Compiler: add local function statements and expressions

[chqrlie]

• local functions are defined using the standard syntax in the body of a function.
• they cannot be templates nor type functions
• they can be named or anonymous
• accept a capture list between square backets fater the parameter list (currently ignored)

[bvdberg]

I'm not really fond of the name mangling. Cant we do:
outer _ _ inner?

and then disallow double underscores in normal names?
It would be nicer during debugging

Another issue is the AST printing. The local function body is not printed.

You could add test cases, they dont depend on the bootstrap.

I tried this and it works...

module test;

import stdio local;

i32[10] numbers;
u32 count;

fn void add(i32 value) {
    numbers[count++] = value;
}

type VisitorFn fn void (void* arg, i32 value);

fn void visit(void* arg, VisitorFn handler) {
    for (u32 i = 0; i < count; i++) {
        handler(arg, numbers[i]);
    }
}


public fn i32 main() {
    add(1);
    add(2);
    add(3);
    add(4);


    i32 total = 0;

    fn void count_total(void* arg, i32 value) {
        i32* total = arg;
        *total += value;
    }

    visit(&total, count_total);

    printf("total %d\n", total);
    return 0;
}

If you generate the C code and check what GCC/Clang make of that, the call completely disappears :)

[chqrlie]

Disallowing double underscores and using them for mangled names, especially #defines, is a sane decision.

Yet the mangling for making local symbols global must handle the case of duplicates: it is quite common in the code to use the same local name in non intersecting scopes. The same could happen for local functions, and should be allowed, so outer__inner is not sufficient, we may need an extra suffix in case of duplicates. The case of anonymous functions must be covered too. I used SrcLoc as a quick and dirty hack, but I agree it makes debugging and testing more cumbersome as the C output is unpredictable

AST printing is on the way, I need to add a new AST node type for this.

I'm glad the optimizer does a good job on these things.