Rollup merge of #107539 - PossiblyAShrub:unused-parens-in-index, r=lcnr

Emit warnings on unused parens in index expressions

Fixes: #96606.

I am not sure what the best term for "index expression" is. Is there a better term we could use?

2 files changed, 41 insertions, 0 deletions

diff --git a/tests/ui/lint/unused/issue-96606.rs b/tests/ui/lint/unused/issue-96606.rs
new file mode 100644
index 00000000000..4e7c290fa2a
--- /dev/null
+++ b/tests/ui/lint/unused/issue-96606.rs
@@ -0,0 +1,8 @@
+#[deny(unused)]
+fn main() {
+    let arr = [0; 10];
+    let _ = arr[(0)]; //~ ERROR unnecessary parentheses around index expression
+    let _ = arr[{0}]; //~ ERROR unnecessary braces around index expression
+    let _ = arr[1 + (0)];
+    let _ = arr[{ let x = 0; x }];
+}
diff --git a/tests/ui/lint/unused/issue-96606.stderr b/tests/ui/lint/unused/issue-96606.stderr
new file mode 100644
index 00000000000..e3627718116
--- /dev/null
+++ b/tests/ui/lint/unused/issue-96606.stderr
@@ -0,0 +1,33 @@
+error: unnecessary parentheses around index expression
+  --> $DIR/issue-96606.rs:4:17
+   |
+LL |     let _ = arr[(0)];
+   |                 ^ ^
+   |
+note: the lint level is defined here
+  --> $DIR/issue-96606.rs:1:8
+   |
+LL | #[deny(unused)]
+   |        ^^^^^^
+   = note: `#[deny(unused_parens)]` implied by `#[deny(unused)]`
+help: remove these parentheses
+   |
+LL -     let _ = arr[(0)];
+LL +     let _ = arr[0];
+   |
+
+error: unnecessary braces around index expression
+  --> $DIR/issue-96606.rs:5:17
+   |
+LL |     let _ = arr[{0}];
+   |                 ^ ^
+   |
+   = note: `#[deny(unused_braces)]` implied by `#[deny(unused)]`
+help: remove these braces
+   |
+LL -     let _ = arr[{0}];
+LL +     let _ = arr[0];
+   |
+
+error: aborting due to 2 previous errors
+