[clang] [Clang] prevent crash in delayed default-argument lambda captures (PR #176749)

[Oleksandr Tarasiuk via cfe-commits]

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@@ -417,6 +417,15 @@ void Parser::ParseLexedMethodDeclaration(LateParsedMethodDeclaration &LM) {
           Actions,
           Sema::ExpressionEvaluationContext::PotentiallyEvaluatedIfUsed, Param);
 
+      // Delayed default arguments may contain lambdas, e.g.
+      //   struct S {
+      //     void ICE(int x, int = sizeof([x] { return x; }()));
+      //   }
+      // Lambda capture handling in tryCaptureVariable() expects an enclosing
+      // function scope in Sema's FunctionScopes stack.
+      Sema::FunctionScopeRAII PopFnContext(Actions);
+      Actions.PushFunctionScope();
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a-tarasyuk wrote:

@AaronBallman Thanks. I’ve moved it outside the loop.

https://github.com/llvm/llvm-project/pull/176749