Fix #6: warn on c-style and function style casts that generate a "bit cast" in the clang tidy analysis. convert those to explicit reinterpret casts if possible

checks/clang-query/prefer-reinterpret-cast/prefer-reinterpret-cast.query

@@ -0,0 +1,13 @@
+# Flags C-style and function-style casts that reinterpret an object's bits
+# (clang's BitCast / LValueBitCast cast kinds); spell these as reinterpret_cast
+# (plus const_cast when constness is also discarded) so the intent is explicit.
+# Template instantiations are traversed so that dependent casts are reported
+# once they resolve to a bit cast.
+set traversal AsIs
+match explicitCastExpr(
+  isExpansionInMainFile(),
+  anyOf(cStyleCastExpr(), cxxFunctionalCastExpr()),
+  anyOf(
+    hasCastKind("CK_BitCast"),
+    hasCastKind("CK_LValueBitCast"),
+    has(implicitCastExpr(anyOf(hasCastKind("CK_BitCast"), hasCastKind("CK_LValueBitCast"))))))

checks/clang-query/prefer-reinterpret-cast/tests/fail/bit_cast_discarding_const.cpp

@@ -0,0 +1,9 @@
+[[nodiscard]] char *mutable_bytes(const int *value)
+{
+  return (char *)value;// expect-finding
+}
+
+[[nodiscard]] void *mutable_address(const int &value)
+{
+  return (void *)&value;// expect-finding
+}

checks/clang-query/prefer-reinterpret-cast/tests/fail/bit_cast_in_template.cpp

@@ -0,0 +1,6 @@
+template<typename To, typename From> [[nodiscard]] To convert(const From value)
+{
+  return (To)value;// expect-finding
+}
+
+[[nodiscard]] const char *as_chars(const int *value) { return convert<const char *>(value); }

checks/clang-query/prefer-reinterpret-cast/tests/fail/c_style_pointer_bit_cast.cpp

@@ -0,0 +1,4 @@
+[[nodiscard]] const unsigned char *object_bytes(const int &value)
+{
+  return (const unsigned char *)&value;// expect-finding
+}

checks/clang-query/prefer-reinterpret-cast/tests/fail/c_style_reference_bit_cast.cpp

@@ -0,0 +1,4 @@
+[[nodiscard]] float &reinterpret_bits(int &value)
+{
+  return (float &)value;// expect-finding
+}

checks/clang-query/prefer-reinterpret-cast/tests/fail/function_style_pointer_bit_cast.cpp

@@ -0,0 +1,6 @@
+using byte_pointer = const unsigned char *;
+
+[[nodiscard]] byte_pointer object_bytes(const int &value)
+{
+  return byte_pointer(&value);// expect-finding
+}

checks/clang-query/prefer-reinterpret-cast/tests/pass/reinterpret_cast.cpp

@@ -0,0 +1,6 @@
+[[nodiscard]] const unsigned char *object_bytes(const int &value)
+{
+  return reinterpret_cast<const unsigned char *>(&value);
+}
+
+[[nodiscard]] float &reinterpret_bits(int &value) { return reinterpret_cast<float &>(value); }

checks/clang-query/prefer-reinterpret-cast/tests/pass/template_without_bit_cast.cpp

@@ -0,0 +1,6 @@
+template<typename To, typename From> [[nodiscard]] constexpr To convert(const From value)
+{
+  return (To)value;
+}
+
+[[nodiscard]] constexpr int truncate(const double value) { return convert<int>(value); }

checks/clang-query/prefer-reinterpret-cast/tests/pass/value_conversions.cpp

@@ -0,0 +1,21 @@
+struct Base
+{
+  int base_value;
+};
+
+struct Derived : Base
+{
+  int derived_value;
+};
+
+using integer = int;
+
+[[nodiscard]] constexpr int truncate(const double value) { return (int)value; }
+
+[[nodiscard]] constexpr int truncate_functional(const double value) { return integer(value); }
+
+[[nodiscard]] const Derived *as_derived(const Base *base) { return (const Derived *)base; }
+
+[[nodiscard]] const Base *as_base(const Derived *derived) { return (const Base *)derived; }
+
+[[nodiscard]] float to_float(const int &value) { return (const float &)value; }