Combo of begin block and return type annotation breaks closure inference

[marius311]

I know there's still ongoing work in making closures fast / fixing #15276, but this seemed weird enough that I thought it could be a bug and would be worth reporting:

function inferred1() :: Any
    a = 1
    (() -> a)()
end

function inferred2()
    begin
        a = 1
        (() -> a)()
    end
end

function not_inferred() :: Any
    begin
        a = 1
        (() -> a)()
    end
end

@code_warntype inferred1()
@code_warntype inferred2()
@code_warntype not_inferred()

As you can see, once you have both the begin block and the return type annotation, it breaks the closure inference, although either alone is fine. I'm seeing this on 0.6.4 and 0.7/1.0.

[yuyichao]

Still dup of #15276 . Hopefully simple enough to be fixed though...