Finish implementing 'selected constructor' rules for triviality in C++11. In

the cases where we can't determine whether special members would be trivial
while building the class, we eagerly declare those special members. The impact
of this is bounded, since it does not trigger implicit declarations of special
members in classes which merely *use* those classes.

In order to determine whether we need to apply this rule, we also need to
eagerly declare move operations and destructors in cases where they might be
deleted. If a move operation were supposed to be deleted, it would instead
be suppressed, and we could need overload resolution to determine if we fall
back to a trivial copy operation. If a destructor were implicitly deleted,
it would cause the move constructor of any derived classes to be suppressed.

As discussed on cxx-abi-dev, C++11's selected constructor rules are also
retroactively applied as a defect resolution in C++03 mode, in order to
identify that class B has a non-trivial copy constructor (since it calls
A's constructor template, not A's copy constructor):

struct A { template<typename T> A(T &); };
struct B { mutable A a; };


git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@169673 91177308-0d34-0410-b5e6-96231b3b80d8

1 files changed, 81 insertions, 49 deletions

diff --git a/lib/Sema/SemaDeclCXX.cpp b/lib/Sema/SemaDeclCXX.cpp
index 8666453c31..5cca43b548 100644
--- a/lib/Sema/SemaDeclCXX.cpp
+++ b/lib/Sema/SemaDeclCXX.cpp
@@ -5036,12 +5036,6 @@ void Sema::DiagnoseNontrivial(const CXXRecordDecl *RD, CXXSpecialMember CSM) {
 /// C++11 [class.copy]p25, and C++11 [class.dtor]p5.
 bool Sema::SpecialMemberIsTrivial(CXXMethodDecl *MD, CXXSpecialMember CSM,
                                   bool Diagnose) {
-  // Note that we can't work out CSM for ourselves. Consider this:
-  //
-  //   struct S { S(int); S(const S&=0) = delete; };
-  //
-  // The same function is a trivial copy constructor but a non-trivial default
-  // constructor.
   assert(!MD->isUserProvided() && CSM != CXXInvalid && "not special enough");
 
   CXXRecordDecl *RD = MD->getParent();
@@ -5337,20 +5331,32 @@ void Sema::AddImplicitlyDeclaredMembersToClass(CXXRecordDecl *ClassDecl) {
   if (!ClassDecl->hasUserDeclaredConstructor())
     ++ASTContext::NumImplicitDefaultConstructors;
 
-  if (!ClassDecl->hasUserDeclaredCopyConstructor())
+  if (!ClassDecl->hasUserDeclaredCopyConstructor()) {
     ++ASTContext::NumImplicitCopyConstructors;
 
-  if (getLangOpts().CPlusPlus0x && ClassDecl->needsImplicitMoveConstructor())
+    // If the properties or semantics of the copy constructor couldn't be
+    // determined while the class was being declared, force a declaration
+    // of it now.
+    if (ClassDecl->needsOverloadResolutionForCopyConstructor())
+      DeclareImplicitCopyConstructor(ClassDecl);
+  }
+
+  if (getLangOpts().CPlusPlus0x && ClassDecl->needsImplicitMoveConstructor()) {
     ++ASTContext::NumImplicitMoveConstructors;
 
+    if (ClassDecl->needsOverloadResolutionForMoveConstructor())
+      DeclareImplicitMoveConstructor(ClassDecl);
+  }
+
   if (!ClassDecl->hasUserDeclaredCopyAssignment()) {
     ++ASTContext::NumImplicitCopyAssignmentOperators;
-    
-    // If we have a dynamic class, then the copy assignment operator may be 
+
+    // If we have a dynamic class, then the copy assignment operator may be
     // virtual, so we have to declare it immediately. This ensures that, e.g.,
-    // it shows up in the right place in the vtable and that we diagnose 
-    // problems with the implicit exception specification.    
-    if (ClassDecl->isDynamicClass())
+    // it shows up in the right place in the vtable and that we diagnose
+    // problems with the implicit exception specification.
+    if (ClassDecl->isDynamicClass() ||
+        ClassDecl->needsOverloadResolutionForCopyAssignment())
       DeclareImplicitCopyAssignment(ClassDecl);
   }
 
@@ -5358,18 +5364,20 @@ void Sema::AddImplicitlyDeclaredMembersToClass(CXXRecordDecl *ClassDecl) {
     ++ASTContext::NumImplicitMoveAssignmentOperators;
 
     // Likewise for the move assignment operator.
-    if (ClassDecl->isDynamicClass())
+    if (ClassDecl->isDynamicClass() ||
+        ClassDecl->needsOverloadResolutionForMoveAssignment())
       DeclareImplicitMoveAssignment(ClassDecl);
   }
 
   if (!ClassDecl->hasUserDeclaredDestructor()) {
     ++ASTContext::NumImplicitDestructors;
-    
-    // If we have a dynamic class, then the destructor may be virtual, so we 
+
+    // If we have a dynamic class, then the destructor may be virtual, so we
     // have to declare the destructor immediately. This ensures that, e.g., it
     // shows up in the right place in the vtable and that we diagnose problems
     // with the implicit exception specification.
-    if (ClassDecl->isDynamicClass())
+    if (ClassDecl->isDynamicClass() ||
+        ClassDecl->needsOverloadResolutionForDestructor())
       DeclareImplicitDestructor(ClassDecl);
   }
 }
@@ -7434,7 +7442,6 @@ CXXConstructorDecl *Sema::DeclareImplicitDefaultConstructor(
   DefaultCon->setAccess(AS_public);
   DefaultCon->setDefaulted();
   DefaultCon->setImplicit();
-  DefaultCon->setTrivial(ClassDecl->hasTrivialDefaultConstructor());
 
   // Build an exception specification pointing back at this constructor.
   FunctionProtoType::ExtProtoInfo EPI;
@@ -7442,16 +7449,20 @@ CXXConstructorDecl *Sema::DeclareImplicitDefaultConstructor(
   EPI.ExceptionSpecDecl = DefaultCon;
   DefaultCon->setType(Context.getFunctionType(Context.VoidTy, 0, 0, EPI));
 
+  // We don't need to use SpecialMemberIsTrivial here; triviality for default
+  // constructors is easy to compute.
+  DefaultCon->setTrivial(ClassDecl->hasTrivialDefaultConstructor());
+
+  if (ShouldDeleteSpecialMember(DefaultCon, CXXDefaultConstructor))
+    DefaultCon->setDeletedAsWritten();
+
   // Note that we have declared this constructor.
   ++ASTContext::NumImplicitDefaultConstructorsDeclared;
-  
+
   if (Scope *S = getScopeForContext(ClassDecl))
     PushOnScopeChains(DefaultCon, S, false);
   ClassDecl->addDecl(DefaultCon);
 
-  if (ShouldDeleteSpecialMember(DefaultCon, CXXDefaultConstructor))
-    DefaultCon->setDeletedAsWritten();
-  
   return DefaultCon;
 }
 
@@ -7785,7 +7796,6 @@ CXXDestructorDecl *Sema::DeclareImplicitDestructor(CXXRecordDecl *ClassDecl) {
   Destructor->setAccess(AS_public);
   Destructor->setDefaulted();
   Destructor->setImplicit();
-  Destructor->setTrivial(ClassDecl->hasTrivialDestructor());
 
   // Build an exception specification pointing back at this destructor.
   FunctionProtoType::ExtProtoInfo EPI;
@@ -7793,6 +7803,15 @@ CXXDestructorDecl *Sema::DeclareImplicitDestructor(CXXRecordDecl *ClassDecl) {
   EPI.ExceptionSpecDecl = Destructor;
   Destructor->setType(Context.getFunctionType(Context.VoidTy, 0, 0, EPI));
 
+  AddOverriddenMethods(ClassDecl, Destructor);
+
+  // We don't need to use SpecialMemberIsTrivial here; triviality for
+  // destructors is easy to compute.
+  Destructor->setTrivial(ClassDecl->hasTrivialDestructor());
+
+  if (ShouldDeleteSpecialMember(Destructor, CXXDestructor))
+    Destructor->setDeletedAsWritten();
+
   // Note that we have declared this destructor.
   ++ASTContext::NumImplicitDestructorsDeclared;
 
@@ -7801,11 +7820,6 @@ CXXDestructorDecl *Sema::DeclareImplicitDestructor(CXXRecordDecl *ClassDecl) {
     PushOnScopeChains(Destructor, S, false);
   ClassDecl->addDecl(Destructor);
 
-  AddOverriddenMethods(ClassDecl, Destructor);
-
-  if (ShouldDeleteSpecialMember(Destructor, CXXDestructor))
-    Destructor->setDeletedAsWritten();
-
   return Destructor;
 }
 
@@ -8278,7 +8292,6 @@ CXXMethodDecl *Sema::DeclareImplicitCopyAssignment(CXXRecordDecl *ClassDecl) {
   CopyAssignment->setAccess(AS_public);
   CopyAssignment->setDefaulted();
   CopyAssignment->setImplicit();
-  CopyAssignment->setTrivial(ClassDecl->hasTrivialCopyAssignment());
 
   // Build an exception specification pointing back at this member.
   FunctionProtoType::ExtProtoInfo EPI;
@@ -8293,14 +8306,14 @@ CXXMethodDecl *Sema::DeclareImplicitCopyAssignment(CXXRecordDecl *ClassDecl) {
                                                SC_None,
                                                SC_None, 0);
   CopyAssignment->setParams(FromParam);
-  
-  // Note that we have added this copy-assignment operator.
-  ++ASTContext::NumImplicitCopyAssignmentOperatorsDeclared;
 
-  if (Scope *S = getScopeForContext(ClassDecl))
-    PushOnScopeChains(CopyAssignment, S, false);
-  ClassDecl->addDecl(CopyAssignment);
-  
+  AddOverriddenMethods(ClassDecl, CopyAssignment);
+
+  CopyAssignment->setTrivial(
+    ClassDecl->needsOverloadResolutionForCopyAssignment()
+      ? SpecialMemberIsTrivial(CopyAssignment, CXXCopyAssignment)
+      : ClassDecl->hasTrivialCopyAssignment());
+
   // C++0x [class.copy]p19:
   //   ....  If the class definition does not explicitly declare a copy
   //   assignment operator, there is no user-declared move constructor, and
@@ -8309,7 +8322,13 @@ CXXMethodDecl *Sema::DeclareImplicitCopyAssignment(CXXRecordDecl *ClassDecl) {
   if (ShouldDeleteSpecialMember(CopyAssignment, CXXCopyAssignment))
     CopyAssignment->setDeletedAsWritten();
 
-  AddOverriddenMethods(ClassDecl, CopyAssignment);
+  // Note that we have added this copy-assignment operator.
+  ++ASTContext::NumImplicitCopyAssignmentOperatorsDeclared;
+
+  if (Scope *S = getScopeForContext(ClassDecl))
+    PushOnScopeChains(CopyAssignment, S, false);
+  ClassDecl->addDecl(CopyAssignment);
+
   return CopyAssignment;
 }
 
@@ -8723,7 +8742,6 @@ CXXMethodDecl *Sema::DeclareImplicitMoveAssignment(CXXRecordDecl *ClassDecl) {
   MoveAssignment->setAccess(AS_public);
   MoveAssignment->setDefaulted();
   MoveAssignment->setImplicit();
-  MoveAssignment->setTrivial(ClassDecl->hasTrivialMoveAssignment());
 
   // Build an exception specification pointing back at this member.
   FunctionProtoType::ExtProtoInfo EPI;
@@ -8739,8 +8757,12 @@ CXXMethodDecl *Sema::DeclareImplicitMoveAssignment(CXXRecordDecl *ClassDecl) {
                                                SC_None, 0);
   MoveAssignment->setParams(FromParam);
 
-  // Note that we have added this copy-assignment operator.
-  ++ASTContext::NumImplicitMoveAssignmentOperatorsDeclared;
+  AddOverriddenMethods(ClassDecl, MoveAssignment);
+
+  MoveAssignment->setTrivial(
+    ClassDecl->needsOverloadResolutionForMoveAssignment()
+      ? SpecialMemberIsTrivial(MoveAssignment, CXXMoveAssignment)
+      : ClassDecl->hasTrivialMoveAssignment());
 
   // C++0x [class.copy]p9:
   //   If the definition of a class X does not explicitly declare a move
@@ -8756,11 +8778,13 @@ CXXMethodDecl *Sema::DeclareImplicitMoveAssignment(CXXRecordDecl *ClassDecl) {
     return 0;
   }
 
+  // Note that we have added this copy-assignment operator.
+  ++ASTContext::NumImplicitMoveAssignmentOperatorsDeclared;
+
   if (Scope *S = getScopeForContext(ClassDecl))
     PushOnScopeChains(MoveAssignment, S, false);
   ClassDecl->addDecl(MoveAssignment);
 
-  AddOverriddenMethods(ClassDecl, MoveAssignment);
   return MoveAssignment;
 }
 
@@ -9071,7 +9095,6 @@ CXXConstructorDecl *Sema::DeclareImplicitCopyConstructor(
       Constexpr);
   CopyConstructor->setAccess(AS_public);
   CopyConstructor->setDefaulted();
-  CopyConstructor->setTrivial(ClassDecl->hasTrivialCopyConstructor());
 
   // Build an exception specification pointing back at this member.
   FunctionProtoType::ExtProtoInfo EPI;
@@ -9080,9 +9103,6 @@ CXXConstructorDecl *Sema::DeclareImplicitCopyConstructor(
   CopyConstructor->setType(
       Context.getFunctionType(Context.VoidTy, &ArgType, 1, EPI));
 
-  // Note that we have declared this constructor.
-  ++ASTContext::NumImplicitCopyConstructorsDeclared;
-  
   // Add the parameter to the constructor.
   ParmVarDecl *FromParam = ParmVarDecl::Create(Context, CopyConstructor,
                                                ClassLoc, ClassLoc,
@@ -9092,9 +9112,10 @@ CXXConstructorDecl *Sema::DeclareImplicitCopyConstructor(
                                                SC_None, 0);
   CopyConstructor->setParams(FromParam);
 
-  if (Scope *S = getScopeForContext(ClassDecl))
-    PushOnScopeChains(CopyConstructor, S, false);
-  ClassDecl->addDecl(CopyConstructor);
+  CopyConstructor->setTrivial(
+    ClassDecl->needsOverloadResolutionForCopyConstructor()
+      ? SpecialMemberIsTrivial(CopyConstructor, CXXCopyConstructor)
+      : ClassDecl->hasTrivialCopyConstructor());
 
   // C++11 [class.copy]p8:
   //   ... If the class definition does not explicitly declare a copy
@@ -9104,6 +9125,13 @@ CXXConstructorDecl *Sema::DeclareImplicitCopyConstructor(
   if (ShouldDeleteSpecialMember(CopyConstructor, CXXCopyConstructor))
     CopyConstructor->setDeletedAsWritten();
 
+  // Note that we have declared this constructor.
+  ++ASTContext::NumImplicitCopyConstructorsDeclared;
+
+  if (Scope *S = getScopeForContext(ClassDecl))
+    PushOnScopeChains(CopyConstructor, S, false);
+  ClassDecl->addDecl(CopyConstructor);
+
   return CopyConstructor;
 }
 
@@ -9254,7 +9282,6 @@ CXXConstructorDecl *Sema::DeclareImplicitMoveConstructor(
       Constexpr);
   MoveConstructor->setAccess(AS_public);
   MoveConstructor->setDefaulted();
-  MoveConstructor->setTrivial(ClassDecl->hasTrivialMoveConstructor());
 
   // Build an exception specification pointing back at this member.
   FunctionProtoType::ExtProtoInfo EPI;
@@ -9272,6 +9299,11 @@ CXXConstructorDecl *Sema::DeclareImplicitMoveConstructor(
                                                SC_None, 0);
   MoveConstructor->setParams(FromParam);
 
+  MoveConstructor->setTrivial(
+    ClassDecl->needsOverloadResolutionForMoveConstructor()
+      ? SpecialMemberIsTrivial(MoveConstructor, CXXMoveConstructor)
+      : ClassDecl->hasTrivialMoveConstructor());
+
   // C++0x [class.copy]p9:
   //   If the definition of a class X does not explicitly declare a move
   //   constructor, one will be implicitly declared as defaulted if and only if: