Improve anonymous class heuristic in ClangASTContext::CreateRecordType

Summary:
Currently the heuristic used in ClangASTContext::CreateRecordType to identify an anonymous class is that there is that name is a nullptr or simply a null terminator. This heuristic is not accurate since it will also sweep up unnamed classes and lambdas. The improved heuristic relies on the requirement that an anonymous class must be contained within a class.

Differential Revision: https://reviews.llvm.org/D66175

llvm-svn: 368937

lldb/packages/Python/lldbsuite/test/expression_command/completion-in-lambda-and-unnnamed-class/TestCompletionInLambdaAndUnnamedClass.py

@@ -0,0 +1,4 @@
+from lldbsuite.test import lldbinline
+from lldbsuite.test import decorators
+
+lldbinline.MakeInlineTest(__file__, globals(),)

lldb/packages/Python/lldbsuite/test/expression_command/completion-in-lambda-and-unnnamed-class/main.cpp

@@ -0,0 +1,11 @@
+int main() {
+  []()
+  { //%self.dbg.GetCommandInterpreter().HandleCompletion("e ", len("e "), 0, -1, lldb.SBStringList())
+  }
+  ();
+  struct {
+      void f()
+      { //%self.dbg.GetCommandInterpreter().HandleCompletion("e ", len("e "), 0, -1, lldb.SBStringList())
+      }
+  } A;
+}

lldb/source/Symbol/ClangASTContext.cpp

@@ -1519,14 +1519,44 @@ CompilerType ClangASTContext::CreateRecordType(DeclContext *decl_ctx,
   // something is struct or a class, so we default to always use the more
   // complete definition just in case.
 
-  bool is_anonymous = (!name) || (!name[0]);
+  bool has_name = name && name[0];
 
   CXXRecordDecl *decl = CXXRecordDecl::Create(
       *ast, (TagDecl::TagKind)kind, decl_ctx, SourceLocation(),
-      SourceLocation(), is_anonymous ? nullptr : &ast->Idents.get(name));
+      SourceLocation(), has_name ?  &ast->Idents.get(name) : nullptr);
 
-  if (is_anonymous)
-    decl->setAnonymousStructOrUnion(true);
+  if (!has_name) {
+    // In C++ a lambda is also represented as an unnamed class. This is
+    // different from an *anonymous class* that the user wrote:
+    //
+    // struct A {
+    //  // anonymous class (GNU/MSVC extension)
+    //  struct {
+    //    int x;
+    //  };
+    //  // unnamed class within a class
+    //  struct {
+    //    int y;
+    //  } B;
+    // };
+    //
+    // void f() {
+    //    // unammed class outside of a class
+    //    struct {
+    //      int z;
+    //    } C;
+    // }
+    //
+    // Anonymous classes is a GNU/MSVC extension that clang supports. It
+    // requires the anonymous class be embedded within a class. So the new
+    // heuristic verifies this condition.
+    //
+    // FIXME: An unnamed class within a class is also wrongly recognized as an
+    // anonymous struct.
+    if (CXXRecordDecl *record = dyn_cast<CXXRecordDecl>(decl_ctx)) {
+      decl->setAnonymousStructOrUnion(true);
+    }
+  }
 
   if (decl) {
     if (metadata)