Merge branch 'trunk' into deps

AUTHORS

@@ -47,3 +47,4 @@ Joshua Warner <joshuawarner32@gmail.com>
 Luiz Carlos L. G. de Oliveira <luizcarlos1405@gmail.com>
 Oleksii Skidan <al.skidan@gmail.com>
 Martin Janiczek <martin@janiczek.cz>
+Eric Newbury <enewbury@users.noreply.github.com>

compiler/builtins/src/std.rs

@@ -979,6 +979,13 @@ pub fn types() -> MutMap<Symbol, (SolvedType, Region)> {
         Box::new(list_type(flex(TVAR1))),
     );
 
+    // dropFirst : List elem -> List elem
+    add_top_level_function_type!(
+        Symbol::LIST_DROP_FIRST,
+        vec![list_type(flex(TVAR1))],
+        Box::new(list_type(flex(TVAR1))),
+    );
+
     // swap : List elem, Nat, Nat -> List elem
     add_top_level_function_type!(
         Symbol::LIST_SWAP,

compiler/can/src/builtins.rs

@@ -92,6 +92,7 @@ pub fn builtin_defs_map(symbol: Symbol, var_store: &mut VarStore) -> Option<Def>
         LIST_MAP4 => list_map4,
         LIST_DROP => list_drop,
         LIST_DROP_AT => list_drop_at,
+        LIST_DROP_FIRST => list_drop_first,
         LIST_DROP_LAST => list_drop_last,
         LIST_SWAP => list_swap,
         LIST_MAP_WITH_INDEX => list_map_with_index,
@@ -2049,6 +2050,30 @@ fn list_drop_at(symbol: Symbol, var_store: &mut VarStore) -> Def {
     )
 }
 
+fn list_drop_first(symbol: Symbol, var_store: &mut VarStore) -> Def {
+    let list_var = var_store.fresh();
+    let index_var = var_store.fresh();
+    let num_var = Variable::NAT;
+    let num_precision_var = Variable::NATURAL;
+
+    let body = RunLowLevel {
+        op: LowLevel::ListDropAt,
+        args: vec![
+            (list_var, Var(Symbol::ARG_1)),
+            (index_var, int(num_var, num_precision_var, 0)),
+        ],
+        ret_var: list_var,
+    };
+
+    defn(
+        symbol,
+        vec![(list_var, Symbol::ARG_1)],
+        var_store,
+        body,
+        list_var,
+    )
+}
+
 /// List.dropLast: List elem -> List elem
 fn list_drop_last(symbol: Symbol, var_store: &mut VarStore) -> Def {
     let list_var = var_store.fresh();

compiler/module/src/symbol.rs

@@ -1061,6 +1061,7 @@ define_builtins! {
         38 LIST_MAX: "max"
         39 LIST_MAX_GT: "#maxGt"
         40 LIST_MAP4: "map4"
+        41 LIST_DROP_FIRST: "dropFirst"
     }
     5 RESULT: "Result" => {
         0 RESULT_RESULT: "Result" imported // the Result.Result type alias

compiler/test_gen/src/gen_list.rs

@@ -267,6 +267,17 @@ fn list_drop_last_mutable() {
     );
 }
 
+#[test]
+fn list_drop_first() {
+    assert_evals_to!(
+        "List.dropFirst [1, 2, 3]",
+        RocList::from_slice(&[2, 3]),
+        RocList<i64>
+    );
+    assert_evals_to!("List.dropFirst []", RocList::from_slice(&[]), RocList<i64>);
+    assert_evals_to!("List.dropFirst [0]", RocList::from_slice(&[]), RocList<i64>);
+}
+
 #[test]
 fn list_swap() {
     assert_evals_to!("List.swap [] 0 1", RocList::from_slice(&[]), RocList<i64>);