Improve 'failed template argument deduction' diagnostic for the case where we

have a direct mismatch between some component of the template and some
component of the argument. The diagnostic now says what the mismatch was, but
doesn't yet say which part of the template doesn't match.

llvm-svn: 174039

1 files changed, 57 insertions, 31 deletions

diff --git a/clang/lib/Sema/SemaOverload.cpp b/clang/lib/Sema/SemaOverload.cpp
index dbab7398328..82fe0c9ed08 100644
--- a/clang/lib/Sema/SemaOverload.cpp
+++ b/clang/lib/Sema/SemaOverload.cpp
@@ -536,12 +536,16 @@ AmbiguousConversionSequence::copyFrom(const AmbiguousConversionSequence &O) {
 
 namespace {
   // Structure used by OverloadCandidate::DeductionFailureInfo to store
-  // template parameter and template argument information.
-  struct DFIParamWithArguments {
-    TemplateParameter Param;
+  // template argument information.
+  struct DFIArguments {
     TemplateArgument FirstArg;
     TemplateArgument SecondArg;
   };
+  // Structure used by OverloadCandidate::DeductionFailureInfo to store
+  // template parameter and template argument information.
+  struct DFIParamWithArguments : DFIArguments {
+    TemplateParameter Param;
+  };
 }
 
 /// \brief Convert from Sema's representation of template deduction information
@@ -567,6 +571,15 @@ static MakeDeductionFailureInfo(ASTContext &Context,
     Result.Data = Info.Param.getOpaqueValue();
     break;
 
+  case Sema::TDK_NonDeducedMismatch: {
+    // FIXME: Should allocate from normal heap so that we can free this later.
+    DFIArguments *Saved = new (Context) DFIArguments;
+    Saved->FirstArg = Info.FirstArg;
+    Saved->SecondArg = Info.SecondArg;
+    Result.Data = Saved;
+    break;
+  }
+
   case Sema::TDK_Inconsistent:
   case Sema::TDK_Underqualified: {
     // FIXME: Should allocate from normal heap so that we can free this later.
@@ -592,7 +605,7 @@ static MakeDeductionFailureInfo(ASTContext &Context,
     Result.Data = Info.Expression;
     break;
 
-  case Sema::TDK_NonDeducedMismatch:
+  case Sema::TDK_MiscellaneousDeductionFailure:
     break;
   }
 
@@ -608,10 +621,12 @@ void OverloadCandidate::DeductionFailureInfo::Destroy() {
   case Sema::TDK_TooManyArguments:
   case Sema::TDK_TooFewArguments:
   case Sema::TDK_InvalidExplicitArguments:
+  case Sema::TDK_FailedOverloadResolution:
     break;
 
   case Sema::TDK_Inconsistent:
   case Sema::TDK_Underqualified:
+  case Sema::TDK_NonDeducedMismatch:
     // FIXME: Destroy the data?
     Data = 0;
     break;
@@ -626,8 +641,7 @@ void OverloadCandidate::DeductionFailureInfo::Destroy() {
     break;
 
   // Unhandled
-  case Sema::TDK_NonDeducedMismatch:
-  case Sema::TDK_FailedOverloadResolution:
+  case Sema::TDK_MiscellaneousDeductionFailure:
     break;
   }
 }
@@ -648,6 +662,8 @@ OverloadCandidate::DeductionFailureInfo::getTemplateParameter() {
   case Sema::TDK_TooManyArguments:
   case Sema::TDK_TooFewArguments:
   case Sema::TDK_SubstitutionFailure:
+  case Sema::TDK_NonDeducedMismatch:
+  case Sema::TDK_FailedOverloadResolution:
     return TemplateParameter();
 
   case Sema::TDK_Incomplete:
@@ -659,8 +675,7 @@ OverloadCandidate::DeductionFailureInfo::getTemplateParameter() {
     return static_cast<DFIParamWithArguments*>(Data)->Param;
 
   // Unhandled
-  case Sema::TDK_NonDeducedMismatch:
-  case Sema::TDK_FailedOverloadResolution:
+  case Sema::TDK_MiscellaneousDeductionFailure:
     break;
   }
 
@@ -670,24 +685,25 @@ OverloadCandidate::DeductionFailureInfo::getTemplateParameter() {
 TemplateArgumentList *
 OverloadCandidate::DeductionFailureInfo::getTemplateArgumentList() {
   switch (static_cast<Sema::TemplateDeductionResult>(Result)) {
-    case Sema::TDK_Success:
-    case Sema::TDK_Invalid:
-    case Sema::TDK_InstantiationDepth:
-    case Sema::TDK_TooManyArguments:
-    case Sema::TDK_TooFewArguments:
-    case Sema::TDK_Incomplete:
-    case Sema::TDK_InvalidExplicitArguments:
-    case Sema::TDK_Inconsistent:
-    case Sema::TDK_Underqualified:
-      return 0;
+  case Sema::TDK_Success:
+  case Sema::TDK_Invalid:
+  case Sema::TDK_InstantiationDepth:
+  case Sema::TDK_TooManyArguments:
+  case Sema::TDK_TooFewArguments:
+  case Sema::TDK_Incomplete:
+  case Sema::TDK_InvalidExplicitArguments:
+  case Sema::TDK_Inconsistent:
+  case Sema::TDK_Underqualified:
+  case Sema::TDK_NonDeducedMismatch:
+  case Sema::TDK_FailedOverloadResolution:
+    return 0;
 
-    case Sema::TDK_SubstitutionFailure:
-      return static_cast<TemplateArgumentList*>(Data);
+  case Sema::TDK_SubstitutionFailure:
+    return static_cast<TemplateArgumentList*>(Data);
 
-    // Unhandled
-    case Sema::TDK_NonDeducedMismatch:
-    case Sema::TDK_FailedOverloadResolution:
-      break;
+  // Unhandled
+  case Sema::TDK_MiscellaneousDeductionFailure:
+    break;
   }
 
   return 0;
@@ -703,15 +719,16 @@ const TemplateArgument *OverloadCandidate::DeductionFailureInfo::getFirstArg() {
   case Sema::TDK_TooFewArguments:
   case Sema::TDK_InvalidExplicitArguments:
   case Sema::TDK_SubstitutionFailure:
+  case Sema::TDK_FailedOverloadResolution:
     return 0;
 
   case Sema::TDK_Inconsistent:
   case Sema::TDK_Underqualified:
-    return &static_cast<DFIParamWithArguments*>(Data)->FirstArg;
+  case Sema::TDK_NonDeducedMismatch:
+    return &static_cast<DFIArguments*>(Data)->FirstArg;
 
   // Unhandled
-  case Sema::TDK_NonDeducedMismatch:
-  case Sema::TDK_FailedOverloadResolution:
+  case Sema::TDK_MiscellaneousDeductionFailure:
     break;
   }
 
@@ -729,15 +746,16 @@ OverloadCandidate::DeductionFailureInfo::getSecondArg() {
   case Sema::TDK_TooFewArguments:
   case Sema::TDK_InvalidExplicitArguments:
   case Sema::TDK_SubstitutionFailure:
+  case Sema::TDK_FailedOverloadResolution:
     return 0;
 
   case Sema::TDK_Inconsistent:
   case Sema::TDK_Underqualified:
-    return &static_cast<DFIParamWithArguments*>(Data)->SecondArg;
+  case Sema::TDK_NonDeducedMismatch:
+    return &static_cast<DFIArguments*>(Data)->SecondArg;
 
   // Unhandled
-  case Sema::TDK_NonDeducedMismatch:
-  case Sema::TDK_FailedOverloadResolution:
+  case Sema::TDK_MiscellaneousDeductionFailure:
     break;
   }
 
@@ -8463,9 +8481,16 @@ void DiagnoseBadDeduction(Sema &S, OverloadCandidate *Cand,
     return;
   }
 
+  case Sema::TDK_NonDeducedMismatch:
+    // FIXME: Provide a source location to indicate what we couldn't match.
+    S.Diag(Fn->getLocation(), diag::note_ovl_candidate_non_deduced_mismatch)
+      << *Cand->DeductionFailure.getFirstArg()
+      << *Cand->DeductionFailure.getSecondArg();
+    return;
+
   // TODO: diagnose these individually, then kill off
   // note_ovl_candidate_bad_deduction, which is uselessly vague.
-  case Sema::TDK_NonDeducedMismatch:
+  case Sema::TDK_MiscellaneousDeductionFailure:
     S.Diag(Fn->getLocation(), diag::note_ovl_candidate_bad_deduction);
     MaybeEmitInheritedConstructorNote(S, Fn);
     return;
@@ -8643,6 +8668,7 @@ RankDeductionFailure(const OverloadCandidate::DeductionFailureInfo &DFI) {
 
   case Sema::TDK_SubstitutionFailure:
   case Sema::TDK_NonDeducedMismatch:
+  case Sema::TDK_MiscellaneousDeductionFailure:
     return 3;
 
   case Sema::TDK_InstantiationDepth: