main can be a inner function?

[ILyoan]

main function can be a inner function.

for example

fn foo() {
    fn main() {
        io::println("i am the inner main");
        foo();
    }
    io::println("i am a outer function");
}

I wonder if it's intended.
If not, main should be always at the top crate level.

[brson]

I would not mind forcing main to always be a crate-level function.

[nikomatsakis]

I think my preference would be that main must be at the root of the crate. I hate when I download some C code and I have to grep around just to find main().

[brson]

Removing from 0.7.

I-nominated (well-defined)

[brson]

I think the main discovery logic needs to get its own pass. It's starting to get a bit complicated.

[brson]

If we do this we'll need extra diagnostics to see if there's a 'main' function defined in the wrong place.

[graydon]

accepted for backwards compat

[ILyoan]

Closing as #6119 landed