Adds castToNat

compiler/builtins/bitcode/src/main.zig

@@ -81,6 +81,7 @@ comptime {
     exportNumFn(num.asin, "asin");
     exportNumFn(num.bytesToU16C, "bytes_to_u16");
     exportNumFn(num.bytesToU32C, "bytes_to_u32");
+    exportNumFn(num.castToNat, "cast_to_nat");
     exportNumFn(num.round, "round");
 }
 

compiler/builtins/bitcode/src/num.zig

@@ -45,6 +45,10 @@ fn bytesToU32(arg: RocList, position: usize) u32 {
     return 41;
 }
 
+pub fn castToNat(num: i64) callconv(.C) usize {
+    return @intCast(usize, num);
+}
+
 pub fn round(num: f64) callconv(.C) i64 {
     return @floatToInt(i32, (@round(num)));
 }

compiler/builtins/src/bitcode.rs

@@ -10,6 +10,7 @@ pub const NUM_IS_FINITE: &str = "roc_builtins.num.is_finite";
 pub const NUM_POW_INT: &str = "roc_builtins.num.pow_int";
 pub const NUM_BYTES_TO_U16: &str = "roc_builtins.num.bytes_to_u16";
 pub const NUM_BYTES_TO_U32: &str = "roc_builtins.num.bytes_to_u32";
+pub const NUM_CAST_TO_NAT: &str = "roc_builtins.num.cast_to_nat";
 pub const NUM_ROUND: &str = "roc_builtins.num.round";
 
 pub const STR_INIT: &str = "roc_builtins.str.init";

compiler/builtins/src/std.rs

@@ -501,6 +501,13 @@ pub fn types() -> MutMap<Symbol, (SolvedType, Region)> {
         Box::new(float_type(flex(TVAR1))),
     );
 
+    // castToNat : Num a -> Nat
+    add_top_level_function_type!(
+        Symbol::NUM_CAST_TO_NAT,
+        vec![int_type(flex(TVAR1))],
+        Box::new(nat_type()),
+    );
+
     // bytesToU16 : List U8, Nat -> U16
     add_top_level_function_type!(
         Symbol::NUM_BYTES_TO_U16,

compiler/gen_llvm/src/llvm/build.rs

@@ -4738,6 +4738,11 @@ fn run_low_level<'a, 'ctx, 'env>(
                 }
             }
         }
+        NumCastToNat => {
+            debug_assert_eq!(args.len(), 1);
+            let num = load_symbol(scope, &args[0]).into_int_value();
+            call_bitcode_fn(env, &[num.into()], bitcode::NUM_CAST_TO_NAT)
+        }
         NumBytesToU16 => {
             debug_assert_eq!(args.len(), 2);
             let list = load_symbol(scope, &args[0]).into_struct_value();

compiler/module/src/low_level.rs

@@ -89,6 +89,7 @@ pub enum LowLevel {
     NumAsin,
     NumBytesToU16,
     NumBytesToU32,
+    NumCastToNat,
     NumBitwiseAnd,
     NumBitwiseXor,
     NumBitwiseOr,
@@ -125,8 +126,8 @@ impl LowLevel {
             | NumSqrtUnchecked | NumLogUnchecked | NumRound | NumToFloat | NumPow | NumCeiling
             | NumPowInt | NumFloor | NumIsFinite | NumAtan | NumAcos | NumAsin | NumBitwiseAnd
             | NumBitwiseXor | NumBitwiseOr | NumShiftLeftBy | NumShiftRightBy | NumBytesToU16
-            | NumBytesToU32 | NumShiftRightZfBy | NumIntCast | Eq | NotEq | And | Or | Not
-            | Hash | ExpectTrue => false,
+            | NumBytesToU32 | NumCastToNat | NumShiftRightZfBy | NumIntCast | Eq | NotEq | And
+            | Or | Not | Hash | ExpectTrue => false,
 
             ListMap | ListMap2 | ListMap3 | ListMapWithIndex | ListKeepIf | ListWalk
             | ListWalkUntil | ListWalkBackwards | ListKeepOks | ListKeepErrs | ListSortWith

compiler/module/src/symbol.rs

@@ -893,6 +893,7 @@ define_builtins! {
         102 NUM_DEC: "Dec" imported // the Num.Dectype alias
         103 NUM_BYTES_TO_U16: "bytesToU16"
         104 NUM_BYTES_TO_U32: "bytesToU32"
+        105 NUM_CAST_TO_NAT: "#castToNat"
     }
     2 BOOL: "Bool" => {
         0 BOOL_BOOL: "Bool" imported // the Bool.Bool type alias

compiler/mono/src/borrow.rs

@@ -1014,6 +1014,7 @@ pub fn lowlevel_borrow_signature(arena: &Bump, op: LowLevel) -> &[bool] {
         | NumIntCast => arena.alloc_slice_copy(&[irrelevant]),
         NumBytesToU16 => arena.alloc_slice_copy(&[borrowed, irrelevant]),
         NumBytesToU32 => arena.alloc_slice_copy(&[borrowed, irrelevant]),
+        NumCastToNat => arena.alloc_slice_copy(&[irrelevant]),
         StrStartsWith | StrEndsWith => arena.alloc_slice_copy(&[owned, borrowed]),
         StrStartsWithCodePt => arena.alloc_slice_copy(&[borrowed, irrelevant]),
         StrFromUtf8 => arena.alloc_slice_copy(&[owned]),