Type inference fails on functions with nested generic functions inside let blocks

[simonbyrne]

I'm not sure if this is a duplicate of the other let block issues, but I came across this:

let
    global foo

    bar(x::Float64) = x+1
    bar(x::Float32) = x+2

    foo(x) = bar(x)
end

julia> @code_warntype foo(1.0)
Variables:
  #self#::#foo
  x::Float64

Body:
  begin 
      return ((Core.getfield)($(QuoteNode(Core.Box(bar))),:contents)::Any)(x::Float64)::Any
  end::Any

This problem goes away if I get rid of the 2nd method for bar.

[yuyichao]

Dup of #15276