From 1ff71e51111a20f8f22b8fa2dd2aa078825a8d2c Mon Sep 17 00:00:00 2001
From: dcode <dcode@dcode.io>
Date: Fri, 6 Jan 2023 23:50:00 +0100
Subject: [PATCH] fix: Support trailing comma in function type parameters
 (#2608)

---
 src/parser.ts                            | 1 +
 tests/parser/function-type.ts            | 1 +
 tests/parser/function-type.ts.fixture.ts | 1 +
 3 files changed, 3 insertions(+)

diff --git a/src/parser.ts b/src/parser.ts
index 166c3d4132..cade050161 100644
--- a/src/parser.ts
+++ b/src/parser.ts
@@ -797,6 +797,7 @@ export class Parser extends DiagnosticEmitter {
           }
         } else {
           if (isSignature) {
+            if (tn.peek() == Token.CloseParen) break; // allow trailing comma
             this.error(
               DiagnosticCode.Identifier_expected,
               tn.range()
diff --git a/tests/parser/function-type.ts b/tests/parser/function-type.ts
index 4c9a385fe5..f547cdeefa 100644
--- a/tests/parser/function-type.ts
+++ b/tests/parser/function-type.ts
@@ -3,3 +3,4 @@ var b: (a: i32, b: i32) => void;
 var c: (a: i32, b: i32) => (a: i32, b: i32) => void;
 var d: (a: i32, a: i32) => void; // NOTE: duplicates in type signatures doesn't in TypeScript
 var e: (a) => void; // TS1110
+var f: (a: i32, b: i32,) => (a: i32, b: i32,) => void;
diff --git a/tests/parser/function-type.ts.fixture.ts b/tests/parser/function-type.ts.fixture.ts
index 061e00711d..e4e6aa7888 100644
--- a/tests/parser/function-type.ts.fixture.ts
+++ b/tests/parser/function-type.ts.fixture.ts
@@ -3,4 +3,5 @@ var b: (a: i32, b: i32) => void;
 var c: (a: i32, b: i32) => (a: i32, b: i32) => void;
 var d: (a: i32, a: i32) => void;
 var e: (a) => void;
+var f: (a: i32, b: i32) => (a: i32, b: i32) => void;
 // ERROR 1110: "Type expected." in function-type.ts(5,10+0)