[clang] [Clang] Correctly handle allocations in the condition of a `if constexpr` (PR #146890)

[Erich Keane via cfe-commits]

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@@ -1931,15 +1931,13 @@ Parser::ParseCXXCondition(StmtResult *InitStmt, SourceLocation Loc,
       return ParseCXXCondition(nullptr, Loc, CK, MissingOK);
     }
 
-    ExprResult Expr = [&] {
-      EnterExpressionEvaluationContext Eval(
-          Actions, Sema::ExpressionEvaluationContext::ConstantEvaluated,
-          /*LambdaContextDecl=*/nullptr,
-          /*ExprContext=*/Sema::ExpressionEvaluationContextRecord::EK_Other,
-          /*ShouldEnter=*/CK == Sema::ConditionKind::ConstexprIf);
-      // Parse the expression.
-      return ParseExpression(); // expression
-    }();
+    EnterExpressionEvaluationContext Eval(
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erichkeane wrote:

Ah, I see!  Though, this covers the `InitStmt`/`ParseCXXCondition` as well.  It isn't 100% clear to me what THAT does here (looks like it is for an init statement?).  I wonder if this doesn't cover that right.  I would imagine the eval context THEN needs to cover the condition after that?  

https://github.com/llvm/llvm-project/pull/146890