[AST] Structural equivalence of methods

[balazske]

Summary

Added structural equivalence check for C++ methods.
Improved structural equivalence tests.
Added related ASTImporter tests.

[a.sidorin]

Hi Balázs,

I think that the test changes unrelated to C++ method equivalence should be moved into a separate patch.

lib/AST/ASTStructuralEquivalence.cpp

851

bool QualifiersEqual = Method1->isStatic() == Method2->isStatic() &&
                       Method1->isConst() == Method2->isConst() &&...

if (!QualifiersEqual)
  return false;

873

if (Method1->getStmtKind() != Method2->getStmtKind())
  return false;

So we need to check only one declaration here and below.

892

These two lines look a bit strange to me. For example, should we return false if one of the methods is an overloaded operator and other one is not? I guess these conditions need to be swapped or written like this:

if (Method1->getOverloadedOperator() != Method2->getOverloadedOperator())
  return false;

const IdentifierInfo *Literal1 = Method1->getLiteralIdentifier();
const IdentifierInfo *Literal2 = Method2->getLiteralIdentifier();
if (!::IsStructurallyEquivalent(Literal1, Literal2))
  return false;

omitting the first condition.

unittests/AST/ASTImporterTest.cpp

1510

This test doesn't look related. Could you please move such tests into a separate patch?They make the review harder.

[balazske]

lib/AST/ASTStructuralEquivalence.cpp

873

What do you mean by getStmtKind? Probably getDeclKind? Anyway after the conversions it is good to check the pointers anyway, so there would be no big simplification.

892

The single if with getOverloadedOperator should be enough. getLiteralIdentifier is not applicable for methods as far as I know (even if yes it is not related to the overloaded operator) (probably it is missing from check at FunctionDecl).

[balazske]

• Updates according to review comments

[balazske]

lib/AST/ASTImporter.cpp

2454

This change with Definition is needed to make the test ImportOfEquivalentMethod work. But this is a general problem with importing, I have a new test that fails and is not related to CXXMethodDecl. Add this new (not directly related) test or remove this change and disable the failing test?

[a_sidorin]

LG with a nit. Thank you!

unittests/AST/StructuralEquivalenceTest.cpp

489

Could you add a comment why this test is disabled?

[balazske]

• Added comment into test StructuralEquivalenceRecordTest.DISABLED_Methods.

[balazske]

unittests/AST/StructuralEquivalenceTest.cpp

489

Methods are not checked, there was no decision about to include this check or not. The problem was related to performance overhead and if order-independent check of methods is needed. (ASTImporter should keep order of imported fields and methods.) (This test is about equivalence of foo.)

[a_sidorin]

unittests/AST/StructuralEquivalenceTest.cpp

489

You mean that imported decl have other order of methods? Do you mean implicit methods (because I see only a single method here)? If so, could you please note this in the comment?

[balazske]

unittests/AST/StructuralEquivalenceTest.cpp

489

The problem with the ordering is in general at structural equivalence check. If a complex structure is imported with ASTImporter the ordering of fields and methods may change in the imported class (relative to the to-be imported) after the import. Either order-independent check is needed in structural equivalence check to match two classes with same methods but in different order, or import should not change ordering. Currently none of these is implemented, methods are not checked at all. The foos in this test should be non-equivalent because one different method x.

lib/AST/ASTImporter.cpp

public:
     bool IsStructuralMatch(RecordDecl *FromRecord, RecordDecl *ToRecord,
                            bool Complain = true);
     bool IsStructuralMatch(VarDecl *FromVar, VarDecl *ToVar,
                            bool Complain = true);
     bool IsStructuralMatch(EnumDecl *FromEnum, EnumDecl *ToRecord);
     bool IsStructuralMatch(EnumConstantDecl *FromEC, EnumConstantDecl *ToEC);
     bool IsStructuralMatch(FunctionTemplateDecl *From,
                            FunctionTemplateDecl *To);
+    bool IsStructuralMatch(FunctionDecl *From, FunctionDecl *To);
     bool IsStructuralMatch(ClassTemplateDecl *From, ClassTemplateDecl *To);
     bool IsStructuralMatch(VarTemplateDecl *From, VarTemplateDecl *To);
     Decl *VisitDecl(Decl *D);
     Decl *VisitEmptyDecl(EmptyDecl *D);
     Decl *VisitAccessSpecDecl(AccessSpecDecl *D);
     Decl *VisitStaticAssertDecl(StaticAssertDecl *D);
     Decl *VisitTranslationUnitDecl(TranslationUnitDecl *D);
     Decl *VisitNamespaceDecl(NamespaceDecl *D);

 bool ASTNodeImporter::IsStructuralMatch(FunctionTemplateDecl *From,
                                         FunctionTemplateDecl *To) {
   StructuralEquivalenceContext Ctx(
       Importer.getFromContext(), Importer.getToContext(),
       Importer.getNonEquivalentDecls(), false, false);
   return Ctx.IsStructurallyEquivalent(From, To);
 }
 
+bool ASTNodeImporter::IsStructuralMatch(FunctionDecl *From, FunctionDecl *To) {
+  StructuralEquivalenceContext Ctx(
+      Importer.getFromContext(), Importer.getToContext(),
+      Importer.getNonEquivalentDecls(), false, false);
+  return Ctx.IsStructurallyEquivalent(From, To);
+}
+
 bool ASTNodeImporter::IsStructuralMatch(EnumConstantDecl *FromEC,
                                         EnumConstantDecl *ToEC) {
   const llvm::APSInt &FromVal = FromEC->getInitVal();
   const llvm::APSInt &ToVal = ToEC->getInitVal();
 
   return FromVal.isSigned() == ToVal.isSigned() &&
          FromVal.getBitWidth() == ToVal.getBitWidth() &&
          FromVal == ToVal;
else if (!LexicalDC->isFunctionOrMethod()) {
     DC->getRedeclContext()->localUncachedLookup(Name, FoundDecls);
     for (auto *FoundDecl : FoundDecls) {
       if (!FoundDecl->isInIdentifierNamespace(IDNS))
         continue;
 
       if (auto *FoundFunction = dyn_cast<FunctionDecl>(FoundDecl)) {
         if (FoundFunction->hasExternalFormalLinkage() &&
             D->hasExternalFormalLinkage()) {
-          if (Importer.IsStructurallyEquivalent(D->getType(), 
-                                                FoundFunction->getType())) {
-              if (D->doesThisDeclarationHaveABody() &&
-                  FoundFunction->hasBody())
-                return Importer.Imported(D, FoundFunction);
-              FoundByLookup = FoundFunction;
-              break;
+          if (IsStructuralMatch(D, FoundFunction)) {
+            const FunctionDecl *Definition = nullptr;
+                FoundFunction->hasBody(Definition)) {
+              return Importer.Imported(
+                  D, const_cast<FunctionDecl *>(Definition));
+            }
           }
 
           // FIXME: Check for overloading more carefully, e.g., by boosting
           // Sema::IsOverload out to the AST library.
 
           // Function overloading is okay in C++.
           if (Importer.getToContext().getLangOpts().CPlusPlus)
             continue;

lib/AST/ASTStructuralEquivalence.cpp

 }
 
 /// Determine structural equivalence of two types.
 static bool IsStructurallyEquivalent(StructuralEquivalenceContext &Context,
                                      QualType T1, QualType T2) {
   if (T1.isNull() || T2.isNull())
     return T1.isNull() && T2.isNull();
 
+  QualType OrigT1 = T1;
+  QualType OrigT2 = T2;
+
   if (!Context.StrictTypeSpelling) {
     // We aren't being strict about token-to-token equivalence of types,
     // so map down to the canonical type.
     T1 = Context.FromCtx.getCanonicalType(T1);
     T2 = Context.ToCtx.getCanonicalType(T2);
   }
 
   if (T1.getQualifiers() != T2.getQualifiers())
case Type::ExtVector: {
     if (Vec1->getVectorKind() != Vec2->getVectorKind())
       return false;
     break;
   }
 
   case Type::FunctionProto: {
     const auto *Proto1 = cast<FunctionProtoType>(T1);
     const auto *Proto2 = cast<FunctionProtoType>(T2);
+
     if (Proto1->getNumParams() != Proto2->getNumParams())
       return false;
     for (unsigned I = 0, N = Proto1->getNumParams(); I != N; ++I) {
       if (!IsStructurallyEquivalent(Context, Proto1->getParamType(I),
                                     Proto2->getParamType(I)))
         return false;
     }
     if (Proto1->isVariadic() != Proto2->isVariadic())
       return false;
-    if (Proto1->getExceptionSpecType() != Proto2->getExceptionSpecType())
-      return false;
-    if (Proto1->getExceptionSpecType() == EST_Dynamic) {
-      if (Proto1->getNumExceptions() != Proto2->getNumExceptions())
-        return false;
-      for (unsigned I = 0, N = Proto1->getNumExceptions(); I != N; ++I) {
-        if (!IsStructurallyEquivalent(Context, Proto1->getExceptionType(I),
-                                      Proto2->getExceptionType(I)))
-          return false;
-      }
-    } else if (isComputedNoexcept(Proto1->getExceptionSpecType())) {
-      if (!IsStructurallyEquivalent(Context, Proto1->getNoexceptExpr(),
-                                    Proto2->getNoexceptExpr()))
+
+    if (Proto1->getTypeQuals() != Proto2->getTypeQuals())
+    
+    // Check exceptions, this information is lost in canonical type.
+    const auto *OrigProto1 =
+        cast<FunctionProtoType>(OrigT1.getDesugaredType(Context.FromCtx));
+    const auto *OrigProto2 =
+        cast<FunctionProtoType>(OrigT2.getDesugaredType(Context.ToCtx));
+    auto Spec1 = OrigProto1->getExceptionSpecType();
+    auto Spec2 = OrigProto2->getExceptionSpecType();
+    
+    if (Spec1 != Spec2)
+      return false;
+    if (Spec1 == EST_Dynamic) {
+      if (OrigProto1->getNumExceptions() != OrigProto2->getNumExceptions())
+        return false;
+      for (unsigned I = 0, N = OrigProto1->getNumExceptions(); I != N; ++I) {
+        if (!IsStructurallyEquivalent(Context, OrigProto1->getExceptionType(I),
+                                      OrigProto2->getExceptionType(I)))
+          return false;
+      }
+    } else if (isComputedNoexcept(Spec1)) {
+      if (!IsStructurallyEquivalent(Context, OrigProto1->getNoexceptExpr(),
+                                    OrigProto2->getNoexceptExpr()))
         return false;
     }
-    if (Proto1->getTypeQuals() != Proto2->getTypeQuals())
-      return false;
 
     // Fall through to check the bits common with FunctionNoProtoType.
     LLVM_FALLTHROUGH;
   }
 
   case Type::FunctionNoProto: {
     const auto *Function1 = cast<FunctionType>(T1);
     const auto *Function2 = cast<FunctionType>(T2);
if (Bits1 != Bits2) {
       }
       return false;
     }
   }
 
   return true;
 }
 
+/// Determine structural equivalence of two methodss.
+static bool IsStructurallyEquivalent(StructuralEquivalenceContext &Context,
+                                     CXXMethodDecl *Method1,
+                                     CXXMethodDecl *Method2) {
+  bool PropertiesEqual =
+      Method1->getDeclKind() == Method2->getDeclKind() &&
+      Method1->getRefQualifier() == Method2->getRefQualifier() &&
+      Method1->getAccess() == Method2->getAccess() &&
+      Method1->getOverloadedOperator() == Method2->getOverloadedOperator() &&
+      Method1->isStatic() == Method2->isStatic() &&
+      Method1->isConst() == Method2->isConst() &&
+      Method1->isVolatile() == Method2->isVolatile() &&
+      Method1->isVirtual() == Method2->isVirtual() &&
+      Method1->isPure() == Method2->isPure() &&
+      Method1->isDefaulted() == Method2->isDefaulted() &&
+      Method1->isDeleted() == Method2->isDeleted();
+  if (!PropertiesEqual)
+    return false;
+  // FIXME: Check for 'final'.
+
+  if (auto *Constructor1 = dyn_cast<CXXConstructorDecl>(Method1)) {
+    auto *Constructor2 = cast<CXXConstructorDecl>(Method2);
+    if (Constructor1->isExplicit() != Constructor2->isExplicit())
+      return false;
+  }
+
+  if (auto *Conversion1 = dyn_cast<CXXConversionDecl>(Method1)) {
+    auto *Conversion2 = cast<CXXConversionDecl>(Method2);
+    if (Conversion1->isExplicit() != Conversion2->isExplicit())
+      return false;
+    if (!IsStructurallyEquivalent(Context, Conversion1->getConversionType(),
+                                  Conversion2->getConversionType()))
+      return false;
+  }
+
+  const IdentifierInfo *Name1 = Method1->getIdentifier();
+  const IdentifierInfo *Name2 = Method2->getIdentifier();
+  if (!::IsStructurallyEquivalent(Name1, Name2)) {
+    return false;
+    // TODO: Names do not match, add warning like at check for FieldDecl.
+  }
+
+  // Check the prototypes.
+  if (!::IsStructurallyEquivalent(Context,
+                                  Method1->getType(), Method2->getType()))
+    return false;
+
+  return true;
+}
+
 /// Determine structural equivalence of two records.
 static bool IsStructurallyEquivalent(StructuralEquivalenceContext &Context,
                                      RecordDecl *D1, RecordDecl *D2) {
   if (D1->isUnion() != D2->isUnion()) {
     if (Context.Complain) {
       Context.Diag2(D2->getLocation(),
                     Context.ErrorOnTagTypeMismatch
                         ? diag::err_odr_tag_type_inconsistent
while (!DeclsToCheck.empty()) {
     } else if (auto *TTP1 = dyn_cast<TemplateTemplateParmDecl>(D1)) {
       if (auto *TTP2 = dyn_cast<TemplateTemplateParmDecl>(D2)) {
         if (!::IsStructurallyEquivalent(*this, TTP1, TTP2))
           Equivalent = false;
       } else {
         // Kind mismatch.
         Equivalent = false;
       }
+    } else if (auto *MD1 = dyn_cast<CXXMethodDecl>(D1)) {
+      if (auto *MD2 = dyn_cast<CXXMethodDecl>(D2)) {
+        if (!::IsStructurallyEquivalent(*this, MD1, MD2))
+          Equivalent = false;
+      } else {
+        // Kind mismatch.
+        Equivalent = false;
+      }
     } else if (FunctionDecl *FD1 = dyn_cast<FunctionDecl>(D1)) {
       if (FunctionDecl *FD2 = dyn_cast<FunctionDecl>(D2)) {
         if (!::IsStructurallyEquivalent(FD1->getIdentifier(),
                                         FD2->getIdentifier()))
           Equivalent = false;
         if (!::IsStructurallyEquivalent(*this, FD1, FD2))
           Equivalent = false;
       } else {

unittests/AST/ASTImporterTest.cpp

TEST_P(ASTImporterTestBase, ImportDefinitionOfClassTemplateAfterFwdDecl) {
     Import(FromD, Lang_CXX);
     auto *FromCTD = FirstDeclMatcher<ClassTemplateDecl>().match(
         FromTU, classTemplateDecl(hasName("B")));
     auto *ToCTD = cast<ClassTemplateDecl>(Import(FromCTD, Lang_CXX));
     EXPECT_TRUE(ToCTD->isThisDeclarationADefinition());
   }
 }
 
 TEST_P(ASTImporterTestBase,
        ImportDefinitionOfClassTemplateIfThereIsAnExistingFwdDeclAndDefinition) {
   Decl *ToTU = getToTuDecl(
       R"(
       template <typename T>
       struct B {
         void f();
       };
 
testImport("struct S { template <typename T> void mem(); };"
              "  s.mem<U>();"
              "}"
              "void instantiate() { declToImport<int>(); }",
              Lang_CXX11, "", Lang_CXX11, Verifier,
              functionTemplateDecl(has(functionDecl(has(
                  compoundStmt(has(callExpr(has(unresolvedMemberExpr())))))))));
 }
 
+TEST_P(ASTImporterTestBase, ImportOfEquivalentRecord) {
+  Decl *ToR1;
+  {
+    Decl *FromTU = getTuDecl(
+        "struct A { };", Lang_CXX, "input0.cc");
+    auto *FromR = FirstDeclMatcher<CXXRecordDecl>().match(
+        FromTU, cxxRecordDecl(hasName("A")));
+
+    ToR1 = Import(FromR, Lang_CXX);
+  }
+
+  Decl *ToR2;
+  {
+    Decl *FromTU = getTuDecl(
+        "struct A { };", Lang_CXX, "input1.cc");
+    auto *FromR = FirstDeclMatcher<CXXRecordDecl>().match(
+        FromTU, cxxRecordDecl(hasName("A")));
+
+    ToR2 = Import(FromR, Lang_CXX);
+  }
+  
+  EXPECT_EQ(ToR1, ToR2);
+}
+
+TEST_P(ASTImporterTestBase, ImportOfNonEquivalentRecord) {
+  Decl *ToR1;
+  {
+    Decl *FromTU = getTuDecl(
+        "struct A { int x; };", Lang_CXX, "input0.cc");
+    auto *FromR = FirstDeclMatcher<CXXRecordDecl>().match(
+        FromTU, cxxRecordDecl(hasName("A")));
+    ToR1 = Import(FromR, Lang_CXX);
+  }
+  Decl *ToR2;
+  {
+    Decl *FromTU = getTuDecl(
+        "struct A { unsigned x; };", Lang_CXX, "input1.cc");
+    auto *FromR = FirstDeclMatcher<CXXRecordDecl>().match(
+        FromTU, cxxRecordDecl(hasName("A")));
+    ToR2 = Import(FromR, Lang_CXX);
+  }
+  EXPECT_NE(ToR1, ToR2);
+}
+
+TEST_P(ASTImporterTestBase, ImportOfEquivalentField) {
+  Decl *ToF1;
+  {
+    Decl *FromTU = getTuDecl(
+        "struct A { int x; };", Lang_CXX, "input0.cc");
+    auto *FromF = FirstDeclMatcher<FieldDecl>().match(
+        FromTU, fieldDecl(hasName("x")));
+    ToF1 = Import(FromF, Lang_CXX);
+  }
+  Decl *ToF2;
+  {
+    Decl *FromTU = getTuDecl(
+        "struct A { int x; };", Lang_CXX, "input1.cc");
+    auto *FromF = FirstDeclMatcher<FieldDecl>().match(
+        FromTU, fieldDecl(hasName("x")));
+    ToF2 = Import(FromF, Lang_CXX);
+  }
+  EXPECT_EQ(ToF1, ToF2);
+}
+
+TEST_P(ASTImporterTestBase, ImportOfNonEquivalentField) {
+  Decl *ToF1;
+  {
+    Decl *FromTU = getTuDecl(
+        "struct A { int x; };", Lang_CXX, "input0.cc");
+    auto *FromF = FirstDeclMatcher<FieldDecl>().match(
+        FromTU, fieldDecl(hasName("x")));
+    ToF1 = Import(FromF, Lang_CXX);
+  }
+  Decl *ToF2;
+  {
+    Decl *FromTU = getTuDecl(
+        "struct A { unsigned x; };", Lang_CXX, "input1.cc");
+    auto *FromF = FirstDeclMatcher<FieldDecl>().match(
+        FromTU, fieldDecl(hasName("x")));
+    ToF2 = Import(FromF, Lang_CXX);
+  }
+  EXPECT_NE(ToF1, ToF2);
+}
+
+TEST_P(ASTImporterTestBase, ImportOfEquivalentMethod) {
+  Decl *ToM1;
+  {
+    Decl *FromTU = getTuDecl(
+        "struct A { void x(); }; void A::x() { }", Lang_CXX, "input0.cc");
+    auto *FromM = FirstDeclMatcher<FunctionDecl>().match(
+        FromTU, functionDecl(hasName("x"), isDefinition()));
+    ToM1 = Import(FromM, Lang_CXX);
+  }
+  Decl *ToM2;
+  {
+    Decl *FromTU = getTuDecl(
+        "struct A { void x(); }; void A::x() { }", Lang_CXX, "input1.cc");
+    auto *FromM = FirstDeclMatcher<FunctionDecl>().match(
+        FromTU, functionDecl(hasName("x"), isDefinition()));
+    ToM2 = Import(FromM, Lang_CXX);
+  }
+  EXPECT_EQ(ToM1, ToM2);
+}
+
+TEST_P(ASTImporterTestBase, ImportOfNonEquivalentMethod) {
+  Decl *ToM1;
+  {
+    Decl *FromTU = getTuDecl(
+        "struct A { void x(); }; void A::x() { }",
+        Lang_CXX, "input0.cc");
+    auto *FromM = FirstDeclMatcher<FunctionDecl>().match(
+        FromTU, functionDecl(hasName("x"), isDefinition()));
+    ToM1 = Import(FromM, Lang_CXX);
+  }
+  Decl *ToM2;
+  {
+    Decl *FromTU = getTuDecl(
+        "struct A { void x() const; }; void A::x() const { }",
+        Lang_CXX, "input1.cc");
+    auto *FromM = FirstDeclMatcher<FunctionDecl>().match(
+        FromTU, functionDecl(hasName("x"), isDefinition()));
+    ToM2 = Import(FromM, Lang_CXX);
+  }
+  EXPECT_NE(ToM1, ToM2);
+}
+
 struct DeclContextTest : ASTImporterTestBase {};
 
 TEST_P(DeclContextTest, removeDeclOfClassTemplateSpecialization) {
   Decl *TU = getTuDecl(
       R"(
       namespace NS {
 
       template <typename T>

unittests/AST/StructuralEquivalenceTest.cpp

 namespace ast_matchers {
 
 using std::get;
 
 struct StructuralEquivalenceTest : ::testing::Test {
   std::unique_ptr<ASTUnit> AST0, AST1;
   std::string Code0, Code1; // Buffers for SourceManager
 
-  // Get a pair of Decl pointers to the synthetised declarations from the given
-  // code snipets. By default we search for the unique Decl with name 'foo' in
-  // both snippets.
-  std::tuple<NamedDecl *, NamedDecl *>
-  makeNamedDecls(const std::string &SrcCode0, const std::string &SrcCode1,
-                 Language Lang, const char *const Identifier = "foo") {
-
+  // Get a pair of node pointers into the synthesized AST from the given code
+  // snippets. To determine the returned node, a separate matcher is specified
+  // for both snippets. The first matching node is returned.
+  template <typename NodeType, typename MatcherType>
+  std::tuple<NodeType *, NodeType *> makeDecls(
+      const std::string &SrcCode0, const std::string &SrcCode1, Language Lang,
+      const MatcherType &Matcher0, const MatcherType &Matcher1) {
     this->Code0 = SrcCode0;
     this->Code1 = SrcCode1;
     ArgVector Args = getBasicRunOptionsForLanguage(Lang);
 
     const char *const InputFileName = "input.cc";
 
     AST0 = tooling::buildASTFromCodeWithArgs(Code0, Args, InputFileName);
     AST1 = tooling::buildASTFromCodeWithArgs(Code1, Args, InputFileName);
 
-    ASTContext &Ctx0 = AST0->getASTContext(), &Ctx1 = AST1->getASTContext();
+    NodeType *D0 = FirstDeclMatcher<NodeType>().match(
+        AST0->getASTContext().getTranslationUnitDecl(), Matcher0);
+    NodeType *D1 = FirstDeclMatcher<NodeType>().match(
+        AST1->getASTContext().getTranslationUnitDecl(), Matcher1);
 
-    auto getDecl = [](ASTContext &Ctx, const std::string &Name) -> NamedDecl * {
-      IdentifierInfo *SearchedII = &Ctx.Idents.get(Name);
-      assert(SearchedII && "Declaration with the identifier "
-                           "should be specified in test!");
-      DeclarationName SearchDeclName(SearchedII);
-      SmallVector<NamedDecl *, 4> FoundDecls;
-      Ctx.getTranslationUnitDecl()->localUncachedLookup(SearchDeclName,
-                                                        FoundDecls);
-
-      // We should find one Decl but one only.
-      assert(FoundDecls.size() == 1);
-
-      return FoundDecls[0];
-    };
-
-    NamedDecl *D0 = getDecl(Ctx0, Identifier);
-    NamedDecl *D1 = getDecl(Ctx1, Identifier);
-    assert(D0);
-    assert(D1);
     return std::make_tuple(D0, D1);
   }
 
+  // Get a pair of node pointers into the synthesized AST from the given code
+  // snippets. The same matcher is used for both snippets.
+  template <typename NodeType, typename MatcherType>
+  std::tuple<NodeType *, NodeType *> makeDecls(
+      const std::string &SrcCode0, const std::string &SrcCode1, Language Lang,
+      const MatcherType &AMatcher) {
+    return makeDecls<NodeType, MatcherType>(
+          SrcCode0, SrcCode1, Lang, AMatcher, AMatcher);
+  }
+
+  // Get a pair of Decl pointers to the synthesized declarations from the given
+  // code snippets. We search for the first NamedDecl with given name in both
+  // snippets.
+  std::tuple<NamedDecl *, NamedDecl *> makeNamedDecls(
+      const std::string &SrcCode0, const std::string &SrcCode1,
+      Language Lang, const char *const Identifier = "foo") {
+    auto Matcher = namedDecl(hasName(Identifier));
+    return makeDecls<NamedDecl>(SrcCode0, SrcCode1, Lang, Matcher);
+  }
+
   bool testStructuralMatch(NamedDecl *D0, NamedDecl *D1) {
     llvm::DenseSet<std::pair<Decl *, Decl *>> NonEquivalentDecls;
     StructuralEquivalenceContext Ctx(D0->getASTContext(), D1->getASTContext(),
                                      NonEquivalentDecls, false, false);
     return Ctx.IsStructurallyEquivalent(D0, D1);
   }
 
   bool testStructuralMatch(std::tuple<NamedDecl *, NamedDecl *> t) {

 
 TEST_F(StructuralEquivalenceTest, CharVsSignedCharInStruct) {
   auto Decls = makeNamedDecls("struct foo { char x; };",
                               "struct foo { signed char x; };", Lang_CXX);
   EXPECT_FALSE(testStructuralMatch(Decls));
 }
 
 TEST_F(StructuralEquivalenceTest, IntVsSignedIntTemplateSpec) {
-  auto Decls = makeNamedDecls(
-      "template <class T> struct foo; template<> struct foo<int>{};",
-      "template <class T> struct foo; template<> struct foo<signed int>{};",
-      Lang_CXX);
-  ClassTemplateSpecializationDecl *Spec0 =
-      *cast<ClassTemplateDecl>(get<0>(Decls))->spec_begin();
-  ClassTemplateSpecializationDecl *Spec1 =
-      *cast<ClassTemplateDecl>(get<1>(Decls))->spec_begin();
-  ASSERT_TRUE(Spec0 != nullptr);
-  ASSERT_TRUE(Spec1 != nullptr);
+  auto Decls = makeDecls<ClassTemplateSpecializationDecl>(
+      R"(template <class T> struct foo; template<> struct foo<int>{};)",
+      R"(template <class T> struct foo; template<> struct foo<signed int>{};)",
+      Lang_CXX,
+      classTemplateSpecializationDecl());
+  auto Spec0 = get<0>(Decls);
+  auto Spec1 = get<1>(Decls);
   EXPECT_TRUE(testStructuralMatch(Spec0, Spec1));
 }
 
 TEST_F(StructuralEquivalenceTest, CharVsSignedCharTemplateSpec) {
-  auto Decls = makeNamedDecls(
-      "template <class T> struct foo; template<> struct foo<char>{};",
-      "template <class T> struct foo; template<> struct foo<signed char>{};",
-      Lang_CXX);
-  ClassTemplateSpecializationDecl *Spec0 =
-      *cast<ClassTemplateDecl>(get<0>(Decls))->spec_begin();
-  ClassTemplateSpecializationDecl *Spec1 =
-      *cast<ClassTemplateDecl>(get<1>(Decls))->spec_begin();
-  ASSERT_TRUE(Spec0 != nullptr);
-  ASSERT_TRUE(Spec1 != nullptr);
+  auto Decls = makeDecls<ClassTemplateSpecializationDecl>(
+      R"(template <class T> struct foo; template<> struct foo<char>{};)",
+      R"(template <class T> struct foo; template<> struct foo<signed char>{};)",
+      Lang_CXX,
+      classTemplateSpecializationDecl());
+  auto Spec0 = get<0>(Decls);
+  auto Spec1 = get<1>(Decls);
   EXPECT_FALSE(testStructuralMatch(Spec0, Spec1));
 }
 
 TEST_F(StructuralEquivalenceTest, CharVsSignedCharTemplateSpecWithInheritance) {
-  auto Decls = makeNamedDecls(
+  auto Decls = makeDecls<ClassTemplateSpecializationDecl>(
       R"(
       struct true_type{};
       template <class T> struct foo;
       template<> struct foo<char> : true_type {};
       )",
       R"(
       struct true_type{};
       template <class T> struct foo;
       template<> struct foo<signed char> : true_type {};
       )",
-      Lang_CXX);
-  ClassTemplateSpecializationDecl *Spec0 =
-      *cast<ClassTemplateDecl>(get<0>(Decls))->spec_begin();
-  ClassTemplateSpecializationDecl *Spec1 =
-      *cast<ClassTemplateDecl>(get<1>(Decls))->spec_begin();
-  ASSERT_TRUE(Spec0 != nullptr);
-  ASSERT_TRUE(Spec1 != nullptr);
-  EXPECT_FALSE(testStructuralMatch(Spec0, Spec1));
+      Lang_CXX,
+      classTemplateSpecializationDecl());
+  EXPECT_FALSE(testStructuralMatch(Decls));
 }
 
 // This test is disabled for now.
 // FIXME Enable it, once the check is implemented.
 TEST_F(StructuralEquivalenceTest, DISABLED_WrongOrderInNamespace) {
   auto Code =
       R"(
       namespace NS {
TEST_F(StructuralEquivalenceTest, WrongOrderOfFieldsInClass) {
 
   // Reorder the FieldDecls
   RD->removeDecl(FD);
   RD->addDeclInternal(FD);
 
   EXPECT_FALSE(testStructuralMatch(Decls));
 }
 
+struct StructuralEquivalenceFunctionTest : StructuralEquivalenceTest {
+};
+
+TEST_F(StructuralEquivalenceFunctionTest, ParamConstWithRef) {
+  auto t = makeNamedDecls("void foo(int&);",
+                          "void foo(const int&);", Lang_CXX);
+  EXPECT_FALSE(testStructuralMatch(t));
+}
+
+TEST_F(StructuralEquivalenceFunctionTest, ParamConstSimple) {
+  auto t = makeNamedDecls("void foo(int);",
+                          "void foo(const int);", Lang_CXX);
+  EXPECT_TRUE(testStructuralMatch(t));
+  // consider this OK
+}
+
+TEST_F(StructuralEquivalenceFunctionTest, Throw) {
+  auto t = makeNamedDecls("void foo();",
+                          "void foo() throw();", Lang_CXX);
+  EXPECT_FALSE(testStructuralMatch(t));
+}
+
+TEST_F(StructuralEquivalenceFunctionTest, Noexcept) {
+  auto t = makeNamedDecls("void foo();",
+                          "void foo() noexcept;", Lang_CXX11);
+  EXPECT_FALSE(testStructuralMatch(t));
+}
+
+TEST_F(StructuralEquivalenceFunctionTest, ThrowVsNoexcept) {
+  auto t = makeNamedDecls("void foo() throw();",
+                          "void foo() noexcept;", Lang_CXX11);
+  EXPECT_FALSE(testStructuralMatch(t));
+}
+
+TEST_F(StructuralEquivalenceFunctionTest, ThrowVsNoexceptFalse) {
+  auto t = makeNamedDecls("void foo() throw();",
+                          "void foo() noexcept(false);", Lang_CXX11);
+  EXPECT_FALSE(testStructuralMatch(t));
+}
+
+TEST_F(StructuralEquivalenceFunctionTest, ThrowVsNoexceptTrue) {
+  auto t = makeNamedDecls("void foo() throw();",
+                          "void foo() noexcept(true);", Lang_CXX11);
+  EXPECT_FALSE(testStructuralMatch(t));
+}
+
+TEST_F(StructuralEquivalenceFunctionTest, DISABLED_NoexceptNonMatch) {
+  // The expression is not checked yet.
+  auto t = makeNamedDecls("void foo() noexcept(false);",
+                          "void foo() noexcept(true);", Lang_CXX11);
+  EXPECT_FALSE(testStructuralMatch(t));
+}
+
+TEST_F(StructuralEquivalenceFunctionTest, NoexceptMatch) {
+  auto t = makeNamedDecls("void foo() noexcept(false);",
+                          "void foo() noexcept(false);", Lang_CXX11);
+  EXPECT_TRUE(testStructuralMatch(t));
+}
+
+TEST_F(StructuralEquivalenceFunctionTest, NoexceptVsNoexceptFalse) {
+  auto t = makeNamedDecls("void foo() noexcept;",
+                          "void foo() noexcept(false);", Lang_CXX11);
+  EXPECT_FALSE(testStructuralMatch(t));
+}
+
+TEST_F(StructuralEquivalenceFunctionTest, NoexceptVsNoexceptTrue) {
+  auto t = makeNamedDecls("void foo() noexcept;",
+                          "void foo() noexcept(true);", Lang_CXX11);
+  EXPECT_FALSE(testStructuralMatch(t));
+}
+
+TEST_F(StructuralEquivalenceFunctionTest, ReturnType) {
+  auto t = makeNamedDecls("char foo();",
+                          "int foo();", Lang_CXX);
+  EXPECT_FALSE(testStructuralMatch(t));
+}
+
+TEST_F(StructuralEquivalenceFunctionTest, ReturnConst) {
+  auto t = makeNamedDecls("char foo();",
+                          "const char foo();", Lang_CXX);
+  EXPECT_FALSE(testStructuralMatch(t));
+}
+
+TEST_F(StructuralEquivalenceFunctionTest, ReturnRef) {
+  auto t = makeNamedDecls("char &foo();",
+                          "char &&foo();", Lang_CXX11);
+  EXPECT_FALSE(testStructuralMatch(t));
+}
+
+TEST_F(StructuralEquivalenceFunctionTest, ParamCount) {
+  auto t = makeNamedDecls("void foo(int);",
+                          "void foo(int, int);", Lang_CXX);
+  EXPECT_FALSE(testStructuralMatch(t));
+}
+
+TEST_F(StructuralEquivalenceFunctionTest, ParamType) {
+  auto t = makeNamedDecls("void foo(int);",
+                          "void foo(char);", Lang_CXX);
+  EXPECT_FALSE(testStructuralMatch(t));
+}
+
+TEST_F(StructuralEquivalenceFunctionTest, ParamName) {
+  auto t = makeNamedDecls("void foo(int a);",
+                          "void foo(int b);", Lang_CXX);
+  EXPECT_TRUE(testStructuralMatch(t));
+}
+
+TEST_F(StructuralEquivalenceFunctionTest, Variadic) {
+  auto t = makeNamedDecls("void foo(int x...);",
+                          "void foo(int x);", Lang_CXX);
+  EXPECT_FALSE(testStructuralMatch(t));
+}
+
+TEST_F(StructuralEquivalenceFunctionTest, ParamPtr) {
+  auto t = makeNamedDecls("void foo(int *);",
+                          "void foo(int);", Lang_CXX);
+  EXPECT_FALSE(testStructuralMatch(t));
+}
+
+TEST_F(StructuralEquivalenceFunctionTest, NameInParen) {
+  auto t = makeNamedDecls(
+      "void ((foo))();",
+      "void foo();",
+      Lang_CXX);
+  EXPECT_TRUE(testStructuralMatch(t));
+}
+
+TEST_F(StructuralEquivalenceFunctionTest, NameInParenWithExceptionSpec) {
+  auto t = makeNamedDecls(
+      "void (foo)() throw(int);",
+      "void (foo)() noexcept;",
+      Lang_CXX11);
+  EXPECT_FALSE(testStructuralMatch(t));
+}
+
+TEST_F(StructuralEquivalenceFunctionTest, NameInParenWithConst) {
+  auto t = makeNamedDecls(
+      "struct A { void (foo)() const; };",
+      "struct A { void (foo)(); };",
+      Lang_CXX11);
+  EXPECT_FALSE(testStructuralMatch(t));
+}
+
+struct StructuralEquivalenceCXXMethodTest : StructuralEquivalenceTest {
+};
+
+TEST_F(StructuralEquivalenceCXXMethodTest, Virtual) {
+  auto t = makeDecls<CXXMethodDecl>(
+      "struct X { void foo(); };",
+      "struct X { virtual void foo(); };", Lang_CXX,
+      cxxMethodDecl(hasName("foo")));
+  EXPECT_FALSE(testStructuralMatch(t));
+}
+
+TEST_F(StructuralEquivalenceCXXMethodTest, Pure) {
+  auto t = makeNamedDecls("struct X { virtual void foo(); };",
+                          "struct X { virtual void foo() = 0; };", Lang_CXX);
+  EXPECT_FALSE(testStructuralMatch(t));
+}
+
+TEST_F(StructuralEquivalenceCXXMethodTest, DISABLED_Final) {
+  // The final-ness is not checked yet.
+  auto t = makeNamedDecls("struct X { virtual void foo(); };",
+                          "struct X { virtual void foo() final; };", Lang_CXX);
+  EXPECT_FALSE(testStructuralMatch(t));
+}
+
+TEST_F(StructuralEquivalenceCXXMethodTest, Const) {
+  auto t = makeNamedDecls("struct X { void foo(); };",
+                          "struct X { void foo() const; };", Lang_CXX);
+  EXPECT_FALSE(testStructuralMatch(t));
+}
+
+TEST_F(StructuralEquivalenceCXXMethodTest, Static) {
+  auto t = makeNamedDecls("struct X { void foo(); };",
+                          "struct X { static void foo(); };", Lang_CXX);
+  EXPECT_FALSE(testStructuralMatch(t));
+}
+
+TEST_F(StructuralEquivalenceCXXMethodTest, Ref1) {
+  auto t = makeNamedDecls("struct X { void foo(); };",
+                          "struct X { void foo() &&; };", Lang_CXX11);
+  EXPECT_FALSE(testStructuralMatch(t));
+}
+
+TEST_F(StructuralEquivalenceCXXMethodTest, Ref2) {
+  auto t = makeNamedDecls("struct X { void foo() &; };",
+                          "struct X { void foo() &&; };", Lang_CXX11);
+  EXPECT_FALSE(testStructuralMatch(t));
+}
+
+TEST_F(StructuralEquivalenceCXXMethodTest, AccessSpecifier) {
+  auto t = makeDecls<CXXMethodDecl>(
+      "struct X { public: void foo(); };",
+      "struct X { private: void foo(); };", Lang_CXX,
+      cxxMethodDecl(hasName("foo")));
+  EXPECT_FALSE(testStructuralMatch(t));
+}
+
+TEST_F(StructuralEquivalenceCXXMethodTest, Delete) {
+  auto t = makeNamedDecls("struct X { void foo(); };",
+                          "struct X { void foo() = delete; };", Lang_CXX11);
+  EXPECT_FALSE(testStructuralMatch(t));
+}
+
+TEST_F(StructuralEquivalenceCXXMethodTest, Constructor) {
+  auto t = makeDecls<FunctionDecl>(
+      "void foo();", "struct foo { foo(); };", Lang_CXX,
+      functionDecl(), cxxConstructorDecl());
+  EXPECT_FALSE(testStructuralMatch(t));
+}
+
+TEST_F(StructuralEquivalenceCXXMethodTest, ConstructorParam) {
+  auto t = makeDecls<CXXConstructorDecl>("struct X { X(); };",
+                                         "struct X { X(int); };", Lang_CXX,
+                                         cxxConstructorDecl());
+  EXPECT_FALSE(testStructuralMatch(t));
+}
+
+TEST_F(StructuralEquivalenceCXXMethodTest, ConstructorExplicit) {
+  auto t = makeDecls<CXXConstructorDecl>("struct X { X(int); };",
+                                         "struct X { explicit X(int); };",
+                                         Lang_CXX11,
+                                         cxxConstructorDecl());
+  EXPECT_FALSE(testStructuralMatch(t));
+}
+
+TEST_F(StructuralEquivalenceCXXMethodTest, ConstructorDefault) {
+  auto t = makeDecls<CXXConstructorDecl>("struct X { X(); };",
+                                         "struct X { X() = default; };",
+                                         Lang_CXX11,
+                                         cxxConstructorDecl());
+  EXPECT_FALSE(testStructuralMatch(t));
+}
+
+TEST_F(StructuralEquivalenceCXXMethodTest, Conversion) {
+  auto t = makeDecls<CXXConversionDecl>("struct X { operator bool(); };",
+                                        "struct X { operator char(); };",
+                                         Lang_CXX11,
+                                         cxxConversionDecl());
+  EXPECT_FALSE(testStructuralMatch(t));
+}
+
+TEST_F(StructuralEquivalenceCXXMethodTest, Operator) {
+  auto t = makeDecls<FunctionDecl>(
+      "struct X { int operator +(int); };",
+      "struct X { int operator -(int); };", Lang_CXX,
+      functionDecl(hasOverloadedOperatorName("+")),
+      functionDecl(hasOverloadedOperatorName("-")));
+  EXPECT_FALSE(testStructuralMatch(t));
+}
+
+TEST_F(StructuralEquivalenceCXXMethodTest, OutOfClass1) {
+  auto t = makeDecls<FunctionDecl>(
+      "struct X { virtual void f(); }; void X::f() { }",
+      "struct X { virtual void f() { }; };",
+      Lang_CXX,
+      functionDecl(allOf(hasName("f"), isDefinition())));
+  EXPECT_TRUE(testStructuralMatch(t));
+}
+
+TEST_F(StructuralEquivalenceCXXMethodTest, OutOfClass2) {
+  auto t = makeDecls<FunctionDecl>(
+      "struct X { virtual void f(); }; void X::f() { }",
+      "struct X { void f(); }; void X::f() { }",
+      Lang_CXX,
+      functionDecl(allOf(hasName("f"), isDefinition())));
+  EXPECT_FALSE(testStructuralMatch(t));
+}
+
+struct StructuralEquivalenceRecordTest : StructuralEquivalenceTest {
+};
+
+TEST_F(StructuralEquivalenceRecordTest, Name) {
+  auto t = makeDecls<CXXRecordDecl>(
+      "struct A{ };",
+      "struct B{ };",
+      Lang_CXX,
+      cxxRecordDecl());
+  EXPECT_FALSE(testStructuralMatch(t));
+}
+
+TEST_F(StructuralEquivalenceRecordTest, Fields) {
+  auto t = makeNamedDecls(
+      "struct foo{ int x; };",
+      "struct foo{ char x; };",
+      Lang_CXX);
+  EXPECT_FALSE(testStructuralMatch(t));
+}
+
+TEST_F(StructuralEquivalenceRecordTest, DISABLED_Methods) {
+  auto t = makeNamedDecls(
+      "struct foo{ int x(); };",
+      "struct foo{ char x(); };",
+      Lang_CXX);
+  EXPECT_FALSE(testStructuralMatch(t));
+}
+
+TEST_F(StructuralEquivalenceRecordTest, Bases) {
+  auto t = makeNamedDecls(
+      "struct A{ }; struct foo: A { };",
+      "struct B{ }; struct foo: B { };",
+      Lang_CXX);
+  EXPECT_FALSE(testStructuralMatch(t));
+}
+
+TEST_F(StructuralEquivalenceRecordTest, InheritanceVirtual) {
+  auto t = makeNamedDecls(
+      "struct A{ }; struct foo: A { };",
+      "struct A{ }; struct foo: virtual A { };",
+      Lang_CXX);
+  EXPECT_FALSE(testStructuralMatch(t));
+}
+
+TEST_F(StructuralEquivalenceRecordTest, DISABLED_InheritanceType) {
+  // Access specifier in inheritance is not checked yet.
+  auto t = makeNamedDecls(
+      "struct A{ }; struct foo: public A { };",
+      "struct A{ }; struct foo: private A { };",
+      Lang_CXX);
+  EXPECT_FALSE(testStructuralMatch(t));
+}
+
+TEST_F(StructuralEquivalenceRecordTest, Match) {
+  auto Code = R"(
+      struct A{ };
+      struct B{ };
+      struct foo: A, virtual B {
+        void x();
+        int a;
+      };
+      )";
+  auto t = makeNamedDecls(Code, Code, Lang_CXX);
+  EXPECT_TRUE(testStructuralMatch(t));
+}
+
+TEST_F(StructuralEquivalenceTest, CompareSameDeclWithMultiple) {
+  auto t = makeNamedDecls(
+      "struct A{ }; struct B{ }; void foo(A a, A b);",
+      "struct A{ }; struct B{ }; void foo(A a, B b);",
+      Lang_CXX);
+  EXPECT_FALSE(testStructuralMatch(t));
+}
+
 } // end namespace ast_matchers
 } // end namespace clang