[PATCH] D65203: [ASTImporter] Do not import FunctionTemplateDecl in record twice.

[Balázs Kéri via Phabricator via cfe-commits]

balazske created this revision.
Herald added subscribers: cfe-commits, gamesh411, Szelethus, dkrupp.
Herald added a reviewer: martong.
Herald added a reviewer: a.sidorin.
Herald added a reviewer: shafik.
Herald added a project: clang.

For functions there is a check to not duplicate the declaration if it is in a
record (class). For function templates there was no similar check, if a
template (in the same class) was imported multiple times the
FunctionTemplateDecl was created multiple times with the same templated
FunctionDecl. This can result in problems with the declaration chain.


Repository:
  rG LLVM Github Monorepo

https://reviews.llvm.org/D65203

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


Index: clang/unittests/AST/ASTImporterTest.cpp
===================================================================
--- clang/unittests/AST/ASTImporterTest.cpp
+++ clang/unittests/AST/ASTImporterTest.cpp
@@ -2389,6 +2389,47 @@
                 functionDecl(hasName("f"), hasDescendant(declRefExpr()))))));
 }
 
+TEST_P(ImportFunctionTemplates, ImportFunctionTemplateInRecordDeclTwice) {
+  auto Code =
+      R"(
+      class X {
+        template <class T>
+        void f(T t);
+      };
+      )";
+  Decl *FromTU1 = getTuDecl(Code, Lang_CXX, "input1.cc");
+  auto *FromD1 = FirstDeclMatcher<FunctionTemplateDecl>().match(
+      FromTU1, functionTemplateDecl(hasName("f")));
+  auto *ToD1 = Import(FromD1, Lang_CXX);
+  Decl *FromTU2 = getTuDecl(Code, Lang_CXX, "input2.cc");
+  auto *FromD2 = FirstDeclMatcher<FunctionTemplateDecl>().match(
+      FromTU2, functionTemplateDecl(hasName("f")));
+  auto *ToD2 = Import(FromD2, Lang_CXX);
+  EXPECT_EQ(ToD1, ToD2);
+}
+
+TEST_P(ImportFunctionTemplates,
+       ImportFunctionTemplateWithDefInRecordDeclTwice) {
+  auto Code =
+      R"(
+      class X {
+        template <class T>
+        void f(T t);
+      };
+      template <class T>
+      void X::f(T t) {};
+      )";
+  Decl *FromTU1 = getTuDecl(Code, Lang_CXX, "input1.cc");
+  auto *FromD1 = FirstDeclMatcher<FunctionTemplateDecl>().match(
+      FromTU1, functionTemplateDecl(hasName("f")));
+  auto *ToD1 = Import(FromD1, Lang_CXX);
+  Decl *FromTU2 = getTuDecl(Code, Lang_CXX, "input2.cc");
+  auto *FromD2 = FirstDeclMatcher<FunctionTemplateDecl>().match(
+      FromTU2, functionTemplateDecl(hasName("f")));
+  auto *ToD2 = Import(FromD2, Lang_CXX);
+  EXPECT_EQ(ToD1, ToD2);
+}
+
 struct ImportFriendFunctions : ImportFunctions {};
 
 TEST_P(ImportFriendFunctions, ImportFriendFunctionRedeclChainProto) {
Index: clang/lib/AST/ASTImporter.cpp
===================================================================
--- clang/lib/AST/ASTImporter.cpp
+++ clang/lib/AST/ASTImporter.cpp
@@ -3066,9 +3066,19 @@
   if (FoundByLookup) {
     if (isa<CXXMethodDecl>(FoundByLookup)) {
       if (D->getLexicalDeclContext() == D->getDeclContext()) {
-        if (!D->doesThisDeclarationHaveABody())
+        if (!D->doesThisDeclarationHaveABody()) {
+          if (FunctionTemplateDecl *DescribedD =
+                  D->getDescribedFunctionTemplate()) {
+            // Handle a "templated" function together with its described
+            // template. This avoids need for a similar check at import of the
+            // described template.
+            assert(FoundByLookup->getDescribedFunctionTemplate() &&
+                   "Templated function mapped to non-templated?");
+            Importer.MapImported(DescribedD,
+                                 FoundByLookup->getDescribedFunctionTemplate());
+          }
           return Importer.MapImported(D, FoundByLookup);
-        else {
+        } else {
           // Let's continue and build up the redecl chain in this case.
           // FIXME Merge the functions into one decl.
         }
@@ -5550,14 +5560,14 @@
     }
   }
 
-  auto ParamsOrErr = import(D->getTemplateParameters());
-  if (!ParamsOrErr)
-    return ParamsOrErr.takeError();
-
   FunctionDecl *TemplatedFD;
   if (Error Err = importInto(TemplatedFD, D->getTemplatedDecl()))
     return std::move(Err);
 
+  auto ParamsOrErr = import(D->getTemplateParameters());
+  if (!ParamsOrErr)
+    return ParamsOrErr.takeError();
+
   FunctionTemplateDecl *ToFunc;
   if (GetImportedOrCreateDecl(ToFunc, D, Importer.getToContext(), DC, Loc, Name,
                               *ParamsOrErr, TemplatedFD))


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