Fixed #6996 (ValueFlow: known and possible values)

lib/valueflow.cpp

@@ -358,6 +358,11 @@ static bool isVariableChanged(const Token *start, const Token *end, const unsign
 /** Add token value. Return true if value is added. */
 static bool addValue(Token *tok, const ValueFlow::Value &value)
 {
+    if (value.isKnown()) {
+        // Clear all other values since value is known
+        tok->values.clear();
+    }
+
     // if value already exists, don't add it again
     std::list<ValueFlow::Value>::iterator it;
     for (it = tok->values.begin(); it != tok->values.end(); ++it) {

test/testvalueflow.cpp

@@ -1775,6 +1775,15 @@ private:
         value = valueOfTok(code, "+");
         ASSERT_EQUALS(13, value.intvalue);
         ASSERT(value.isPossible());
+
+        // known and possible value
+        code = "void f() {\n"
+               "    int x = 1;\n"
+               "    int y = 2 + x;\n" // <- known value, don't care about condition
+               "    if (x == 2) {}\n"
+               "}";
+        ASSERT_EQUALS(true,  testValueOfX(code, 3U, 1)); // value of x can be 1
+        ASSERT_EQUALS(false, testValueOfX(code, 3U, 2)); // value of x can't be 2
     }
 };