[ASTImporter] Fix inequivalence of ClassTemplateInstantiations

[martong]

Summary

We falsely state inequivalence if the template parameter is a
qualified/nonquialified template in the first/second instantiation.
Also, different kinds of TemplateName should be equal if the template
decl (if available) is equal (even if the name kind is different).

[a_sidorin]

Hi Gabor,
This looks fine, but could you please add a test showing how decl shadowing is handled? I.e. if we have Arg in one TU and both Arg and N::Arg in another TU.

[martong]

• Add test case ClassTemplSpecWithInequivalentShadowedTemplArg

[martong]

In D64241#1584972, @a_sidorin wrote:

Hi Gabor,
This looks fine, but could you please add a test showing how decl shadowing is handled? I.e. if we have Arg in one TU and both Arg and N::Arg in another TU.

Alexei,

Thanks for the review! I've added a new test case for that.

[martong]

@a_sidorin This is a polite Ping.

[a_sidorin]

Looks good! Sorry for the delay :(

clang/lib/AST/ASTStructuralEquivalence.cpp

return IsStructurallyEquivalent(Context, NNS1->getAsRecordDecl(),
                                     NNS2->getAsRecordDecl());
   }
   return false;
 }
 
 static bool IsStructurallyEquivalent(StructuralEquivalenceContext &Context,
                                      const TemplateName &N1,
                                      const TemplateName &N2) {
+  TemplateDecl *TemplateDeclN1 = N1.getAsTemplateDecl();
+  TemplateDecl *TemplateDeclN2 = N2.getAsTemplateDecl();
+  if (TemplateDeclN1 && TemplateDeclN2) {
+    if (!IsStructurallyEquivalent(Context, TemplateDeclN1, TemplateDeclN2))
+      return false;
+    // If the kind is different we compare only the template decl.
     if (N1.getKind() != N2.getKind())
+      return true;
+  } else if (TemplateDeclN1 || TemplateDeclN2)
     return false;
+  else if (N1.getKind() != N2.getKind())
+    return false;
+
+  // Check for special case incompatibilities.
   switch (N1.getKind()) {
-  case TemplateName::Template:
-    return IsStructurallyEquivalent(Context, N1.getAsTemplateDecl(),
-                                    N2.getAsTemplateDecl());
 
   case TemplateName::OverloadedTemplate: {
     OverloadedTemplateStorage *OS1 = N1.getAsOverloadedTemplate(),
                               *OS2 = N2.getAsOverloadedTemplate();
     OverloadedTemplateStorage::iterator I1 = OS1->begin(), I2 = OS2->begin(),
                                         E1 = OS1->end(), E2 = OS2->end();
     for (; I1 != E1 && I2 != E2; ++I1, ++I2)
       if (!IsStructurallyEquivalent(Context, *I1, *I2))
         return false;
     return I1 == E1 && I2 == E2;
   }
 
   case TemplateName::AssumedTemplate: {
     AssumedTemplateStorage *TN1 = N1.getAsAssumedTemplateName(),
                            *TN2 = N1.getAsAssumedTemplateName();
     return TN1->getDeclName() == TN2->getDeclName();
   }
 
-  case TemplateName::QualifiedTemplate: {
-    QualifiedTemplateName *QN1 = N1.getAsQualifiedTemplateName(),
-                          *QN2 = N2.getAsQualifiedTemplateName();
-    return IsStructurallyEquivalent(Context, QN1->getDecl(), QN2->getDecl()) &&
-           IsStructurallyEquivalent(Context, QN1->getQualifier(),
-                                    QN2->getQualifier());
-  }
-
   case TemplateName::DependentTemplate: {
     DependentTemplateName *DN1 = N1.getAsDependentTemplateName(),
                           *DN2 = N2.getAsDependentTemplateName();
     if (!IsStructurallyEquivalent(Context, DN1->getQualifier(),
                                   DN2->getQualifier()))
       return false;
     if (DN1->isIdentifier() && DN2->isIdentifier())
       return IsStructurallyEquivalent(DN1->getIdentifier(),
                                       DN2->getIdentifier());
     else if (DN1->isOverloadedOperator() && DN2->isOverloadedOperator())
       return DN1->getOperator() == DN2->getOperator();
     return false;
   }
 
-  case TemplateName::SubstTemplateTemplateParm: {
-    SubstTemplateTemplateParmStorage *TS1 = N1.getAsSubstTemplateTemplateParm(),
-                                     *TS2 = N2.getAsSubstTemplateTemplateParm();
-    return IsStructurallyEquivalent(Context, TS1->getParameter(),
-                                    TS2->getParameter()) &&
-           IsStructurallyEquivalent(Context, TS1->getReplacement(),
-                                    TS2->getReplacement());
-  }
-
   case TemplateName::SubstTemplateTemplateParmPack: {
     SubstTemplateTemplateParmPackStorage
         *P1 = N1.getAsSubstTemplateTemplateParmPack(),
         *P2 = N2.getAsSubstTemplateTemplateParmPack();
     return IsStructurallyEquivalent(Context, P1->getArgumentPack(),
                                     P2->getArgumentPack()) &&
            IsStructurallyEquivalent(Context, P1->getParameterPack(),
                                     P2->getParameterPack());
   }
+
+   case TemplateName::Template:
+   case TemplateName::QualifiedTemplate:
+   case TemplateName::SubstTemplateTemplateParm:
+     // It is sufficient to check value of getAsTemplateDecl.
+     break;
+
   }
-  return false;
+
+  return true;
 }
 
 /// Determine whether two template arguments are equivalent.
 static bool IsStructurallyEquivalent(StructuralEquivalenceContext &Context,
                                      const TemplateArgument &Arg1,
                                      const TemplateArgument &Arg2) {
   if (Arg1.getKind() != Arg2.getKind())
     return false;

clang/unittests/AST/StructuralEquivalenceTest.cpp

auto Decls = makeNamedDecls("template <bool b> struct foo {explicit(b) foo(int);};",
                               "template <bool b> struct foo {explicit(!b) foo(int);};", Lang_CXX2a);
   CXXConstructorDecl *First = FirstDeclMatcher<CXXConstructorDecl>().match(
       get<0>(Decls), cxxConstructorDecl(hasName("foo<b>")));
   CXXConstructorDecl *Second = FirstDeclMatcher<CXXConstructorDecl>().match(
       get<1>(Decls), cxxConstructorDecl(hasName("foo<b>")));
   EXPECT_FALSE(testStructuralMatch(First, Second));
 }
 
+TEST_F(StructuralEquivalenceTemplateTest,
+       TemplateVsSubstTemplateTemplateParmInArgEq) {
+  auto t = makeDecls<ClassTemplateSpecializationDecl>(
+      R"(
+template <typename P1> class Arg { };
+template <template <typename PP1> class P1> class Primary { };
+
+void f() {
+  // Make specialization with simple template.
+  Primary <Arg> A;
+}
+      )",
+      R"(
+template <typename P1> class Arg { };
+template <template <typename PP1> class P1> class Primary { };
+
+template <template <typename PP1> class P1> class Templ {
+  void f() {
+    // Make specialization with substituted template template param.
+    Primary <P1> A;
+  };
+};
+
+// Instantiate with substitution Arg into P1.
+template class Templ <Arg>;
+      )",
+      Lang_CXX, classTemplateSpecializationDecl(hasName("Primary")));
+  EXPECT_TRUE(testStructuralMatch(t));
+}
+
+TEST_F(StructuralEquivalenceTemplateTest,
+       TemplateVsSubstTemplateTemplateParmInArgNotEq) {
+  auto t = makeDecls<ClassTemplateSpecializationDecl>(
+      R"(
+template <typename P1> class Arg { };
+template <template <typename PP1> class P1> class Primary { };
+
+void f() {
+  // Make specialization with simple template.
+  Primary <Arg> A;
+}
+      )",
+      R"(
+// Arg is different from the other, this should cause non-equivalence.
+template <typename P1> class Arg { int X; };
+template <template <typename PP1> class P1> class Primary { };
+
+template <template <typename PP1> class P1> class Templ {
+  void f() {
+    // Make specialization with substituted template template param.
+    Primary <P1> A;
+  };
+};
+
+// Instantiate with substitution Arg into P1.
+template class Templ <Arg>;
+      )",
+      Lang_CXX, classTemplateSpecializationDecl(hasName("Primary")));
+  EXPECT_FALSE(testStructuralMatch(t));
+}
+
 struct StructuralEquivalenceDependentTemplateArgsTest
     : StructuralEquivalenceTemplateTest {};
 
 TEST_F(StructuralEquivalenceDependentTemplateArgsTest,
        SameStructsInDependentArgs) {
   std::string Code =
       R"(
       template <typename>
auto t = makeDecls<FunctionTemplateDecl>(Code + R"(
         void f();
       };
       )",
                                            Lang_CXX,
                                            functionTemplateDecl(hasName("f")));
   EXPECT_FALSE(testStructuralMatch(t));
 }
 
+TEST_F(
+    StructuralEquivalenceTemplateTest,
+    ClassTemplSpecWithQualifiedAndNonQualifiedTypeArgsShouldBeEqual) {
+  auto t = makeDecls<ClassTemplateSpecializationDecl>(
+      R"(
+      template <class T> struct Primary {};
+      namespace N {
+        struct Arg;
+      }
+      // Explicit instantiation with qualified name.
+      template struct Primary<N::Arg>;
+      )",
+      R"(
+      template <class T> struct Primary {};
+      namespace N {
+        struct Arg;
+      }
+      using namespace N;
+      // Explicit instantiation with UNqualified name.
+      template struct Primary<Arg>;
+      )",
+      Lang_CXX,
+      classTemplateSpecializationDecl(hasName("Primary")));
+  EXPECT_TRUE(testStructuralMatch(t));
+}
+
+TEST_F(
+    StructuralEquivalenceTemplateTest,
+    ClassTemplSpecWithInequivalentQualifiedAndNonQualifiedTypeArgs) {
+  auto t = makeDecls<ClassTemplateSpecializationDecl>(
+      R"(
+      template <class T> struct Primary {};
+      namespace N {
+        struct Arg { int a; };
+      }
+      // Explicit instantiation with qualified name.
+      template struct Primary<N::Arg>;
+      )",
+      R"(
+      template <class T> struct Primary {};
+      namespace N {
+        // This struct is not equivalent with the other in the prev TU.
+        struct Arg { double b; }; // -- Field mismatch.
+      }
+      using namespace N;
+      // Explicit instantiation with UNqualified name.
+      template struct Primary<Arg>;
+      )",
+      Lang_CXX,
+      classTemplateSpecializationDecl(hasName("Primary")));
+  EXPECT_FALSE(testStructuralMatch(t));
+}
+
+TEST_F(
+    StructuralEquivalenceTemplateTest,
+    ClassTemplSpecWithQualifiedAndNonQualifiedTemplArgsShouldBeEqual) {
+  auto t = makeDecls<ClassTemplateSpecializationDecl>(
+      R"(
+      template <template <class> class T> struct Primary {};
+      namespace N {
+        template <class T> struct Arg;
+      }
+      // Explicit instantiation with qualified name.
+      template struct Primary<N::Arg>;
+      )",
+      R"(
+      template <template <class> class T> struct Primary {};
+      namespace N {
+        template <class T> struct Arg;
+      }
+      using namespace N;
+      // Explicit instantiation with UNqualified name.
+      template struct Primary<Arg>;
+      )",
+      Lang_CXX,
+      classTemplateSpecializationDecl(hasName("Primary")));
+  EXPECT_TRUE(testStructuralMatch(t));
+}
+
+TEST_F(
+    StructuralEquivalenceTemplateTest,
+    ClassTemplSpecWithInequivalentQualifiedAndNonQualifiedTemplArgs) {
+  auto t = makeDecls<ClassTemplateSpecializationDecl>(
+      R"(
+      template <template <class> class T> struct Primary {};
+      namespace N {
+        template <class T> struct Arg { int a; };
+      }
+      // Explicit instantiation with qualified name.
+      template struct Primary<N::Arg>;
+      )",
+      R"(
+      template <template <class> class T> struct Primary {};
+      namespace N {
+        // This template is not equivalent with the other in the prev TU.
+        template <class T> struct Arg { double b; }; // -- Field mismatch.
+      }
+      using namespace N;
+      // Explicit instantiation with UNqualified name.
+      template struct Primary<Arg>;
+      )",
+      Lang_CXX,
+      classTemplateSpecializationDecl(hasName("Primary")));
+  EXPECT_FALSE(testStructuralMatch(t));
+}
+
+TEST_F(
+    StructuralEquivalenceTemplateTest,
+    ClassTemplSpecWithInequivalentShadowedTemplArg) {
+  auto t = makeDecls<ClassTemplateSpecializationDecl>(
+      R"(
+      template <template <class> class T> struct Primary {};
+      template <class T> struct Arg { int a; };
+      // Explicit instantiation with ::Arg
+      template struct Primary<Arg>;
+      )",
+      R"(
+      template <template <class> class T> struct Primary {};
+      template <class T> struct Arg { int a; };
+      namespace N {
+        // This template is not equivalent with the other in the global scope.
+        template <class T> struct Arg { double b; }; // -- Field mismatch.
+        // Explicit instantiation with N::Arg which shadows ::Arg
+        template struct Primary<Arg>;
+      }
+      )",
+      Lang_CXX,
+      classTemplateSpecializationDecl(hasName("Primary")));
+  EXPECT_FALSE(testStructuralMatch(t));
+}
+
 } // end namespace ast_matchers
 } // end namespace clang