Teach the evaluation of the __is_convertible_to trait to translate

access control errors into SFINAE errors, so that the trait provides
enough support to implement the C++0x std::is_convertible type trait.

To get there, the SFINAETrap now knows how to set up a SFINAE context
independent of any template instantiations or template argument
deduction steps, and (separately) can set a Sema flag to translate
access control errors into SFINAE errors. The latter can also be
useful if we decide that access control errors during template argument
deduction should cause substitution failure (rather than a hard error)
as has been proposed for C++0x.

llvm-svn: 124446

1 files changed, 52 insertions, 17 deletions

diff --git a/clang/lib/Sema/SemaTemplateInstantiate.cpp b/clang/lib/Sema/SemaTemplateInstantiate.cpp
index 45fde296e3c..f58e744578a 100644
--- a/clang/lib/Sema/SemaTemplateInstantiate.cpp
+++ b/clang/lib/Sema/SemaTemplateInstantiate.cpp
@@ -147,7 +147,10 @@ Sema::InstantiatingTemplate::
 InstantiatingTemplate(Sema &SemaRef, SourceLocation PointOfInstantiation,
                       Decl *Entity,
                       SourceRange InstantiationRange)
-  :  SemaRef(SemaRef) {
+  : SemaRef(SemaRef),
+    SavedInNonInstantiationSFINAEContext(
+                                        SemaRef.InNonInstantiationSFINAEContext)
+{
   Invalid = CheckInstantiationDepth(PointOfInstantiation,
                                     InstantiationRange);
   if (!Invalid) {
@@ -158,6 +161,7 @@ InstantiatingTemplate(Sema &SemaRef, SourceLocation PointOfInstantiation,
     Inst.TemplateArgs = 0;
     Inst.NumTemplateArgs = 0;
     Inst.InstantiationRange = InstantiationRange;
+    SemaRef.InNonInstantiationSFINAEContext = false;
     SemaRef.ActiveTemplateInstantiations.push_back(Inst);
   }
 }
@@ -168,8 +172,10 @@ Sema::InstantiatingTemplate::InstantiatingTemplate(Sema &SemaRef,
                                          const TemplateArgument *TemplateArgs,
                                          unsigned NumTemplateArgs,
                                          SourceRange InstantiationRange)
-  : SemaRef(SemaRef) {
-
+  : SemaRef(SemaRef),
+    SavedInNonInstantiationSFINAEContext(
+                                     SemaRef.InNonInstantiationSFINAEContext)
+{
   Invalid = CheckInstantiationDepth(PointOfInstantiation,
                                     InstantiationRange);
   if (!Invalid) {
@@ -181,6 +187,7 @@ Sema::InstantiatingTemplate::InstantiatingTemplate(Sema &SemaRef,
     Inst.TemplateArgs = TemplateArgs;
     Inst.NumTemplateArgs = NumTemplateArgs;
     Inst.InstantiationRange = InstantiationRange;
+    SemaRef.InNonInstantiationSFINAEContext = false;
     SemaRef.ActiveTemplateInstantiations.push_back(Inst);
   }
 }
@@ -193,8 +200,10 @@ Sema::InstantiatingTemplate::InstantiatingTemplate(Sema &SemaRef,
                          ActiveTemplateInstantiation::InstantiationKind Kind,
                                    sema::TemplateDeductionInfo &DeductionInfo,
                                               SourceRange InstantiationRange)
-  : SemaRef(SemaRef) {
-
+  : SemaRef(SemaRef),
+    SavedInNonInstantiationSFINAEContext(
+                                     SemaRef.InNonInstantiationSFINAEContext)
+{
   Invalid = CheckInstantiationDepth(PointOfInstantiation,
                                     InstantiationRange);
   if (!Invalid) {
@@ -206,6 +215,7 @@ Sema::InstantiatingTemplate::InstantiatingTemplate(Sema &SemaRef,
     Inst.NumTemplateArgs = NumTemplateArgs;
     Inst.DeductionInfo = &DeductionInfo;
     Inst.InstantiationRange = InstantiationRange;
+    SemaRef.InNonInstantiationSFINAEContext = false;
     SemaRef.ActiveTemplateInstantiations.push_back(Inst);
     
     if (!Inst.isInstantiationRecord())
@@ -220,8 +230,10 @@ Sema::InstantiatingTemplate::InstantiatingTemplate(Sema &SemaRef,
                                          unsigned NumTemplateArgs,
                                     sema::TemplateDeductionInfo &DeductionInfo,
                                          SourceRange InstantiationRange)
-  : SemaRef(SemaRef) {
-
+  : SemaRef(SemaRef),
+    SavedInNonInstantiationSFINAEContext(
+                                     SemaRef.InNonInstantiationSFINAEContext)
+{
   Invalid = false;
     
   ActiveTemplateInstantiation Inst;
@@ -232,6 +244,7 @@ Sema::InstantiatingTemplate::InstantiatingTemplate(Sema &SemaRef,
   Inst.NumTemplateArgs = NumTemplateArgs;
   Inst.DeductionInfo = &DeductionInfo;
   Inst.InstantiationRange = InstantiationRange;
+  SemaRef.InNonInstantiationSFINAEContext = false;
   SemaRef.ActiveTemplateInstantiations.push_back(Inst);
       
   assert(!Inst.isInstantiationRecord());
@@ -244,8 +257,10 @@ Sema::InstantiatingTemplate::InstantiatingTemplate(Sema &SemaRef,
                                           const TemplateArgument *TemplateArgs,
                                           unsigned NumTemplateArgs,
                                           SourceRange InstantiationRange)
-  : SemaRef(SemaRef) {
-
+  : SemaRef(SemaRef),
+    SavedInNonInstantiationSFINAEContext(
+                                     SemaRef.InNonInstantiationSFINAEContext)
+{
   Invalid = CheckInstantiationDepth(PointOfInstantiation, InstantiationRange);
 
   if (!Invalid) {
@@ -257,6 +272,7 @@ Sema::InstantiatingTemplate::InstantiatingTemplate(Sema &SemaRef,
     Inst.TemplateArgs = TemplateArgs;
     Inst.NumTemplateArgs = NumTemplateArgs;
     Inst.InstantiationRange = InstantiationRange;
+    SemaRef.InNonInstantiationSFINAEContext = false;
     SemaRef.ActiveTemplateInstantiations.push_back(Inst);
   }
 }
@@ -267,7 +283,11 @@ InstantiatingTemplate(Sema &SemaRef, SourceLocation PointOfInstantiation,
                       NonTypeTemplateParmDecl *Param,
                       const TemplateArgument *TemplateArgs,
                       unsigned NumTemplateArgs,
-                      SourceRange InstantiationRange) : SemaRef(SemaRef) {
+                      SourceRange InstantiationRange) 
+  : SemaRef(SemaRef),
+    SavedInNonInstantiationSFINAEContext(
+                                     SemaRef.InNonInstantiationSFINAEContext)
+{
   Invalid = false;
   
   ActiveTemplateInstantiation Inst;
@@ -278,6 +298,7 @@ InstantiatingTemplate(Sema &SemaRef, SourceLocation PointOfInstantiation,
   Inst.TemplateArgs = TemplateArgs;
   Inst.NumTemplateArgs = NumTemplateArgs;
   Inst.InstantiationRange = InstantiationRange;
+  SemaRef.InNonInstantiationSFINAEContext = false;
   SemaRef.ActiveTemplateInstantiations.push_back(Inst);
   
   assert(!Inst.isInstantiationRecord());
@@ -290,7 +311,11 @@ InstantiatingTemplate(Sema &SemaRef, SourceLocation PointOfInstantiation,
                       TemplateTemplateParmDecl *Param,
                       const TemplateArgument *TemplateArgs,
                       unsigned NumTemplateArgs,
-                      SourceRange InstantiationRange) : SemaRef(SemaRef) {
+                      SourceRange InstantiationRange) 
+  : SemaRef(SemaRef),
+    SavedInNonInstantiationSFINAEContext(
+                                     SemaRef.InNonInstantiationSFINAEContext)
+{
   Invalid = false;
   ActiveTemplateInstantiation Inst;
   Inst.Kind = ActiveTemplateInstantiation::PriorTemplateArgumentSubstitution;
@@ -300,6 +325,7 @@ InstantiatingTemplate(Sema &SemaRef, SourceLocation PointOfInstantiation,
   Inst.TemplateArgs = TemplateArgs;
   Inst.NumTemplateArgs = NumTemplateArgs;
   Inst.InstantiationRange = InstantiationRange;
+  SemaRef.InNonInstantiationSFINAEContext = false;
   SemaRef.ActiveTemplateInstantiations.push_back(Inst);
   
   assert(!Inst.isInstantiationRecord());
@@ -312,7 +338,11 @@ InstantiatingTemplate(Sema &SemaRef, SourceLocation PointOfInstantiation,
                       NamedDecl *Param,
                       const TemplateArgument *TemplateArgs,
                       unsigned NumTemplateArgs,
-                      SourceRange InstantiationRange) : SemaRef(SemaRef) {
+                      SourceRange InstantiationRange) 
+  : SemaRef(SemaRef),
+    SavedInNonInstantiationSFINAEContext(
+                                     SemaRef.InNonInstantiationSFINAEContext)
+{
   Invalid = false;
   
   ActiveTemplateInstantiation Inst;
@@ -323,6 +353,7 @@ InstantiatingTemplate(Sema &SemaRef, SourceLocation PointOfInstantiation,
   Inst.TemplateArgs = TemplateArgs;
   Inst.NumTemplateArgs = NumTemplateArgs;
   Inst.InstantiationRange = InstantiationRange;
+  SemaRef.InNonInstantiationSFINAEContext = false;
   SemaRef.ActiveTemplateInstantiations.push_back(Inst);
   
   assert(!Inst.isInstantiationRecord());
@@ -335,7 +366,8 @@ void Sema::InstantiatingTemplate::Clear() {
       assert(SemaRef.NonInstantiationEntries > 0);
       --SemaRef.NonInstantiationEntries;
     }
-    
+    SemaRef.InNonInstantiationSFINAEContext
+      = SavedInNonInstantiationSFINAEContext;
     SemaRef.ActiveTemplateInstantiations.pop_back();
     Invalid = true;
   }
@@ -530,8 +562,11 @@ void Sema::PrintInstantiationStack() {
   }
 }
 
-TemplateDeductionInfo *Sema::isSFINAEContext() const {
+llvm::Optional<TemplateDeductionInfo *> Sema::isSFINAEContext() const {
   using llvm::SmallVector;
+  if (InNonInstantiationSFINAEContext)
+    return llvm::Optional<TemplateDeductionInfo *>(0);
+
   for (SmallVector<ActiveTemplateInstantiation, 16>::const_reverse_iterator
          Active = ActiveTemplateInstantiations.rbegin(),
          ActiveEnd = ActiveTemplateInstantiations.rend();
@@ -539,10 +574,10 @@ TemplateDeductionInfo *Sema::isSFINAEContext() const {
        ++Active) 
   {
     switch(Active->Kind) {
-    case ActiveTemplateInstantiation::TemplateInstantiation:
     case ActiveTemplateInstantiation::DefaultFunctionArgumentInstantiation:
+    case ActiveTemplateInstantiation::TemplateInstantiation:
       // This is a template instantiation, so there is no SFINAE.
-      return 0;
+      return llvm::Optional<TemplateDeductionInfo *>();
 
     case ActiveTemplateInstantiation::DefaultTemplateArgumentInstantiation:
     case ActiveTemplateInstantiation::PriorTemplateArgumentSubstitution:
@@ -561,7 +596,7 @@ TemplateDeductionInfo *Sema::isSFINAEContext() const {
     }
   }
 
-  return 0;
+  return llvm::Optional<TemplateDeductionInfo *>();
 }
 
 /// \brief Retrieve the depth and index of a parameter pack.