Add pointer offset expression unit tests

Author: thomasspriggs

unit/Makefile

@@ -161,6 +161,7 @@ SRC += analyses/ai/ai.cpp \
        util/optional_utils.cpp \
        util/parse_options.cpp \
        util/piped_process.cpp \
+       util/pointer_expr.cpp \
        util/pointer_offset_size.cpp \
        util/prefix_filter.cpp \
        util/range.cpp \

unit/util/pointer_expr.cpp

@@ -0,0 +1,66 @@
+// Author: Diffblue Ltd.
+
+#include <util/c_types.h>
+#include <util/pointer_expr.h>
+#include <util/pointer_predicates.h>
+
+#include <testing-utils/invariant.h>
+#include <testing-utils/use_catch.h>
+
+TEST_CASE("pointer_offset_exprt", "[core][util]")
+{
+  const exprt pointer = symbol_exprt{"foo", pointer_type(void_type())};
+  const pointer_offset_exprt pointer_offset{pointer, signed_size_type()};
+  SECTION("Is equivalent to free function.")
+  {
+    CHECK(::pointer_offset(pointer) == pointer_offset);
+  }
+  SECTION("Result type")
+  {
+    CHECK(pointer_offset.type() == signed_size_type());
+  }
+  SECTION("Pointer operand accessor")
+  {
+    CHECK(pointer_offset.pointer() == pointer);
+  }
+  SECTION("Downcasting")
+  {
+    const exprt &upcast = pointer_offset;
+    CHECK(expr_try_dynamic_cast<pointer_offset_exprt>(pointer_offset));
+    CHECK_FALSE(expr_try_dynamic_cast<pointer_object_exprt>(upcast));
+    SECTION("Validation")
+    {
+      SECTION("Invalid operand")
+      {
+        unary_exprt invalid_type = pointer_offset;
+        invalid_type.op().type() = bool_typet{};
+        const cbmc_invariants_should_throwt invariants_throw;
+        REQUIRE_THROWS_MATCHES(
+          expr_try_dynamic_cast<pointer_offset_exprt>(invalid_type),
+          invariant_failedt,
+          invariant_failure_containing(
+            "pointer_offset must have pointer-typed operand"));
+      }
+      SECTION("Missing operand")
+      {
+        exprt missing_operand = pointer_offset;
+        missing_operand.operands().clear();
+        const cbmc_invariants_should_throwt invariants_throw;
+        REQUIRE_THROWS_MATCHES(
+          expr_try_dynamic_cast<pointer_offset_exprt>(missing_operand),
+          invariant_failedt,
+          invariant_failure_containing("pointer_offset must have one operand"));
+      }
+      SECTION("Too many operands")
+      {
+        exprt two_operands = pointer_offset;
+        two_operands.operands().push_back(pointer);
+        const cbmc_invariants_should_throwt invariants_throw;
+        REQUIRE_THROWS_MATCHES(
+          expr_try_dynamic_cast<pointer_offset_exprt>(two_operands),
+          invariant_failedt,
+          invariant_failure_containing("pointer_offset must have one operand"));
+      }
+    }
+  }
+}