Regression in decl_macro emitted item resolutions

[IsaacWoods]

On the current nightly (2019-03-13), the following code fails (link to the playground):

#![feature(decl_macro)]

macro bar() {
    pub enum Bar {
        A,
        B,
        C
    }
}

bar!();

fn main() {
    let _ = Bar::A;
    let _ = Bar::B;
    let _ = Bar::C;
}

with the error:

error[E0433]: failed to resolve: use of undeclared type or module `Bar`
  --> src/main.rs:14:13
   |
14 |     let _ = Bar::A;
   |             ^^^ use of undeclared type or module `Bar`

error[E0433]: failed to resolve: use of undeclared type or module `Bar`
  --> src/main.rs:15:13
   |
15 |     let _ = Bar::B;
   |             ^^^ use of undeclared type or module `Bar`

error[E0433]: failed to resolve: use of undeclared type or module `Bar`
  --> src/main.rs:16:13
   |
16 |     let _ = Bar::C;
   |             ^^^ use of undeclared type or module `Bar`

This seems to be an issue with the decl_macro feature specifically - declaring the same macro with macro_rules works as intended.

[estebank]

CC @petrochenkov

[Centril]

Is this actually a bug?

[IsaacWoods]

@Centril I hope it is - otherwise it would be impossible for a macro to declare items that could then be used?

Note: the macro is being invoked; I’m not expecting to access the item from inside the macro, but the item it generates.

[petrochenkov]

This works as expected, macro macros are fully hygienic (unlike macro_rules macros that are hygienic only for local variables).
As a result, Bar created by the macro and Bar used in main are totally different Bars.

Opt-out from that hygiene is supposed to be explicit (rust-lang/rfcs#2498 or something like that), but it's not yet implemented.

macro bar() {
    pub enum #Bar {
        ...
    }
}

In the meantime, identifiers that are not supposed to be hygienic can be passed to a macro as arguments.

macro bar($Bar: ident) {
    pub enum $Bar {
        ....
    }
}

bar!(Bar);

[IsaacWoods]

Okay, thanks for clarifying @petrochenkov (and apologies @Centril) - I didn't realise macros 2.0 would be that hygienic.