From c1897960c016d7296b945175b0fef9546f6326a6 Mon Sep 17 00:00:00 2001
From: Ralf Jung <post@ralfj.de>
Date: Wed, 7 Aug 2024 15:29:00 +0200
Subject: [PATCH] unused_parens: do not lint against parens around &raw

---
 compiler/rustc_lint/src/unused.rs            |  7 ++
 tests/ui/lint/lint-unnecessary-parens.fixed  |  8 ++
 tests/ui/lint/lint-unnecessary-parens.rs     |  8 ++
 tests/ui/lint/lint-unnecessary-parens.stderr | 88 +++++++++++++-------
 4 files changed, 79 insertions(+), 32 deletions(-)

diff --git a/compiler/rustc_lint/src/unused.rs b/compiler/rustc_lint/src/unused.rs
index 795333224ba00..e2c05129ee238 100644
--- a/compiler/rustc_lint/src/unused.rs
+++ b/compiler/rustc_lint/src/unused.rs
@@ -675,6 +675,13 @@ trait UnusedDelimLint {
             return true;
         }
 
+        // Do not lint against parentheses around `&raw [const|mut] expr`.
+        // These parentheses will have to be added e.g. when calling a method on the result of this
+        // expression, and we want to avoid churn wrt adding and removing parentheses.
+        if matches!(inner.kind, ast::ExprKind::AddrOf(ast::BorrowKind::Raw, ..)) {
+            return true;
+        }
+
         // Check if LHS needs parens to prevent false-positives in cases like
         // `fn x() -> u8 { ({ 0 } + 1) }`.
         //
diff --git a/tests/ui/lint/lint-unnecessary-parens.fixed b/tests/ui/lint/lint-unnecessary-parens.fixed
index 760897c5143f1..089aa1b7ab7de 100644
--- a/tests/ui/lint/lint-unnecessary-parens.fixed
+++ b/tests/ui/lint/lint-unnecessary-parens.fixed
@@ -1,6 +1,7 @@
 //@ run-rustfix
 
 #![deny(unused_parens)]
+#![feature(raw_ref_op)]
 #![allow(while_true)] // for rustfix
 
 #[derive(Eq, PartialEq)]
@@ -125,4 +126,11 @@ fn main() {
         // FIXME: false positive. This parenthesis is required.
         unit! {} - One //~ ERROR unnecessary parentheses around block return value
     };
+
+    // Do *not* lint around `&raw` (but do lint when `&` creates a reference).
+    let mut x = 0;
+    let _r = &x; //~ ERROR unnecessary parentheses
+    let _r = &mut x; //~ ERROR unnecessary parentheses
+    let _r = (&raw const x);
+    let _r = (&raw mut x);
 }
diff --git a/tests/ui/lint/lint-unnecessary-parens.rs b/tests/ui/lint/lint-unnecessary-parens.rs
index 7cbaac8ae5403..dc77ee003523e 100644
--- a/tests/ui/lint/lint-unnecessary-parens.rs
+++ b/tests/ui/lint/lint-unnecessary-parens.rs
@@ -1,6 +1,7 @@
 //@ run-rustfix
 
 #![deny(unused_parens)]
+#![feature(raw_ref_op)]
 #![allow(while_true)] // for rustfix
 
 #[derive(Eq, PartialEq)]
@@ -125,4 +126,11 @@ fn main() {
         // FIXME: false positive. This parenthesis is required.
         (unit! {} - One) //~ ERROR unnecessary parentheses around block return value
     };
+
+    // Do *not* lint around `&raw` (but do lint when `&` creates a reference).
+    let mut x = 0;
+    let _r = (&x); //~ ERROR unnecessary parentheses
+    let _r = (&mut x); //~ ERROR unnecessary parentheses
+    let _r = (&raw const x);
+    let _r = (&raw mut x);
 }
diff --git a/tests/ui/lint/lint-unnecessary-parens.stderr b/tests/ui/lint/lint-unnecessary-parens.stderr
index 755dd5fc3094b..c9422437a9fcd 100644
--- a/tests/ui/lint/lint-unnecessary-parens.stderr
+++ b/tests/ui/lint/lint-unnecessary-parens.stderr
@@ -1,5 +1,5 @@
 error: unnecessary parentheses around `return` value
-  --> $DIR/lint-unnecessary-parens.rs:13:12
+  --> $DIR/lint-unnecessary-parens.rs:14:12
    |
 LL |     return (1);
    |            ^ ^
@@ -16,7 +16,7 @@ LL +     return 1;
    |
 
 error: unnecessary parentheses around `return` value
-  --> $DIR/lint-unnecessary-parens.rs:16:12
+  --> $DIR/lint-unnecessary-parens.rs:17:12
    |
 LL |     return (X { y });
    |            ^       ^
@@ -28,7 +28,7 @@ LL +     return X { y };
    |
 
 error: unnecessary parentheses around type
-  --> $DIR/lint-unnecessary-parens.rs:19:46
+  --> $DIR/lint-unnecessary-parens.rs:20:46
    |
 LL | pub fn unused_parens_around_return_type() -> (u32) {
    |                                              ^   ^
@@ -40,7 +40,7 @@ LL + pub fn unused_parens_around_return_type() -> u32 {
    |
 
 error: unnecessary parentheses around block return value
-  --> $DIR/lint-unnecessary-parens.rs:25:9
+  --> $DIR/lint-unnecessary-parens.rs:26:9
    |
 LL |         (5)
    |         ^ ^
@@ -52,7 +52,7 @@ LL +         5
    |
 
 error: unnecessary parentheses around block return value
-  --> $DIR/lint-unnecessary-parens.rs:27:5
+  --> $DIR/lint-unnecessary-parens.rs:28:5
    |
 LL |     (5)
    |     ^ ^
@@ -64,7 +64,7 @@ LL +     5
    |
 
 error: unnecessary parentheses around `if` condition
-  --> $DIR/lint-unnecessary-parens.rs:39:7
+  --> $DIR/lint-unnecessary-parens.rs:40:7
    |
 LL |     if(true) {}
    |       ^    ^
@@ -76,7 +76,7 @@ LL +     if true {}
    |
 
 error: unnecessary parentheses around `while` condition
-  --> $DIR/lint-unnecessary-parens.rs:40:10
+  --> $DIR/lint-unnecessary-parens.rs:41:10
    |
 LL |     while(true) {}
    |          ^    ^
@@ -88,7 +88,7 @@ LL +     while true {}
    |
 
 error: unnecessary parentheses around `for` iterator expression
-  --> $DIR/lint-unnecessary-parens.rs:41:13
+  --> $DIR/lint-unnecessary-parens.rs:42:13
    |
 LL |     for _ in(e) {}
    |             ^ ^
@@ -100,7 +100,7 @@ LL +     for _ in e {}
    |
 
 error: unnecessary parentheses around `match` scrutinee expression
-  --> $DIR/lint-unnecessary-parens.rs:42:10
+  --> $DIR/lint-unnecessary-parens.rs:43:10
    |
 LL |     match(1) { _ => ()}
    |          ^ ^
@@ -112,7 +112,7 @@ LL +     match 1 { _ => ()}
    |
 
 error: unnecessary parentheses around `return` value
-  --> $DIR/lint-unnecessary-parens.rs:43:11
+  --> $DIR/lint-unnecessary-parens.rs:44:11
    |
 LL |     return(1);
    |           ^ ^
@@ -124,7 +124,7 @@ LL +     return 1;
    |
 
 error: unnecessary parentheses around assigned value
-  --> $DIR/lint-unnecessary-parens.rs:74:31
+  --> $DIR/lint-unnecessary-parens.rs:75:31
    |
 LL | pub const CONST_ITEM: usize = (10);
    |                               ^  ^
@@ -136,7 +136,7 @@ LL + pub const CONST_ITEM: usize = 10;
    |
 
 error: unnecessary parentheses around assigned value
-  --> $DIR/lint-unnecessary-parens.rs:75:33
+  --> $DIR/lint-unnecessary-parens.rs:76:33
    |
 LL | pub static STATIC_ITEM: usize = (10);
    |                                 ^  ^
@@ -148,7 +148,7 @@ LL + pub static STATIC_ITEM: usize = 10;
    |
 
 error: unnecessary parentheses around function argument
-  --> $DIR/lint-unnecessary-parens.rs:79:9
+  --> $DIR/lint-unnecessary-parens.rs:80:9
    |
 LL |     bar((true));
    |         ^    ^
@@ -160,7 +160,7 @@ LL +     bar(true);
    |
 
 error: unnecessary parentheses around `if` condition
-  --> $DIR/lint-unnecessary-parens.rs:81:8
+  --> $DIR/lint-unnecessary-parens.rs:82:8
    |
 LL |     if (true) {}
    |        ^    ^
@@ -172,7 +172,7 @@ LL +     if true {}
    |
 
 error: unnecessary parentheses around `while` condition
-  --> $DIR/lint-unnecessary-parens.rs:82:11
+  --> $DIR/lint-unnecessary-parens.rs:83:11
    |
 LL |     while (true) {}
    |           ^    ^
@@ -184,7 +184,7 @@ LL +     while true {}
    |
 
 error: unnecessary parentheses around `match` scrutinee expression
-  --> $DIR/lint-unnecessary-parens.rs:83:11
+  --> $DIR/lint-unnecessary-parens.rs:84:11
    |
 LL |     match (true) {
    |           ^    ^
@@ -196,7 +196,7 @@ LL +     match true {
    |
 
 error: unnecessary parentheses around `let` scrutinee expression
-  --> $DIR/lint-unnecessary-parens.rs:86:16
+  --> $DIR/lint-unnecessary-parens.rs:87:16
    |
 LL |     if let 1 = (1) {}
    |                ^ ^
@@ -208,7 +208,7 @@ LL +     if let 1 = 1 {}
    |
 
 error: unnecessary parentheses around `let` scrutinee expression
-  --> $DIR/lint-unnecessary-parens.rs:87:19
+  --> $DIR/lint-unnecessary-parens.rs:88:19
    |
 LL |     while let 1 = (2) {}
    |                   ^ ^
@@ -220,7 +220,7 @@ LL +     while let 1 = 2 {}
    |
 
 error: unnecessary parentheses around method argument
-  --> $DIR/lint-unnecessary-parens.rs:103:24
+  --> $DIR/lint-unnecessary-parens.rs:104:24
    |
 LL |     X { y: false }.foo((true));
    |                        ^    ^
@@ -232,7 +232,7 @@ LL +     X { y: false }.foo(true);
    |
 
 error: unnecessary parentheses around assigned value
-  --> $DIR/lint-unnecessary-parens.rs:105:18
+  --> $DIR/lint-unnecessary-parens.rs:106:18
    |
 LL |     let mut _a = (0);
    |                  ^ ^
@@ -244,7 +244,7 @@ LL +     let mut _a = 0;
    |
 
 error: unnecessary parentheses around assigned value
-  --> $DIR/lint-unnecessary-parens.rs:106:10
+  --> $DIR/lint-unnecessary-parens.rs:107:10
    |
 LL |     _a = (0);
    |          ^ ^
@@ -256,7 +256,7 @@ LL +     _a = 0;
    |
 
 error: unnecessary parentheses around assigned value
-  --> $DIR/lint-unnecessary-parens.rs:107:11
+  --> $DIR/lint-unnecessary-parens.rs:108:11
    |
 LL |     _a += (1);
    |           ^ ^
@@ -268,7 +268,7 @@ LL +     _a += 1;
    |
 
 error: unnecessary parentheses around pattern
-  --> $DIR/lint-unnecessary-parens.rs:109:8
+  --> $DIR/lint-unnecessary-parens.rs:110:8
    |
 LL |     let(mut _a) = 3;
    |        ^      ^
@@ -280,7 +280,7 @@ LL +     let mut _a = 3;
    |
 
 error: unnecessary parentheses around pattern
-  --> $DIR/lint-unnecessary-parens.rs:110:9
+  --> $DIR/lint-unnecessary-parens.rs:111:9
    |
 LL |     let (mut _a) = 3;
    |         ^      ^
@@ -292,7 +292,7 @@ LL +     let mut _a = 3;
    |
 
 error: unnecessary parentheses around pattern
-  --> $DIR/lint-unnecessary-parens.rs:111:8
+  --> $DIR/lint-unnecessary-parens.rs:112:8
    |
 LL |     let( mut _a) = 3;
    |        ^^      ^
@@ -304,7 +304,7 @@ LL +     let mut _a = 3;
    |
 
 error: unnecessary parentheses around pattern
-  --> $DIR/lint-unnecessary-parens.rs:113:8
+  --> $DIR/lint-unnecessary-parens.rs:114:8
    |
 LL |     let(_a) = 3;
    |        ^  ^
@@ -316,7 +316,7 @@ LL +     let _a = 3;
    |
 
 error: unnecessary parentheses around pattern
-  --> $DIR/lint-unnecessary-parens.rs:114:9
+  --> $DIR/lint-unnecessary-parens.rs:115:9
    |
 LL |     let (_a) = 3;
    |         ^  ^
@@ -328,7 +328,7 @@ LL +     let _a = 3;
    |
 
 error: unnecessary parentheses around pattern
-  --> $DIR/lint-unnecessary-parens.rs:115:8
+  --> $DIR/lint-unnecessary-parens.rs:116:8
    |
 LL |     let( _a) = 3;
    |        ^^  ^
@@ -340,7 +340,7 @@ LL +     let _a = 3;
    |
 
 error: unnecessary parentheses around block return value
-  --> $DIR/lint-unnecessary-parens.rs:121:9
+  --> $DIR/lint-unnecessary-parens.rs:122:9
    |
 LL |         (unit!() - One)
    |         ^             ^
@@ -352,7 +352,7 @@ LL +         unit!() - One
    |
 
 error: unnecessary parentheses around block return value
-  --> $DIR/lint-unnecessary-parens.rs:123:9
+  --> $DIR/lint-unnecessary-parens.rs:124:9
    |
 LL |         (unit![] - One)
    |         ^             ^
@@ -364,7 +364,7 @@ LL +         unit![] - One
    |
 
 error: unnecessary parentheses around block return value
-  --> $DIR/lint-unnecessary-parens.rs:126:9
+  --> $DIR/lint-unnecessary-parens.rs:127:9
    |
 LL |         (unit! {} - One)
    |         ^              ^
@@ -375,5 +375,29 @@ LL -         (unit! {} - One)
 LL +         unit! {} - One
    |
 
-error: aborting due to 31 previous errors
+error: unnecessary parentheses around assigned value
+  --> $DIR/lint-unnecessary-parens.rs:132:14
+   |
+LL |     let _r = (&x);
+   |              ^  ^
+   |
+help: remove these parentheses
+   |
+LL -     let _r = (&x);
+LL +     let _r = &x;
+   |
+
+error: unnecessary parentheses around assigned value
+  --> $DIR/lint-unnecessary-parens.rs:133:14
+   |
+LL |     let _r = (&mut x);
+   |              ^      ^
+   |
+help: remove these parentheses
+   |
+LL -     let _r = (&mut x);
+LL +     let _r = &mut x;
+   |
+
+error: aborting due to 33 previous errors