Some ty::sty values are being inferred as ast::ty_

[bleibig]

Consider this program:

use rustc;
import rustc::middle::ty;
fn main() {
    let _t: ty::sty = ty::ty_nil;
}

It fails to compile with this error:

infer_err.rs:4:22: 4:32 error: mismatched types: expected `rustc::middle::ty::sty` but found `rustsyntax::ast::ty_` (enum rustc::middle::ty::sty vs enum rustsyntax::ast::ty_)
infer_err.rs:4     let _t: ty::sty = ty::ty_nil;
                                     ^~~~~~~~~~

This happens for other ty::sty variants such as ty::ty_nil and ty::ty_bool, but not for ty::ty_type and possibly some others. It's also worth noting that this might only happen outside the rustc crate, as I could not reproduce this error by doing similar things inside rustc.

[catamorphism]

I'm looking at this.

[catamorphism]

Interestingly, I get the same type error if I change it to:

use rustc;
import rustc::middle::ty;
fn main() {
  let _t: ty::sty = rustc::middle::ty::ty_nil;
}

which rules out my first hypothesis that it was a resolve issue.

[catamorphism]

A fine bug! Not in type inference, it turns out, but in resolve. You'll notice that middle::ty glob-imports syntax::ast::*; both middle::ty and syntax::ast define a value ty_nil, and it happened that in the export declaration export ty_nil in middle::ty, the name ty_nil was resolved to ast::ty_nil. Which is what caused the type error.

I have a fix, just waiting for make check.

[catamorphism]

Fixed in 164039e