Allow assigning contants to enumeration members

1 files changed, 35 insertions, 19 deletions

diff --git a/boot/evaluator.cc b/boot/evaluator.cc
index 67fc42a..18633ba 100644
--- a/boot/evaluator.cc
+++ b/boot/evaluator.cc
@@ -48,6 +48,10 @@ namespace elna::boot
                 return "Array dimensions for type '" + payload.array_type.to_string()
                     + "' should be constant";
             }
+            else if constexpr (std::is_same_v<T, enumeration_value>)
+            {
+                return "Enumeration member value must be an integer constant expression";
+            }
         }, this->payload);
     }
 
@@ -63,6 +67,21 @@ namespace elna::boot
         }
     }
 
+    /**
+     * Builds the constant for an enumeration value.
+     *
+     * Goes through the bit pattern because \c integer_literal::from imports
+     * the magnitude of a negative value, not its two's complement.
+     *
+     * \param value Member value.
+     * \param size Size of the enumeration type in bytes.
+     * \return Signed constant of the given size.
+     */
+    static integer_literal enumeration_constant(const std::ptrdiff_t value, const std::size_t size)
+    {
+        return integer_literal::from(static_cast<std::size_t>(value)).cast_to(true, size);
+    }
+
     std::optional<type_properties> get_type_properties(const type& subject, const target_info& target)
     {
         const type resolved = resolve_underlying_type(subject);
@@ -330,10 +349,12 @@ namespace elna::boot
                             {
                                 return std::nullopt;
                             }
-                            const std::size_t enumeration_position = static_cast<std::size_t>(
-                                    std::distance(enumeration->members.begin(), member_iterator));
+                            const std::ptrdiff_t enumeration_position =
+                                    std::distance(enumeration->members.begin(), member_iterator);
 
-                            return constant_value{ integer_literal::from(enumeration_position + 1U) };
+                            return constant_value{ enumeration_constant(
+                                    enumeration->values.at(static_cast<std::size_t>(enumeration_position)),
+                                    this->target.word_properties.front().size) };
                         }
                     }
                 }
@@ -897,21 +918,21 @@ namespace elna::boot
     }
 
     std::optional<constant_value> evaluator::cast_to_enumeration(const constant_value& source_expression,
-            const std::size_t member_count, const std::size_t target_size)
+            const enumeration_type& enumeration, const std::size_t target_size)
     {
-        std::optional<constant_value> position = cast_to_integer(source_expression, false, target_size);
+        std::optional<constant_value> value = cast_to_integer(source_expression, true, target_size);
 
-        if (!position.has_value())
+        if (!value.has_value())
         {
             return std::nullopt;
         }
-        const auto *converted = std::get_if<integer_literal>(&position.value());
+        const auto *converted = std::get_if<integer_literal>(&value.value());
 
-        if (converted == nullptr || *converted < std::size_t{ 1 } || *converted > member_count)
+        if (converted == nullptr || *converted < enumeration.minimum() || *converted > enumeration.maximum())
         {
             return std::nullopt;
         }
-        return position;
+        return value;
     }
 
     std::optional<constant_value> evaluator::cast_to_pointer(const constant_value& source_expression)
@@ -952,7 +973,7 @@ namespace elna::boot
             {
                 return std::nullopt;
             }
-            return cast_to_enumeration(value.value(), enumeration->members.size(), properties->size);
+            return cast_to_enumeration(value.value(), *enumeration, properties->size);
         }
         if (is_integral_type(target_type))
         {
@@ -1055,10 +1076,8 @@ namespace elna::boot
             }
             if (const auto enumeration = resolved.get<enumeration_type>())
             {
-                return constant_value{
-                    integer_literal::from<std::size_t>(
-                        this->target.word_properties.front().size, 1U).value()
-                };
+                return constant_value{ enumeration_constant(enumeration->minimum(),
+                        this->target.word_properties.front().size) };
             }
         }
         else if (subject.name.name() == "max")
@@ -1104,11 +1123,8 @@ namespace elna::boot
             }
             if (const auto enumeration = resolved.get<enumeration_type>())
             {
-                return constant_value{
-                    integer_literal::from<std::size_t>(
-                        this->target.word_properties.front().size,
-                        enumeration->members.size()).value()
-                };
+                return constant_value{ enumeration_constant(enumeration->maximum(),
+                        this->target.word_properties.front().size) };
             }
         }
         else if (subject.name.name() == "offset")