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Andrew V. Teylu
e15897f6c4
The AST pretty printer was dropping parentheses around or-patterns
when they appeared inside `@` bindings, `&` references, or `box`
patterns. For example:
- `v @ (1 | 2 | 3)` was printed as `v @ 1 | 2 | 3`
- `&(1 | 2 | 3)` was printed as `&1 | 2 | 3`
- `box (1 | 2 | 3)` was printed as `box 1 | 2 | 3`
Since `|` has the lowest precedence among pattern operators, all of
these are parsed incorrectly without parentheses — e.g. `v @ 1 | 2 | 3`
becomes `(v @ 1) | 2 | 3`, binding `v` only to the first alternative.
This caused E0408 ("variable not bound in all patterns") when the
expanded output was fed back to the compiler, affecting crates like
html5ever and wgpu-core that use macros expanding to or-patterns
after `@`.
The fix adds a `print_pat_paren_if_or` helper that wraps `PatKind::Or`
subpatterns in parentheses, and uses it in the `@`, `&`, and `box`
printing arms. This is similar in spirit to the existing `FixupContext`
parenthesization approach used for expression printing.
Signed-off-by: Andrew V. Teylu <andrew.teylu@vector.com>
28 lines
672 B
Rust
28 lines
672 B
Rust
#![feature(prelude_import)]
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#![no_std]
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#![feature(box_patterns)]
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extern crate std;
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#[prelude_import]
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use ::std::prelude::rust_2015::*;
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//@ pretty-compare-only
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//@ pretty-mode:expanded
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//@ pp-exact:or-pattern-paren.pp
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macro_rules! or_pat { ($($name:pat),+) => { $($name)|+ } }
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fn check_at(x: Option<i32>) {
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match x {
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Some(v @ (1 | 2 | 3)) =>
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{
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::std::io::_print(format_args!("{0}\n", v));
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}
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_ => {}
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}
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}
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fn check_ref(x: &i32) { match x { &(1 | 2 | 3) => {} _ => {} } }
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fn check_box(x: Box<i32>) { match x { box (1 | 2 | 3) => {} _ => {} } }
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fn main() { check_at(Some(2)); check_ref(&1); check_box(Box::new(1)); }
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