destruct record at high level

compiler/builtins/bitcode/src/list.zig

@@ -893,11 +893,10 @@ pub fn listSublist(
     list: RocList,
     alignment: u32,
     element_width: usize,
-    rec: extern struct { len: usize, start: usize },
+    start: usize,
+    len: usize,
     dec: Dec,
 ) callconv(.C) RocList {
-    const start = rec.start;
-    const len = rec.len;
     if (list.bytes) |source_ptr| {
         const size = list.len();
 
@@ -922,9 +921,9 @@ pub fn listSublist(
         utils.decref(list.bytes, size * element_width, alignment);
 
         return output;
-    } else {
+    } 
-        return RocList.empty();
+
-    }
+    return RocList.empty();
 }
 
 pub fn listTakeLast(

compiler/can/src/builtins.rs

@@ -2070,9 +2070,32 @@ fn list_sublist(symbol: Symbol, var_store: &mut VarStore) -> Def {
     let sym_list = Symbol::ARG_1;
     let sym_rec = Symbol::ARG_2;
 
+    let start_var = var_store.fresh();
+    let len_var = var_store.fresh();
+
+    let get_start = Access {
+        record_var: rec_var,
+        ext_var: var_store.fresh(),
+        field_var: var_store.fresh(),
+        loc_expr: Box::new(no_region(Var(sym_rec))),
+        field: "start".into(),
+    };
+
+    let get_len = Access {
+        record_var: rec_var,
+        ext_var: var_store.fresh(),
+        field_var: var_store.fresh(),
+        loc_expr: Box::new(no_region(Var(sym_rec))),
+        field: "len".into(),
+    };
+
     let body = RunLowLevel {
         op: LowLevel::ListSublist,
-        args: vec![(list_var, Var(sym_list)), (rec_var, Var(sym_rec))],
+        args: vec![
+            (list_var, Var(sym_list)),
+            (start_var, get_start),
+            (len_var, get_len),
+        ],
         ret_var: list_var,
     };
 

compiler/gen_llvm/src/llvm/build.rs

@@ -5212,12 +5212,16 @@ fn run_low_level<'a, 'ctx, 'env>(
         }
         ListSublist => {
             // List.sublist : List elem, { start : Nat, len : Nat } -> List elem
-            debug_assert_eq!(args.len(), 2);
+            //
+            // As a low-level, record is destructed
+            // List.sublist : List elem, start : Nat, len : Nat -> List elem
+            debug_assert_eq!(args.len(), 3);
 
             let (list, list_layout) = load_symbol_and_layout(scope, &args[0]);
             let original_wrapper = list.into_struct_value();
 
-            let rec = load_symbol(scope, &args[1]);
+            let start = load_symbol(scope, &args[1]);
+            let len = load_symbol(scope, &args[2]);
 
             match list_layout {
                 Layout::Builtin(Builtin::EmptyList) => empty_list(env),
@@ -5225,7 +5229,8 @@ fn run_low_level<'a, 'ctx, 'env>(
                     env,
                     layout_ids,
                     original_wrapper,
-                    rec.into_struct_value(),
+                    start.into_int_value(),
+                    len.into_int_value(),
                     element_layout,
                 ),
                 _ => unreachable!("Invalid layout {:?} in List.sublist", list_layout),

compiler/gen_llvm/src/llvm/build_list.rs

@@ -343,7 +343,8 @@ pub fn list_sublist<'a, 'ctx, 'env>(
     env: &Env<'a, 'ctx, 'env>,
     layout_ids: &mut LayoutIds<'a>,
     original_wrapper: StructValue<'ctx>,
-    len_and_start: StructValue<'ctx>,
+    start: IntValue<'ctx>,
+    len: IntValue<'ctx>,
     element_layout: &Layout<'a>,
 ) -> BasicValueEnum<'ctx> {
     let dec_element_fn = build_dec_wrapper(env, layout_ids, element_layout);
@@ -353,12 +354,8 @@ pub fn list_sublist<'a, 'ctx, 'env>(
             pass_list_cc(env, original_wrapper.into()),
             env.alignment_intvalue(element_layout),
             layout_width(env, element_layout),
-            complex_bitcast(
+            start.into(),
-                env.builder,
+            len.into(),
-                len_and_start.into(),
-                env.str_list_c_abi().into(),
-                "to_i128",
-            ),
             dec_element_fn.as_global_value().as_pointer_value().into(),
         ],
         bitcode::LIST_SUBLIST,

compiler/mono/src/borrow.rs

@@ -968,7 +968,7 @@ pub fn lowlevel_borrow_signature(arena: &Bump, op: LowLevel) -> &[bool] {
         ListAppend => arena.alloc_slice_copy(&[owned, owned]),
         ListTakeFirst => arena.alloc_slice_copy(&[owned, irrelevant]),
         ListTakeLast => arena.alloc_slice_copy(&[owned, irrelevant]),
-        ListSublist => arena.alloc_slice_copy(&[owned, irrelevant]),
+        ListSublist => arena.alloc_slice_copy(&[owned, irrelevant, irrelevant]),
         ListDrop => arena.alloc_slice_copy(&[owned, irrelevant]),
         ListDropAt => arena.alloc_slice_copy(&[owned, irrelevant]),
         ListSwap => arena.alloc_slice_copy(&[owned, irrelevant, irrelevant]),