[clang] 27ab138 - [clang][ASTImporter] Import TemplateName correctly

[Balázs Kéri via cfe-commits]

Author: Balázs Kéri
Date: 2023-03-03T09:16:43+01:00
New Revision: 27ab138c69fc61b22ef898a0f4d0f5c9bad649bd

URL: https://github.com/llvm/llvm-project/commit/27ab138c69fc61b22ef898a0f4d0f5c9bad649bd
DIFF: https://github.com/llvm/llvm-project/commit/27ab138c69fc61b22ef898a0f4d0f5c9bad649bd.diff

LOG: [clang][ASTImporter] Import TemplateName correctly

This is a fix for a problem when multiple template
specializations are created by ASTImporter for the
same specialization. The problem happens if a
TemplateName is imported that points to a template
delcaration (for a template template argument)
(specialization) that has multiple instances in the
declaration chain. If two TemplateName objects contain
different pointers to a template specialization,
these TemplateName objects will have different checksum
even if they point into the same declaration chain.
The problem is fixed if the canonical declaration is used.

Reviewed By: vabridgers, donat.nagy

Differential Revision: https://reviews.llvm.org/D144622

Added: 
    

Modified: 
    clang/lib/AST/ASTImporter.cpp
    clang/unittests/AST/ASTImporterTest.cpp

Removed: 
    


################################################################################
diff  --git a/clang/lib/AST/ASTImporter.cpp b/clang/lib/AST/ASTImporter.cpp
index 4c173ebb10d1e..bd055082778df 100644
--- a/clang/lib/AST/ASTImporter.cpp
+++ b/clang/lib/AST/ASTImporter.cpp
@@ -9385,7 +9385,7 @@ Expected<TemplateName> ASTImporter::Import(TemplateName From) {
   switch (From.getKind()) {
   case TemplateName::Template:
     if (ExpectedDecl ToTemplateOrErr = Import(From.getAsTemplateDecl()))
-      return TemplateName(cast<TemplateDecl>(*ToTemplateOrErr));
+      return TemplateName(cast<TemplateDecl>((*ToTemplateOrErr)->getCanonicalDecl()));
     else
       return ToTemplateOrErr.takeError();
 

diff  --git a/clang/unittests/AST/ASTImporterTest.cpp b/clang/unittests/AST/ASTImporterTest.cpp
index 87b9fe52d906c..3c9b804a92e13 100644
--- a/clang/unittests/AST/ASTImporterTest.cpp
+++ b/clang/unittests/AST/ASTImporterTest.cpp
@@ -8378,6 +8378,66 @@ TEST_P(ImportInjectedClassNameType, ImportTypedefType) {
   EXPECT_TRUE(ToCtx.hasSameType(ToInjTypedef, ToInjParmVar));
 }
 
+TEST_P(ASTImporterOptionSpecificTestBase, ImportCorrectTemplateName) {
+  constexpr auto TestCode = R"(
+      template <class T>
+      struct A;
+      template <class T>
+      struct A {};
+      template <template<class> class T = A>
+      struct B {};
+      using C = B<>;
+      )";
+  Decl *ToTU = getToTuDecl(TestCode, Lang_CXX11);
+  Decl *FromTU = getTuDecl(TestCode, Lang_CXX11);
+
+  auto *ToUsingFirst = FirstDeclMatcher<TypeAliasDecl>().match(
+      ToTU, typeAliasDecl(hasName("C")));
+
+  auto *FromUsing = FirstDeclMatcher<TypeAliasDecl>().match(
+      FromTU, typeAliasDecl(hasName("C")));
+  auto *ToUsing = Import(FromUsing, Lang_CXX11);
+  EXPECT_TRUE(ToUsing);
+
+  auto *ToB = FirstDeclMatcher<ClassTemplateDecl>().match(
+      ToTU, classTemplateDecl(hasName("B")));
+  auto *ToB1 = LastDeclMatcher<ClassTemplateDecl>().match(
+      ToTU, classTemplateDecl(hasName("B")));
+  // One template definition of 'B' should exist.
+  EXPECT_EQ(ToB, ToB1);
+
+  // These declarations are imported separately.
+  EXPECT_NE(ToUsingFirst, ToUsing);
+
+  auto SpB = ToB->spec_begin();
+  auto SpE = ToB->spec_end();
+  EXPECT_TRUE(SpB != SpE);
+  ClassTemplateSpecializationDecl *Spec1 = *SpB;
+  ++SpB;
+  // The template 'B' should have one specialization (with default argument).
+  EXPECT_TRUE(SpB == SpE);
+
+  // Even if 'B' has one specialization with the default arguments, the AST
+  // contains after the import two specializations that are linked in the
+  // declaration chain. The 'spec_begin' iteration does not find these because
+  // the template arguments are the same. But the imported type alias has the
+  // link to the second specialization. The template name object in these
+  // specializations must point to the same (and one) instance of definition of
+  // 'B'.
+  auto *Spec2 = cast<ClassTemplateSpecializationDecl>(
+      ToUsing->getUnderlyingType()
+          ->getAs<TemplateSpecializationType>()
+          ->getAsRecordDecl());
+  EXPECT_NE(Spec1, Spec2);
+  EXPECT_TRUE(Spec1->getPreviousDecl() == Spec2 ||
+              Spec2->getPreviousDecl() == Spec1);
+  TemplateDecl *Templ1 =
+      Spec1->getTemplateArgs()[0].getAsTemplate().getAsTemplateDecl();
+  TemplateDecl *Templ2 =
+      Spec2->getTemplateArgs()[0].getAsTemplate().getAsTemplateDecl();
+  EXPECT_EQ(Templ1, Templ2);
+}
+
 INSTANTIATE_TEST_SUITE_P(ParameterizedTests, ASTImporterLookupTableTest,
                          DefaultTestValuesForRunOptions);