Add support for nested functions

[philberty]

This is a missed pieces of functionality for statements in rust.

[CohenArthur]

It might be interesting to add a test checking for an error when using a nested function outside of its scope, just to make sure

fn test() {
   fn nested() {}
}

fn main() {
    nested(); // dg-error etc...
}

[philberty]

Good point I will add that test case.

Another missing piece is: "error[E0434]: can't capture dynamic environment in a fn item" but it will need a little more work to add that in a general wayl.

[CohenArthur]

Yeah I don't know how difficult that would be to implement, considering lambdas can use their dynamic environment etc etc

[dkm]

Maybe similar to the GNU extension for nested function in C https://gcc.gnu.org/onlinedocs/gcc/Nested-Functions.html

[philberty]

Yeah, I think I will likely need to wait to implement that error until closures are implemented.

[philberty]

Maybe similar to the GNU extension for nested function in C https://gcc.gnu.org/onlinedocs/gcc/Nested-Functions.html

Good point let me add this link to the closures issue #195

I think a lot of this we get kind of for free. The abstraction we have in place allows us to say this function definition is enclosed within a parent scope to be able to reference outside variables. I think in theory closures are easy 'ish to implement in terms of GCC and this abstraction was used in gccgo so its full of them :D

[philberty]

bors r+

[bors]

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