Don't allow const to begin a nonterminal
#80135
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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
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Beta-nominating because this fixes a P-critical regression from stable to beta. |
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@bors r+ rollup |
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📌 Commit d6f1787 has been approved by |
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Should this be p=1 because it fixes a P-critical regression? |
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Likewise, I don't think this should be |
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Dec 18, 2020
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`
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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
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Ok, looks like the questions above already resolved themselves without my involvement. |
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Oh well :) |
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…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`
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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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Fixes #79908.
Thanks to Vadim Petrochenkov who told me what the fix was!
r? @petrochenkov