[AST] No longer visiting CXXMethodDecl bodies created by compiler when method was default created.

Summary:
Clang generates function bodies and puts them in the AST for default methods if it is defaulted outside the class definition.

`
struct A {
   A &operator=(A &&O);
};

A &A::operator=(A &&O) = default;
`

This will generate a function body for the `A &A::operator=(A &&O)` and put it in the AST. This body should not be visited if implicit code is not visited as it is implicit.

This was causing SemanticHighlighting in clangd to generate duplicate tokens and putting them in weird places.

Reviewers: hokein, ilya-biryukov, gribozavr

Subscribers: mgorny, jkorous, arphaman, kadircet, cfe-commits

Tags: #clang

Differential Revision: https://reviews.llvm.org/D65938

llvm-svn: 368402

clang-tools-extra/clangd/unittests/SemanticHighlightingTests.cpp

@@ -55,7 +55,7 @@ void checkHighlightings(llvm::StringRef Code) {
   Annotations Test(Code);
   auto AST = TestTU::withCode(Test.code()).build();
   std::vector<HighlightingToken> ActualTokens = getSemanticHighlightings(AST);
-  EXPECT_THAT(ActualTokens, getExpectedTokens(Test));
+  EXPECT_THAT(ActualTokens, getExpectedTokens(Test)) << Code;
 }
 
 // Any annotations in OldCode and NewCode are converted into their corresponding
@@ -276,6 +276,15 @@ TEST(SemanticHighlighting, GetsCorrectTokens) {
         $Class[[Foo]] *$Variable[[FP]] = ($Class[[Foo]]*)$Variable[[B]];
         $Primitive[[int]] $Variable[[I]] = ($Primitive[[int]])$Variable[[B]];
       }
+    )cpp"
+    R"cpp(
+      struct $Class[[B]] {};
+      struct $Class[[A]] {
+        $Class[[B]] $Field[[BB]];
+        $Class[[A]] &operator=($Class[[A]] &&$Variable[[O]]);
+      };
+
+      $Class[[A]] &$Class[[A]]::operator=($Class[[A]] &&$Variable[[O]]) = default;
     )cpp"};
   for (const auto &TestCase : TestCases) {
     checkHighlightings(TestCase);

clang/include/clang/AST/RecursiveASTVisitor.h

@@ -2027,7 +2027,13 @@ bool RecursiveASTVisitor<Derived>::TraverseFunctionHelper(FunctionDecl *D) {
     }
   }
 
-  if (D->isThisDeclarationADefinition()) {
+  bool VisitBody = D->isThisDeclarationADefinition();
+  // If a method is set to default outside the class definition the compiler
+  // generates the method body and adds it to the AST.
+  if (const auto *MD = dyn_cast<CXXMethodDecl>(D))
+    VisitBody &= !MD->isDefaulted() || getDerived().shouldVisitImplicitCode();
+
+  if (VisitBody) {
     TRY_TO(TraverseStmt(D->getBody())); // Function body.
   }
   return true;

clang/unittests/Tooling/CMakeLists.txt

@@ -28,6 +28,7 @@ add_clang_unittest(ToolingTests
   RecursiveASTVisitorTests/ConstructExpr.cpp
   RecursiveASTVisitorTests/CXXBoolLiteralExpr.cpp
   RecursiveASTVisitorTests/CXXMemberCall.cpp
+  RecursiveASTVisitorTests/CXXMethodDecl.cpp
   RecursiveASTVisitorTests/CXXOperatorCallExprTraverser.cpp
   RecursiveASTVisitorTests/DeclRefExpr.cpp
   RecursiveASTVisitorTests/ImplicitCtor.cpp

clang/unittests/Tooling/RecursiveASTVisitorTests/CXXMethodDecl.cpp

@@ -0,0 +1,58 @@
+//=------ unittest/Tooling/RecursiveASTVisitorTests/CXXMethodDecl.cpp ------=//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+
+#include "TestVisitor.h"
+#include "clang/AST/Expr.h"
+
+using namespace clang;
+
+namespace {
+
+class CXXMethodDeclVisitor
+    : public ExpectedLocationVisitor<CXXMethodDeclVisitor> {
+public:
+  CXXMethodDeclVisitor(bool VisitImplicitCode)
+      : VisitImplicitCode(VisitImplicitCode) {}
+
+  bool shouldVisitImplicitCode() const { return VisitImplicitCode; }
+
+  bool VisitDeclRefExpr(DeclRefExpr *D) {
+    Match("declref", D->getLocation());
+    return true;
+  }
+  bool VisitParmVarDecl(ParmVarDecl *P) {
+    Match("parm", P->getLocation());
+    return true;
+  }
+
+private:
+  bool VisitImplicitCode;
+};
+
+TEST(RecursiveASTVisitor, CXXMethodDeclNoDefaultBodyVisited) {
+  for (bool VisitImplCode : {false, true}) {
+    CXXMethodDeclVisitor Visitor(VisitImplCode);
+    if (VisitImplCode)
+      Visitor.ExpectMatch("declref", 8, 28);
+    else
+      Visitor.DisallowMatch("declref", 8, 28);
+
+    Visitor.ExpectMatch("parm", 8, 27);
+    llvm::StringRef Code = R"cpp(
+      struct B {};
+      struct A {
+        B BB;
+        A &operator=(A &&O);
+      };
+
+      A &A::operator=(A &&O) = default;
+    )cpp";
+    EXPECT_TRUE(Visitor.runOver(Code, CXXMethodDeclVisitor::Lang_CXX11));
+  }
+}
+} // end anonymous namespace