From a591ca3fdcf056fbb70d4b4a964c8dd47bd412b4 Mon Sep 17 00:00:00 2001
From: "Oleksandr T." <oleksandr.tarasiuk@outlook.com>
Date: Fri, 6 Jun 2025 02:37:40 +0300
Subject: [PATCH] fix(61747): for (using of = is incorrectly parsed (#61764)

---
 src/compiler/parser.ts                            |  9 ++++++++-
 .../usingDeclarationsInForOf.4.errors.txt         | 10 ++++++++++
 .../reference/usingDeclarationsInForOf.4.js       | 15 +++++++++++++++
 .../usingDeclarationsInForOf.4.ts                 |  8 ++++++++
 4 files changed, 41 insertions(+), 1 deletion(-)
 create mode 100644 tests/baselines/reference/usingDeclarationsInForOf.4.errors.txt
 create mode 100644 tests/baselines/reference/usingDeclarationsInForOf.4.js
 create mode 100644 tests/cases/conformance/statements/VariableStatements/usingDeclarations/usingDeclarationsInForOf.4.ts

diff --git a/src/compiler/parser.ts b/src/compiler/parser.ts
index 8c69cccba12..e7df1250364 100644
--- a/src/compiler/parser.ts
+++ b/src/compiler/parser.ts
@@ -7328,9 +7328,16 @@ namespace Parser {
         return nextTokenIsBindingIdentifierOrStartOfDestructuringOnSameLine(/*disallowOf*/ true);
     }
 
+    function nextTokenIsEqualsOrSemicolonOrColonToken() {
+        nextToken();
+        return token() === SyntaxKind.EqualsToken || token() === SyntaxKind.SemicolonToken || token() === SyntaxKind.ColonToken;
+    }
+
     function nextTokenIsBindingIdentifierOrStartOfDestructuringOnSameLine(disallowOf?: boolean) {
         nextToken();
-        if (disallowOf && token() === SyntaxKind.OfKeyword) return false;
+        if (disallowOf && token() === SyntaxKind.OfKeyword) {
+            return lookAhead(nextTokenIsEqualsOrSemicolonOrColonToken);
+        }
         return (isBindingIdentifier() || token() === SyntaxKind.OpenBraceToken) && !scanner.hasPrecedingLineBreak();
     }
 
diff --git a/tests/baselines/reference/usingDeclarationsInForOf.4.errors.txt b/tests/baselines/reference/usingDeclarationsInForOf.4.errors.txt
new file mode 100644
index 00000000000..2f75f6f5beb
--- /dev/null
+++ b/tests/baselines/reference/usingDeclarationsInForOf.4.errors.txt
@@ -0,0 +1,10 @@
+usingDeclarationsInForOf.4.ts(3,12): error TS1155: 'using' declarations must be initialized.
+
+
+==== usingDeclarationsInForOf.4.ts (1 errors) ====
+    for (using of = null;;) break;
+    for (using of: null = null;;) break;
+    for (using of;;) break;
+               ~~
+!!! error TS1155: 'using' declarations must be initialized.
+    
\ No newline at end of file
diff --git a/tests/baselines/reference/usingDeclarationsInForOf.4.js b/tests/baselines/reference/usingDeclarationsInForOf.4.js
new file mode 100644
index 00000000000..f16eec71148
--- /dev/null
+++ b/tests/baselines/reference/usingDeclarationsInForOf.4.js
@@ -0,0 +1,15 @@
+//// [tests/cases/conformance/statements/VariableStatements/usingDeclarations/usingDeclarationsInForOf.4.ts] ////
+
+//// [usingDeclarationsInForOf.4.ts]
+for (using of = null;;) break;
+for (using of: null = null;;) break;
+for (using of;;) break;
+
+
+//// [usingDeclarationsInForOf.4.js]
+for (using of = null;;)
+    break;
+for (using of = null;;)
+    break;
+for (using of;;)
+    break;
diff --git a/tests/cases/conformance/statements/VariableStatements/usingDeclarations/usingDeclarationsInForOf.4.ts b/tests/cases/conformance/statements/VariableStatements/usingDeclarations/usingDeclarationsInForOf.4.ts
new file mode 100644
index 00000000000..359a01d2b06
--- /dev/null
+++ b/tests/cases/conformance/statements/VariableStatements/usingDeclarations/usingDeclarationsInForOf.4.ts
@@ -0,0 +1,8 @@
+// @target: esnext
+// @module: esnext
+// @lib: esnext
+// @noTypesAndSymbols: true
+
+for (using of = null;;) break;
+for (using of: null = null;;) break;
+for (using of;;) break;