Added utility functions for checking expressions

Use namespace rather than class with static functions as more semantically
correct.

Author: thk123

unit/Makefile

@@ -1,12 +1,17 @@
 .PHONY: all cprover.dir test
 
-SRC = unit_tests.cpp \
-      analyses/does_remove_const/does_expr_lose_const.cpp \
-      analyses/does_remove_const/does_type_preserve_const_correctness.cpp \
-      analyses/does_remove_const/is_type_at_least_as_const_as.cpp \
-      catch_example.cpp \
+# Source files for test utilities
+SRC = src/expr/require_expr.cpp \
       # Empty last line
 
+# Test source files
+SRC += unit_tests.cpp \
+       analyses/does_remove_const/does_expr_lose_const.cpp \
+       analyses/does_remove_const/does_type_preserve_const_correctness.cpp \
+       analyses/does_remove_const/is_type_at_least_as_const_as.cpp \
+       catch_example.cpp \
+       # Empty last line
+
 INCLUDES= -I ../src/ -I.
 
 include ../src/config.inc

unit/src/expr/require_expr.cpp

@@ -0,0 +1,76 @@
+/*******************************************************************\
+
+ Module: Unit test utilities
+
+ Author: DiffBlue Limited. All rights reserved.
+
+\*******************************************************************/
+
+/// \file
+/// Helper functions for requiring specific expressions
+/// If the expression is of the wrong type, throw a CATCH exception
+/// Also checks associated properties and returns a casted version of the
+/// expression.
+
+#include "require_expr.h"
+
+#include <catch.hpp>
+#include <util/arith_tools.h>
+
+/// Verify a given exprt is an index_exprt with a a constant value equal to the
+/// expected value
+/// \param expr: The expression.
+/// \param expected_index: The constant value that should be the index.
+/// \return The expr cast to an index_exprt
+index_exprt require_expr::require_index(const exprt &expr, int expected_index)
+{
+  REQUIRE(expr.id()==ID_index);
+  const index_exprt &index_expr=to_index_expr(expr);
+  REQUIRE(index_expr.index().id()==ID_constant);
+  const constant_exprt &index_value=to_constant_expr(index_expr.index());
+  mp_integer index_integer_value;
+  to_integer(index_value, index_integer_value);
+  REQUIRE(index_integer_value==expected_index);
+
+  return index_expr;
+}
+
+/// Verify a given exprt is an index_exprt with a nil value as its index
+/// \param expr: The expression.
+/// \return The expr cast to an index_exprt
+index_exprt require_expr::require_top_index(const exprt &expr)
+{
+  REQUIRE(expr.id()==ID_index);
+  const index_exprt &index_expr=to_index_expr(expr);
+  REQUIRE(index_expr.index().id()==ID_nil);
+  return index_expr;
+}
+
+/// Verify a given exprt is an member_exprt with a component name equal to the
+/// component_identifier
+/// \param expr: The expression.
+/// \param component_identifier: The name of the component that should be being
+///   accessed.
+/// \return The expr cast to a member_exprt.
+member_exprt require_expr::require_member(
+  const exprt &expr, const irep_idt &component_identifier)
+{
+  REQUIRE(expr.id()==ID_member);
+  const member_exprt &member_expr=to_member_expr(expr);
+  REQUIRE(member_expr.get_component_name()==component_identifier);
+  return member_expr;
+}
+
+/// Verify a given exprt is an symbol_exprt with a identifier name equal to the
+/// symbol_name.
+/// \param expr: The expression.
+/// \param symbol_name: The intended identifier of the symbol
+/// \return The expr cast to a symbol_exprt
+symbol_exprt require_expr::require_symbol(
+  const exprt &expr, const irep_idt &symbol_name)
+{
+  REQUIRE(expr.id()==ID_symbol);
+  const symbol_exprt &symbol_expr=to_symbol_expr(expr);
+  REQUIRE(symbol_expr.get_identifier()==symbol_name);
+  return symbol_expr;
+}

unit/src/expr/require_expr.h

@@ -0,0 +1,33 @@
+/*******************************************************************\
+
+ Module: Unit test utilities
+
+ Author: DiffBlue Limited. All rights reserved.
+
+\*******************************************************************/
+
+/// \file
+/// Helper functions for requiring specific expressions
+/// If the expression is of the wrong type, throw a CATCH exception
+/// Also checks associated properties and returns a casted version of the
+/// expression.
+
+#ifndef CPROVER_SRC_EXPR_REQUIRE_EXPR_H
+#define CPROVER_SRC_EXPR_REQUIRE_EXPR_H
+
+#include <util/std_expr.h>
+
+// NOLINTNEXTLINE(readability/namespace)
+namespace require_expr
+{
+  index_exprt require_index(const exprt &expr, int expected_index);
+  index_exprt require_top_index(const exprt &expr);
+
+  member_exprt require_member(
+    const exprt &expr, const irep_idt &component_identifier);
+
+  symbol_exprt require_symbol(
+    const exprt &expr, const irep_idt &symbol_name);
+}
+
+#endif // CPROVER_SRC_EXPR_REQUIRE_EXPR_H