Resolution Design

[NalaGinrut]

I think it's better to separate type and name resolution, fortunately, if we do it now, it's just a little change. Here're the steps:

1. Create Resolution class inherited from AST::ASTVisitor, and move static bool ResolveNamesAndTypes into it.
2. Separate TypeResolution and NameResolution class inherited from Resolution class.
3. Put them in different files.

This is better for maintenance and working parallelly.
And the name resolution will distinct names from different namespaces, like values, macros, so it's an important prerequisite for the rest of the work.

If it's OK, then I can raise PR for it.

What do you think? @philberty @SimplyTheOther

[NalaGinrut]

BTW, to perform type resolution correctly, I think the order should be:

name resolution -> macro expansion -> type resolution

But it's fine if we implement each step parallelly.

[philberty]

Yes this is a really good idea.

The way i envision things is many "Passes" and a pass i mean a Class using the ASTVisitor pattern and we have a state machine to work the work in there. We can even flesh out later with warning passes such as DeadCode recounting the names as it goes and when things go out of scope we iterate all nodes with a refcount == 0 as dead code.

I recently Added a simple pass rust-scan.cc which we will need in subsequent passes to know about global declarations as functions can be declared after they are used etc.

[bjorn3]

Name resolution and macro expansion need to be interleaved for the following to work:

macro_rules! a {
    () => {
        macro_rules! b {
            () => {}
        }
    }
}

a!();
b!();

#![feature(decl_macro)]

macro a($b:ident) {
    macro $b() {}
}

b!();
a!(b);

[NalaGinrut]

@bjorn3 Ah yes, thanks for mention, I'll keep it.

[NalaGinrut]

@philberty Yes, the pass, I think this term implies everything, extensible and can be disabled for certain purposes. We need a tiny framework for these passes (and options for disabling and debug), maybe we can do it after resolution an expansion.