[clang] [Clang] use constant evaluation context for constexpr if conditions (PR #123667)

[Oleksandr T. via cfe-commits]

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@@ -2203,8 +2203,18 @@ Parser::ParseCXXCondition(StmtResult *InitStmt, SourceLocation Loc,
       return ParseCXXCondition(nullptr, Loc, CK, MissingOK);
     }
 
-    // Parse the expression.
-    ExprResult Expr = ParseExpression(); // expression
+    ExprResult Expr;
+    {
+      EnterExpressionEvaluationContext Eval(
+          Actions, Sema::ExpressionEvaluationContext::ConstantEvaluated,
+          /*LambdaContextDecl=*/nullptr,
+          /*ExprContext=*/Sema::ExpressionEvaluationContextRecord::EK_Other,
+          /*ShouldEnter=*/CK == Sema::ConditionKind::ConstexprIf);
+
+      // Parse the expression.
+      Expr = ParseExpression(); // expression
+    }
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a-tarasyuk wrote:

@zyn0217 Thanks for the suggestion. I've added changes.

https://github.com/llvm/llvm-project/pull/123667