Add a rendezvous mechanism for reflection functions

This adds a reflection mechanism for the various reflection functions
defined by Base. These functions are mostly interactive affordances and
for ease of Compiler development, it tends to be important that these
reflect the user's expectation of what the compiler is. This is currently
the case using the existing `Revise.track(Core.Compiler)` workflow,
because it runs in the latest world-age, not the inference world.

This commit adds a special binding that if present in `Main` (because
it was imported by a `using Compiler`) will switch the compiler used
for reflection to whatever the binding points to.

In this way, we can replace the old
`using Revise; Revise.track(Core.Compiler)` workflow by
`using Revise, Compiler` without additional headache.

base/loading.jl

@@ -2762,9 +2762,6 @@ function require_stdlib(package_uuidkey::PkgId, ext::Union{Nothing, String}=noth
     end
 end
 
-
-
-
 # relative-path load
 
 """

base/opaque_closure.jl

@@ -45,17 +45,17 @@ function compute_ir_rettype(ir::IRCode)
     rt = Union{}
     for i = 1:length(ir.stmts)
         stmt = ir[SSAValue(i)][:stmt]
-        if isa(stmt, Core.Compiler.ReturnNode) && isdefined(stmt, :val)
-            rt = Core.Compiler.tmerge(Core.Compiler.argextype(stmt.val, ir), rt)
+        if isa(stmt, Core.ReturnNode) && isdefined(stmt, :val)
+            rt = Compiler.tmerge(Compiler.argextype(stmt.val, ir), rt)
         end
     end
-    return Core.Compiler.widenconst(rt)
+    return Compiler.widenconst(rt)
 end
 
 function compute_oc_signature(ir::IRCode, nargs::Int, isva::Bool)
     argtypes = Vector{Any}(undef, nargs)
     for i = 1:nargs
-        argtypes[i] = Core.Compiler.widenconst(ir.argtypes[i+1])
+        argtypes[i] = Compiler.widenconst(ir.argtypes[i+1])
     end
     if isva
         lastarg = pop!(argtypes)

base/reflection.jl

@@ -346,17 +346,41 @@ function raise_match_failure(name::Symbol, @nospecialize(tt))
     error("$name: unanalyzable call given $sig_str")
 end
 
+"""
+    default_compiler_module()
+
+In order to facilitate working on the compiler, we'd like to make it easy for
+our users to switch all the ordinary compiler-based reflection to a new copy of the
+compiler, if they `dev` and load a new version of the compiler. However, it would
+be confusing if the result of reflection functions changed, simply because some
+downstream package happens to load a new copy of `Compiler`. Thus, we look for
+a special rendezvous binding `var"#_interactive_compiler_reference` in Main.
+This binding is exported by the compiler, so if the user does `using Compiler` to
+load a dev'ed version of the Compiler from `Main`, we will see that and pick up
+the new Compiler, but if the using statement is in some downstream package, we
+will not.
+"""
+function default_compiler_module()
+    # If the user has explicitly loaded a new compiler into Main, prefer that.
+    if isdefined(Core.Main, :var"#_interactive_compiler_reference")
+        return Core.Main.var"#_interactive_compiler_reference"
+    end
+    # Otherwise return a private reference to the internal compiler
+    return Base.Compiler
+end
+
 """
     code_typed_by_type(types::Type{<:Tuple}; ...)
 
 Similar to [`code_typed`](@ref), except the argument is a tuple type describing
 a full signature to query.
 """
 function code_typed_by_type(@nospecialize(tt::Type);
+                            Compiler::Module = default_compiler_module(),
                             optimize::Bool=true,
                             debuginfo::Symbol=:default,
                             world::UInt=get_world_counter(),
-                            interp::Compiler.AbstractInterpreter=Compiler.NativeInterpreter(world))
+                            interp=Compiler.NativeInterpreter(world))
     (ccall(:jl_is_in_pure_context, Bool, ()) || world == typemax(UInt)) &&
         error("code reflection cannot be used from generated functions")
     if @isdefined(IRShow)
@@ -384,7 +408,7 @@ function code_typed_by_type(@nospecialize(tt::Type);
     return asts
 end
 
-function get_oc_code_rt(oc::Core.OpaqueClosure, types, optimize::Bool)
+function get_oc_code_rt(Compiler::Module, oc::Core.OpaqueClosure, types, optimize::Bool)
     @nospecialize oc types
     ccall(:jl_is_in_pure_context, Bool, ()) &&
         error("code reflection cannot be used from generated functions")
@@ -416,11 +440,12 @@ function get_oc_code_rt(oc::Core.OpaqueClosure, types, optimize::Bool)
 end
 
 function code_typed_opaque_closure(oc::Core.OpaqueClosure, types;
+                                   Compiler::Module = default_compiler_module(),
                                    debuginfo::Symbol=:default,
                                    optimize::Bool=true,
                                    _...)
     @nospecialize oc types
-    (code, rt) = get_oc_code_rt(oc, types, optimize)
+    (code, rt) = get_oc_code_rt(Compiler, oc, types, optimize)
     debuginfo === :none && remove_linenums!(code)
     return Any[Pair{CodeInfo,Any}(code, rt)]
 end
@@ -484,8 +509,9 @@ a full signature to query.
 """
 function code_ircode_by_type(
     @nospecialize(tt::Type);
+    Compiler::Module = default_compiler_module(),
     world::UInt=get_world_counter(),
-    interp::Compiler.AbstractInterpreter=Compiler.NativeInterpreter(world),
+    interp=Compiler.NativeInterpreter(world),
     optimize_until::Union{Integer,AbstractString,Nothing}=nothing,
 )
     (ccall(:jl_is_in_pure_context, Bool, ()) || world == typemax(UInt)) &&
@@ -506,22 +532,25 @@ function code_ircode_by_type(
     return asts
 end
 
-function _builtin_return_type(interp::Compiler.AbstractInterpreter,
+function _builtin_return_type(interp,
                               @nospecialize(f::Core.Builtin), @nospecialize(types))
+    Compiler = typename(typeof(interp))
     argtypes = Any[to_tuple_type(types).parameters...]
     rt = Compiler.builtin_tfunction(interp, f, argtypes, nothing)
     return Compiler.widenconst(rt)
 end
 
-function _builtin_effects(interp::Compiler.AbstractInterpreter,
+function _builtin_effects(interp,
                           @nospecialize(f::Core.Builtin), @nospecialize(types))
+    Compiler = typename(typeof(interp))
     argtypes = Any[to_tuple_type(types).parameters...]
     rt = Compiler.builtin_tfunction(interp, f, argtypes, nothing)
     return Compiler.builtin_effects(Compiler.typeinf_lattice(interp), f, argtypes, rt)
 end
 
-function _builtin_exception_type(interp::Compiler.AbstractInterpreter,
+function _builtin_exception_type(interp,
                                  @nospecialize(f::Core.Builtin), @nospecialize(types))
+    Compiler = typename(typeof(interp))
     effects = _builtin_effects(interp, f, types)
     return Compiler.is_nothrow(effects) ? Union{} : Any
 end
@@ -578,11 +607,12 @@ julia> Base.return_types(sum, (Union{Vector{Int},UnitRange{Int}},))
     doing so will result in an error.
 """
 function return_types(@nospecialize(f), @nospecialize(types=default_tt(f));
+                      Compiler::Module = default_compiler_module(),
                       world::UInt=get_world_counter(),
-                      interp::Compiler.AbstractInterpreter=Compiler.NativeInterpreter(world))
+                      interp=Compiler.NativeInterpreter(world))
     check_generated_context(world)
     if isa(f, Core.OpaqueClosure)
-        _, rt = only(code_typed_opaque_closure(f, types))
+        _, rt = only(code_typed_opaque_closure(Compiler, f, types))
         return Any[rt]
     elseif isa(f, Core.Builtin)
         return Any[_builtin_return_type(interp, f, types)]
@@ -646,11 +676,12 @@ On the other hand `Base.infer_return_type` returns one collective result that su
     doing so will result in an error.
 """
 function infer_return_type(@nospecialize(f), @nospecialize(types=default_tt(f));
+                           Compiler::Module = default_compiler_module(),
                            world::UInt=get_world_counter(),
-                           interp::Compiler.AbstractInterpreter=Compiler.NativeInterpreter(world))
+                           interp=Compiler.NativeInterpreter(world))
     check_generated_context(world)
     if isa(f, Core.OpaqueClosure)
-        return last(only(code_typed_opaque_closure(f, types)))
+        return last(only(code_typed_opaque_closure(Compiler, f, types)))
     elseif isa(f, Core.Builtin)
         return _builtin_return_type(interp, f, types)
     end
@@ -716,8 +747,9 @@ julia> Base.infer_exception_types(throw_if_number, (Any,))
     doing so will result in an error.
 """
 function infer_exception_types(@nospecialize(f), @nospecialize(types=default_tt(f));
+                               Compiler::Module = default_compiler_module(),
                                world::UInt=get_world_counter(),
-                               interp::Compiler.AbstractInterpreter=Compiler.NativeInterpreter(world))
+                               interp=Compiler.NativeInterpreter(world))
     check_generated_context(world)
     if isa(f, Core.OpaqueClosure)
         return Any[Any] # TODO
@@ -795,8 +827,9 @@ signature, the exception type is widened to `MethodError`.
     doing so will result in an error.
 """
 function infer_exception_type(@nospecialize(f), @nospecialize(types=default_tt(f));
+                              Compiler::Module = default_compiler_module(),
                               world::UInt=get_world_counter(),
-                              interp::Compiler.AbstractInterpreter=Compiler.NativeInterpreter(world))
+                              interp=Compiler.NativeInterpreter(world))
     check_generated_context(world)
     if isa(f, Core.OpaqueClosure)
         return Any # TODO
@@ -880,9 +913,10 @@ signature, the `:nothrow` bit gets tainted.
 - [`Base.@assume_effects`](@ref): A macro for making assumptions about the effects of a method.
 """
 function infer_effects(@nospecialize(f), @nospecialize(types=default_tt(f));
+                       Compiler::Module = default_compiler_module(),
                        optimize::Bool=true,
                        world::UInt=get_world_counter(),
-                       interp::Compiler.AbstractInterpreter=Compiler.NativeInterpreter(world))
+                       interp=Compiler.NativeInterpreter(world))
     check_generated_context(world)
     if isa(f, Core.Builtin)
         return _builtin_effects(interp, f, types)
@@ -916,8 +950,9 @@ function print_statement_costs(io::IO, @nospecialize(f), @nospecialize(t); kwarg
 end
 
 function print_statement_costs(io::IO, @nospecialize(tt::Type);
+                               Compiler::Module = default_compiler_module(),
                                world::UInt=get_world_counter(),
-                               interp::Compiler.AbstractInterpreter=Compiler.NativeInterpreter(world))
+                               interp=Compiler.NativeInterpreter(world))
     tt = to_tuple_type(tt)
     world == typemax(UInt) && error("code reflection cannot be used from generated functions")
     matches = Compiler.findall(tt, Compiler.method_table(interp))

stdlib/Compiler/src/Compiler.jl

@@ -27,6 +27,13 @@ ccall(:jl_set_module_uuid, Cvoid, (Any, NTuple{2, UInt64}), Compiler,
     (0x807dbc54_b67e_4c79, 0x8afb_eafe4df6f2e1))
 ccall(:jl_set_module_parent, Cvoid, (Any, Any), Compiler, Compiler)
 
+# The interactive reflection utilities (`code_`, etc.) look for this symbol
+# in Main and if present use that Compiler instead of the builtin one. By
+# exporting this symbol, we can make `using Compiler` switch over these utilities
+# to the loaded compiler.
+const var"#_interactive_compiler_reference" = Compiler
+export var"#_interactive_compiler_reference"
+
 using Core.Intrinsics, Core.IR
 
 import Core: print, println, show, write, unsafe_write,