[Sema] Add -Wno-self-assign-overloaded

Summary:
It seems there isn't much enthusiasm for `-wtest` D45685.

This is more conservative version, which i had in the very first
revision of D44883, but that 'erroneously' got removed because of the review.

**Based on some [irc] discussions, it must really be documented that
we want all the new diagnostics to have their own flags, to ease
rollouts, transitions, etc.**

Please do note that i'm only adding `-Wno-self-assign-overloaded`,
but not `-Wno-self-assign-field-overloaded`, because i'm honestly
not aware of any false-positives from the `-field` variant,
but i can just as easily add it if wanted.
https://reviews.llvm.org/D44883#1068561

Reviewers: dblaikie, aaron.ballman, thakis, rjmccall, rsmith

Reviewed By: dblaikie

Subscribers: Quuxplusone, chandlerc, cfe-commits

Differential Revision: https://reviews.llvm.org/D45766

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@330651 91177308-0d34-0410-b5e6-96231b3b80d8

docs/ReleaseNotes.rst

@@ -62,8 +62,9 @@ Improvements to Clang's diagnostics
 - ``-Wself-assign`` and ``-Wself-assign-field`` were extended to diagnose
   self-assignment operations using overloaded operators (i.e. classes).
   If you are doing such an assignment intentionally, e.g. in a unit test for
-  a data structure, the warning can be suppressed by adding ``*&`` to the
-  right-hand side or casting it to the appropriate reference type.
+  a data structure, the first warning can be disabled by passing
+  ``-Wno-self-assign-overloaded``, also the warning can be suppressed by adding
+  ``*&`` to the right-hand side or casting it to the appropriate reference type.
 
 Non-comprehensive list of changes in this release
 -------------------------------------------------

include/clang/Basic/DiagnosticGroups.td

@@ -404,7 +404,8 @@ def ReturnType : DiagGroup<"return-type", [ReturnTypeCLinkage]>;
 def BindToTemporaryCopy : DiagGroup<"bind-to-temporary-copy",
                                     [CXX98CompatBindToTemporaryCopy]>;
 def SelfAssignmentField : DiagGroup<"self-assign-field">;
-def SelfAssignment : DiagGroup<"self-assign", [SelfAssignmentField]>;
+def SelfAssignmentOverloaded : DiagGroup<"self-assign-overloaded">;
+def SelfAssignment : DiagGroup<"self-assign", [SelfAssignmentOverloaded, SelfAssignmentField]>;
 def SelfMove : DiagGroup<"self-move">;
 def SemiBeforeMethodBody : DiagGroup<"semicolon-before-method-body">;
 def Sentinel : DiagGroup<"sentinel">;

include/clang/Basic/DiagnosticSemaKinds.td

@@ -5612,9 +5612,12 @@ def warn_addition_in_bitshift : Warning<
   "operator '%0' has lower precedence than '%1'; "
   "'%1' will be evaluated first">, InGroup<ShiftOpParentheses>;
 
-def warn_self_assignment : Warning<
+def warn_self_assignment_builtin : Warning<
   "explicitly assigning value of variable of type %0 to itself">,
   InGroup<SelfAssignment>, DefaultIgnore;
+def warn_self_assignment_overloaded : Warning<
+  "explicitly assigning value of variable of type %0 to itself">,
+  InGroup<SelfAssignmentOverloaded>, DefaultIgnore;
 def warn_self_move : Warning<
   "explicitly moving variable of type %0 to itself">,
   InGroup<SelfMove>, DefaultIgnore;

lib/Sema/SemaExpr.cpp

@@ -11497,7 +11497,7 @@ static inline UnaryOperatorKind ConvertTokenKindToUnaryOpcode(
 /// DiagnoseSelfAssignment - Emits a warning if a value is assigned to itself.
 /// This warning suppressed in the event of macro expansions.
 static void DiagnoseSelfAssignment(Sema &S, Expr *LHSExpr, Expr *RHSExpr,
-                                   SourceLocation OpLoc) {
+                                   SourceLocation OpLoc, bool IsBuiltin) {
   if (S.inTemplateInstantiation())
     return;
   if (S.isUnevaluatedContext())
@@ -11524,9 +11524,10 @@ static void DiagnoseSelfAssignment(Sema &S, Expr *LHSExpr, Expr *RHSExpr,
     if (RefTy->getPointeeType().isVolatileQualified())
       return;
 
-  S.Diag(OpLoc, diag::warn_self_assignment)
-      << LHSDeclRef->getType()
-      << LHSExpr->getSourceRange() << RHSExpr->getSourceRange();
+  S.Diag(OpLoc, IsBuiltin ? diag::warn_self_assignment_builtin
+                          : diag::warn_self_assignment_overloaded)
+      << LHSDeclRef->getType() << LHSExpr->getSourceRange()
+      << RHSExpr->getSourceRange();
 }
 
 /// Check if a bitwise-& is performed on an Objective-C pointer.  This
@@ -11719,7 +11720,7 @@ ExprResult Sema::CreateBuiltinBinOp(SourceLocation OpLoc,
       OK = LHS.get()->getObjectKind();
     }
     if (!ResultTy.isNull()) {
-      DiagnoseSelfAssignment(*this, LHS.get(), RHS.get(), OpLoc);
+      DiagnoseSelfAssignment(*this, LHS.get(), RHS.get(), OpLoc, true);
       DiagnoseSelfMove(LHS.get(), RHS.get(), OpLoc);
     }
     RecordModifiableNonNullParam(*this, LHS.get());
@@ -11817,7 +11818,7 @@ ExprResult Sema::CreateBuiltinBinOp(SourceLocation OpLoc,
     break;
   case BO_AndAssign:
   case BO_OrAssign: // fallthrough
-    DiagnoseSelfAssignment(*this, LHS.get(), RHS.get(), OpLoc);
+    DiagnoseSelfAssignment(*this, LHS.get(), RHS.get(), OpLoc, true);
     LLVM_FALLTHROUGH;
   case BO_XorAssign:
     CompResultTy = CheckBitwiseOperands(LHS, RHS, OpLoc, Opc);
@@ -12124,7 +12125,7 @@ static ExprResult BuildOverloadedBinOp(Sema &S, Scope *Sc, SourceLocation OpLoc,
   case BO_AndAssign:
   case BO_OrAssign:
   case BO_XorAssign:
-    DiagnoseSelfAssignment(S, LHS, RHS, OpLoc);
+    DiagnoseSelfAssignment(S, LHS, RHS, OpLoc, false);
     CheckIdentityFieldAssignment(LHS, RHS, OpLoc, S);
     break;
   default:

test/SemaCXX/warn-self-assign-overloaded-disable.cpp

@@ -0,0 +1,18 @@
+// RUN: %clang_cc1 -fsyntax-only -Wall -verify %s
+// RUN: %clang_cc1 -fsyntax-only -Wself-assign -verify %s
+// RUN: %clang_cc1 -fsyntax-only -Wself-assign-overloaded -verify %s
+// RUN: %clang_cc1 -fsyntax-only -Wall -Wno-self-assign-overloaded -DSILENCE -verify %s
+// RUN: %clang_cc1 -fsyntax-only -Wself-assign -Wno-self-assign-overloaded -DSILENCE -verify %s
+// RUN: %clang_cc1 -fsyntax-only -Wself-assign-overloaded -Wno-self-assign-overloaded -DSILENCE -verify %s
+
+struct S {};
+
+void f() {
+  S a;
+#ifndef SILENCE
+  a = a; // expected-warning{{explicitly assigning}}
+#else
+  // expected-no-diagnostics
+  a = a;
+#endif
+}

test/SemaCXX/warn-self-assign-overloaded.cpp

@@ -4,6 +4,12 @@
 // RUN: %clang_cc1 -fsyntax-only -Wself-assign -DV2 -verify %s
 // RUN: %clang_cc1 -fsyntax-only -Wself-assign -DV3 -verify %s
 // RUN: %clang_cc1 -fsyntax-only -Wself-assign -DV4 -verify %s
+// RUN: %clang_cc1 -fsyntax-only -Wno-self-assign -Wself-assign-overloaded -DDUMMY -verify %s
+// RUN: %clang_cc1 -fsyntax-only -Wno-self-assign -Wself-assign-overloaded -DV0 -verify %s
+// RUN: %clang_cc1 -fsyntax-only -Wno-self-assign -Wself-assign-overloaded -DV1 -verify %s
+// RUN: %clang_cc1 -fsyntax-only -Wno-self-assign -Wself-assign-overloaded -DV2 -verify %s
+// RUN: %clang_cc1 -fsyntax-only -Wno-self-assign -Wself-assign-overloaded -DV3 -verify %s
+// RUN: %clang_cc1 -fsyntax-only -Wno-self-assign -Wself-assign-overloaded -DV4 -verify %s
 
 #ifdef DUMMY
 struct S {};