Fixed #8914 (False positive with unary_function argument)

lib/astutils.cpp

@@ -1277,6 +1277,11 @@ bool FwdAnalysis::isGlobalData(const Token *expr) const
                 return ChildrenToVisit::none;
             }
         }
+        // Unknown argument type => it might be some reference type..
+        if (mCpp && tok->str() == "." && tok->astOperand1() && tok->astOperand1()->variable() && !tok->astOperand1()->valueType()) {
+            globalData = true;
+            return ChildrenToVisit::none;
+        }
         if (Token::Match(tok, ".|["))
             return ChildrenToVisit::op1;
         return ChildrenToVisit::op1_and_op2;

test/testunusedvar.cpp

@@ -4412,7 +4412,7 @@ private:
         );
         ASSERT_EQUALS("", errout.str());
 
-        // Unknown variable
+        // Unknown argument type
         functionVariableUsage(
             "void A::b(Date& result) {"
             "  result = 12;\n"
@@ -4420,6 +4420,32 @@ private:
         );
         ASSERT_EQUALS("", errout.str());
 
+        {
+            // #8914
+            functionVariableUsage( // assume unknown argument type is reference
+                "void fun(Date result) {"
+                "  result.x = 12;\n"
+                "}"
+            );
+            ASSERT_EQUALS("", errout.str());
+
+            functionVariableUsage( // there is no reference type in C
+                "void fun(Date result) {"
+                "  result.x = 12;\n"
+                "}",
+                "test.c"
+            );
+            ASSERT_EQUALS("[test.c:1]: (style) Variable 'result.x' is assigned a value that is never used.\n", errout.str());
+
+            functionVariableUsage(
+                "struct Date { int x; };\n"
+                "void fun(Date result) {"
+                "  result.x = 12;\n"
+                "}"
+            );
+            ASSERT_EQUALS("[test.cpp:2]: (style) Variable 'result.x' is assigned a value that is never used.\n", errout.str());
+        }
+
         // Unknown struct type
         functionVariableUsage(
             "void fun() {"