From c33f83ac9b80b2a38d208128c89f1b908ce6257d Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Mateusz=20Burzy=C5=84ski?= <mateuszburzynski@gmail.com>
Date: Mon, 30 Jun 2025 20:14:10 +0200
Subject: [PATCH] Fixed a printer crash caused by empty parameter modifiers
 (#60537)

---
 src/compiler/expressionToTypeNode.ts          |  2 +-
 ...sMembersWithInferredFunctionReturnType1.ts | 31 +++++++++++++++++++
 2 files changed, 32 insertions(+), 1 deletion(-)
 create mode 100644 tests/cases/fourslash/completionEntryClassMembersWithInferredFunctionReturnType1.ts

diff --git a/src/compiler/expressionToTypeNode.ts b/src/compiler/expressionToTypeNode.ts
index bb3db3bd0cc..0df3a399b8f 100644
--- a/src/compiler/expressionToTypeNode.ts
+++ b/src/compiler/expressionToTypeNode.ts
@@ -1113,7 +1113,7 @@ export function createSyntacticTypeNodeBuilder(
     function ensureParameter(p: ParameterDeclaration, context: SyntacticTypeNodeBuilderContext) {
         return factory.updateParameterDeclaration(
             p,
-            [],
+            /*modifiers*/ undefined,
             reuseNode(context, p.dotDotDotToken),
             resolver.serializeNameOfParameter(context, p),
             resolver.isOptionalParameter(p) ? factory.createToken(SyntaxKind.QuestionToken) : undefined,
diff --git a/tests/cases/fourslash/completionEntryClassMembersWithInferredFunctionReturnType1.ts b/tests/cases/fourslash/completionEntryClassMembersWithInferredFunctionReturnType1.ts
new file mode 100644
index 00000000000..902022da8a1
--- /dev/null
+++ b/tests/cases/fourslash/completionEntryClassMembersWithInferredFunctionReturnType1.ts
@@ -0,0 +1,31 @@
+///<reference path="fourslash.ts" />
+
+// @filename: /tokenizer.ts
+//// export default abstract class Tokenizer {
+////   errorBuilder() {
+////     return (pos: number, lineStart: number, curLine: number) => {};
+////   }
+//// }
+
+// @filename: /expression.ts
+//// import Tokenizer from "./tokenizer.js";
+////
+//// export default abstract class ExpressionParser extends Tokenizer {
+////   /**/
+//// }
+
+verify.completions({
+  marker: "",
+  includes: [
+    {
+      name: "errorBuilder",
+      insertText: "errorBuilder(): (pos: number, lineStart: number, curLine: number) => void {\n}",
+      filterText: "errorBuilder",
+    },
+  ],
+  preferences: {
+    includeCompletionsWithInsertText: true,
+    includeCompletionsWithClassMemberSnippets: true,
+  },
+  isNewIdentifierLocation: true,
+});