[Clang][Sema] Attempt to fix CTAD faulty copy of non-local typedefs

http://lists.llvm.org/pipermail/cfe-dev/2020-November/067252.html

Differential Revision: https://reviews.llvm.org/D92101

Author: Gabor Marton

clang/lib/Sema/SemaTemplate.cpp

@@ -2077,27 +2077,28 @@ class ExtractTypeForDeductionGuide
   QualType TransformTypedefType(TypeLocBuilder &TLB, TypedefTypeLoc TL) {
     ASTContext &Context = SemaRef.getASTContext();
     TypedefNameDecl *OrigDecl = TL.getTypedefNameDecl();
-    TypeLocBuilder InnerTLB;
-    QualType Transformed =
-        TransformType(InnerTLB, OrigDecl->getTypeSourceInfo()->getTypeLoc());
-    TypeSourceInfo *TSI =
-        TransformType(InnerTLB.getTypeSourceInfo(Context, Transformed));
-
-    TypedefNameDecl *Decl = nullptr;
-
-    if (isa<TypeAliasDecl>(OrigDecl))
-      Decl = TypeAliasDecl::Create(
-          Context, Context.getTranslationUnitDecl(), OrigDecl->getBeginLoc(),
-          OrigDecl->getLocation(), OrigDecl->getIdentifier(), TSI);
-    else {
-      assert(isa<TypedefDecl>(OrigDecl) && "Not a Type alias or typedef");
-      Decl = TypedefDecl::Create(
-          Context, Context.getTranslationUnitDecl(), OrigDecl->getBeginLoc(),
-          OrigDecl->getLocation(), OrigDecl->getIdentifier(), TSI);
+    TypedefNameDecl *Decl = OrigDecl;
+    // Transform the underlying type of the typedef and clone the Decl only if
+    // the typedef has a dependent context.
+    if (OrigDecl->getDeclContext()->isDependentContext()) {
+      TypeLocBuilder InnerTLB;
+      QualType Transformed =
+          TransformType(InnerTLB, OrigDecl->getTypeSourceInfo()->getTypeLoc());
+      TypeSourceInfo *TSI =
+          TransformType(InnerTLB.getTypeSourceInfo(Context, Transformed));
+      if (isa<TypeAliasDecl>(OrigDecl))
+        Decl = TypeAliasDecl::Create(
+            Context, Context.getTranslationUnitDecl(), OrigDecl->getBeginLoc(),
+            OrigDecl->getLocation(), OrigDecl->getIdentifier(), TSI);
+      else {
+        assert(isa<TypedefDecl>(OrigDecl) && "Not a Type alias or typedef");
+        Decl = TypedefDecl::Create(
+            Context, Context.getTranslationUnitDecl(), OrigDecl->getBeginLoc(),
+            OrigDecl->getLocation(), OrigDecl->getIdentifier(), TSI);
+      }
+      MaterializedTypedefs.push_back(Decl);
     }
 
-    MaterializedTypedefs.push_back(Decl);
-
     QualType TDTy = Context.getTypedefType(Decl);
     TypedefTypeLoc TypedefTL = TLB.push<TypedefTypeLoc>(TDTy);
     TypedefTL.setNameLoc(TL.getNameLoc());

clang/unittests/AST/ASTImporterTest.cpp

@@ -5998,6 +5998,77 @@ TEST_P(ImportFunctions, CTADUserDefinedExplicit) {
   EXPECT_TRUE(ToD->isExplicit());
 }
 
+// FIXME Move these tests out of ASTImporterTest. For that we need to factor
+// out the ASTImporter specific pars from ASTImporterOptionSpecificTestBase
+// into a new test Fixture. Then we should lift up this Fixture to its own
+// implementation file and only then could we reuse the Fixture in other AST
+// unitttests.
+struct CTAD : ASTImporterOptionSpecificTestBase {};
+
+TEST_P(CTAD, DeductionGuideShouldReferToANonLocalTypedef) {
+  Decl *TU = getTuDecl(
+      R"(
+      typedef int U;
+      template <typename T> struct A {
+        A(U, T);
+      };
+      A a{(int)0, (int)0};
+      )",
+      Lang_CXX17, "input.cc");
+  auto *Guide = FirstDeclMatcher<CXXDeductionGuideDecl>().match(
+      TU, cxxDeductionGuideDecl());
+  auto *Typedef = FirstDeclMatcher<TypedefNameDecl>().match(
+      TU, typedefNameDecl(hasName("U")));
+  ParmVarDecl *Param = Guide->getParamDecl(0);
+  // The type of the first param (which is a typedef) should match the typedef
+  // in the global scope.
+  EXPECT_EQ(Param->getType()->getAs<TypedefType>()->getDecl(), Typedef);
+}
+
+TEST_P(CTAD, DeductionGuideShouldReferToANonLocalTypedefInParamPtr) {
+  Decl *TU = getTuDecl(
+      R"(
+      typedef int U;
+      template <typename T> struct A {
+        A(U*, T);
+      };
+      A a{(int*)0, (int)0};
+      )",
+      Lang_CXX17, "input.cc");
+  auto *Guide = FirstDeclMatcher<CXXDeductionGuideDecl>().match(
+      TU, cxxDeductionGuideDecl());
+  auto *Typedef = FirstDeclMatcher<TypedefNameDecl>().match(
+      TU, typedefNameDecl(hasName("U")));
+  ParmVarDecl *Param = Guide->getParamDecl(0);
+  EXPECT_EQ(Param->getType()
+                ->getAs<PointerType>()
+                ->getPointeeType()
+                ->getAs<TypedefType>()
+                ->getDecl(),
+            Typedef);
+}
+
+TEST_P(CTAD, DeductionGuideShouldCopyALocalTypedef) {
+  Decl *TU = getTuDecl(
+      R"(
+      template <typename T> struct A {
+        typedef T U;
+        A(U, T);
+      };
+      A a{(int)0, (int)0};
+      )",
+      Lang_CXX17, "input.cc");
+  auto *Guide = FirstDeclMatcher<CXXDeductionGuideDecl>().match(
+      TU, cxxDeductionGuideDecl());
+  auto *Typedef = FirstDeclMatcher<TypedefNameDecl>().match(
+      TU, typedefNameDecl(hasName("U")));
+  ParmVarDecl *Param = Guide->getParamDecl(0);
+  EXPECT_NE(Param->getType()->getAs<TypedefType>()->getDecl(), Typedef);
+}
+
+INSTANTIATE_TEST_CASE_P(ParameterizedTests, CTAD,
+                        DefaultTestValuesForRunOptions, );
+
 INSTANTIATE_TEST_CASE_P(ParameterizedTests, ASTImporterLookupTableTest,
                         DefaultTestValuesForRunOptions, );