fix(linter/eslint/no-useless-concat): see through parenthesized expressions (#27984)

Part of #27982 (the `no-useless-concat` half; the `no-unassigned-vars`
half is in a separate PR).

`get_left` and `get_right` stopped walking at a
`ParenthesizedExpression`, so `'a' + ('b')`, `('a') + 'b'`, and the
outer `+` in `(foo + 'a') + ('b' + 'c')` were never compared as two
string literals. ESTree has no parenthesis nodes, so ESLint flags all of
these. Both helpers now call `without_parentheses()` before and while
following the `+` chain.

### AI disclosure

I used an AI coding assistant to help write this change and its tests. I
reviewed the diff and the snapshot output before opening the PR.

---------

Co-authored-by: Cursor Agent <cursoragent@cursor.com>
Co-authored-by: Rahul Kashyap <itisrmk@users.noreply.github.com>
Co-authored-by: Cameron <cameron.clark@hey.com>

crates/oxc_linter/src/rules/eslint/no_useless_concat.rs

@@ -84,12 +84,12 @@ impl Rule for NoUselessConcat {
 }
 
 fn get_left<'a>(expr: &'a BinaryExpression<'a>) -> &'a Expression<'a> {
-    let mut left = &expr.left;
+    let mut left = expr.left.without_parentheses();
     loop {
         if let Expression::BinaryExpression(binary_expr) = left
             && binary_expr.operator == BinaryOperator::Addition
         {
-            left = &binary_expr.right;
+            left = binary_expr.right.without_parentheses();
             continue;
         }
         break;
@@ -98,12 +98,12 @@ fn get_left<'a>(expr: &'a BinaryExpression<'a>) -> &'a Expression<'a> {
 }
 
 fn get_right<'a>(expr: &'a BinaryExpression<'a>) -> &'a Expression<'a> {
-    let mut right = &expr.right;
+    let mut right = expr.right.without_parentheses();
     loop {
         if let Expression::BinaryExpression(binary_expr) = right
             && binary_expr.operator == BinaryOperator::Addition
         {
-            right = &binary_expr.left;
+            right = binary_expr.left.without_parentheses();
             continue;
         }
         break;
@@ -147,6 +147,7 @@ fn test() {
         "foo['a'] + foo['b']",
         "`${1 + 1}`",
         "`${'1' + 1}`",
+        "'a' +\n('b')",
     ];
 
     let fail = vec![
@@ -167,6 +168,15 @@ fn test() {
         "'a' + 'b' + 'c' + 'd' + 'e' + foo",
         "`${'a' + 'b'}` + 'c'",
         "foo['a' + 'b']",
+        "var a = 'a' + ('b');\nvar b = ('a') + 'b';\nvar c = (foo + 'a') + ('b' + 'c');",
+        "'a' + ('b')",
+        "('a') + 'b'",
+        "('a') + ('b')",
+        "((('a'))) + 'b'",
+        "(foo + 'a') + 'b'",
+        "'a' + ('b' + 'c')",
+        "foo + ('a' + 'b')",
+        "'a' + ('b' + foo)",
     ];
 
     // TODO: Implement a suggestion for this rule.

crates/oxc_linter/src/snapshots/eslint_no_useless_concat.snap

@@ -38,6 +38,13 @@ source: crates/oxc_linter/src/tester.rs
    ╰────
   help: Rewrite into one string literal.
 
+  ⚠ eslint(no-useless-concat): Unexpected string concatenation of literals.
+   ╭─[no_useless_concat.tsx:1:8]
+ 1 │ (foo + 'a') + ('b' + 'c')
+   ·        ───────────
+   ╰────
+  help: Rewrite into one string literal.
+
   ⚠ eslint(no-useless-concat): Unexpected string concatenation of literals.
    ╭─[no_useless_concat.tsx:1:16]
  1 │ (foo + 'a') + ('b' + 'c')
@@ -130,3 +137,99 @@ source: crates/oxc_linter/src/tester.rs
    ·     ─────────
    ╰────
   help: Rewrite into one string literal.
+
+  ⚠ eslint(no-useless-concat): Unexpected string concatenation of literals.
+   ╭─[no_useless_concat.tsx:1:9]
+ 1 │ var a = 'a' + ('b');
+   ·         ──────────
+ 2 │ var b = ('a') + 'b';
+   ╰────
+  help: Rewrite into one string literal.
+
+  ⚠ eslint(no-useless-concat): Unexpected string concatenation of literals.
+   ╭─[no_useless_concat.tsx:2:10]
+ 1 │ var a = 'a' + ('b');
+ 2 │ var b = ('a') + 'b';
+   ·          ──────────
+ 3 │ var c = (foo + 'a') + ('b' + 'c');
+   ╰────
+  help: Rewrite into one string literal.
+
+  ⚠ eslint(no-useless-concat): Unexpected string concatenation of literals.
+   ╭─[no_useless_concat.tsx:3:16]
+ 2 │ var b = ('a') + 'b';
+ 3 │ var c = (foo + 'a') + ('b' + 'c');
+   ·                ───────────
+   ╰────
+  help: Rewrite into one string literal.
+
+  ⚠ eslint(no-useless-concat): Unexpected string concatenation of literals.
+   ╭─[no_useless_concat.tsx:3:24]
+ 2 │ var b = ('a') + 'b';
+ 3 │ var c = (foo + 'a') + ('b' + 'c');
+   ·                        ─────────
+   ╰────
+  help: Rewrite into one string literal.
+
+  ⚠ eslint(no-useless-concat): Unexpected string concatenation of literals.
+   ╭─[no_useless_concat.tsx:1:1]
+ 1 │ 'a' + ('b')
+   · ──────────
+   ╰────
+  help: Rewrite into one string literal.
+
+  ⚠ eslint(no-useless-concat): Unexpected string concatenation of literals.
+   ╭─[no_useless_concat.tsx:1:2]
+ 1 │ ('a') + 'b'
+   ·  ──────────
+   ╰────
+  help: Rewrite into one string literal.
+
+  ⚠ eslint(no-useless-concat): Unexpected string concatenation of literals.
+   ╭─[no_useless_concat.tsx:1:2]
+ 1 │ ('a') + ('b')
+   ·  ───────────
+   ╰────
+  help: Rewrite into one string literal.
+
+  ⚠ eslint(no-useless-concat): Unexpected string concatenation of literals.
+   ╭─[no_useless_concat.tsx:1:4]
+ 1 │ ((('a'))) + 'b'
+   ·    ────────────
+   ╰────
+  help: Rewrite into one string literal.
+
+  ⚠ eslint(no-useless-concat): Unexpected string concatenation of literals.
+   ╭─[no_useless_concat.tsx:1:8]
+ 1 │ (foo + 'a') + 'b'
+   ·        ──────────
+   ╰────
+  help: Rewrite into one string literal.
+
+  ⚠ eslint(no-useless-concat): Unexpected string concatenation of literals.
+   ╭─[no_useless_concat.tsx:1:1]
+ 1 │ 'a' + ('b' + 'c')
+   · ──────────
+   ╰────
+  help: Rewrite into one string literal.
+
+  ⚠ eslint(no-useless-concat): Unexpected string concatenation of literals.
+   ╭─[no_useless_concat.tsx:1:8]
+ 1 │ 'a' + ('b' + 'c')
+   ·        ─────────
+   ╰────
+  help: Rewrite into one string literal.
+
+  ⚠ eslint(no-useless-concat): Unexpected string concatenation of literals.
+   ╭─[no_useless_concat.tsx:1:8]
+ 1 │ foo + ('a' + 'b')
+   ·        ─────────
+   ╰────
+  help: Rewrite into one string literal.
+
+  ⚠ eslint(no-useless-concat): Unexpected string concatenation of literals.
+   ╭─[no_useless_concat.tsx:1:1]
+ 1 │ 'a' + ('b' + foo)
+   · ──────────
+   ╰────
+  help: Rewrite into one string literal.