Add types for Str.startsWith

compiler/builtins/src/std.rs

@@ -505,6 +505,12 @@ pub fn types() -> MutMap<Symbol, (SolvedType, Region)> {
         top_level_function(vec![str_type()], Box::new(bool_type())),
     );
 
+    // startsWith : Str, Str -> Bool
+    add_type(
+        Symbol::STR_STARTS_WITH,
+        SolvedType::Func(vec![str_type(), str_type()], Box::new(bool_type())),
+    );
+
     // List module
 
     // get : List elem, Int -> Result elem [ OutOfBounds ]*

compiler/builtins/src/unique.rs

@@ -1134,6 +1134,12 @@ pub fn types() -> MutMap<Symbol, (SolvedType, Region)> {
         unique_function(vec![str_type(star1), str_type(star2)], str_type(star3))
     });
 
+    // Str.startsWith : Attr * Str, Attr * Str -> Attr * Bool
+    add_type(Symbol::STR_STARTS_WITH, {
+        let_tvars! { star1, star2, star3 };
+        unique_function(vec![str_type(star1), str_type(star2)], bool_type(star3))
+    });
+
     // Result module
 
     // map : Attr * (Result (Attr a e))

compiler/solve/tests/solve_expr.rs

@@ -192,6 +192,18 @@ mod solve_expr {
         );
     }
 
+    #[test]
+    fn string_starts_with() {
+        infer_eq_without_problem(
+            indoc!(
+                r#"
+                Str.startsWith
+                "#
+            ),
+            "Str, Str -> Bool",
+        );
+    }
+
     // #[test]
     // fn block_string_literal() {
     //     infer_eq(