Fix integer casting (#605)

* Separate variables for better legibility

* Fix proper_cast test

cairo-tests/src/integer_test.cairo

@@ -1088,9 +1088,7 @@ fn validate_cast_bounds_overlapping<
     validate_max_strictly_contained::<A, B>(err);
 }
 
-// TODO: fails
 #[test]
-#[ignore]
 fn proper_cast() {
     validate_cast_bounds_contained_same_min::<u8, u16>('u8 u16 casts');
     validate_cast_bounds_contained_same_min::<u8, u32>('u8 u32 casts');

src/libfuncs/cast.rs

@@ -81,24 +81,27 @@ pub fn build_downcast<'ctx, 'this>(
         location,
     );
 
-    let is_signed = src_type.is_integer_signed().ok_or_else(|| {
+    let src_is_signed = src_type.is_integer_signed().ok_or_else(|| {
         Error::SierraAssert("casts always happen between numerical types".to_string())
-    })? || dst_type.is_integer_signed().ok_or_else(|| {
+    })?;
+    let dst_is_signed = dst_type.is_integer_signed().ok_or_else(|| {
         Error::SierraAssert("casts always happen between numerical types".to_string())
     })?;
-    let is_felt = matches!(src_type, CoreTypeConcrete::Felt252(_));
+
+    let is_signed = src_is_signed || dst_is_signed;
+    let src_is_felt = matches!(src_type, CoreTypeConcrete::Felt252(_));
 
     let src_value: melior::ir::Value = entry.argument(1)?.into();
 
     let mut block = entry;
 
-    let (is_in_range, result) = if src_ty == dst_ty {
+    let (is_in_range, result) = if info.from_ty == info.to_ty {
         let k0 = block.const_int(context, location, 0, 1)?;
         (k0, src_value)
     } else {
         // make unsigned felt into signed felt
         // felt > half prime = negative
-        let src_value = if is_felt {
+        let src_value = if src_is_felt {
             let attr_halfprime_i252 = metadata
                 .get::<PrimeModuloMeta<Felt>>()
                 .ok_or(Error::MissingMetadata)?
@@ -184,7 +187,8 @@ pub fn build_downcast<'ctx, 'this>(
             info.to_range
                 .intersection(&info.from_range)
                 .ok_or_else(|| Error::SierraAssert("range should always interesct".to_string()))?
-                .upper,
+                .upper
+                - 1,
             compare_ty,
         )?;
 
@@ -201,9 +205,9 @@ pub fn build_downcast<'ctx, 'this>(
         let is_in_range_upper = block.append_op_result(arith::cmpi(
             context,
             if is_signed {
-                CmpiPredicate::Slt
+                CmpiPredicate::Sle
             } else {
-                CmpiPredicate::Ult
+                CmpiPredicate::Ule
             },
             compare_value,
             max_value,