Fix #12742 FP containerOutOfBounds for increment in loop (danmar#8230)

Author: chrchr-github

lib/valueflow.cpp

@@ -4531,7 +4531,7 @@ struct ConditionHandler {
                 }
 
                 // Variable changed in loop code
-                const Token* const start = top;
+                const Token* const start = top->strAt(-1) == "for" ? top->astOperand2() : top; // skip init statement
                 const Token* const block = top->link()->next();
                 const Token* const end = block->link();
 

test/teststl.cpp

@@ -1010,6 +1010,12 @@ class TestStl : public TestFixture {
         ASSERT_EQUALS(
             "[test.cpp:2:12] -> [test.cpp:4:21]: (warning) Either the condition 'col>textline.size()' is redundant or 'col' can have the value textline.size(). Expression 'textline[col]' causes access out of bounds. [containerOutOfBounds]\n",
             errout_str());
+
+        check("void f(const std::vector<int>& v) {\n" // #12742
+              "    for (unsigned i = 0; i < v.size();)\n"
+              "        (void)v[i++];\n"
+              "}\n");
+        ASSERT_EQUALS("", errout_str());
     }
 
     void outOfBoundsIndexExpression() {