Compiler.return_type is broken for Compiler.jl as the standard library

[aviatesk]

julia> using Compiler
Precompiling Compiler finished.
  1 dependency successfully precompiled in 2 seconds

julia> @assert Base.Compiler !== Compiler

julia> Compiler.return_type(sin, Tuple{Int})
ERROR: MethodError: no method matching _return_type(::Compiler.NativeInterpreter, ::Type{Tuple{typeof(sin), Int64}})
You may have intended to import Base._return_type
The applicable method may be too new: running in world age 6455, while current world is 23669.

Closest candidates are:
  _return_type(::Compiler.AbstractInterpreter, ::DataType) (method too new to be called from this world context.)
   @ Compiler ~/julia/julia3/Compiler/src/typeinfer.jl:1243

Stacktrace:
 [1] return_type(f::Any, t::DataType)
   @ Compiler ~/julia/julia3/Compiler/src/typeinfer.jl:1226
 [2] top-level scope
   @ REPL[3]:1

This definition of return_type assumes the use of :jl_call_in_typeinf_world, so it won’t work if Compiler.jl is loaded as a stdlib.

julia/Compiler/src/typeinfer.jl

Lines 1223 to 1260 in e624440

	function return_type(@nospecialize(f), t::DataType) # this method has a special tfunc
	world = tls_world_age()
	args = Any[_return_type, NativeInterpreter(world), Tuple{Core.Typeof(f), t.parameters...}]
	return ccall(:jl_call_in_typeinf_world, Any, (Ptr{Any}, Cint), args, length(args))
	end
	function return_type(@nospecialize(f), t::DataType, world::UInt)
	return return_type(Tuple{Core.Typeof(f), t.parameters...}, world)
	end
	function return_type(t::DataType)
	world = tls_world_age()
	return return_type(t, world)
	end
	function return_type(t::DataType, world::UInt)
	args = Any[_return_type, NativeInterpreter(world), t]
	return ccall(:jl_call_in_typeinf_world, Any, (Ptr{Any}, Cint), args, length(args))
	end
	function _return_type(interp::AbstractInterpreter, t::DataType)
	rt = Union{}
	f = singleton_type(t.parameters[1])
	if isa(f, Builtin)
	args = Any[t.parameters...]
	popfirst!(args)
	rt = builtin_tfunction(interp, f, args, nothing)
	rt = widenconst(rt)
	else
	for match in _methods_by_ftype(t, -1, get_inference_world(interp))::Vector
	ty = typeinf_type(interp, match::MethodMatch)
	ty === nothing && return Any
	rt = tmerge(rt, ty)
	rt === Any && break
	end
	end
	return rt
	end

In other words, since this is a feature specific to Base.Compiler, it might be better to define this function on the Base side.