avoid false positive unused static const struct member (#2598)

lib/checkunusedvar.cpp

@@ -1400,6 +1400,8 @@ void CheckUnusedVar::checkStructMemberUsage()
             // Check if the struct member variable is used anywhere in the file
             if (Token::findsimplematch(mTokenizer->tokens(), (". " + var.name()).c_str()))
                 continue;
+            if (Token::findsimplematch(mTokenizer->tokens(), (":: " + var.name()).c_str()))
+                continue;
 
             unusedStructMemberError(var.nameToken(), scope.className, var.name(), scope.type == Scope::eUnion);
         }

test/testunusedvar.cpp

@@ -511,6 +511,17 @@ private:
                                "    ab.b = 0;\n"
                                "}");
         ASSERT_EQUALS("[test.cpp:3]: (style) struct member 'AB::a' is never used.\n", errout.str());
+
+        checkStructMemberUsage("struct A\n"
+            "{\n"
+            "    static const int a = 0;\n"
+            "};\n"
+            "\n"
+            "int foo()\n"
+            "{\n"
+            "    return A::a;\n"
+            "}");
+        ASSERT_EQUALS("", errout.str());
     }
 
     void structmember_sizeof() {