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Macros: Add a 'literal' fragment specifier
Implements RFC 1576. See: https://github.com/rust-lang/rfcs/blob/master/text/1576-macros-literal-matcher.md Changes are mostly in libsyntax, docs, and tests. Feature gate is enabled for 1.27.0. Many thanks to Vadim Petrochenkov for following through code reviews and suggestions. Example: ````rust macro_rules! test_literal { ($l:literal) => { println!("literal: {}", $l); }; ($e:expr) => { println!("expr: {}", $e); }; } fn main() { let a = 1; test_literal!(a); test_literal!(2); test_literal!(-3); } ``` Output: ``` expr: 1 literal: 2 literal: -3 ```
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src/doc/unstable-book/src/language-features/macro-literal-matcher.md
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| # `macro_literal_matcher` | ||
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| The tracking issue for this feature is: [#35625] | ||
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| The RFC is: [rfc#1576]. | ||
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| With this feature gate enabled, the [list of fragment specifiers][frags] gains one more entry: | ||
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| * `literal`: a literal. Examples: 2, "string", 'c' | ||
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| A `literal` may be followed by anything, similarly to the `ident` specifier. | ||
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| [rfc#1576]: http://rust-lang.github.io/rfcs/1576-macros-literal-matcher.html | ||
| [#35625]: https://github.com/rust-lang/rust/issues/35625 | ||
| [frags]: ../book/first-edition/macros.html#syntactic-requirements | ||
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| ------------------------ |
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| // 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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| #![feature(macro_literal_matcher)] | ||
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| macro_rules! mtester { | ||
| ($l:literal) => { | ||
| &format!("macro caught literal: {}", $l) | ||
| }; | ||
| ($e:expr) => { | ||
| &format!("macro caught expr: {}", $e) | ||
| }; | ||
| } | ||
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| macro_rules! two_negative_literals { | ||
| ($l1:literal $l2:literal) => { | ||
| &format!("macro caught literals: {}, {}", $l1, $l2) | ||
| }; | ||
| } | ||
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| macro_rules! only_expr { | ||
| ($e:expr) => { | ||
| &format!("macro caught expr: {}", $e) | ||
| }; | ||
| } | ||
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| macro_rules! mtester_dbg { | ||
| ($l:literal) => { | ||
| &format!("macro caught literal: {:?}", $l) | ||
| }; | ||
| ($e:expr) => { | ||
| &format!("macro caught expr: {:?}", $e) | ||
| }; | ||
| } | ||
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| macro_rules! catch_range { | ||
| ($s:literal ... $e:literal) => { | ||
| &format!("macro caught literal: {} ... {}", $s, $e) | ||
| }; | ||
| (($s:expr) ... ($e:expr)) => { // Must use ')' before '...' | ||
| &format!("macro caught expr: {} ... {}", $s, $e) | ||
| }; | ||
| } | ||
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| macro_rules! pat_match { | ||
| ($s:literal ... $e:literal) => { | ||
| match 3 { | ||
| $s ... $e => "literal, in range", | ||
| _ => "literal, other", | ||
| } | ||
| }; | ||
| ($s:pat) => { | ||
| match 3 { | ||
| $s => "pat, single", | ||
| _ => "pat, other", | ||
| } | ||
| }; | ||
| } | ||
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| macro_rules! match_attr { | ||
| (#[$attr:meta] $e:literal) => { | ||
| "attr matched literal" | ||
| }; | ||
| (#[$attr:meta] $e:expr) => { | ||
| "attr matched expr" | ||
| }; | ||
| } | ||
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| macro_rules! match_produced_attr { | ||
| ($lit: literal) => { | ||
| // Struct with doc comment passed via $literal | ||
| #[doc = $lit] | ||
| struct LiteralProduced; | ||
| }; | ||
| ($expr: expr) => { | ||
| struct ExprProduced; | ||
| }; | ||
| } | ||
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| macro_rules! test_user { | ||
| ($s:literal, $e:literal) => { | ||
| { | ||
| let mut v = Vec::new(); | ||
| for i in $s .. $e { | ||
| v.push(i); | ||
| } | ||
| "literal" | ||
| } | ||
| }; | ||
| ($s:expr, $e: expr) => { | ||
| { | ||
| let mut v = Vec::new(); | ||
| for i in $s .. $e { | ||
| v.push(i); | ||
| } | ||
| "expr" | ||
| } | ||
| }; | ||
| } | ||
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| pub fn main() { | ||
| // Cases where 'literal' catches | ||
| assert_eq!(mtester!("str"), "macro caught literal: str"); | ||
| assert_eq!(mtester!(2), "macro caught literal: 2"); | ||
| assert_eq!(mtester!(2.2), "macro caught literal: 2.2"); | ||
| assert_eq!(mtester!(1u32), "macro caught literal: 1"); | ||
| assert_eq!(mtester!(0x32), "macro caught literal: 50"); | ||
| assert_eq!(mtester!('c'), "macro caught literal: c"); | ||
| assert_eq!(mtester!(-1.2), "macro caught literal: -1.2"); | ||
| assert_eq!(two_negative_literals!(-2 -3), "macro caught literals: -2, -3"); | ||
| assert_eq!(catch_range!(2 ... 3), "macro caught literal: 2 ... 3"); | ||
| assert_eq!(match_attr!(#[attr] 1), "attr matched literal"); | ||
| assert_eq!(test_user!(10, 20), "literal"); | ||
| assert_eq!(mtester!(false), "macro caught literal: false"); | ||
| assert_eq!(mtester!(true), "macro caught literal: true"); | ||
| match_produced_attr!("a"); | ||
| let _a = LiteralProduced; | ||
| assert_eq!(pat_match!(1 ... 3), "literal, in range"); | ||
| assert_eq!(pat_match!(4 ... 6), "literal, other"); | ||
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| // Cases where 'expr' catches | ||
| assert_eq!(mtester!((-1.2)), "macro caught expr: -1.2"); | ||
| assert_eq!(only_expr!(-1.2), "macro caught expr: -1.2"); | ||
| assert_eq!(mtester!((1 + 3)), "macro caught expr: 4"); | ||
| assert_eq!(mtester_dbg!(()), "macro caught expr: ()"); | ||
| assert_eq!(catch_range!((1 + 1) ... (2 + 2)), "macro caught expr: 2 ... 4"); | ||
| assert_eq!(match_attr!(#[attr] (1 + 2)), "attr matched expr"); | ||
| assert_eq!(test_user!(10, (20 + 2)), "expr"); | ||
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| match_produced_attr!((3 + 2)); | ||
| let _b = ExprProduced; | ||
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| // Cases where 'pat' matched | ||
| assert_eq!(pat_match!(3), "pat, single"); | ||
| assert_eq!(pat_match!(6), "pat, other"); | ||
| } |
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