Rollup merge of #54820 - kleimkuhler:issue-54538-unused_patterns-lint, r=nikomatsakis
Closes #54538: `unused_patterns` lint Closes #54538 r? @nikomatsakis
This commit is contained in:
Manish Goregaokar
GitHub
commit
7ba24e8fcf
4 changed files with 150 additions and 42 deletions
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@ -272,7 +272,7 @@ declare_lint! {
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pub struct UnusedParens;
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impl UnusedParens {
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fn check_unused_parens_core(&self,
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fn check_unused_parens_expr(&self,
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cx: &EarlyContext,
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value: &ast::Expr,
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msg: &str,
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@ -281,46 +281,57 @@ impl UnusedParens {
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let necessary = struct_lit_needs_parens &&
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parser::contains_exterior_struct_lit(&inner);
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if !necessary {
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let span_msg = format!("unnecessary parentheses around {}", msg);
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let mut err = cx.struct_span_lint(UNUSED_PARENS,
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value.span,
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&span_msg);
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// Remove exactly one pair of parentheses (rather than naïvely
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// stripping all paren characters)
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let mut ate_left_paren = false;
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let mut ate_right_paren = false;
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let parens_removed = pprust::expr_to_string(value)
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.trim_matches(|c| {
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match c {
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'(' => {
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if ate_left_paren {
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false
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} else {
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ate_left_paren = true;
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true
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}
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},
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')' => {
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if ate_right_paren {
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false
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} else {
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ate_right_paren = true;
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true
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}
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},
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_ => false,
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}
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}).to_owned();
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err.span_suggestion_short_with_applicability(
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value.span,
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"remove these parentheses",
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parens_removed,
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Applicability::MachineApplicable
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);
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err.emit();
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let pattern = pprust::expr_to_string(value);
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Self::remove_outer_parens(cx, value.span, &pattern, msg);
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}
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}
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}
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fn check_unused_parens_pat(&self,
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cx: &EarlyContext,
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value: &ast::Pat,
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msg: &str) {
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if let ast::PatKind::Paren(_) = value.node {
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let pattern = pprust::pat_to_string(value);
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Self::remove_outer_parens(cx, value.span, &pattern, msg);
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}
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}
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fn remove_outer_parens(cx: &EarlyContext, span: Span, pattern: &str, msg: &str) {
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let span_msg = format!("unnecessary parentheses around {}", msg);
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let mut err = cx.struct_span_lint(UNUSED_PARENS, span, &span_msg);
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let mut ate_left_paren = false;
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let mut ate_right_paren = false;
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let parens_removed = pattern
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.trim_matches(|c| {
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match c {
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'(' => {
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if ate_left_paren {
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false
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} else {
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ate_left_paren = true;
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true
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}
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},
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')' => {
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if ate_right_paren {
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false
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} else {
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ate_right_paren = true;
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true
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}
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},
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_ => false,
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}
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}).to_owned();
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err.span_suggestion_short_with_applicability(
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span,
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"remove these parentheses",
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parens_removed,
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Applicability::MachineApplicable
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);
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err.emit();
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}
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}
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impl LintPass for UnusedParens {
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@ -349,7 +360,9 @@ impl EarlyLintPass for UnusedParens {
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// first "argument" is self (which sometimes needs parens)
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MethodCall(_, ref args) => (&args[1..], "method"),
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// actual catch-all arm
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_ => { return; }
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_ => {
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return;
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}
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};
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// Don't lint if this is a nested macro expansion: otherwise, the lint could
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// trigger in situations that macro authors shouldn't have to care about, e.g.,
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@ -362,18 +375,32 @@ impl EarlyLintPass for UnusedParens {
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}
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let msg = format!("{} argument", call_kind);
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for arg in args_to_check {
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self.check_unused_parens_core(cx, arg, &msg, false);
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self.check_unused_parens_expr(cx, arg, &msg, false);
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}
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return;
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}
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};
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self.check_unused_parens_core(cx, &value, msg, struct_lit_needs_parens);
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self.check_unused_parens_expr(cx, &value, msg, struct_lit_needs_parens);
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}
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fn check_pat(&mut self, cx: &EarlyContext, p: &ast::Pat) {
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use ast::PatKind::{Paren, Range};
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// The lint visitor will visit each subpattern of `p`. We do not want to lint any range
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// pattern no matter where it occurs in the pattern. For something like `&(a..=b)`, there
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// is a recursive `check_pat` on `a` and `b`, but we will assume that if there are
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// unnecessry parens they serve a purpose of readability.
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if let Paren(ref pat) = p.node {
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match pat.node {
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Range(..) => {}
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_ => self.check_unused_parens_pat(cx, &p, "pattern")
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}
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}
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}
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fn check_stmt(&mut self, cx: &EarlyContext, s: &ast::Stmt) {
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if let ast::StmtKind::Local(ref local) = s.node {
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if let Some(ref value) = local.init {
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self.check_unused_parens_core(cx, &value, "assigned value", false);
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self.check_unused_parens_expr(cx, &value, "assigned value", false);
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}
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}
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}
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@ -11,6 +11,7 @@
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// run-pass
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fn main() {
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#[allow(unused_parens)]
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match 0 {
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(pat) => assert_eq!(pat, 0)
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}
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38
src/test/ui/lint/issue-54538-unused-parens-lint.rs
Normal file
38
src/test/ui/lint/issue-54538-unused-parens-lint.rs
Normal file
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@ -0,0 +1,38 @@
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// Copyright 2018 The Rust Project Developers. See the COPYRIGHT
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// file at the top-level directory of this distribution and at
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// http://rust-lang.org/COPYRIGHT.
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//
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// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
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// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
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// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
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// option. This file may not be copied, modified, or distributed
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// except according to those terms.
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// compile-pass
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#![allow(unreachable_patterns)]
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#![allow(unused_variables)]
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#![warn(unused_parens)]
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fn main() {
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match 1 {
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(_) => {} //~ WARNING: unnecessary parentheses around pattern
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(y) => {} //~ WARNING: unnecessary parentheses around pattern
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(ref r) => {} //~ WARNING: unnecessary parentheses around pattern
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(e @ 1..=2) => {} //~ WARNING: unnecessary parentheses around outer pattern
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(1..=2) => {} // Non ambiguous range pattern should not warn
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e @ (3..=4) => {} // Non ambiguous range pattern should not warn
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}
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match &1 {
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(e @ &(1...2)) => {} //~ WARNING: unnecessary parentheses around outer pattern
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&(_) => {} //~ WARNING: unnecessary parentheses around pattern
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e @ &(1...2) => {} // Ambiguous range pattern should not warn
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&(1..=2) => {} // Ambiguous range pattern should not warn
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}
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match &1 {
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e @ &(1...2) | e @ &(3..=4) => {} // Complex ambiguous pattern should not warn
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&_ => {}
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}
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}
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42
src/test/ui/lint/issue-54538-unused-parens-lint.stderr
Normal file
42
src/test/ui/lint/issue-54538-unused-parens-lint.stderr
Normal file
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@ -0,0 +1,42 @@
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warning: unnecessary parentheses around pattern
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--> $DIR/issue-54538-unused-parens-lint.rs:19:9
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LL | (_) => {} //~ WARNING: unnecessary parentheses around pattern
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| ^^^ help: remove these parentheses
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note: lint level defined here
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--> $DIR/issue-54538-unused-parens-lint.rs:15:9
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LL | #![warn(unused_parens)]
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| ^^^^^^^^^^^^^
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warning: unnecessary parentheses around pattern
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--> $DIR/issue-54538-unused-parens-lint.rs:20:9
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LL | (y) => {} //~ WARNING: unnecessary parentheses around pattern
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| ^^^ help: remove these parentheses
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warning: unnecessary parentheses around pattern
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--> $DIR/issue-54538-unused-parens-lint.rs:21:9
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LL | (ref r) => {} //~ WARNING: unnecessary parentheses around pattern
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| ^^^^^^^ help: remove these parentheses
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warning: unnecessary parentheses around pattern
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--> $DIR/issue-54538-unused-parens-lint.rs:22:9
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LL | (e @ 1..=2) => {} //~ WARNING: unnecessary parentheses around outer pattern
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| ^^^^^^^^^^^ help: remove these parentheses
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warning: unnecessary parentheses around pattern
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--> $DIR/issue-54538-unused-parens-lint.rs:28:9
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LL | (e @ &(1...2)) => {} //~ WARNING: unnecessary parentheses around outer pattern
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| ^^^^^^^^^^^^^^ help: remove these parentheses
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warning: unnecessary parentheses around pattern
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--> $DIR/issue-54538-unused-parens-lint.rs:29:10
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LL | &(_) => {} //~ WARNING: unnecessary parentheses around pattern
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| ^^^ help: remove these parentheses
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