Improve diagnostics when a default template argument does not match

with its corresponding template parameter. This can happen when we
performed some substitution into the default template argument and
what we had doesn't match any more, e.g.,

  template<int> struct A;
  template<typename T, template<T> class X = A> class B;

  B<long> b;

Previously, we'd emit a pretty but disembodied diagnostic showing how
the default argument didn't match the template parameter. The
diagnostic was good, but nothing tied it to the *use* of the default
argument in "B<long>". This commit fixes that.

Also, tweak the counting of active template instantiations to avoid
counting non-instantiation records, such as those we create for
(surprise!) checking default arguments, instantiating default
arguments, and performing substitutions as part of template argument
deduction.

llvm-svn: 86884

1 files changed, 105 insertions, 46 deletions

diff --git a/clang/lib/Sema/SemaTemplateInstantiate.cpp b/clang/lib/Sema/SemaTemplateInstantiate.cpp
index b1e0481932f..b303dce06ff 100644
--- a/clang/lib/Sema/SemaTemplateInstantiate.cpp
+++ b/clang/lib/Sema/SemaTemplateInstantiate.cpp
@@ -96,6 +96,23 @@ Sema::getTemplateInstantiationArgs(NamedDecl *D,
   return Result;
 }
 
+bool Sema::ActiveTemplateInstantiation::isInstantiationRecord() const {
+  switch (Kind) {
+  case TemplateInstantiation:
+  case DefaultTemplateArgumentInstantiation:
+  case DefaultFunctionArgumentInstantiation:
+    return true;
+      
+  case ExplicitTemplateArgumentSubstitution:
+  case DeducedTemplateArgumentSubstitution:
+  case PriorTemplateArgumentSubstitution:
+  case DefaultTemplateArgumentChecking:
+    return false;
+  }
+  
+  return true;
+}
+
 Sema::InstantiatingTemplate::
 InstantiatingTemplate(Sema &SemaRef, SourceLocation PointOfInstantiation,
                       Decl *Entity,
@@ -113,7 +130,6 @@ InstantiatingTemplate(Sema &SemaRef, SourceLocation PointOfInstantiation,
     Inst.NumTemplateArgs = 0;
     Inst.InstantiationRange = InstantiationRange;
     SemaRef.ActiveTemplateInstantiations.push_back(Inst);
-    Invalid = false;
   }
 }
 
@@ -137,7 +153,6 @@ Sema::InstantiatingTemplate::InstantiatingTemplate(Sema &SemaRef,
     Inst.NumTemplateArgs = NumTemplateArgs;
     Inst.InstantiationRange = InstantiationRange;
     SemaRef.ActiveTemplateInstantiations.push_back(Inst);
-    Invalid = false;
   }
 }
 
@@ -161,7 +176,9 @@ Sema::InstantiatingTemplate::InstantiatingTemplate(Sema &SemaRef,
     Inst.NumTemplateArgs = NumTemplateArgs;
     Inst.InstantiationRange = InstantiationRange;
     SemaRef.ActiveTemplateInstantiations.push_back(Inst);
-    Invalid = false;
+    
+    if (!Inst.isInstantiationRecord())
+      ++SemaRef.NonInstantiationEntries;
   }
 }
 
@@ -173,20 +190,19 @@ Sema::InstantiatingTemplate::InstantiatingTemplate(Sema &SemaRef,
                                          SourceRange InstantiationRange)
   : SemaRef(SemaRef) {
 
-  Invalid = CheckInstantiationDepth(PointOfInstantiation,
-                                    InstantiationRange);
-  if (!Invalid) {
-    ActiveTemplateInstantiation Inst;
-    Inst.Kind
-      = ActiveTemplateInstantiation::DeducedTemplateArgumentSubstitution;
-    Inst.PointOfInstantiation = PointOfInstantiation;
-    Inst.Entity = reinterpret_cast<uintptr_t>(PartialSpec);
-    Inst.TemplateArgs = TemplateArgs;
-    Inst.NumTemplateArgs = NumTemplateArgs;
-    Inst.InstantiationRange = InstantiationRange;
-    SemaRef.ActiveTemplateInstantiations.push_back(Inst);
-    Invalid = false;
-  }
+  Invalid = false;
+    
+  ActiveTemplateInstantiation Inst;
+  Inst.Kind = ActiveTemplateInstantiation::DeducedTemplateArgumentSubstitution;
+  Inst.PointOfInstantiation = PointOfInstantiation;
+  Inst.Entity = reinterpret_cast<uintptr_t>(PartialSpec);
+  Inst.TemplateArgs = TemplateArgs;
+  Inst.NumTemplateArgs = NumTemplateArgs;
+  Inst.InstantiationRange = InstantiationRange;
+  SemaRef.ActiveTemplateInstantiations.push_back(Inst);
+      
+  assert(!Inst.isInstantiationRecord());
+  ++SemaRef.NonInstantiationEntries;
 }
 
 Sema::InstantiatingTemplate::InstantiatingTemplate(Sema &SemaRef,
@@ -219,19 +235,20 @@ InstantiatingTemplate(Sema &SemaRef, SourceLocation PointOfInstantiation,
                       const TemplateArgument *TemplateArgs,
                       unsigned NumTemplateArgs,
                       SourceRange InstantiationRange) : SemaRef(SemaRef) {
-  Invalid = CheckInstantiationDepth(PointOfInstantiation, InstantiationRange);
+  Invalid = false;
   
-  if (!Invalid) {
-    ActiveTemplateInstantiation Inst;
-    Inst.Kind = ActiveTemplateInstantiation::PriorTemplateArgumentSubstitution;
-    Inst.PointOfInstantiation = PointOfInstantiation;
-    Inst.Template = Template;
-    Inst.Entity = reinterpret_cast<uintptr_t>(Param);
-    Inst.TemplateArgs = TemplateArgs;
-    Inst.NumTemplateArgs = NumTemplateArgs;
-    Inst.InstantiationRange = InstantiationRange;
-    SemaRef.ActiveTemplateInstantiations.push_back(Inst);
-  }
+  ActiveTemplateInstantiation Inst;
+  Inst.Kind = ActiveTemplateInstantiation::PriorTemplateArgumentSubstitution;
+  Inst.PointOfInstantiation = PointOfInstantiation;
+  Inst.Template = Template;
+  Inst.Entity = reinterpret_cast<uintptr_t>(Param);
+  Inst.TemplateArgs = TemplateArgs;
+  Inst.NumTemplateArgs = NumTemplateArgs;
+  Inst.InstantiationRange = InstantiationRange;
+  SemaRef.ActiveTemplateInstantiations.push_back(Inst);
+  
+  assert(!Inst.isInstantiationRecord());
+  ++SemaRef.NonInstantiationEntries;
 }
 
 Sema::InstantiatingTemplate::
@@ -241,23 +258,51 @@ InstantiatingTemplate(Sema &SemaRef, SourceLocation PointOfInstantiation,
                       const TemplateArgument *TemplateArgs,
                       unsigned NumTemplateArgs,
                       SourceRange InstantiationRange) : SemaRef(SemaRef) {
-  Invalid = CheckInstantiationDepth(PointOfInstantiation, InstantiationRange);
+  Invalid = false;
+  ActiveTemplateInstantiation Inst;
+  Inst.Kind = ActiveTemplateInstantiation::PriorTemplateArgumentSubstitution;
+  Inst.PointOfInstantiation = PointOfInstantiation;
+  Inst.Template = Template;
+  Inst.Entity = reinterpret_cast<uintptr_t>(Param);
+  Inst.TemplateArgs = TemplateArgs;
+  Inst.NumTemplateArgs = NumTemplateArgs;
+  Inst.InstantiationRange = InstantiationRange;
+  SemaRef.ActiveTemplateInstantiations.push_back(Inst);
   
-  if (!Invalid) {
-    ActiveTemplateInstantiation Inst;
-    Inst.Kind = ActiveTemplateInstantiation::PriorTemplateArgumentSubstitution;
-    Inst.PointOfInstantiation = PointOfInstantiation;
-    Inst.Template = Template;
-    Inst.Entity = reinterpret_cast<uintptr_t>(Param);
-    Inst.TemplateArgs = TemplateArgs;
-    Inst.NumTemplateArgs = NumTemplateArgs;
-    Inst.InstantiationRange = InstantiationRange;
-    SemaRef.ActiveTemplateInstantiations.push_back(Inst);
-  }
+  assert(!Inst.isInstantiationRecord());
+  ++SemaRef.NonInstantiationEntries;
+}
+
+Sema::InstantiatingTemplate::
+InstantiatingTemplate(Sema &SemaRef, SourceLocation PointOfInstantiation,
+                      TemplateDecl *Template,
+                      NamedDecl *Param,
+                      const TemplateArgument *TemplateArgs,
+                      unsigned NumTemplateArgs,
+                      SourceRange InstantiationRange) : SemaRef(SemaRef) {
+  Invalid = false;
+  
+  ActiveTemplateInstantiation Inst;
+  Inst.Kind = ActiveTemplateInstantiation::DefaultTemplateArgumentChecking;
+  Inst.PointOfInstantiation = PointOfInstantiation;
+  Inst.Template = Template;
+  Inst.Entity = reinterpret_cast<uintptr_t>(Param);
+  Inst.TemplateArgs = TemplateArgs;
+  Inst.NumTemplateArgs = NumTemplateArgs;
+  Inst.InstantiationRange = InstantiationRange;
+  SemaRef.ActiveTemplateInstantiations.push_back(Inst);
+  
+  assert(!Inst.isInstantiationRecord());
+  ++SemaRef.NonInstantiationEntries;
 }
 
 void Sema::InstantiatingTemplate::Clear() {
   if (!Invalid) {
+    if (!SemaRef.ActiveTemplateInstantiations.back().isInstantiationRecord()) {
+      assert(SemaRef.NonInstantiationEntries > 0);
+      --SemaRef.NonInstantiationEntries;
+    }
+    
     SemaRef.ActiveTemplateInstantiations.pop_back();
     Invalid = true;
   }
@@ -266,8 +311,11 @@ void Sema::InstantiatingTemplate::Clear() {
 bool Sema::InstantiatingTemplate::CheckInstantiationDepth(
                                         SourceLocation PointOfInstantiation,
                                            SourceRange InstantiationRange) {
-  if (SemaRef.ActiveTemplateInstantiations.size()
-       <= SemaRef.getLangOptions().InstantiationDepth)
+  assert(SemaRef.NonInstantiationEntries <=
+                                   SemaRef.ActiveTemplateInstantiations.size());
+  if ((SemaRef.ActiveTemplateInstantiations.size() - 
+          SemaRef.NonInstantiationEntries)
+        <= SemaRef.getLangOptions().InstantiationDepth)
     return false;
 
   SemaRef.Diag(PointOfInstantiation,
@@ -391,6 +439,17 @@ void Sema::PrintInstantiationStack() {
         << Active->InstantiationRange;
       break;
     }
+
+    case ActiveTemplateInstantiation::DefaultTemplateArgumentChecking: {
+      Diags.Report(FullSourceLoc(Active->PointOfInstantiation, SourceMgr),
+                   diag::note_template_default_arg_checking)
+        << getTemplateArgumentBindingsText(
+                                     Active->Template->getTemplateParameters(), 
+                                           Active->TemplateArgs, 
+                                           Active->NumTemplateArgs)
+        << Active->InstantiationRange;
+      break;
+    }
     }
   }
 }
@@ -401,17 +460,17 @@ bool Sema::isSFINAEContext() const {
          Active = ActiveTemplateInstantiations.rbegin(),
          ActiveEnd = ActiveTemplateInstantiations.rend();
        Active != ActiveEnd;
-       ++Active) {
-
+       ++Active) 
+  {
     switch(Active->Kind) {
     case ActiveTemplateInstantiation::TemplateInstantiation:
     case ActiveTemplateInstantiation::DefaultFunctionArgumentInstantiation:
-
       // This is a template instantiation, so there is no SFINAE.
       return false;
 
     case ActiveTemplateInstantiation::DefaultTemplateArgumentInstantiation:
     case ActiveTemplateInstantiation::PriorTemplateArgumentSubstitution:
+    case ActiveTemplateInstantiation::DefaultTemplateArgumentChecking:
       // A default template argument instantiation and substitution into
       // template parameters with arguments for prior parameters may or may 
       // not be a SFINAE context; look further up the stack.