fix(js_formatter): keep parens around infer in unions/intersections

biomejs · Jul 16, 2024 · d30c173 · d30c173
1 parent 46ab996
commit d30c173
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diff --git a/CHANGELOG.md b/CHANGELOG.md
@@ -40,6 +40,10 @@ our [guidelines for writing a good changelog entry](https://github.com/biomejs/b
 
 ### Formatter
 
+#### Bug fixes
+
+- Keep the parentheses around `infer` declarations in type unions and type intersections ([#3419](https://github.com/biomejs/biome/issues/3419)). Contributed by @Conaclos
+
 ### JavaScript APIs
 
 ### Linter

diff --git a/crates/biome_js_formatter/src/ts/types/infer_type.rs b/crates/biome_js_formatter/src/ts/types/infer_type.rs
@@ -33,6 +33,12 @@ impl NeedsParentheses for TsInferType {
     fn needs_parentheses_with_parent(&self, parent: &JsSyntaxNode) -> bool {
         if parent.kind() == JsSyntaxKind::TS_REST_TUPLE_TYPE_ELEMENT {
             false
+        } else if matches!(
+            parent.kind(),
+            JsSyntaxKind::TS_INTERSECTION_TYPE_ELEMENT_LIST
+                | JsSyntaxKind::TS_UNION_TYPE_VARIANT_LIST
+        ) {
+            true
         } else {
             operator_type_or_higher_needs_parens(self.syntax(), parent)
         }
@@ -64,6 +70,10 @@ mod tests {
             "type A = T extends [(infer string)?] ? string : never",
             TsInferType
         );
+        assert_needs_parentheses!(
+            "type A = T extends [(infer string) | undefined] ? string : never",
+            TsInferType
+        );
 
         assert_needs_parentheses!(
             "type A = T extends (infer string)[a] ? string : never",