Implement compile time castings for integers

1 files changed, 72 insertions, 1 deletions

diff --git a/boot/evaluator.cc b/boot/evaluator.cc
index 407370a..14ca889 100644
--- a/boot/evaluator.cc
+++ b/boot/evaluator.cc
@@ -370,7 +370,7 @@ namespace elna::boot
         }
         auto& index_literal = std::get<integer_literal>(evaluated_index.value());
 
-        return index_literal.is_negative() ? std::nullopt : index_literal.to_unsigned();
+        return index_literal < 0 ? std::nullopt : index_literal.try_to<std::size_t>();
     }
 
     std::optional<constant_value> evaluator::evaluate_slicing(slicing_expression& subject)
@@ -694,6 +694,66 @@ namespace elna::boot
         }, lhs.value());
     }
 
+    std::optional<constant_value> evaluator::cast_to_int(const constant_value& source_expression)
+    {
+        return std::visit([](auto&& source_value) -> std::optional<constant_value> {
+            using T = std::decay_t<decltype(source_value)>;
+
+            if constexpr (std::is_same_v<T, integer_literal>)
+            {
+                std::optional<std::ptrdiff_t> signed_value = source_value.template try_to<std::ptrdiff_t>();
+
+                return signed_value.has_value()
+                    ? std::optional(integer_literal::from(signed_value.value()))
+                    : std::nullopt;
+            }
+            else if constexpr (std::is_same_v<T, double>
+                    || std::is_same_v<T, bool>
+                    || std::is_same_v<T, unsigned char>)
+            {
+                return integer_literal::from(static_cast<std::ptrdiff_t>(source_value));
+            }
+            else if constexpr (std::is_same_v<T, std::nullptr_t>)
+            {
+                return integer_literal::from<std::ptrdiff_t>(0);
+            }
+            else
+            {
+                return std::nullopt;
+            }
+        }, source_expression);
+    }
+
+    std::optional<constant_value> evaluator::cast_to_word(const constant_value& source_expression)
+    {
+        return std::visit([](auto&& source_value) -> std::optional<constant_value> {
+            using T = std::decay_t<decltype(source_value)>;
+
+            if constexpr (std::is_same_v<T, integer_literal>)
+            {
+                std::optional<std::size_t> unsigned_value = source_value.template try_to<std::size_t>();
+
+                return unsigned_value.has_value()
+                    ? std::optional(integer_literal::from(unsigned_value.value()))
+                    : std::nullopt;
+            }
+            else if constexpr (std::is_same_v<T, double>
+                    || std::is_same_v<T, bool>
+                    || std::is_same_v<T, unsigned char>)
+            {
+                return integer_literal::from(static_cast<std::size_t>(source_value));
+            }
+            else if constexpr (std::is_same_v<T, std::nullptr_t>)
+            {
+                return integer_literal::from<std::ptrdiff_t>(0U);
+            }
+            else
+            {
+                return std::nullopt;
+            }
+        }, source_expression);
+    }
+
     std::optional<constant_value> evaluator::evaluate_cast(cast_expression& subject)
     {
         auto value = evaluate(subject.value());
@@ -702,6 +762,17 @@ namespace elna::boot
         {
             return std::nullopt;
         }
+        const type resolved = resolve_underlying_type(subject.type_decoration);
+
+        if (is_primitive_type(resolved, "Int"))
+        {
+            return cast_to_int(value.value());
+        }
+        else if (is_primitive_type(resolved, "Word"))
+        {
+            return cast_to_word(value.value());
+        }
+
         return constant_value{ value.value() };
     }