fix(formatter): keep parens around await/yield in instantiation expressions (#10758)

henrybrewer00-dotcom · henrybrewer93-design · ematipico · web-flow · commit e36fd8a9f131 · 2026-06-25T07:16:59.000+01:00
Co-authored-by: Henry &lt;henrybrewer93@icloud.com&gt;
Co-authored-by: Emanuele Stoppa &lt;my.burning@gmail.com&gt;
diff --git a/.changeset/fix-instantiation-expression-parens.md b/.changeset/fix-instantiation-expression-parens.md
@@ -0,0 +1,5 @@
+---
+"@biomejs/biome": patch
+---
+
+Fixed [#10697](https://github.com/biomejs/biome/issues/10697): The formatter no longer removes the parentheses around an `await` or `yield` expression used as the target of a TypeScript instantiation expression. For example, `(await makeFactory)<Value>` is no longer reformatted to `await makeFactory<Value>`, which would change the meaning of the code.
diff --git a/crates/biome_js_formatter/tests/specs/ts/expression/instantiation_expression.ts b/crates/biome_js_formatter/tests/specs/ts/expression/instantiation_expression.ts
@@ -0,0 +1,17 @@
+const a = makeFactory<Value>;
+const b = obj.makeFactory<Value>;
+
+// Parentheses around await/yield must be kept, otherwise the type
+// arguments would bind to the inner expression and change the meaning.
+async function withAwait() {
+  const c = (await makeFactory)<Value>;
+}
+
+function* withYield() {
+  const d = (yield* makeFactory)<Value>;
+  const e = (yield makeFactory)<Value>;
+}
+
+// Parentheses around other lower-precedence expressions must be kept too.
+const f = (cond ? a : b)<Value>;
+const g = (x++)<Value>;
diff --git a/crates/biome_js_formatter/tests/specs/ts/expression/instantiation_expression.ts.snap b/crates/biome_js_formatter/tests/specs/ts/expression/instantiation_expression.ts.snap
@@ -0,0 +1,51 @@
+---
+source: crates/biome_formatter_test/src/snapshot_builder.rs
+info: ts/expression/instantiation_expression.ts
+---
+
+# Input
+
+```ts
+const a = makeFactory<Value>;
+const b = obj.makeFactory<Value>;
+
+// Parentheses around await/yield must be kept, otherwise the type
+// arguments would bind to the inner expression and change the meaning.
+async function withAwait() {
+  const c = (await makeFactory)<Value>;
+}
+
+function* withYield() {
+  const d = (yield* makeFactory)<Value>;
+  const e = (yield makeFactory)<Value>;
+}
+
+// Parentheses around other lower-precedence expressions must be kept too.
+const f = (cond ? a : b)<Value>;
+const g = (x++)<Value>;
+
+```
+
+
+# Formatted
+
+```ts
+const a = makeFactory<Value>;
+const b = obj.makeFactory<Value>;
+
+// Parentheses around await/yield must be kept, otherwise the type
+// arguments would bind to the inner expression and change the meaning.
+async function withAwait() {
+	const c = (await makeFactory)<Value>;
+}
+
+function* withYield() {
+	const d = (yield* makeFactory)<Value>;
+	const e = (yield makeFactory)<Value>;
+}
+
+// Parentheses around other lower-precedence expressions must be kept too.
+const f = (cond ? a : b)<Value>;
+const g = (x++)<Value>;
+
+```
diff --git a/crates/biome_js_syntax/src/parentheses/expression.rs b/crates/biome_js_syntax/src/parentheses/expression.rs
@@ -954,6 +954,7 @@ fn update_or_lower_expression_needs_parens(
         parent.kind(),
         JsSyntaxKind::JS_EXTENDS_CLAUSE
             | JsSyntaxKind::TS_NON_NULL_ASSERTION_EXPRESSION
+            | JsSyntaxKind::TS_INSTANTIATION_EXPRESSION
             // Callee
             | JsSyntaxKind::JS_CALL_EXPRESSION
             | JsSyntaxKind::JS_NEW_EXPRESSION

-Original file line number
+Diff line change
@@ @@ -0,0 +1,5 @@ @@
 +---
 +"@biomejs/biome": patch
 +---
++
 +Fixed [#10697](https://github.com/biomejs/biome/issues/10697): The formatter no longer removes the parentheses around an `await` or `yield` expression used as the target of a TypeScript instantiation expression. For example, `(await makeFactory)<Value>` is no longer reformatted to `await makeFactory<Value>`, which would change the meaning of the code.