[AST][ObjC] Fix crash when printing invalid objc categories

[dgoldman]

Summary

If no valid interface definition was found previously we would crash.

With this change instead we just print <<error-type>> in place
of the NULL interface. In the future this could be improved by
saving the invalid interface's name and using that.

[gribozavr2]

clang/unittests/AST/DeclPrinterTest.cpp

180

/*PolicyModifier=*/ (with equal sign) (also below for AllowError comments)

clang/lib/AST/DeclPrinter.cpp

if (!Protocols.empty()) {
     Out << ">\n";
   } else
     Out << "@protocol " << *PID << '\n';
   VisitDeclContext(PID, false);
   Out << "@end";
 }
 
 void DeclPrinter::VisitObjCCategoryImplDecl(ObjCCategoryImplDecl *PID) {
-  Out << "@implementation " << *PID->getClassInterface() << '(' << *PID <<")\n";
+  Out << "@implementation ";
+  if (const auto *CID = PID->getClassInterface())
+    Out << *CID;
+  else
+    Out << "<<error-type>>";
+  Out << '(' << *PID << ")\n";
 
   VisitDeclContext(PID, false);
   Out << "@end";
   // FIXME: implement the rest...
 }
 
 void DeclPrinter::VisitObjCCategoryDecl(ObjCCategoryDecl *PID) {
-  Out << "@interface " << *PID->getClassInterface();
+  Out << "@interface ";
+  if (const auto *CID = PID->getClassInterface())
+    Out << *CID;
+  else
+    Out << "<<error-type>>";
   if (auto TypeParams = PID->getTypeParamList()) {
     PrintObjCTypeParams(TypeParams);
   }
   Out << "(" << *PID << ")\n";
   if (PID->ivar_size() > 0) {
     Out << "{\n";
     Indentation += Policy.Indentation;
     for (const auto *I : PID->ivars())

clang/unittests/AST/DeclPrinterTest.cpp

unsigned getNumFoundDecls() const {
     return NumFoundDecls;
   }
 };
 
 ::testing::AssertionResult
 PrintedDeclMatches(StringRef Code, const std::vector<std::string> &Args,
                    const DeclarationMatcher &NodeMatch,
                    StringRef ExpectedPrinted, StringRef FileName,
-                   PrintingPolicyModifier PolicyModifier = nullptr) {
+                   PrintingPolicyModifier PolicyModifier = nullptr,
+                   bool AllowError = false) {
   PrintMatch Printer(PolicyModifier);
   MatchFinder Finder;
   Finder.addMatcher(NodeMatch, &Printer);
   std::unique_ptr<FrontendActionFactory> Factory(
       newFrontendActionFactory(&Finder));
 
-  if (!runToolOnCodeWithArgs(Factory->create(), Code, Args, FileName))
+  if (!runToolOnCodeWithArgs(Factory->create(), Code, Args, FileName) &&
+      !AllowError)
     return testing::AssertionFailure()
       << "Parsing error in \"" << Code.str() << "\"";
 
   if (Printer.getNumFoundDecls() == 0)
     return testing::AssertionFailure()
         << "Matcher didn't find any declarations";
 
   if (Printer.getNumFoundDecls() > 1)
PrintedDeclCXX1ZMatches(StringRef Code, const DeclarationMatcher &NodeMatch,
   std::vector<std::string> Args(1, "-std=c++1z");
   return PrintedDeclMatches(Code,
                             Args,
                             NodeMatch,
                             ExpectedPrinted,
                             "input.cc");
 }
 
-::testing::AssertionResult PrintedDeclObjCMatches(
-                                  StringRef Code,
-                                  const DeclarationMatcher &NodeMatch,
-                                  StringRef ExpectedPrinted) {
+::testing::AssertionResult
+PrintedDeclObjCMatches(StringRef Code, const DeclarationMatcher &NodeMatch,
+                       StringRef ExpectedPrinted, bool AllowError = false) {
   std::vector<std::string> Args(1, "");
-  return PrintedDeclMatches(Code,
-                            Args,
-                            NodeMatch,
-                            ExpectedPrinted,
-                            "input.m");
+  return PrintedDeclMatches(Code, Args, NodeMatch, ExpectedPrinted, "input.m",
+                            /*PolicyModifier=*/nullptr, AllowError);
 }
 
 } // unnamed namespace
 
 TEST(DeclPrinter, TestTypedef1) {
   ASSERT_TRUE(PrintedDeclCXX98Matches(
     "typedef int A;",
     "A",

 
 TEST(DeclPrinter, TestObjCProtocol2) {
   ASSERT_TRUE(PrintedDeclObjCMatches(
     "@protocol P2 @end"
     "@protocol P1<P2> @end",
     namedDecl(hasName("P1")).bind("id"),
     "@protocol P1<P2>\n@end"));
 }
+
+TEST(DeclPrinter, TestObjCCategoryInvalidInterface) {
+  ASSERT_TRUE(PrintedDeclObjCMatches(
+      "@interface I (Extension) @end",
+      namedDecl(hasName("Extension")).bind("id"),
+      "@interface <<error-type>>(Extension)\n@end", /*AllowError=*/true));
+}
+
+TEST(DeclPrinter, TestObjCCategoryImplInvalidInterface) {
+  ASSERT_TRUE(PrintedDeclObjCMatches(
+      "@implementation I (Extension) @end",
+      namedDecl(hasName("Extension")).bind("id"),
+      "@implementation <<error-type>>(Extension)\n@end", /*AllowError=*/true));
+}