syntax: Unsupport `foo! bar { ... }` macros in the parser #62258

petrochenkov · 2019-06-30T22:30:31Z

Their support in expansion was removed in #61606.

Also un-reserve macro_rules as a macro name, there's no ambiguity between macro_rules definitions and macro calls (it also wasn't reserved correctly).

cc rust-lang/wg-grammar#51

rust-highfive · 2019-06-30T22:30:34Z

r? @eddyb

(rust_highfive has picked a reviewer for you, use r? to override)

Centril

r=me with or without nits.

src/libsyntax/parse/parser.rs

Centril · 2019-06-30T23:34:05Z

r? @Centril

eddyb · 2019-07-01T06:55:57Z

cc @rust-lang/lang This PR lets one define macros named macro_rules which would be used for an invocation like macro_rules!(...), while macro_rules! foo {...} would still refer to the builtin macro.

While from an implementation point of view this seems reasonable (treating macro_rules! foo {...} as a special syntax and not a macro invocation), I do want to make sure this is not a compatibility hazard (in case we want to, say, allow something like macro foo = macro_rules! {...}; in the future).

That said, I think we can land this PR as-is, and revert it later if we really don't want to do this.

petrochenkov · 2019-07-01T07:41:05Z

Two notes:

macro_rules was already a special syntax, not a macro invocation, this PR doesn't change that

the "reservation" could be worked around by use foo as macro_rules previously

macro_rules! foo { () => (0) }

use foo as macro_rules;

fn main() {
    println!("{}", macro_rules!());
}

eddyb · 2019-07-01T08:39:43Z

@petrochenkov Oh, and that use wouldn't affect macro_rules! ident {...} syntax anyway?
I can see how that makes this PR even more of a slam-dunk.

Like I said, I think we should just land it and if anyone has any concerns, they can be raised async.

petrochenkov · 2019-07-01T09:13:16Z

Oh, and that use wouldn't affect macro_rules! ident {...} syntax anyway?

Yes, macro_rules in macro_rules! foo { ... } doesn't go through name resolution, since it's a context-dependent keyword like union and processed during parsing.
https://play.rust-lang.org/?version=nightly&mode=debug&edition=2018&gist=aa35ddb773e577d4d2b9842d3f0059d1

Unreserve `macro_rules` as a macro name

petrochenkov · 2019-07-01T09:58:28Z

@bors r=Centril

bors · 2019-07-01T09:58:30Z

📌 Commit d0dc41a has been approved by Centril

Centril · 2019-07-01T14:31:04Z

Removing nomination per @eddyb's note re. async and since the whole team was pinged.

(It's clear to me that this is a slam dunk)

syntax: Unsupport `foo! bar { ... }` macros in the parser Their support in expansion was removed in rust-lang#61606. Also un-reserve `macro_rules` as a macro name, there's no ambiguity between `macro_rules` definitions and macro calls (it also wasn't reserved correctly). cc rust-lang/wg-grammar#51

@ghost

Rollup of 17 pull requests Successful merges: - #62039 (Remove needless lifetimes (rustc)) - #62153 (Update the `rust-installer` submodule) - #62173 (rename InterpretCx -> InterpCx) - #62240 (wfcheck: resolve the type-vars in `AdtField` types) - #62249 (Use mem::take instead of mem::replace with default) - #62252 (Update mem::replace example to not be identical to mem::take) - #62258 (syntax: Unsupport `foo! bar { ... }` macros in the parser) - #62268 (Clean up inherent_impls) - #62287 (Use link attributes on extern "C" blocks with llvm-libuwind) - #62295 (miri realloc: do not require giving old size+align) - #62297 (refactor check_for_substitution) - #62316 (When possible without changing semantics, implement Iterator::last in terms of DoubleEndedIterator::next_back for types in liballoc and libcore.) - #62317 (Migrate `compile-pass` annotations to `build-pass`) - #62337 (Fix bucket in CPU usage script) - #62344 (simplify Option::get_or_insert) - #62346 (enable a few more tests in Miri and update the comment for others) - #62351 (remove bogus example from drop_in_place) Failed merges: r? @ghost

syntax: Unsupport `foo! bar { ... }` macros in the parser Their support in expansion was removed in rust-lang#61606. Also un-reserve `macro_rules` as a macro name, there's no ambiguity between `macro_rules` definitions and macro calls (it also wasn't reserved correctly). cc rust-lang/wg-grammar#51

@ghost

Rollup of 16 pull requests Successful merges: - #62039 (Remove needless lifetimes (rustc)) - #62173 (rename InterpretCx -> InterpCx) - #62240 (wfcheck: resolve the type-vars in `AdtField` types) - #62249 (Use mem::take instead of mem::replace with default) - #62252 (Update mem::replace example to not be identical to mem::take) - #62258 (syntax: Unsupport `foo! bar { ... }` macros in the parser) - #62268 (Clean up inherent_impls) - #62287 (Use link attributes on extern "C" blocks with llvm-libuwind) - #62295 (miri realloc: do not require giving old size+align) - #62297 (refactor check_for_substitution) - #62316 (When possible without changing semantics, implement Iterator::last in terms of DoubleEndedIterator::next_back for types in liballoc and libcore.) - #62317 (Migrate `compile-pass` annotations to `build-pass`) - #62337 (Fix bucket in CPU usage script) - #62344 (simplify Option::get_or_insert) - #62346 (enable a few more tests in Miri and update the comment for others) - #62351 (remove bogus example from drop_in_place) Failed merges: r? @ghost

This is now unsupported and treated as a hard syntax error. cc rust-lang/rust#62258.

rust-highfive assigned eddyb Jun 30, 2019

rust-highfive added the S-waiting-on-review Status: Awaiting review from the assignee but also interested parties. label Jun 30, 2019

petrochenkov mentioned this pull request Jun 30, 2019

Should MacroCall include optional ident? rust-lang/wg-grammar#51

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petrochenkov force-pushed the idclean branch from 778f43e to e3779f1 Compare June 30, 2019 23:03

Centril reviewed Jun 30, 2019

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eddyb added I-nominated T-lang Relevant to the language team labels Jul 1, 2019

petrochenkov added 2 commits July 1, 2019 12:20

syntax: Unsupport foo! bar { ... } macros in the parser

3f39dc1

Unreserve `macro_rules` as a macro name

Address review comments

d0dc41a

petrochenkov force-pushed the idclean branch from e3779f1 to d0dc41a Compare July 1, 2019 09:34

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 Jul 1, 2019

Centril removed the I-nominated label Jul 1, 2019

Centril mentioned this pull request Jul 1, 2019

Rollup of 12 pull requests #62271

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Centril mentioned this pull request Jul 3, 2019

Rollup of 17 pull requests #62349

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Centril mentioned this pull request Jul 3, 2019

Rollup of 18 pull requests #62352

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Centril mentioned this pull request Jul 3, 2019

Rollup of 17 pull requests #62354

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Centril mentioned this pull request Jul 3, 2019

Rollup of 16 pull requests #62355

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bors merged commit d0dc41a into rust-lang:master Jul 4, 2019

petrochenkov deleted the idclean branch July 8, 2019 13:33

topecongiro added a commit to topecongiro/rustfmt that referenced this pull request Jul 28, 2019

Remove macros with optional ident

bdbe7a7

This is now unsupported and treated as a hard syntax error. cc rust-lang/rust#62258.

This was referenced Aug 24, 2019

Crater runs for Rust 1.38.0 #63628

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[1.38] Regression: expected open delimiter #63889

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EliseZeroTwo mentioned this pull request Dec 14, 2023

Better errors with bad/missing identifiers in MBEs #118939

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syntax: Unsupport `foo! bar { ... }` macros in the parser #62258

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