add Str.getUnsafe

crates/compiler/builtins/roc/Str.roc

@@ -221,3 +221,6 @@ toU16 : Str -> Result U16 [InvalidNumStr]*
 toI16 : Str -> Result I16 [InvalidNumStr]*
 toU8 : Str -> Result U8 [InvalidNumStr]*
 toI8 : Str -> Result I8 [InvalidNumStr]*
+
+## Gets the byte at the given index, without performing a bounds check
+getUnsafe : Str, Nat -> U8

crates/compiler/builtins/src/bitcode.rs

@@ -330,6 +330,7 @@ pub const STR_REPEAT: &str = "roc_builtins.str.repeat";
 pub const STR_TRIM: &str = "roc_builtins.str.trim";
 pub const STR_TRIM_LEFT: &str = "roc_builtins.str.trim_left";
 pub const STR_TRIM_RIGHT: &str = "roc_builtins.str.trim_right";
+pub const STR_GET_UNSAFE: &str = "roc_builtins.str.get_unsafe";
 
 pub const DICT_HASH: &str = "roc_builtins.dict.hash";
 pub const DICT_HASH_STR: &str = "roc_builtins.dict.hash_str";

crates/compiler/can/src/builtins.rs

@@ -74,6 +74,7 @@ pub fn builtin_defs_map(symbol: Symbol, var_store: &mut VarStore) -> Option<Def>
         STR_CONCAT => str_concat,
         STR_JOIN_WITH => str_join_with,
         STR_TO_SCALARS => str_to_scalars,
+        STR_GET_UNSAFE => str_get_unsafe,
         STR_SPLIT => str_split,
         STR_IS_EMPTY => str_is_empty,
         STR_STARTS_WITH => str_starts_with,
@@ -1669,67 +1670,24 @@ fn str_concat(symbol: Symbol, var_store: &mut VarStore) -> Def {
     )
 }
 
+/// List.getUnsafe : Str, Nat -> U8
+fn str_get_unsafe(symbol: Symbol, var_store: &mut VarStore) -> Def {
+    lowlevel_2(symbol, LowLevel::StrGetUnsafe, var_store)
+}
+
 /// Str.toScalars : Str -> List U32
 fn str_to_scalars(symbol: Symbol, var_store: &mut VarStore) -> Def {
-    let str_var = var_store.fresh();
+    lowlevel_1(symbol, LowLevel::StrToScalars, var_store)
-    let list_u32_var = var_store.fresh();
-
-    let body = RunLowLevel {
-        op: LowLevel::StrToScalars,
-        args: vec![(str_var, Var(Symbol::ARG_1))],
-        ret_var: list_u32_var,
-    };
-
-    defn(
-        symbol,
-        vec![(str_var, Symbol::ARG_1)],
-        var_store,
-        body,
-        list_u32_var,
-    )
 }
 
 /// Str.joinWith : List Str, Str -> Str
 fn str_join_with(symbol: Symbol, var_store: &mut VarStore) -> Def {
-    let list_str_var = var_store.fresh();
+    lowlevel_2(symbol, LowLevel::StrJoinWith, var_store)
-    let str_var = var_store.fresh();
-
-    let body = RunLowLevel {
-        op: LowLevel::StrJoinWith,
-        args: vec![
-            (list_str_var, Var(Symbol::ARG_1)),
-            (str_var, Var(Symbol::ARG_2)),
-        ],
-        ret_var: str_var,
-    };
-
-    defn(
-        symbol,
-        vec![(list_str_var, Symbol::ARG_1), (str_var, Symbol::ARG_2)],
-        var_store,
-        body,
-        str_var,
-    )
 }
 
 /// Str.isEmpty : Str -> Bool
 fn str_is_empty(symbol: Symbol, var_store: &mut VarStore) -> Def {
-    let str_var = var_store.fresh();
+    lowlevel_1(symbol, LowLevel::StrIsEmpty, var_store)
-    let bool_var = var_store.fresh();
-
-    let body = RunLowLevel {
-        op: LowLevel::StrIsEmpty,
-        args: vec![(str_var, Var(Symbol::ARG_1))],
-        ret_var: bool_var,
-    };
-
-    defn(
-        symbol,
-        vec![(str_var, Symbol::ARG_1)],
-        var_store,
-        body,
-        bool_var,
-    )
 }
 
 /// Str.startsWith : Str, Str -> Bool

crates/compiler/gen_llvm/src/llvm/build.rs

@@ -5468,8 +5468,17 @@ fn run_low_level<'a, 'ctx, 'env>(
 
             list_prepend(env, original_wrapper, elem, elem_layout)
         }
+        StrGetUnsafe => {
+            // List.getUnsafe : List elem, Nat -> elem
+            debug_assert_eq!(args.len(), 2);
+
+            let wrapper_struct = load_symbol(scope, &args[0]);
+            let elem_index = load_symbol(scope, &args[1]);
+
+            call_bitcode_fn(env, &[wrapper_struct, elem_index], bitcode::STR_GET_UNSAFE)
+        }
         ListGetUnsafe => {
-            // List.get : List elem, Nat -> [Ok elem, OutOfBounds]*
+            // List.getUnsafe : List elem, Nat -> elem
             debug_assert_eq!(args.len(), 2);
 
             let (wrapper_struct, list_layout) = load_symbol_and_layout(scope, &args[0]);

crates/compiler/gen_wasm/src/low_level.rs

@@ -218,6 +218,7 @@ impl<'a> LowLevelCall<'a> {
             // Str
             StrConcat => self.load_args_and_call_zig(backend, bitcode::STR_CONCAT),
             StrToScalars => self.load_args_and_call_zig(backend, bitcode::STR_TO_SCALARS),
+            StrGetUnsafe => self.load_args_and_call_zig(backend, bitcode::STR_GET_UNSAFE),
             StrJoinWith => self.load_args_and_call_zig(backend, bitcode::STR_JOIN_WITH),
             StrIsEmpty => match backend.storage.get(&self.arguments[0]) {
                 StoredValue::StackMemory { location, .. } => {

crates/compiler/module/src/low_level.rs

@@ -24,6 +24,7 @@ pub enum LowLevel {
     StrTrimRight,
     StrToNum,
     StrToScalars,
+    StrGetUnsafe,
     ListLen,
     ListWithCapacity,
     ListGetUnsafe,
@@ -167,6 +168,7 @@ impl LowLevelWrapperType {
 
         match symbol {
             Symbol::STR_CONCAT => CanBeReplacedBy(StrConcat),
+            Symbol::STR_GET_UNSAFE => CanBeReplacedBy(StrGetUnsafe),
             Symbol::STR_TO_SCALARS => CanBeReplacedBy(StrToScalars),
             Symbol::STR_JOIN_WITH => CanBeReplacedBy(StrJoinWith),
             Symbol::STR_IS_EMPTY => CanBeReplacedBy(StrIsEmpty),

crates/compiler/module/src/symbol.rs

@@ -1190,6 +1190,7 @@ define_builtins! {
         32 STR_TO_U8: "toU8"
         33 STR_TO_I8: "toI8"
         34 STR_TO_SCALARS: "toScalars"
+        35 STR_GET_UNSAFE: "getUnsafe"
     }
     5 LIST: "List" => {
         0 LIST_LIST: "List" imported // the List.List type alias

crates/compiler/mono/src/borrow.rs

@@ -892,7 +892,7 @@ pub fn lowlevel_borrow_signature(arena: &Bump, op: LowLevel) -> &[bool] {
         }
         ListWithCapacity => arena.alloc_slice_copy(&[irrelevant]),
         ListReplaceUnsafe => arena.alloc_slice_copy(&[owned, irrelevant, irrelevant]),
-        ListGetUnsafe => arena.alloc_slice_copy(&[borrowed, irrelevant]),
+        StrGetUnsafe | ListGetUnsafe => arena.alloc_slice_copy(&[borrowed, irrelevant]),
         ListConcat => arena.alloc_slice_copy(&[owned, owned]),
         StrConcat => arena.alloc_slice_copy(&[owned, borrowed]),
         StrTrim => arena.alloc_slice_copy(&[owned]),