1 files changed, 60 insertions, 82 deletions

diff --git a/clang/lib/Sema/SemaTemplate.cpp b/clang/lib/Sema/SemaTemplate.cpp
index 3f642b5c426..2e73096a9ba 100644
--- a/clang/lib/Sema/SemaTemplate.cpp
+++ b/clang/lib/Sema/SemaTemplate.cpp
@@ -66,20 +66,17 @@ static Expr *clang::formAssociatedConstraints(TemplateParameterList *Params,
 
 /// Determine whether the declaration found is acceptable as the name
 /// of a template and, if so, return that template declaration. Otherwise,
-/// returns null.
-///
-/// Note that this may return an UnresolvedUsingValueDecl if AllowDependent
-/// is true. In all other cases it will return a TemplateDecl (or null).
-NamedDecl *Sema::getAsTemplateNameDecl(NamedDecl *D,
-                                       bool AllowFunctionTemplates,
-                                       bool AllowDependent) {
-  D = D->getUnderlyingDecl();
+/// returns NULL.
+static NamedDecl *isAcceptableTemplateName(ASTContext &Context,
+                                           NamedDecl *Orig,
+                                           bool AllowFunctionTemplates) {
+  NamedDecl *D = Orig->getUnderlyingDecl();
 
   if (isa<TemplateDecl>(D)) {
     if (!AllowFunctionTemplates && isa<FunctionTemplateDecl>(D))
       return nullptr;
 
-    return D;
+    return Orig;
   }
 
   if (CXXRecordDecl *Record = dyn_cast<CXXRecordDecl>(D)) {
@@ -110,29 +107,54 @@ NamedDecl *Sema::getAsTemplateNameDecl(NamedDecl *D,
   // 'using Dependent::foo;' can resolve to a template name.
   // 'using typename Dependent::foo;' cannot (not even if 'foo' is an
   // injected-class-name).
-  if (AllowDependent && isa<UnresolvedUsingValueDecl>(D))
+  if (isa<UnresolvedUsingValueDecl>(D))
     return D;
 
   return nullptr;
 }
 
 void Sema::FilterAcceptableTemplateNames(LookupResult &R,
-                                         bool AllowFunctionTemplates,
-                                         bool AllowDependent) {
+                                         bool AllowFunctionTemplates) {
+  // The set of class templates we've already seen.
+  llvm::SmallPtrSet<ClassTemplateDecl *, 8> ClassTemplates;
   LookupResult::Filter filter = R.makeFilter();
   while (filter.hasNext()) {
     NamedDecl *Orig = filter.next();
-    if (!getAsTemplateNameDecl(Orig, AllowFunctionTemplates, AllowDependent))
+    NamedDecl *Repl = isAcceptableTemplateName(Context, Orig,
+                                               AllowFunctionTemplates);
+    if (!Repl)
       filter.erase();
+    else if (Repl != Orig) {
+
+      // C++ [temp.local]p3:
+      //   A lookup that finds an injected-class-name (10.2) can result in an
+      //   ambiguity in certain cases (for example, if it is found in more than
+      //   one base class). If all of the injected-class-names that are found
+      //   refer to specializations of the same class template, and if the name
+      //   is used as a template-name, the reference refers to the class
+      //   template itself and not a specialization thereof, and is not
+      //   ambiguous.
+      if (ClassTemplateDecl *ClassTmpl = dyn_cast<ClassTemplateDecl>(Repl))
+        if (!ClassTemplates.insert(ClassTmpl).second) {
+          filter.erase();
+          continue;
+        }
+
+      // FIXME: we promote access to public here as a workaround to
+      // the fact that LookupResult doesn't let us remember that we
+      // found this template through a particular injected class name,
+      // which means we end up doing nasty things to the invariants.
+      // Pretending that access is public is *much* safer.
+      filter.replace(Repl, AS_public);
+    }
   }
   filter.done();
 }
 
 bool Sema::hasAnyAcceptableTemplateNames(LookupResult &R,
-                                         bool AllowFunctionTemplates,
-                                         bool AllowDependent) {
+                                         bool AllowFunctionTemplates) {
   for (LookupResult::iterator I = R.begin(), IEnd = R.end(); I != IEnd; ++I)
-    if (getAsTemplateNameDecl(*I, AllowFunctionTemplates, AllowDependent))
+    if (isAcceptableTemplateName(Context, *I, AllowFunctionTemplates))
       return true;
 
   return false;
@@ -176,45 +198,20 @@ TemplateNameKind Sema::isTemplateName(Scope *S,
                          MemberOfUnknownSpecialization))
     return TNK_Non_template;
   if (R.empty()) return TNK_Non_template;
-
-  NamedDecl *D = nullptr;
   if (R.isAmbiguous()) {
-    // If we got an ambiguity involving a non-function template, treat this
-    // as a template name, and pick an arbitrary template for error recovery.
-    bool AnyFunctionTemplates = false;
-    for (NamedDecl *FoundD : R) {
-      if (NamedDecl *FoundTemplate = getAsTemplateNameDecl(FoundD)) {
-        if (isa<FunctionTemplateDecl>(FoundTemplate))
-          AnyFunctionTemplates = true;
-        else {
-          D = FoundTemplate;
-          break;
-        }
-      }
-    }
-
-    // If we didn't find any templates at all, this isn't a template name.
-    // Leave the ambiguity for a later lookup to diagnose.
-    if (!D && !AnyFunctionTemplates) {
-      R.suppressDiagnostics();
-      return TNK_Non_template;
-    }
+    // Suppress diagnostics;  we'll redo this lookup later.
+    R.suppressDiagnostics();
 
-    // If the only templates were function templates, filter out the rest.
-    // We'll diagnose the ambiguity later.
-    if (!D)
-      FilterAcceptableTemplateNames(R);
+    // FIXME: we might have ambiguous templates, in which case we
+    // should at least parse them properly!
+    return TNK_Non_template;
   }
 
-  // At this point, we have either picked a single template name declaration D
-  // or we have a non-empty set of results R containing either one template name
-  // declaration or a set of function templates.
-
   TemplateName Template;
   TemplateNameKind TemplateKind;
 
   unsigned ResultCount = R.end() - R.begin();
-  if (!D && ResultCount > 1) {
+  if (ResultCount > 1) {
     // We assume that we'll preserve the qualifier from a function
     // template name in other ways.
     Template = Context.getOverloadedTemplateName(R.begin(), R.end());
@@ -222,19 +219,12 @@ TemplateNameKind Sema::isTemplateName(Scope *S,
 
     // We'll do this lookup again later.
     R.suppressDiagnostics();
+  } else if (isa<UnresolvedUsingValueDecl>((*R.begin())->getUnderlyingDecl())) {
+    // We don't yet know whether this is a template-name or not.
+    MemberOfUnknownSpecialization = true;
+    return TNK_Non_template;
   } else {
-    if (!D) {
-      D = getAsTemplateNameDecl(*R.begin());
-      assert(D && "unambiguous result is not a template name");
-    }
-
-    if (isa<UnresolvedUsingValueDecl>(D)) {
-      // We don't yet know whether this is a template-name or not.
-      MemberOfUnknownSpecialization = true;
-      return TNK_Non_template;
-    }
-
-    TemplateDecl *TD = cast<TemplateDecl>(D);
+    TemplateDecl *TD = cast<TemplateDecl>((*R.begin())->getUnderlyingDecl());
 
     if (SS.isSet() && !SS.isInvalid()) {
       NestedNameSpecifier *Qualifier = SS.getScopeRep();
@@ -326,8 +316,6 @@ bool Sema::LookupTemplateName(LookupResult &Found,
                               bool EnteringContext,
                               bool &MemberOfUnknownSpecialization,
                               SourceLocation TemplateKWLoc) {
-  Found.setTemplateNameLookup(true);
-
   // Determine where to perform name lookup
   MemberOfUnknownSpecialization = false;
   DeclContext *LookupCtx = nullptr;
@@ -402,9 +390,6 @@ bool Sema::LookupTemplateName(LookupResult &Found,
     IsDependent |= Found.wasNotFoundInCurrentInstantiation();
   }
 
-  if (Found.isAmbiguous())
-    return false;
-
   if (Found.empty() && !IsDependent) {
     // If we did not find any names, attempt to correct any typos.
     DeclarationName Name = Found.getLookupName();
@@ -422,9 +407,7 @@ bool Sema::LookupTemplateName(LookupResult &Found,
       if (auto *ND = Corrected.getFoundDecl())
         Found.addDecl(ND);
       FilterAcceptableTemplateNames(Found);
-      if (Found.isAmbiguous()) {
-        Found.clear();
-      } else if (!Found.empty()) {
+      if (!Found.empty()) {
         if (LookupCtx) {
           std::string CorrectedStr(Corrected.getAsString(getLangOpts()));
           bool DroppedSpecifier = Corrected.WillReplaceSpecifier() &&
@@ -474,19 +457,14 @@ bool Sema::LookupTemplateName(LookupResult &Found,
     // Note: C++11 does not perform this second lookup.
     LookupResult FoundOuter(*this, Found.getLookupName(), Found.getNameLoc(),
                             LookupOrdinaryName);
-    FoundOuter.setTemplateNameLookup(true);
     LookupName(FoundOuter, S);
-    // FIXME: We silently accept an ambiguous lookup here, in violation of
-    // [basic.lookup]/1.
     FilterAcceptableTemplateNames(FoundOuter, /*AllowFunctionTemplates=*/false);
 
-    NamedDecl *OuterTemplate;
     if (FoundOuter.empty()) {
       //   - if the name is not found, the name found in the class of the
       //     object expression is used, otherwise
-    } else if (FoundOuter.isAmbiguous() || !FoundOuter.isSingleResult() ||
-               !(OuterTemplate =
-                     getAsTemplateNameDecl(FoundOuter.getFoundDecl()))) {
+    } else if (!FoundOuter.getAsSingle<ClassTemplateDecl>() ||
+               FoundOuter.isAmbiguous()) {
       //   - if the name is found in the context of the entire
       //     postfix-expression and does not name a class template, the name
       //     found in the class of the object expression is used, otherwise
@@ -496,8 +474,8 @@ bool Sema::LookupTemplateName(LookupResult &Found,
       //     entity as the one found in the class of the object expression,
       //     otherwise the program is ill-formed.
       if (!Found.isSingleResult() ||
-          getAsTemplateNameDecl(Found.getFoundDecl())->getCanonicalDecl() !=
-              OuterTemplate->getCanonicalDecl()) {
+          Found.getFoundDecl()->getCanonicalDecl()
+            != FoundOuter.getFoundDecl()->getCanonicalDecl()) {
         Diag(Found.getNameLoc(),
              diag::ext_nested_name_member_ref_lookup_ambiguous)
           << Found.getLookupName()
@@ -567,8 +545,7 @@ void Sema::diagnoseExprIntendedAsTemplateName(Scope *S, ExprResult TemplateName,
 
   // Try to correct the name by looking for templates and C++ named casts.
   struct TemplateCandidateFilter : CorrectionCandidateCallback {
-    Sema &S;
-    TemplateCandidateFilter(Sema &S) : S(S) {
+    TemplateCandidateFilter() {
       WantTypeSpecifiers = false;
       WantExpressionKeywords = false;
       WantRemainingKeywords = false;
@@ -576,7 +553,7 @@ void Sema::diagnoseExprIntendedAsTemplateName(Scope *S, ExprResult TemplateName,
     };
     bool ValidateCandidate(const TypoCorrection &Candidate) override {
       if (auto *ND = Candidate.getCorrectionDecl())
-        return S.getAsTemplateNameDecl(ND);
+        return isAcceptableTemplateName(ND->getASTContext(), ND, true);
       return Candidate.isKeyword();
     }
   };
@@ -584,11 +561,12 @@ void Sema::diagnoseExprIntendedAsTemplateName(Scope *S, ExprResult TemplateName,
   DeclarationName Name = NameInfo.getName();
   if (TypoCorrection Corrected =
           CorrectTypo(NameInfo, LookupKind, S, &SS,
-                      llvm::make_unique<TemplateCandidateFilter>(*this),
+                      llvm::make_unique<TemplateCandidateFilter>(),
                       CTK_ErrorRecovery, LookupCtx)) {
     auto *ND = Corrected.getFoundDecl();
     if (ND)
-      ND = getAsTemplateNameDecl(ND);
+      ND = isAcceptableTemplateName(Context, ND,
+                                    /*AllowFunctionTemplates*/ true);
     if (ND || Corrected.isKeyword()) {
       if (LookupCtx) {
         std::string CorrectedStr(Corrected.getAsString(getLangOpts()));
@@ -4284,7 +4262,7 @@ TemplateNameKind Sema::ActOnDependentTemplateName(Scope *S,
                      LookupOrdinaryName);
       bool MOUS;
       if (!LookupTemplateName(R, S, SS, ObjectType.get(), EnteringContext,
-                              MOUS, TemplateKWLoc) && !R.isAmbiguous())
+                              MOUS, TemplateKWLoc))
         Diag(Name.getBeginLoc(), diag::err_no_member)
             << DNI.getName() << LookupCtx << SS.getRange();
       return TNK_Non_template;