ValueFlow: Infer possible symbolic values (#4947)

lib/infer.cpp

@@ -148,7 +148,8 @@ struct Interval {
                 result.setMinValue(minValue->intvalue + 1, minValue);
             if (minValue->isPossible() && minValue->bound == ValueFlow::Value::Bound::Lower)
                 result.setMinValue(minValue->intvalue, minValue);
-            if (minValue->isKnown())
+            if (!minValue->isImpossible() && minValue->bound == ValueFlow::Value::Bound::Point &&
+                std::count_if(values.begin(), values.end(), predicate) == 1)
                 return Interval::fromInt(minValue->intvalue, minValue);
         }
         const ValueFlow::Value* maxValue = getCompareValue(values, predicate, std::greater<MathLib::bigint>{});

lib/valueflow.cpp

@@ -6767,8 +6767,6 @@ static void valueFlowInferCondition(TokenList* tokenlist,
             if (result.size() != 1)
                 continue;
             ValueFlow::Value value = result.front();
-            value.intvalue = 1;
-            value.bound = ValueFlow::Value::Bound::Point;
             setTokenValue(tok, std::move(value), settings);
         }
     }

test/testother.cpp

@@ -67,6 +67,7 @@ private:
         TEST_CASE(zeroDiv15); // #8319
         TEST_CASE(zeroDiv16); // #11158
         TEST_CASE(zeroDiv17); // #9931
+        TEST_CASE(zeroDiv18);
 
         TEST_CASE(zeroDivCond); // division by zero / useless condition
 
@@ -652,6 +653,17 @@ private:
         ASSERT_EQUALS("", errout.str());
     }
 
+    void zeroDiv18()
+    {
+        check("int f(int x, int y) {\n"
+              "    if (x == y) {}\n"
+              "    return 1 / (x-y);\n"
+              "}\n");
+        ASSERT_EQUALS(
+            "[test.cpp:2] -> [test.cpp:3]: (warning) Either the condition 'x==y' is redundant or there is division by zero at line 3.\n",
+            errout.str());
+    }
+
     void zeroDivCond() {
         check("void f(unsigned int x) {\n"
               "  int y = 17 / x;\n"

test/testvalueflow.cpp

@@ -5453,6 +5453,7 @@ private:
 
     void valueFlowConditionExpressions() {
         const char* code;
+        std::list<ValueFlow::Value> values;
 
         // opposite condition
         code = "void f(int i, int j) {\n"
@@ -5559,7 +5560,11 @@ private:
                "        if (i != j) {}\n"
                "    }\n"
                "}\n";
-        ASSERT_EQUALS(true, removeImpossible(tokenValues(code, "!=")).empty());
+        values = removeImpossible(tokenValues(code, "!="));
+        ASSERT_EQUALS(1, values.size());
+        ASSERT_EQUALS(0, values.front().intvalue);
+        ASSERT_EQUALS(true, values.front().isIntValue());
+        ASSERT_EQUALS(true, values.front().isPossible());
 
         code = "void f(bool b, int i, int j) {\n"
                "    if (b || i == j) {} else {\n"