r332338 - [ASTImporter] Extend lookup logic in class templates

[Aleksei Sidorin via cfe-commits]

Author: a.sidorin
Date: Tue May 15 04:09:07 2018
New Revision: 332338

URL: http://llvm.org/viewvc/llvm-project?rev=332338&view=rev
Log:
[ASTImporter] Extend lookup logic in class templates

During import of a class template, lookup may find a forward
declaration and structural match falsely reports equivalency
between a forward decl and a definition. The result is that
some definitions are not imported if we had imported a forward
decl previously. This patch gives a fix.

Patch by Gabor Marton!

Differential Revision: https://reviews.llvm.org/D46353


Modified:
    cfe/trunk/lib/AST/ASTImporter.cpp
    cfe/trunk/unittests/AST/ASTImporterTest.cpp

Modified: cfe/trunk/lib/AST/ASTImporter.cpp
URL: http://llvm.org/viewvc/llvm-project/cfe/trunk/lib/AST/ASTImporter.cpp?rev=332338&r1=332337&r2=332338&view=diff
==============================================================================
--- cfe/trunk/lib/AST/ASTImporter.cpp (original)
+++ cfe/trunk/lib/AST/ASTImporter.cpp Tue May 15 04:09:07 2018
@@ -4108,8 +4108,14 @@ Decl *ASTNodeImporter::VisitClassTemplat
       if (auto *FoundTemplate = dyn_cast<ClassTemplateDecl>(Found)) {
         if (IsStructuralMatch(D, FoundTemplate)) {
           // The class templates structurally match; call it the same template.
-          // FIXME: We may be filling in a forward declaration here. Handle
-          // this case!
+
+          // We found a forward declaration but the class to be imported has a
+          // definition.
+          // FIXME Add this forward declaration to the redeclaration chain.
+          if (D->isThisDeclarationADefinition() &&
+              !FoundTemplate->isThisDeclarationADefinition())
+            continue;
+
           Importer.Imported(D->getTemplatedDecl(), 
                             FoundTemplate->getTemplatedDecl());
           return Importer.Imported(D, FoundTemplate);

Modified: cfe/trunk/unittests/AST/ASTImporterTest.cpp
URL: http://llvm.org/viewvc/llvm-project/cfe/trunk/unittests/AST/ASTImporterTest.cpp?rev=332338&r1=332337&r2=332338&view=diff
==============================================================================
--- cfe/trunk/unittests/AST/ASTImporterTest.cpp (original)
+++ cfe/trunk/unittests/AST/ASTImporterTest.cpp Tue May 15 04:09:07 2018
@@ -1431,6 +1431,39 @@ TEST_P(ASTImporterTestBase,
       MatchVerifier<Decl>{}.match(To->getTranslationUnitDecl(), Pattern));
 }
 
+TEST_P(ASTImporterTestBase, ImportDefinitionOfClassTemplateAfterFwdDecl) {
+  {
+    Decl *FromTU = getTuDecl(
+        R"(
+            template <typename T>
+            struct B;
+            )",
+        Lang_CXX, "input0.cc");
+    auto *FromD = FirstDeclMatcher<ClassTemplateDecl>().match(
+        FromTU, classTemplateDecl(hasName("B")));
+
+    Import(FromD, Lang_CXX);
+  }
+
+  {
+    Decl *FromTU = getTuDecl(
+        R"(
+            template <typename T>
+            struct B {
+              void f();
+            };
+            )",
+        Lang_CXX, "input1.cc");
+    FunctionDecl *FromD = FirstDeclMatcher<FunctionDecl>().match(
+        FromTU, functionDecl(hasName("f")));
+    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());
+  }
+}
+
 INSTANTIATE_TEST_CASE_P(
     ParameterizedTests, ASTImporterTestBase,
     ::testing::Values(ArgVector(), ArgVector{"-fdelayed-template-parsing"}),);