[clang] [clang][ASTImporter] Not using primary context in lookup table (PR #118466)

[Balázs Kéri via cfe-commits]

================
@@ -10181,6 +10184,151 @@ TEST_P(ImportTemplateParmDeclDefaultValue,
       FromD, FromDInherited);
 }
 
+TEST_P(ASTImporterOptionSpecificTestBase, ImportIntoReopenedNamespaceNoMatch1) {
+  const char *ToCode =
+      R"(
+      namespace a {
+      }
+      namespace a {
+        struct X { int A; };
+      }
+      )";
+  Decl *ToTU = getToTuDecl(ToCode, Lang_CXX11);
+  const char *Code =
+      R"(
+      namespace a {
+        struct X { char A; };
+      }
+      )";
+  Decl *FromTU = getTuDecl(Code, Lang_CXX11);
+  auto *FromX = FirstDeclMatcher<CXXRecordDecl>().match(
+      FromTU, cxxRecordDecl(hasName("X")));
+  auto *ImportedX = Import(FromX, Lang_CXX11);
+  EXPECT_FALSE(ImportedX);
+}
+
+TEST_P(ASTImporterOptionSpecificTestBase, ImportIntoReopenedNamespaceNoMatch2) {
+  const char *ToCode =
+      R"(
+      namespace a {
+        struct X { int A; };
+      }
+      namespace a {
+      }
+      )";
+  Decl *ToTU = getToTuDecl(ToCode, Lang_CXX11);
+  const char *Code =
+      R"(
+      namespace a {
+        struct X { char A; };
+      }
+      )";
+  Decl *FromTU = getTuDecl(Code, Lang_CXX11);
+  auto *FromX = FirstDeclMatcher<CXXRecordDecl>().match(
+      FromTU, cxxRecordDecl(hasName("X")));
+  auto *ImportedX = Import(FromX, Lang_CXX11);
+  EXPECT_FALSE(ImportedX);
+}
+
+TEST_P(ASTImporterOptionSpecificTestBase, ImportIntoReopenedNamespaceMatch1) {
+  const char *ToCode =
+      R"(
+      namespace a {
+      }
+      namespace a {
+        struct X { int A; };
+      }
+      )";
+  Decl *ToTU = getToTuDecl(ToCode, Lang_CXX11);
+  const char *Code =
+      R"(
+      namespace a {
+        struct X { int A; };
+      }
+      )";
+  Decl *FromTU = getTuDecl(Code, Lang_CXX11);
+  auto *FromX = FirstDeclMatcher<CXXRecordDecl>().match(
+      FromTU, cxxRecordDecl(hasName("X")));
+  auto *ToX = FirstDeclMatcher<CXXRecordDecl>().match(
+      ToTU, cxxRecordDecl(hasName("X")));
+  auto *ImportedX = Import(FromX, Lang_CXX11);
+  EXPECT_EQ(ImportedX, ToX);
----------------
balazske wrote:

The last test is the ones that fails before the changes. The template parameter objects have the record declaration (of the template) as DeclContext and in that case a definition of it is imported. This results in change of the primary context (even for first `struct X` in the ToTU) and the lookup table will contain `class T` template parameter in the wrong place.

https://github.com/llvm/llvm-project/pull/118466