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Auto merge of #48056 - ExpHP:macro-commas, r=dtolnay
Comprehensively support trailing commas in std/core macros I carefully organized the changes into four commits: * Test cases * Fixes for `macro_rules!` macros * Fixes for builtin macros * Docs for builtins **I can easily scale this back to just the first two commits for now if such is desired.** ### Breaking (?) changes * This fixes #48042, which is a breaking change that I hope people can agree is just a bugfix for an extremely dark corner case. * To fix five of the builtins, this changes `syntax::ext::base::get_single_str_from_tts` to accept a trailing comma, and revises the documentation so that this aspect is not surprising. **I made this change under the (hopefully correct) understanding that `libsyntax` is private rustc implementation detail.** After reviewing all call sites (which were, you guessed it, *precisely those five macros*), I believe the revised semantics are closer to the intended spirit of the function. ### Changes which may require concensus Up until now, it could be argued that some or all the following macros did not conceptually take a comma-separated list, because they only took one argument: * **`cfg(unix,)`** (most notable since cfg! is unique in taking a meta tag) * **`include{,_bytes,_str}("file.rs",)`** (in item form this might be written as "`include!{"file.rs",}`" which is even slightly more odd) * **`compile_error("message",);`** * **`option_env!("PATH",)`** * **`try!(Ok(()),)`** So I think these particular changes may require some sort of consensus. **All of the fixes for builtins are included this list, so if we want to defer these decisions to later then I can scale this PR back to just the first two commits.** ### Other notes/general requests for comment * Do we have a big checklist somewhere of "things to do when adding macros?" My hope is for `run-pass/macro-comma-support.rs` to remain comprehensive. * Originally I wanted the tests to also comprehensively forbid double trailing commas. However, this didn't work out too well: [see this gist and the giant FIXME in it](https://gist.github.com/ExpHP/6fc40e82f3d73267c4e590a9a94966f1#file-compile-fail_macro-comma-support-rs-L33-L50) * I did not touch `select!`. It appears to me to be a complete mess, and its trailing comma mishaps are only the tip of the iceberg. * There are [some compile-fail test cases](https://github.com/ExpHP/rust/blob/5fa97c35da2f0ee/src/test/compile-fail/macro-comma-behavior.rs#L49-L52) that didn't seem to work (rustc emits errors, but compile-fail doesn't acknowledge them), so they are disabled. Any clues? (Possibly related: These happen to be precisely the set of errors which are tagged by rustc as "this error originates in a macro outside of the current crate".) --- Fixes #48042 Closes #46241
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| Original file line number | Diff line number | Diff line change |
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| @@ -0,0 +1,101 @@ | ||
| // Copyright 2018 The Rust Project Developers. See the COPYRIGHT | ||
| // file at the top-level directory of this distribution and at | ||
| // http://rust-lang.org/COPYRIGHT. | ||
| // | ||
| // Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or | ||
| // http://www.apache.org/licenses/LICENSE-2.0> or the MIT license | ||
| // <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your | ||
| // option. This file may not be copied, modified, or distributed | ||
| // except according to those terms. | ||
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| // Companion test to the similarly-named file in run-pass. | ||
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| // compile-flags: -C debug_assertions=yes | ||
| // revisions: std core | ||
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| #![cfg_attr(core, no_std)] | ||
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| #[cfg(std)] use std::fmt; | ||
| #[cfg(core)] use core::fmt; | ||
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| // (see documentation of the similarly-named test in run-pass) | ||
| fn to_format_or_not_to_format() { | ||
| let falsum = || false; | ||
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| // assert!(true, "{}",); // see run-pass | ||
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| assert_eq!(1, 1, "{}",); | ||
| //[core]~^ ERROR no arguments | ||
| //[std]~^^ ERROR no arguments | ||
| assert_ne!(1, 2, "{}",); | ||
| //[core]~^ ERROR no arguments | ||
| //[std]~^^ ERROR no arguments | ||
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| // debug_assert!(true, "{}",); // see run-pass | ||
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| debug_assert_eq!(1, 1, "{}",); | ||
| //[core]~^ ERROR no arguments | ||
| //[std]~^^ ERROR no arguments | ||
| debug_assert_ne!(1, 2, "{}",); | ||
| //[core]~^ ERROR no arguments | ||
| //[std]~^^ ERROR no arguments | ||
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| #[cfg(std)] { | ||
| eprint!("{}",); | ||
| //[std]~^ ERROR no arguments | ||
| } | ||
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| #[cfg(std)] { | ||
| // FIXME: compile-fail says "expected error not found" even though | ||
| // rustc does emit an error | ||
| // eprintln!("{}",); | ||
| // <DISABLED> [std]~^ ERROR no arguments | ||
| } | ||
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| #[cfg(std)] { | ||
| format!("{}",); | ||
| //[std]~^ ERROR no arguments | ||
| } | ||
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| format_args!("{}",); | ||
| //[core]~^ ERROR no arguments | ||
| //[std]~^^ ERROR no arguments | ||
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| // if falsum() { panic!("{}",); } // see run-pass | ||
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| #[cfg(std)] { | ||
| print!("{}",); | ||
| //[std]~^ ERROR no arguments | ||
| } | ||
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| #[cfg(std)] { | ||
| // FIXME: compile-fail says "expected error not found" even though | ||
| // rustc does emit an error | ||
| // println!("{}",); | ||
| // <DISABLED> [std]~^ ERROR no arguments | ||
| } | ||
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| unimplemented!("{}",); | ||
| //[core]~^ ERROR no arguments | ||
| //[std]~^^ ERROR no arguments | ||
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| // if falsum() { unreachable!("{}",); } // see run-pass | ||
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| struct S; | ||
| impl fmt::Display for S { | ||
| fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result { | ||
| write!(f, "{}",)?; | ||
| //[core]~^ ERROR no arguments | ||
| //[std]~^^ ERROR no arguments | ||
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| // FIXME: compile-fail says "expected error not found" even though | ||
| // rustc does emit an error | ||
| // writeln!(f, "{}",)?; | ||
| // <DISABLED> [core]~^ ERROR no arguments | ||
| // <DISABLED> [std]~^^ ERROR no arguments | ||
| Ok(()) | ||
| } | ||
| } | ||
| } | ||
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| fn main() {} |
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,20 @@ | ||
| // Copyright 2018 The Rust Project Developers. See the COPYRIGHT | ||
| // file at the top-level directory of this distribution and at | ||
| // http://rust-lang.org/COPYRIGHT. | ||
| // | ||
| // Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or | ||
| // http://www.apache.org/licenses/LICENSE-2.0> or the MIT license | ||
| // <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your | ||
| // option. This file may not be copied, modified, or distributed | ||
| // except according to those terms. | ||
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| // This is a companion to the similarly-named test in run-pass. | ||
| // | ||
| // It tests macros that unavoidably produce compile errors. | ||
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| fn compile_error() { | ||
| compile_error!("lel"); //~ ERROR lel | ||
| compile_error!("lel",); //~ ERROR lel | ||
| } | ||
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| fn main() {} |
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,11 @@ | ||
| // Copyright 2018 The Rust Project Developers. See the COPYRIGHT | ||
| // file at the top-level directory of this distribution and at | ||
| // http://rust-lang.org/COPYRIGHT. | ||
| // | ||
| // Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or | ||
| // http://www.apache.org/licenses/LICENSE-2.0> or the MIT license | ||
| // <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your | ||
| // option. This file may not be copied, modified, or distributed | ||
| // except according to those terms. | ||
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| () |
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