire.rs
index 4409ad757..91c7bef91 100644
--- a/crates/erg_compiler/context/inquire.rs
+++ b/crates/erg_compiler/context/inquire.rs
@@ -1362,18 +1362,21 @@ impl Context {
             }
         }
         let mut checked = vec![];
-        for ctx in self
-            .get_nominal_super_type_ctxs(&obj.ref_t().lower_bounded())
-            .ok_or_else(|| {
-                TyCheckError::type_not_found(
-                    self.cfg.input.clone(),
-                    line!() as usize,
-                    obj.loc(),
-                    self.caused_by(),
-                    obj.ref_t(),
-                )
-            })?
-        {
+        // FIXME: tests/should_ok/collection.er
+        let obj_t = if obj.ref_t().lower_bounded().is_dict() {
+            obj.t()
+        } else {
+            obj.ref_t().lower_bounded()
+        };
+        for ctx in self.get_nominal_super_type_ctxs(&obj_t).ok_or_else(|| {
+            TyCheckError::type_not_found(
+                self.cfg.input.clone(),
+                line!() as usize,
+                obj.loc(),
+                self.caused_by(),
+                obj.ref_t(),
+            )
+        })? {
             checked.push(&ctx.typ);
             if let Some(vi) = ctx.get_current_scope_non_param(&attr_name.name) {
                 self.validate_visibility(attr_name, vi, input, namespace)?;
@@ -4058,12 +4061,14 @@ impl Context {
     /// Int.meta_type() == ClassType (<: Type)
     /// Show.meta_type() == TraitType (<: Type)
     /// [Int; 3].meta_type() == [ClassType; 3] (<: Type)
+    /// (Int, Str).meta_type() == (ClassType, ClassType) (<: Type)
+    /// {Str: Int}.meta_type() == {ClassType: ClassType} (<: Type)
     /// Indexable(T).meta_type() == TraitType (<: Type)
     /// NamedTuple({ .x = Int; .y = Str }).meta_type() == NamedTuple({ .x = ClassType; .y = ClassType })
     /// ```
     pub fn meta_type(&self, typ: &Type) -> Type {
         match typ {
-            Type::Poly { name, params } if &name[..] == "List" || &name[..] == "Set" => poly(
+            Type::Poly { name, params } if typ.is_list() || typ.is_set() || typ.is_tuple() => poly(
                 name.clone(),
                 params
                     .iter()
@@ -4076,6 +4081,26 @@ impl Context {
                     })
                     .collect(),
             ),
+            Type::Poly { params, .. } if typ.is_dict() => self
+                .convert_tp_into_value(params[0].clone())
+                .map(|value| {
+                    if let ValueObj::Dict(dict) = value {
+                        let mut ty = dict! {};
+                        for (k, v) in dict {
+                            let Ok(k) = self.convert_value_into_type(k) else {
+                                return Type;
+                            };
+                            let Ok(v) = self.convert_value_into_type(v) else {
+                                return Type;
+                            };
+                            ty.insert(self.meta_type(&k), self.meta_type(&v));
+                        }
+                        Type::from(ty)
+                    } else {
+                        Type
+                    }
+                })
+                .unwrap_or(Type),
             NamedTuple(tuple) => NamedTuple(
                 tuple
                     .iter()
diff --git a/crates/erg_compiler/context/unify.rs b/crates/erg_compiler/context/unify.rs
index f1baec45a..b9d3d5526 100644
--- a/crates/erg_compiler/context/unify.rs
+++ b/crates/erg_compiler/context/unify.rs
@@ -1497,11 +1497,7 @@ impl<'c, 'l, 'u, L: Locational> Unifier<'c, 'l, 'u, L> {
                         return Ok(());
                     }
                     let sub = mem::take(&mut sub);
-                    let new_sup = if let Some(new_sup) = self.ctx.min(&sup, maybe_sup).either() {
-                        new_sup.clone()
-                    } else {
-                        self.ctx.intersection(&sup, maybe_sup)
-                    };
+                    let new_sup = self.ctx.intersection(&sup, maybe_sup);
                     self.sub_unify(&sub, &new_sup)?;
                     // ?T(:> Int, <: Int) ==> ?T == Int
                     // ?T(:> List(Int, 3), <: List(?T, ?N)) ==> ?T == List(Int, 3)
diff --git a/crates/erg_compiler/ty/typaram.rs b/crates/erg_compiler/ty/typaram.rs
index 3ec3aca90..747621bed 100644
--- a/crates/erg_compiler/ty/typaram.rs
+++ b/crates/erg_compiler/ty/typaram.rs
@@ -688,6 +688,10 @@ impl TryFrom<TyParam> for Dict<TyParam, TyParam> {
         match tp {
             TyParam::FreeVar(fv) if fv.is_linked() => Dict::try_from(fv.crack().clone()),
             TyParam::Dict(tps) => Ok(tps),
+            TyParam::Value(ValueObj::Dict(dict)) => Ok(dict
+                .into_iter()
+                .map(|(k, v)| (TyParam::value(k), TyParam::value(v)))
+                .collect()),
             _ => Err(()),
         }
     }
@@ -699,6 +703,9 @@ impl TryFrom<TyParam> for Vec<TyParam> {
         match tp {
             TyParam::FreeVar(fv) if fv.is_linked() => Vec::try_from(fv.crack().clone()),
             TyParam::List(tps) => Ok(tps),
+            TyParam::Value(ValueObj::List(list)) => {
+                Ok(list.iter().cloned().map(TyParam::value).collect::<Vec<_>>())
+            }
             _ => Err(()),
         }
     }
diff --git a/tests/should_ok/collection.er b/tests/should_ok/collection.er
index f01a97bc2..2ff20c082 100644
--- a/tests/should_ok/collection.er
+++ b/tests/should_ok/collection.er
@@ -10,3 +10,6 @@ ab = if True: # x: {"a"} or {"b"}
     do "a"
     do "b"
 _ = ["c", "d", ab] # OK
+
+d2 = [{"a": 1}]
+assert d2[0]["a"] == 1