From 945d8dd3c4cea58f3d9f36e8fa123137f64e180e Mon Sep 17 00:00:00 2001
From: Yong He <yonghe@outlook.com>
Date: Tue, 10 Dec 2024 03:47:16 -0800
Subject: Fix parsing logic of for loops' initial statement. (#5813)

---
 source/slang/slang-parser.cpp | 21 ++++++++++++---------
 1 file changed, 12 insertions(+), 9 deletions(-)

(limited to 'source/slang/slang-parser.cpp')

diff --git a/source/slang/slang-parser.cpp b/source/slang/slang-parser.cpp
index 172e3130f..4dc962ce6 100644
--- a/source/slang/slang-parser.cpp
+++ b/source/slang/slang-parser.cpp
@@ -5953,22 +5953,25 @@ ForStmt* Parser::ParseForStatement()
     FillPosition(stmt);
     ReadToken("for");
     ReadToken(TokenType::LParent);
-    auto modifiers = ParseModifiers(this);
-    if (peekTypeName(this) || !modifiers.isEmpty())
-    {
-        stmt->initialStatement = parseVarDeclrStatement(modifiers);
-    }
-    else
+    if (!LookAheadToken(TokenType::Semicolon))
     {
-        if (!LookAheadToken(TokenType::Semicolon))
+        stmt->initialStatement = ParseStatement();
+        if (as<DeclStmt>(stmt->initialStatement) || as<ExpressionStmt>(stmt->initialStatement))
         {
-            stmt->initialStatement = ParseExpressionStatement();
+            // These are the only allowed form of initial statements of a for loop.
         }
         else
         {
-            ReadToken(TokenType::Semicolon);
+            sink->diagnose(
+                stmt->initialStatement->loc,
+                Diagnostics::unexpectedTokenExpectedTokenType,
+                "expression");
         }
     }
+    else
+    {
+        ReadToken(TokenType::Semicolon);
+    }
     if (!LookAheadToken(TokenType::Semicolon))
         stmt->predicateExpression = ParseExpression();
     ReadToken(TokenType::Semicolon);
-- 
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