[clang] fix canonicalization of nested name specifiers

[mizvekov]

Summary

See PR47174.

When canonicalizing nested name specifiers of the type kind,
the prefix for 'DependentTemplateSpecialization' types was being
dropped, leading to malformed types which would cause failures
when rebuilding template names.

Signed-off-by: Matheus Izvekov <[e-mail]>

[mizvekov]

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[mizvekov]

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[mizvekov]

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[mizvekov]

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clang/include/clang/Sema/Sema.h

bool CheckTemplateArgumentList(TemplateDecl *Template,
                                  SmallVectorImpl<TemplateArgument> &Converted,
                                  bool UpdateArgsWithConversions = true,
                                  bool *ConstraintsNotSatisfied = nullptr);
 
   bool CheckTemplateTypeArgument(TemplateTypeParmDecl *Param,
                                  TemplateArgumentLoc &Arg,
                            SmallVectorImpl<TemplateArgument> &Converted);
 
-  bool CheckTemplateArgument(TemplateTypeParmDecl *Param,
-                             TypeSourceInfo *Arg);
+  bool CheckTemplateArgument(TypeSourceInfo *Arg);
   ExprResult CheckTemplateArgument(NonTypeTemplateParmDecl *Param,
                                    QualType InstantiatedParamType, Expr *Arg,
                                    TemplateArgument &Converted,
                                CheckTemplateArgumentKind CTAK = CTAK_Specified);
   bool CheckTemplateTemplateArgument(TemplateTemplateParmDecl *Param,
                                      TemplateParameterList *Params,
                                      TemplateArgumentLoc &Arg);
 

clang/lib/AST/ASTContext.cpp

ASTContext::getCanonicalNestedNameSpecifier(NestedNameSpecifier *NNS) const {
 
   case NestedNameSpecifier::NamespaceAlias:
     // A namespace is canonical; build a nested-name-specifier with
     // this namespace and no prefix.
     return NestedNameSpecifier::Create(*this, nullptr,
                                     NNS->getAsNamespaceAlias()->getNamespace()
                                                       ->getOriginalNamespace());
 
+  // The difference between TypeSpec and TypeSpecWithTemplate is that the
+  // latter will have the 'template' keyword when printed.
   case NestedNameSpecifier::TypeSpec:
   case NestedNameSpecifier::TypeSpecWithTemplate: {
-    QualType T = getCanonicalType(QualType(NNS->getAsType(), 0));
+    const Type *T = getCanonicalType(NNS->getAsType());
 
     // If we have some kind of dependent-named type (e.g., "typename T::type"),
     // break it apart into its prefix and identifier, then reconsititute those
     // as the canonical nested-name-specifier. This is required to canonicalize
     // a dependent nested-name-specifier involving typedefs of dependent-name
     // types, e.g.,
     //   typedef typename T::type T1;
     //   typedef typename T1::type T2;
     if (const auto *DNT = T->getAs<DependentNameType>())
-      return NestedNameSpecifier::Create(*this, DNT->getQualifier(),
-                           const_cast<IdentifierInfo *>(DNT->getIdentifier()));
+      return NestedNameSpecifier::Create(
+          *this, DNT->getQualifier(),
+    if (const auto *DTST = T->getAs<DependentTemplateSpecializationType>())
+      return NestedNameSpecifier::Create(*this, DTST->getQualifier(), true,
+                                         const_cast<Type *>(T));
 
-    // Otherwise, just canonicalize the type, and force it to be a TypeSpec.
-    // FIXME: Why are TypeSpec and TypeSpecWithTemplate distinct in the
-    // first place?
+    // TODO: Set 'Template' parameter to true for other template types.
     return NestedNameSpecifier::Create(*this, nullptr, false,
-                                       const_cast<Type *>(T.getTypePtr()));
+                                       const_cast<Type *>(T));
   }
 
   case NestedNameSpecifier::Global:
   case NestedNameSpecifier::Super:
     // The global specifier and __super specifer are canonical and unique.
     return NNS;
   }
 

clang/lib/Sema/SemaDeclCXX.cpp

if (Qual->isDependent() && !HasTypenameKeyword) {
           Diag(D->getLocation(), diag::note_previous_definition);
           return true;
         }
       }
     }
     return false;
   }
 
+  const NestedNameSpecifier *CNNS =
+      Context.getCanonicalNestedNameSpecifier(Qual);
   for (LookupResult::iterator I = Prev.begin(), E = Prev.end(); I != E; ++I) {
     NamedDecl *D = *I;
 
     bool DTypename;
     NestedNameSpecifier *DQual;
     if (UsingDecl *UD = dyn_cast<UsingDecl>(D)) {
       DTypename = UD->hasTypename();
       DQual = UD->getQualifier();
for (LookupResult::iterator I = Prev.begin(), E = Prev.end(); I != E; ++I) {
 
     // using decls differ if one says 'typename' and the other doesn't.
     // FIXME: non-dependent using decls?
     if (HasTypenameKeyword != DTypename) continue;
 
     // using decls differ if they name different scopes (but note that
     // template instantiation can cause this check to trigger when it
     // didn't before instantiation).
-    if (Context.getCanonicalNestedNameSpecifier(Qual) !=
-        Context.getCanonicalNestedNameSpecifier(DQual))
+    if (CNNS != Context.getCanonicalNestedNameSpecifier(DQual))
       continue;
 
     Diag(NameLoc, diag::err_using_decl_redeclaration) << SS.getRange();
     Diag(D->getLocation(), diag::note_using_decl) << 1;
     return true;
   }
 
   return false;

clang/lib/Sema/SemaTemplate.cpp

if (DefaultArg) {
     assert(DefaultTInfo && "expected source information for type");
 
     // Check for unexpanded parameter packs.
     if (DiagnoseUnexpandedParameterPack(ParamNameLoc, DefaultTInfo,
                                         UPPC_DefaultArgument))
       return Param;
 
     // Check the template argument itself.
-    if (CheckTemplateArgument(Param, DefaultTInfo)) {
+    if (CheckTemplateArgument(DefaultTInfo)) {
       Param->setInvalidDecl();
       return Param;
     }
 
     Param->setDefaultArgument(DefaultTInfo);
   }
 
   return Param;
default: {
     SourceRange SR = AL.getSourceRange();
     Diag(SR.getBegin(), diag::err_template_arg_must_be_type) << SR;
     Diag(Param->getLocation(), diag::note_template_param_here);
 
     return true;
   }
   }
 
-  if (CheckTemplateArgument(Param, TSI))
+  if (CheckTemplateArgument(TSI))
     return true;
 
   // Add the converted template type argument.
   ArgType = Context.getCanonicalType(ArgType);
 
   // Objective-C ARC:
   //   If an explicitly-specified template argument type is a lifetime type
   //   with no lifetime qualifier, the __strong lifetime qualifier is inferred.
if (ConstraintsNotSatisfied)
     *ConstraintsNotSatisfied = false;
 
   // Make a copy of the template arguments for processing.  Only make the
   // changes at the end when successful in matching the arguments to the
   // template.
   TemplateArgumentListInfo NewArgs = TemplateArgs;
 
   // Make sure we get the template parameter list from the most
-  // recentdeclaration, since that is the only one that has is guaranteed to
+  // recent declaration, since that is the only one that is guaranteed to
   // have all the default template argument information.
   TemplateParameterList *Params =
       cast<TemplateDecl>(Template->getMostRecentDecl())
           ->getTemplateParameters();
 
   SourceLocation RAngleLoc = NewArgs.getRAngleLoc();
 
   // C++ [temp.arg]p1:
bool UnnamedLocalNoLinkageFinder::VisitNestedNameSpecifier(
   llvm_unreachable("Invalid NestedNameSpecifier::Kind!");
 }
 
 /// Check a template argument against its corresponding
 /// template type parameter.
 ///
 /// This routine implements the semantics of C++ [temp.arg.type]. It
 /// returns true if an error occurred, and false otherwise.
-bool Sema::CheckTemplateArgument(TemplateTypeParmDecl *Param,
-                                 TypeSourceInfo *ArgInfo) {
+bool Sema::CheckTemplateArgument(TypeSourceInfo *ArgInfo) {
   assert(ArgInfo && "invalid TypeSourceInfo");
   QualType Arg = ArgInfo->getType();
   SourceRange SR = ArgInfo->getTypeLoc().getSourceRange();
 
   if (Arg->isVariablyModifiedType()) {
     return Diag(SR.getBegin(), diag::err_variably_modified_template_arg) << Arg;
   } else if (Context.hasSameUnqualifiedType(Arg, Context.OverloadTy)) {
     return Diag(SR.getBegin(), diag::err_template_arg_overload_type) << SR;

clang/test/CXX/temp/temp.constr/temp.constr.normal/p1.cpp

 template <True T, True U>
 requires true struct S3<T, U>; // expected-error {{class template partial specialization is not more specialized than the primary template}}
 
 // Same as above, for the second position (but this was already working).
 template <True T, Bar2 U>
 requires true struct S4; // expected-note {{template is declared here}}
 template <True T, True U>
 requires true struct S4<T, U>; // expected-error {{class template partial specialization is not more specialized than the primary template}}
+
+struct X {
+  template<int> struct Y {
+    using type = int;
+  };
+};
+
+template<class T> concept C1 = sizeof(T) != 0;
+template<class T> concept C2 = C1<typename T::template Y<1>::type>;
+
+template<class T> requires C1<T> void t1() = delete;          // expected-note {{candidate function}}
+template<class T> requires C1<T> && C2<T> void t1() = delete; // expected-note {{candidate function}}
+template void t1<X>();
+void t1() { t1<X>(); } // expected-error {{call to deleted function 't1'}}
+
+template<class T> requires C1<T> void t2() {}; // expected-note 2 {{candidate function}} 
+template<class T> requires C2<T> void t2() {}; // expected-note 2 {{candidate function}}
+template void t2<X>(); // expected-error {{partial ordering for explicit instantiation of 't2' is ambiguous}}
+void t2() { t2<X>(); } // expected-error {{call to 't2' is ambiguous}}
 } // namespace PR47174