Treat trailing semicolon as a statement in macro call #78376

Aaron1011 · 2020-10-25T21:15:41Z

See #61733 (comment)

We now preserve the trailing semicolon in a macro invocation, even if
the macro expands to nothing. As a result, the following code no longer
compiles:

macro_rules! empty {
    () => { }
}

fn foo() -> bool { //~ ERROR mismatched
    { true } //~ ERROR mismatched
    empty!();
}

Previously, { true } would be considered the trailing expression, even
though there's a semicolon in empty!();

This makes macro expansion more token-based.

rust-highfive · 2020-10-25T21:15:45Z

r? @varkor

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

Aaron1011 · 2020-10-25T21:15:50Z

r? @ghost

Aaron1011 · 2020-10-25T21:15:54Z

@bors try

bors · 2020-10-25T21:16:04Z

⌛ Trying commit 6d426c227a0be2819845c1072548536ce540643f with merge 1c5262aa6c045a581fb974488793f09ed51fc498...

bors · 2020-10-25T22:02:09Z

☀️ Try build successful - checks-actions
Build commit: 1c5262aa6c045a581fb974488793f09ed51fc498 (1c5262aa6c045a581fb974488793f09ed51fc498)

Aaron1011 · 2020-10-25T22:17:11Z

@craterbot check

craterbot · 2020-10-25T22:17:15Z

👌 Experiment pr-78376 created and queued.
🤖 Automatically detected try build 1c5262aa6c045a581fb974488793f09ed51fc498
🔍 You can check out the queue and this experiment's details.

ℹ️ Crater is a tool to run experiments across parts of the Rust ecosystem. Learn more

Aaron1011 · 2020-10-25T22:31:27Z

compiler/rustc_expand/src/placeholders.rs

-                stmts.push(stmt.add_trailing_semicolon());
+                if stmt.has_trailing_semicolon() {
+                    stmts.push(stmt);
+                    stmts.push(empty_stmt);


I think this is only observable in the post-expansion AST JSON. When we invoke a bang macro, there are no attribute macros left that could observe this.

craterbot · 2020-10-30T20:57:39Z

🚧 Experiment pr-78376 is now running

ℹ️ Crater is a tool to run experiments across parts of the Rust ecosystem. Learn more

craterbot · 2020-11-02T16:56:34Z

🎉 Experiment pr-78376 is completed!
📊 4 regressed and 10 fixed (127687 total)
📰 Open the full report.

⚠️ If you notice any spurious failure please add them to the blacklist!
ℹ️ Crater is a tool to run experiments across parts of the Rust ecosystem. Learn more

Aaron1011 · 2020-11-02T17:36:37Z

There appear to be no actual regressions 🎉

See rust-lang#61733 (comment) We now preserve the trailing semicolon in a macro invocation, even if the macro expands to nothing. As a result, the following code no longer compiles: ```rust macro_rules! empty { () => { } } fn foo() -> bool { //~ ERROR mismatched { true } //~ ERROR mismatched empty!(); } ``` Previously, `{ true }` would be considered the trailing expression, even though there's a semicolon in `empty!();` This makes macro expansion more token-based.

Aaron1011 · 2020-11-02T18:06:18Z

@petrochenkov: This is now ready to merge

petrochenkov · 2020-11-02T21:02:38Z

@bors r+

bors · 2020-11-02T21:02:40Z

📌 Commit e78e9d4 has been approved by petrochenkov

…expr, r=petrochenkov Treat trailing semicolon as a statement in macro call See rust-lang#61733 (comment) We now preserve the trailing semicolon in a macro invocation, even if the macro expands to nothing. As a result, the following code no longer compiles: ```rust macro_rules! empty { () => { } } fn foo() -> bool { //~ ERROR mismatched { true } //~ ERROR mismatched empty!(); } ``` Previously, `{ true }` would be considered the trailing expression, even though there's a semicolon in `empty!();` This makes macro expansion more token-based.

Rollup of 8 pull requests Successful merges: - rust-lang#78376 (Treat trailing semicolon as a statement in macro call) - rust-lang#78400 (Fix unindent in doc comments) - rust-lang#78575 (Add a test for compiletest rustc-env & unset-rustc-env directives) - rust-lang#78616 (Document -Zinstrument-coverage) - rust-lang#78663 (Fix ICE when a future-incompat-report has its command-line level capped) - rust-lang#78664 (Fix intrinsic size_of stable link) - rust-lang#78668 (inliner: Remove redundant loop) - rust-lang#78676 (add mipsel-unknown-none target) Failed merges: r? `@ghost` `@rustbot` modify labels: rollup

bors · 2020-11-03T09:18:28Z

⌛ Testing commit e78e9d4 with merge d662f80...

Pkgsrc changes: * Adjust patches, convert tabs to spaces so that tests pass. * Remove patches which are no longer needed (upstream changed) * Minor adjustments for SunOS, e.g. disable stack probes. * Adjust cargo checksum patching accordingly. * Remove commented-out use of PATCHELF on NetBSD, which doesn't work anyway... Upstream changes: Version 1.49.0 (2020-12-31) ============================ Language ----------------------- - [Unions can now implement `Drop`, and you can now have a field in a union with `ManuallyDrop<T>`.][77547] - [You can now cast uninhabited enums to integers.][76199] - [You can now bind by reference and by move in patterns.][76119] This allows you to selectively borrow individual components of a type. E.g. ```rust #[derive(Debug)] struct Person { name: String, age: u8, } let person = Person { name: String::from("Alice"), age: 20, }; // `name` is moved out of person, but `age` is referenced. let Person { name, ref age } = person; println!("{} {}", name, age); ``` Compiler ----------------------- - [Added tier 1\* support for `aarch64-unknown-linux-gnu`.][78228] - [Added tier 2 support for `aarch64-apple-darwin`.][75991] - [Added tier 2 support for `aarch64-pc-windows-msvc`.][75914] - [Added tier 3 support for `mipsel-unknown-none`.][78676] - [Raised the minimum supported LLVM version to LLVM 9.][78848] - [Output from threads spawned in tests is now captured.][78227] - [Change os and vendor values to "none" and "unknown" for some targets][78951] \* Refer to Rust's [platform support page][forge-platform-support] for more information on Rust's tiered platform support. Libraries ----------------------- - [`RangeInclusive` now checks for exhaustion when calling `contains` and indexing.][78109] - [`ToString::to_string` now no longer shrinks the internal buffer in the default implementation.][77997] - [`ops::{Index, IndexMut}` are now implemented for fixed sized arrays of any length.][74989] Stabilized APIs --------------- - [`slice::select_nth_unstable`] - [`slice::select_nth_unstable_by`] - [`slice::select_nth_unstable_by_key`] The following previously stable methods are now `const`. - [`Poll::is_ready`] - [`Poll::is_pending`] Cargo ----------------------- - [Building a crate with `cargo-package` should now be independently reproducible.][cargo/8864] - [`cargo-tree` now marks proc-macro crates.][cargo/8765] - [Added `CARGO_PRIMARY_PACKAGE` build-time environment variable.] [cargo/8758] This variable will be set if the crate being built is one the user selected to build, either with `-p` or through defaults. - [You can now use glob patterns when specifying packages & targets.][cargo/8752] Compatibility Notes ------------------- - [Demoted `i686-unknown-freebsd` from host tier 2 to target tier 2 support.][78746] - [Macros that end with a semi-colon are now treated as statements even if they expand to nothing.][78376] - [Rustc will now check for the validity of some built-in attributes on enum variants.][77015] Previously such invalid or unused attributes could be ignored. - Leading whitespace is stripped more uniformly in documentation comments, which may change behavior. You read [this post about the changes][rustdoc-ws-post] for more details. - [Trait bounds are no longer inferred for associated types.][79904] Internal Only ------------- These changes provide no direct user facing benefits, but represent significant improvements to the internals and overall performance of rustc and related tools. - [rustc's internal crates are now compiled using the `initial-exec` Thread Local Storage model.][78201] - [Calculate visibilities once in resolve.][78077] - [Added `system` to the `llvm-libunwind` bootstrap config option.][77703] - [Added `--color` for configuring terminal color support to bootstrap.][79004] [75991]: rust-lang/rust#75991 [78951]: rust-lang/rust#78951 [78848]: rust-lang/rust#78848 [78746]: rust-lang/rust#78746 [78376]: rust-lang/rust#78376 [78228]: rust-lang/rust#78228 [78227]: rust-lang/rust#78227 [78201]: rust-lang/rust#78201 [78109]: rust-lang/rust#78109 [78077]: rust-lang/rust#78077 [77997]: rust-lang/rust#77997 [77703]: rust-lang/rust#77703 [77547]: rust-lang/rust#77547 [77015]: rust-lang/rust#77015 [76199]: rust-lang/rust#76199 [76119]: rust-lang/rust#76119 [75914]: rust-lang/rust#75914 [74989]: rust-lang/rust#74989 [79004]: rust-lang/rust#79004 [78676]: rust-lang/rust#78676 [79904]: rust-lang/rust#79904 [cargo/8864]: rust-lang/cargo#8864 [cargo/8765]: rust-lang/cargo#8765 [cargo/8758]: rust-lang/cargo#8758 [cargo/8752]: rust-lang/cargo#8752 [`slice::select_nth_unstable`]: https://doc.rust-lang.org/nightly/std/primitive.slice.html#method.select_nth_unstable [`slice::select_nth_unstable_by`]: https://doc.rust-lang.org/nightly/std/primitive.slice.html#method.select_nth_unstable_by [`slice::select_nth_unstable_by_key`]: https://doc.rust-lang.org/nightly/std/primitive.slice.html#method.select_nth_unstable_by_key [`hint::spin_loop`]: https://doc.rust-lang.org/stable/std/hint/fn.spin_loop.html [`Poll::is_ready`]: https://doc.rust-lang.org/stable/std/task/enum.Poll.html#method.is_ready [`Poll::is_pending`]: https://doc.rust-lang.org/stable/std/task/enum.Poll.html#method.is_pending [rustdoc-ws-post]: https://blog.guillaume-gomez.fr/articles/2020-11-11+New+doc+comment+handling+in+rustdoc

rust-highfive assigned varkor Oct 25, 2020

rust-highfive added the S-waiting-on-review Status: Awaiting review from the assignee but also interested parties. label Oct 25, 2020

petrochenkov assigned petrochenkov and unassigned varkor Oct 25, 2020

petrochenkov added S-waiting-on-crater Status: Waiting on a crater run to be completed. and removed S-waiting-on-review Status: Awaiting review from the assignee but also interested parties. labels Oct 25, 2020

Aaron1011 commented Oct 25, 2020

View reviewed changes

craterbot added S-waiting-on-review Status: Awaiting review from the assignee but also interested parties. and removed S-waiting-on-crater Status: Waiting on a crater run to be completed. labels Nov 2, 2020

Aaron1011 changed the title ~~[DO NOT MERGE] Treat trailing semicolon as a statement in macro call~~ Treat trailing semicolon as a statement in macro call Nov 2, 2020

Aaron1011 force-pushed the feature/consistent-empty-expr branch from 6d426c2 to e78e9d4 Compare November 2, 2020 18:05

Aaron1011 added the relnotes Marks issues that should be documented in the release notes of the next release. label Nov 2, 2020

Aaron1011 added the A-proc-macros Area: Procedural macros label Nov 2, 2020

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 Nov 2, 2020

Dylan-DPC-zz mentioned this pull request Nov 3, 2020

Rollup of 9 pull requests #78693

Closed

JohnTitor mentioned this pull request Nov 3, 2020

Rollup of 8 pull requests #78697

Merged

bors merged commit 0716724 into rust-lang:master Nov 3, 2020

rustbot added this to the 1.49.0 milestone Nov 3, 2020

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