[CodeComplete] Suggest 'return nullptr' in functions returning pointers

[merge_guards_bot]

Unit tests: pass. 61741 tests passed, 0 failed and 780 were skipped.

clang-tidy: fail. Please fix clang-tidy findings.

clang-format: fail. Please format your changes with clang-format by running git-clang-format HEAD^ or applying this patch.

Build artifacts: diff.json, clang-tidy.txt, clang-format.patch, CMakeCache.txt, console-log.txt, test-results.xml

clang/lib/Sema/SemaCodeComplete.cpp

if (ReturnType.isNull() || ReturnType->isVoidType()) {
         Builder.AddTypedTextChunk("return true");
         Builder.AddChunk(CodeCompletionString::CK_SemiColon);
         Results.AddResult(Result(Builder.TakeString()));
 
         Builder.AddTypedTextChunk("return false");
         Builder.AddChunk(CodeCompletionString::CK_SemiColon);
         Results.AddResult(Result(Builder.TakeString()));
       }
+      // For pointers, suggest 'return nullptr' in C++.
+      if (SemaRef.getLangOpts().CPlusPlus11 &&
+          (ReturnType->isPointerType() || ReturnType->isMemberPointerType())) {
+        Builder.AddTypedTextChunk("return nullptr");
+        Builder.AddChunk(CodeCompletionString::CK_SemiColon);
+        Results.AddResult(Result(Builder.TakeString()));
+      }
     }
 
     // goto identifier ;
     Builder.AddTypedTextChunk("goto");
     Builder.AddChunk(CodeCompletionString::CK_HorizontalSpace);
     Builder.AddPlaceholderChunk("label");
     Builder.AddChunk(CodeCompletionString::CK_SemiColon);
     Results.AddResult(Result(Builder.TakeString()));

clang/test/CodeCompletion/patterns.cpp

 int value_return() {
   // line 28
 }
 void void_return() {
   // line 31
 }
 bool bool_return() {
   // line 34
 }
+int *ptr_return() {
+  // line 37
+}
+struct Cls {};
+int Cls::*memptr_return() {
+  // line 41
+}
 // RUN: %clang_cc1 -fsyntax-only -code-completion-patterns -code-completion-at=%s:28:1 %s -o - | FileCheck -check-prefix=RETURN-VAL %s
 // RETURN-VAL-NOT: COMPLETION: Pattern : return;
 // RETURN-VAL-NOT: COMPLETION: Pattern : return false;
 // RETURN-VAL-NOT: COMPLETION: Pattern : return true;
+// RETURN-VAL-NOT: COMPLETION: Pattern : return nullptr;
 // RETURN-VAL: COMPLETION: Pattern : return <#expression#>;{{$}}
 
 // RUN: %clang_cc1 -fsyntax-only -code-completion-patterns -code-completion-at=%s:31:1 %s -o - | FileCheck -check-prefix=RETURN-VOID %s
 // RETURN-VOID-NOT: COMPLETION: Pattern : return false;
 // RETURN-VOID-NOT: COMPLETION: Pattern : return true;
 // RETURN-VOID-NOT: COMPLETION: Pattern : return <#expression#>;
+// RETURN-VOID-NOT: COMPLETION: Pattern : return nullptr;
 // RETURN-VOID: COMPLETION: Pattern : return;{{$}}
 
 // RUN: %clang_cc1 -fsyntax-only -code-completion-patterns -code-completion-at=%s:34:1 %s -o - | FileCheck -check-prefix=RETURN-BOOL %s
 // RETURN-BOOL-NOT: COMPLETION: Pattern : return;
+// RETURN-BOOL-NOT: COMPLETION: Pattern : return nullptr;
 // RETURN-BOOL: COMPLETION: Pattern : return <#expression#>;{{$}}
 // RETURN-BOOL: COMPLETION: Pattern : return false;{{$}}
 // RETURN-BOOL: COMPLETION: Pattern : return true;{{$}}
+
+// Check both pointer and member pointer return types.
+// RUN: %clang_cc1 -fsyntax-only -std=c++11 -code-completion-patterns -code-completion-at=%s:37:1 %s -o - | FileCheck -check-prefix=RETURN-PTR %s
+// RUN: %clang_cc1 -fsyntax-only -std=c++11 -code-completion-patterns -code-completion-at=%s:41:1 %s -o - | FileCheck -check-prefix=RETURN-PTR %s
+// RETURN-PTR-NOT: COMPLETION: Pattern : return false;{{$}}
+// RETURN-PTR-NOT: COMPLETION: Pattern : return true;{{$}}
+// RETURN-PTR-NOT: COMPLETION: Pattern : return;
+// RETURN-PTR: COMPLETION: Pattern : return <#expression#>;{{$}}
+// RETURN-PTR: COMPLETION: Pattern : return nullptr;
+
+// 'return nullptr' is not available before C++11.
+// RUN: %clang_cc1 -fsyntax-only -std=c++03 -code-completion-patterns -code-completion-at=%s:37:1 %s -o - | FileCheck -check-prefix=RETURN-PTR-STD03 %s
+// RUN: %clang_cc1 -fsyntax-only -std=c++03 -code-completion-patterns -code-completion-at=%s:41:1 %s -o - | FileCheck -check-prefix=RETURN-PTR-STD03 %s
+// RETURN-PTR-STD03-NOT: COMPLETION: Pattern : return nullptr;