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Don't allow const to begin a nonterminal #80135

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merged 1 commit into from
Dec 18, 2020
Merged

Don't allow const to begin a nonterminal #80135

merged 1 commit into from
Dec 18, 2020

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camelid
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@camelid camelid commented Dec 17, 2020

Fixes #79908.

Thanks to Vadim Petrochenkov who told me what the fix was!

r? @petrochenkov

@camelid camelid added A-macros Area: All kinds of macros (custom derive, macro_rules!, proc macros, ..) A-parser Area: The parsing of Rust source code to an AST. T-compiler Relevant to the compiler team, which will review and decide on the PR/issue. labels Dec 17, 2020
@rust-highfive rust-highfive added the S-waiting-on-review Status: Awaiting review from the assignee but also interested parties. label Dec 17, 2020
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camelid commented Dec 17, 2020

Beta-nominating because this fixes a P-critical regression from stable to beta.

@camelid camelid added the beta-nominated Nominated for backporting to the compiler in the beta channel. label Dec 17, 2020
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@bors r+ rollup

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bors commented Dec 17, 2020

📌 Commit d6f1787 has been approved by petrochenkov

@bors bors added S-waiting-on-bors Status: Waiting on bors to run and complete tests. Bors will change the label on completion. and removed S-waiting-on-review Status: Awaiting review from the assignee but also interested parties. labels Dec 17, 2020
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camelid commented Dec 17, 2020

Should this be p=1 because it fixes a P-critical regression?

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camelid commented Dec 17, 2020 •
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Likewise, I don't think this should be rollup because we want to be able to easily bisect in case this causes any issues.

RalfJung added a commit to RalfJung/rust that referenced this pull request Dec 18, 2020
@RalfJung
Rollup merge of rust-lang#80135 - camelid:const-macro-nt, r=petrochenkov
bd40604 
Don't allow `const` to begin a nonterminal

Fixes rust-lang#79908.

Thanks to Vadim Petrochenkov who [told me what the fix was][z]!

[z]: https://rust-lang.zulipchat.com/#narrow/stream/182449-t-compiler.2Fhelp/topic/finding.20which.20macro.20rule.20to.20use/near/220240422

r? `@petrochenkov`
@RalfJung RalfJung mentioned this pull request Dec 18, 2020
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@RalfJung RalfJung mentioned this pull request Dec 18, 2020
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bors added a commit to rust-lang-ci/rust that referenced this pull request Dec 18, 2020
@bors
Auto merge of rust-lang#80156 - RalfJung:rollup-m3poz8z, r=RalfJung
e4297ba 
Rollup of 6 pull requests

Successful merges:

 - rust-lang#80121 (Change the message for `if_let_guard` feature gate)
 - rust-lang#80130 (docs: Edit rustc_span::symbol::Symbol method)
 - rust-lang#80135 (Don't allow `const` to begin a nonterminal)
 - rust-lang#80145 (Fix typo in rustc_typeck docs)
 - rust-lang#80146 (Edit formatting in Rust Prelude docs)
 - rust-lang#80147 (Add missing punctuation to std::alloc docs)

Failed merges:

r? `@ghost`
`@rustbot` modify labels: rollup
@bors bors merged commit 9269995 into rust-lang:master Dec 18, 2020
@rustbot rustbot added this to the 1.50.0 milestone Dec 18, 2020
@camelid camelid deleted the const-macro-nt branch December 18, 2020 19:42
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Ok, looks like the questions above already resolved themselves without my involvement.

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camelid commented Dec 19, 2020

Oh well :)

@Mark-Simulacrum Mark-Simulacrum added the beta-accepted Accepted for backporting to the compiler in the beta channel. label Dec 25, 2020
@Mark-Simulacrum Mark-Simulacrum mentioned this pull request Dec 27, 2020
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@Mark-Simulacrum Mark-Simulacrum removed the beta-nominated Nominated for backporting to the compiler in the beta channel. label Dec 27, 2020
@Mark-Simulacrum Mark-Simulacrum modified the milestones: 1.50.0, 1.49.0 Dec 27, 2020
bors added a commit to rust-lang-ci/rust that referenced this pull request Dec 28, 2020
@bors
Auto merge of rust-lang#80417 - Mark-Simulacrum:beta-next, r=Mark-Sim…
136dfc1 
…ulacrum

[beta] backports

This backports the following to 1.49:

*  Revert change to trait evaluation order rust-lang#80132
*  Don't allow `const` to begin a nonterminal rust-lang#80135
*  Prevent caching normalization results with a cycle rust-lang#80246

r? `@Mark-Simulacrum`
@petrochenkov petrochenkov mentioned this pull request Apr 13, 2021
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@lf- lf- mentioned this pull request Apr 20, 2021
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lf- added a commit to lf-/rust that referenced this pull request Apr 26, 2021
@lf-
Add expr202x macro pattern
dbb3841 
This makes it possible to use `inline_const` (rust-lang#76001) and `let_chains`
(rust-lang#53667) inside macros' `expr` patterns in a future edition by
bifurcating the `expr` nonterminal in a similar way to `pat2021` to
remove some backwards compatibility exceptions that disallow
`const`/`let` at the beginning of an `expr` match.

Fixes rust-lang#84155 and relaxes the backward compat restriction from rust-lang#80135 for
a future edition. This is not intended to go into 2021 as it I don't
think it's simple to write an automatic fix, and certainly not now that
it's past the soft deadline for inclusion in 2021 by a long shot.

Here is a pathological case of rust-lang#79908 that forces this to be an edition
change:

```rust
macro_rules! evil {
    ($e:expr) => {
        // or something else
        const {$e-1}
    };
    (const $b:block) => {
        const {$b}
    }
}
fn main() {
    let x = 5;
    match x {
        evil!(const { 5 }) => panic!("oh no"),
        _ => (),
    };
}
```
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A-macros Area: All kinds of macros (custom derive, macro_rules!, proc macros, ..) A-parser Area: The parsing of Rust source code to an AST. beta-accepted Accepted for backporting to the compiler in the beta channel. S-waiting-on-bors Status: Waiting on bors to run and complete tests. Bors will change the label on completion. T-compiler Relevant to the compiler team, which will review and decide on the PR/issue.
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regression 1.49: macro_rules unexpected tokens
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