loplugin:unusedenumconstants ignore common pattern

Ignore a common pattern that does not introduce any new information,
merely removes information.

Change-Id: I37da352c9295ec12b9dac7aad4b4792a6d726b0d
Reviewed-on: https://gerrit.libreoffice.org/64255
Tested-by: Jenkins
Reviewed-by: Noel Grandin <noel.grandin@collabora.co.uk>

compilerplugins/clang/test/unusedenumconstants.cxx

@@ -81,6 +81,8 @@ struct Test4 : public Test4Base
 };
 };
 
+//-----------------------------------------------------------------------------------
+
 // check that conditional operator walks up the tree
 namespace test5
 {
@@ -93,4 +95,24 @@ enum Enum
 Enum foo(int x) { return x == 1 ? Enum::ONE : Enum::TWO; }
 };
 
+//-----------------------------------------------------------------------------------
+// Ignore a common pattern that does not introduce any new information, merely removes
+// information.
+enum class Enum6
+{
+    Modules = 0x01, // expected-error {{write Modules [loplugin:unusedenumconstants]}}
+    Top = 0x02,
+};
+namespace o3tl
+{
+template <> struct typed_flags<Enum6> : is_typed_flags<Enum6, 0x03>
+{
+};
+}
+void test6()
+{
+    Enum6 foo = Enum6::Modules;
+    foo &= ~Enum6::Top;
+};
+
 /* vim:set shiftwidth=4 softtabstop=4 expandtab cinoptions=b1,g0,N-s cinkeys+=0=break: */

compilerplugins/clang/unusedenumconstants.cxx

@@ -174,12 +174,24 @@ walk_up:
     else if (const CXXOperatorCallExpr * operatorCall = dyn_cast<CXXOperatorCallExpr>(parent))
     {
         auto oo = operatorCall->getOperator();
-        // if assignment op
-        if (oo == OO_Equal || oo == OO_StarEqual || oo == OO_SlashEqual || oo == OO_PercentEqual
+        if (oo == OO_AmpEqual)
+        {
+            // Ignore a common pattern that does not introduce any new information, merely removes
+            // information:     foo &= ~Enum6::Top
+            bool found = false;
+            if (auto innerOperatorCall = dyn_cast<CXXOperatorCallExpr>(operatorCall->getArg(1)))
+            {
+                found = innerOperatorCall->getOperator() == OO_Tilde;
+            }
+            if (!found)
+                bWrite = true;
+        }
+            // if assignment op
+        else if (oo == OO_Equal || oo == OO_StarEqual || oo == OO_SlashEqual || oo == OO_PercentEqual
            || oo == OO_PlusEqual || oo == OO_MinusEqual || oo == OO_LessLessEqual
-           || oo == OO_AmpEqual || oo == OO_CaretEqual || oo == OO_PipeEqual)
+           || oo == OO_CaretEqual || oo == OO_PipeEqual)
             bWrite = true;
-        // else if comparison op
+            // else if comparison op
         else if (oo == OO_AmpAmp || oo == OO_PipePipe || oo == OO_Subscript
             || oo == OO_Less || oo == OO_Greater || oo == OO_LessEqual || oo == OO_GreaterEqual || oo == OO_EqualEqual || oo == OO_ExclaimEqual)
             bRead = true;

compilerplugins/clang/unusedenumconstants.py

@@ -105,6 +105,11 @@ def is_ignore(srcLoc):
          "sc/source/filter/inc/flttypes.hxx", # BiffTyp
          "sc/inc/optutil.hxx", # ScOptionsUtil::KeyBindingType
          "include/sfx2/chalign.hxx", # SfxChildAlignment
+         "drawinglayer/source/tools/emfpbrush.hxx",
+         "drawinglayer/source/tools/emfppen.cxx",
+         "include/oox/ppt/animationspersist.hxx",
+         "include/vcl/fontcapabilities.hxx",
+         "sw/inc/poolfmt.hxx",
         # unit test code
          "cppu/source/uno/check.cxx",
         # general weird nonsense going on