Add tests for cppcheck-opensource#6092, #9995, #13766 (cppcheck-opensource#9007)

Author: chrchr-github

test/testbufferoverrun.cpp

@@ -164,6 +164,7 @@ class TestBufferOverrun : public TestFixture {
         TEST_CASE(array_index_74); // #11088
         TEST_CASE(array_index_75);
         TEST_CASE(array_index_76);
+        TEST_CASE(array_index_77);
         TEST_CASE(array_index_multidim);
         TEST_CASE(array_index_switch_in_for);
         TEST_CASE(array_index_for_in_for);   // FP: #2634
@@ -2014,6 +2015,21 @@ class TestBufferOverrun : public TestFixture {
                       errout_str());
     }
 
+    void array_index_77()
+    {
+        check("int f(bool b) {\n" // #6092
+              "    const int a[2] = {};\n"
+              "    int i = 0, s = 0;\n"
+              "    s += a[i++];\n"
+              "    if (b)\n"
+              "        s += a[i++];\n"
+              "    s += a[i++];\n"
+              "    return s + i;\n"
+              "}\n");
+        ASSERT_EQUALS("[test.cpp:7:11]: (error) Array 'a[2]' accessed at index 2, which is out of bounds. [arrayIndexOutOfBounds]\n",
+                      errout_str());
+    }
+
     void array_index_multidim() {
         check("void f()\n"
               "{\n"

test/testother.cpp

@@ -2367,6 +2367,11 @@ class TestOther : public TestFixture {
                                  "    return N::f(float_ptr(b.data()));\n" // <- the cast is safe
                                  "}\n");
         ASSERT_EQUALS("[test.cpp:9:17]: (style) C-style pointer casting [cstyleCast]\n", errout_str());
+
+        checkOldStylePointerCast("void f(const T& x) {\n" // #13766
+                                 "    const U& y = (typename const U&)(x);\n"
+                                 "}\n");
+        ASSERT_EQUALS("[test.cpp:2:18]: (warning) Potentially invalid type conversion in old-style C cast, clarify/fix with C++ cast [dangerousTypeCast]\n", errout_str());
     }
 
 #define checkIntToPointerCast(...) checkIntToPointerCast_(__FILE__, __LINE__, __VA_ARGS__)

test/testunusedvar.cpp

@@ -5688,6 +5688,20 @@ class TestUnusedVar : public TestFixture {
                               "    a[0].b = 0;\n"
                               "}\n");
         ASSERT_EQUALS("", errout_str());
+
+        functionVariableUsage("struct S {\n" // #9995
+                              "    int& operator[](int i) { return r[i]; }\n"
+                              "    std::map<int, int>& r;\n"
+                              "};\n"
+                              "struct T {\n"
+                              "    std::map<int, int>& m;\n"
+                              "    S get() { return { m }; }\n"
+                              "};\n"
+                              "void f(T& t) {\n"
+                              "    S s = t.get();\n"
+                              "    s[1] = 0;\n"
+                              "}\n");
+        ASSERT_EQUALS("", errout_str());
     }
 
     void localvarUnion1() {