Fix an edge case of mangling involving the combination of a lambda and typeid.

typeid (and a couple other non-standard places where we can transform an
unevaluated expression into an evaluated expression) is special
because it introduces an an expression evaluation context,
which conflicts with the mechanism to compute the current
lambda mangling context.  PR12123.

I would appreciate if someone would double-check that we get the mangling
correct with this patch.

llvm-svn: 164658

clang/include/clang/Sema/Sema.h

@@ -2721,7 +2721,10 @@ public:
   void PushExpressionEvaluationContext(ExpressionEvaluationContext NewContext,
                                        Decl *LambdaContextDecl = 0,
                                        bool IsDecltype = false);
-
+  enum ReuseLambdaContextDecl_t { ReuseLambdaContextDecl };
+  void PushExpressionEvaluationContext(ExpressionEvaluationContext NewContext,
+                                       ReuseLambdaContextDecl_t,
+                                       bool IsDecltype = false);
   void PopExpressionEvaluationContext();
 
   void DiscardCleanupsInEvaluationContext();
@@ -7295,6 +7298,15 @@ public:
     Actions.PushExpressionEvaluationContext(NewContext, LambdaContextDecl,
                                             IsDecltype);
   }
+  EnterExpressionEvaluationContext(Sema &Actions,
+                                   Sema::ExpressionEvaluationContext NewContext,
+                                   Sema::ReuseLambdaContextDecl_t,
+                                   bool IsDecltype = false)
+    : Actions(Actions) {
+    Actions.PushExpressionEvaluationContext(NewContext, 
+                                            Sema::ReuseLambdaContextDecl,
+                                            IsDecltype);
+  }
 
   ~EnterExpressionEvaluationContext() {
     Actions.PopExpressionEvaluationContext();

clang/lib/Parse/ParseDecl.cpp

@@ -5078,7 +5078,8 @@ void Parser::ParseTypeofSpecifier(DeclSpec &DS) {
 
   const bool hasParens = Tok.is(tok::l_paren);
 
-  EnterExpressionEvaluationContext Unevaluated(Actions, Sema::Unevaluated);
+  EnterExpressionEvaluationContext Unevaluated(Actions, Sema::Unevaluated,
+                                               Sema::ReuseLambdaContextDecl);
 
   bool isCastExpr;
   ParsedType CastTy;

clang/lib/Parse/ParseExpr.cpp

@@ -1723,7 +1723,8 @@ ExprResult Parser::ParseUnaryExprOrTypeTraitExpression() {
   if (OpTok.is(tok::kw_alignof) || OpTok.is(tok::kw__Alignof))
     Diag(OpTok, diag::warn_cxx98_compat_alignof);
 
-  EnterExpressionEvaluationContext Unevaluated(Actions, Sema::Unevaluated);
+  EnterExpressionEvaluationContext Unevaluated(Actions, Sema::Unevaluated,
+                                               Sema::ReuseLambdaContextDecl);
 
   bool isCastExpr;
   ParsedType CastTy;

clang/lib/Parse/ParseExprCXX.cpp

@@ -1001,7 +1001,8 @@ ExprResult Parser::ParseCXXTypeid() {
   // We enter the unevaluated context before trying to determine whether we
   // have a type-id, because the tentative parse logic will try to resolve
   // names, and must treat them as unevaluated.
-  EnterExpressionEvaluationContext Unevaluated(Actions, Sema::Unevaluated);
+  EnterExpressionEvaluationContext Unevaluated(Actions, Sema::Unevaluated,
+                                               Sema::ReuseLambdaContextDecl);
 
   if (isTypeIdInParens()) {
     TypeResult Ty = ParseTypeName();

clang/lib/Sema/SemaExpr.cpp

@@ -10135,6 +10135,14 @@ Sema::PushExpressionEvaluationContext(ExpressionEvaluationContext NewContext,
     std::swap(MaybeODRUseExprs, ExprEvalContexts.back().SavedMaybeODRUseExprs);
 }
 
+void
+Sema::PushExpressionEvaluationContext(ExpressionEvaluationContext NewContext,
+                                      ReuseLambdaContextDecl_t,
+                                      bool IsDecltype) {
+  Decl *LambdaContextDecl = ExprEvalContexts.back().LambdaContextDecl;
+  PushExpressionEvaluationContext(NewContext, LambdaContextDecl, IsDecltype);
+}
+
 void Sema::PopExpressionEvaluationContext() {
   ExpressionEvaluationContextRecord& Rec = ExprEvalContexts.back();
 

clang/lib/Sema/TreeTransform.h

@@ -4275,7 +4275,8 @@ template<typename Derived>
 QualType TreeTransform<Derived>::TransformTypeOfExprType(TypeLocBuilder &TLB,
                                                       TypeOfExprTypeLoc TL) {
   // typeof expressions are not potentially evaluated contexts
-  EnterExpressionEvaluationContext Unevaluated(SemaRef, Sema::Unevaluated);
+  EnterExpressionEvaluationContext Unevaluated(SemaRef, Sema::Unevaluated,
+                                               Sema::ReuseLambdaContextDecl);
 
   ExprResult E = getDerived().TransformExpr(TL.getUnderlyingExpr());
   if (E.isInvalid())
@@ -6266,7 +6267,8 @@ TreeTransform<Derived>::TransformUnaryExprOrTypeTraitExpr(
   // C++0x [expr.sizeof]p1:
   //   The operand is either an expression, which is an unevaluated operand
   //   [...]
-  EnterExpressionEvaluationContext Unevaluated(SemaRef, Sema::Unevaluated);
+  EnterExpressionEvaluationContext Unevaluated(SemaRef, Sema::Unevaluated,
+                                               Sema::ReuseLambdaContextDecl);
 
   ExprResult SubExpr = getDerived().TransformExpr(E->getArgumentExpr());
   if (SubExpr.isInvalid())
@@ -7002,7 +7004,8 @@ TreeTransform<Derived>::TransformCXXTypeidExpr(CXXTypeidExpr *E) {
   // after we perform semantic analysis.  We speculatively assume it is
   // unevaluated; it will get fixed later if the subexpression is in fact
   // potentially evaluated.
-  EnterExpressionEvaluationContext Unevaluated(SemaRef, Sema::Unevaluated);
+  EnterExpressionEvaluationContext Unevaluated(SemaRef, Sema::Unevaluated,
+                                               Sema::ReuseLambdaContextDecl);
 
   ExprResult SubExpr = getDerived().TransformExpr(E->getExprOperand());
   if (SubExpr.isInvalid())

clang/test/CodeGenCXX/mangle-lambdas.cpp

@@ -172,6 +172,19 @@ template<typename...T> int PR12917<T...>::n[3] = {
 PR12917<int, char, double> pr12917;
 int *pr12917_p = PR12917<int, int>::n;
 
+namespace std {
+  struct type_info;
+}
+namespace PR12123 {
+  struct A { virtual ~A(); } g;
+  struct B {
+    void f(const std::type_info& x = typeid([]()->A& { return g; }()));
+    void h();
+  };
+  void B::h() { f(); }
+}
+// CHECK: define linkonce_odr %"struct.PR12123::A"* @_ZZN7PR121231B1fERKSt9type_infoEd_NKUlvE_clEv
+
 namespace PR12808 {
   template <typename> struct B {
     int a;