Improve our handling of lambda expressions that occur within default

arguments. There are two aspects to this:

  - Make sure that when marking the declarations referenced in a
  default argument, we don't try to mark local variables, both because
  it's a waste of time and because the semantics are wrong: we're not
  in a place where we could capture these variables again even if it
  did make sense.
  - When a lambda expression occurs in a default argument of a
  function template, make sure that the corresponding closure type is
  considered dependent, so that it will get properly instantiated. The
  second bit is a bit of a hack; to fix it properly, we may have to
  rearchitect our handling of default arguments, parsing them only
  after creating the function definition. However, I'd like to
  separate that work from the lambdas work.

llvm-svn: 151076

2 files changed, 34 insertions, 7 deletions

diff --git a/clang/lib/Sema/SemaExpr.cpp b/clang/lib/Sema/SemaExpr.cpp
index 1008a3ab431..be3fa6c0dc6 100644
--- a/clang/lib/Sema/SemaExpr.cpp
+++ b/clang/lib/Sema/SemaExpr.cpp
@@ -3146,7 +3146,8 @@ ExprResult Sema::BuildCXXDefaultArgExpr(SourceLocation CallLoc,
   // We already type-checked the argument, so we know it works. 
   // Just mark all of the declarations in this potentially-evaluated expression
   // as being "referenced".
-  MarkDeclarationsReferencedInExpr(Param->getDefaultArg());
+  MarkDeclarationsReferencedInExpr(Param->getDefaultArg(),
+                                   /*SkipLocalVariables=*/true);
   return Owned(CXXDefaultArgExpr::Create(Context, CallLoc, Param));
 }
 
@@ -10145,13 +10146,22 @@ namespace {
   /// potentially-evaluated subexpressions as "referenced".
   class EvaluatedExprMarker : public EvaluatedExprVisitor<EvaluatedExprMarker> {
     Sema &S;
+    bool SkipLocalVariables;
     
   public:
     typedef EvaluatedExprVisitor<EvaluatedExprMarker> Inherited;
     
-    explicit EvaluatedExprMarker(Sema &S) : Inherited(S.Context), S(S) { }
+    EvaluatedExprMarker(Sema &S, bool SkipLocalVariables) 
+      : Inherited(S.Context), S(S), SkipLocalVariables(SkipLocalVariables) { }
     
     void VisitDeclRefExpr(DeclRefExpr *E) {
+      // If we were asked not to visit local variables, don't.
+      if (SkipLocalVariables) {
+        if (VarDecl *VD = dyn_cast<VarDecl>(E->getDecl()))
+          if (VD->hasLocalStorage())
+            return;
+      }
+      
       S.MarkDeclRefReferenced(E);
     }
     
@@ -10193,6 +10203,10 @@ namespace {
     }
     
     void VisitBlockDeclRefExpr(BlockDeclRefExpr *E) {
+      // If we were asked not to visit local variables, don't.
+      if (SkipLocalVariables && E->getDecl()->hasLocalStorage())
+          return;
+
       S.MarkBlockDeclRefReferenced(E);
     }
     
@@ -10211,8 +10225,12 @@ namespace {
 
 /// \brief Mark any declarations that appear within this expression or any
 /// potentially-evaluated subexpressions as "referenced".
-void Sema::MarkDeclarationsReferencedInExpr(Expr *E) {
-  EvaluatedExprMarker(*this).Visit(E);
+///
+/// \param SkipLocalVariables If true, don't mark local variables as 
+/// 'referenced'.
+void Sema::MarkDeclarationsReferencedInExpr(Expr *E, 
+                                            bool SkipLocalVariables) {
+  EvaluatedExprMarker(*this, SkipLocalVariables).Visit(E);
 }
 
 /// \brief Emit a diagnostic that describes an effect on the run-time behavior
diff --git a/clang/lib/Sema/SemaLambda.cpp b/clang/lib/Sema/SemaLambda.cpp
index 694fee67762..42040084e10 100644
--- a/clang/lib/Sema/SemaLambda.cpp
+++ b/clang/lib/Sema/SemaLambda.cpp
@@ -21,14 +21,16 @@
 using namespace clang;
 using namespace sema;
 
-CXXRecordDecl *Sema::createLambdaClosureType(SourceRange IntroducerRange) {
+CXXRecordDecl *Sema::createLambdaClosureType(SourceRange IntroducerRange,
+                                             bool KnownDependent) {
   DeclContext *DC = CurContext;
   while (!(DC->isFunctionOrMethod() || DC->isRecord() || DC->isFileContext()))
     DC = DC->getParent();
   
   // Start constructing the lambda class.
   CXXRecordDecl *Class = CXXRecordDecl::CreateLambda(Context, DC, 
-                                                     IntroducerRange.getBegin());
+                                                     IntroducerRange.getBegin(),
+                                                     KnownDependent);
   DC->addDecl(Class);
   
   return Class;
@@ -142,7 +144,14 @@ void Sema::addLambdaParameters(CXXMethodDecl *CallOperator, Scope *CurScope) {
 void Sema::ActOnStartOfLambdaDefinition(LambdaIntroducer &Intro,
                                         Declarator &ParamInfo,
                                         Scope *CurScope) {
-  CXXRecordDecl *Class = createLambdaClosureType(Intro.Range);
+  // Determine if we're within a context where we know that the lambda will
+  // be dependent, because there are template parameters in scope.
+  bool KnownDependent = false;
+  if (Scope *TmplScope = CurScope->getTemplateParamParent())
+    if (!TmplScope->decl_empty())
+      KnownDependent = true;
+  
+  CXXRecordDecl *Class = createLambdaClosureType(Intro.Range, KnownDependent);
   
   // Determine the signature of the call operator.
   TypeSourceInfo *MethodTyInfo;