2020-12-31 08:59:09 -06:00
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#![feature(rustc_attrs)]
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#[rustc_dummy = stringify!(a)] // OK
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macro_rules! bar {
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() => {};
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}
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// FIXME?: `bar` here expands before `stringify` has a chance to expand.
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// `#[rustc_dummy = ...]` is validated and dropped during expansion of `bar`,
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Overhaul `MacArgs::Eq`.
The value in `MacArgs::Eq` is currently represented as a `Token`.
Because of `TokenKind::Interpolated`, `Token` can be either a token or
an arbitrary AST fragment. In practice, a `MacArgs::Eq` starts out as a
literal or macro call AST fragment, and then is later lowered to a
literal token. But this is very non-obvious. `Token` is a much more
general type than what is needed.
This commit restricts things, by introducing a new type `MacArgsEqKind`
that is either an AST expression (pre-lowering) or an AST literal
(post-lowering). The downside is that the code is a bit more verbose in
a few places. The benefit is that makes it much clearer what the
possibilities are (though also shorter in some other places). Also, it
removes one use of `TokenKind::Interpolated`, taking us a step closer to
removing that variant, which will let us make `Token` impl `Copy` and
remove many "handle Interpolated" code paths in the parser.
Things to note:
- Error messages have improved. Messages like this:
```
unexpected token: `"bug" + "found"`
```
now say "unexpected expression", which makes more sense. Although
arbitrary expressions can exist within tokens thanks to
`TokenKind::Interpolated`, that's not obvious to anyone who doesn't
know compiler internals.
- In `parse_mac_args_common`, we no longer need to collect tokens for
the value expression.
2022-04-28 15:52:01 -05:00
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// the "unexpected expression" errors comes from the validation.
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#[rustc_dummy = stringify!(b)] //~ ERROR unexpected expression: `stringify!(b)`
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2020-12-31 08:59:09 -06:00
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bar!();
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fn main() {}
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