implemented Result.isErr

compiler/can/src/builtins.rs

@@ -193,6 +193,7 @@ pub fn builtin_defs_map(symbol: Symbol, var_store: &mut VarStore) -> Option<Def>
         RESULT_AFTER => result_after,
         RESULT_WITH_DEFAULT => result_with_default,
         RESULT_IS_OK => result_is_ok,
+        RESULT_IS_ERR => result_is_err,
     }
 }
 
@@ -3992,6 +3993,83 @@ fn result_with_default(symbol: Symbol, var_store: &mut VarStore) -> Def {
     )
 }
 
+fn result_is_err(symbol: Symbol, var_store: &mut VarStore) -> Def {
+    let ret_var = var_store.fresh();
+    let result_var = var_store.fresh();
+
+    let mut branches = vec![];
+
+    {
+        // ok branch
+        let tag_name = TagName::Global("Ok".into());
+
+        let pattern = Pattern::AppliedTag {
+            whole_var: result_var,
+            ext_var: var_store.fresh(),
+            tag_name,
+            arguments: vec![(var_store.fresh(), no_region(Pattern::Underscore))],
+        };
+
+        let false_expr = Tag {
+            variant_var: var_store.fresh(),
+            ext_var: var_store.fresh(),
+            name: TagName::Global("False".into()),
+            arguments: vec![],
+        };
+
+        let branch = WhenBranch {
+            patterns: vec![no_region(pattern)],
+            value: no_region(false_expr),
+            guard: None,
+        };
+
+        branches.push(branch);
+    }
+
+    {
+        // err branch
+        let tag_name = TagName::Global("Err".into());
+
+        let pattern = Pattern::AppliedTag {
+            whole_var: result_var,
+            ext_var: var_store.fresh(),
+            tag_name,
+            arguments: vec![(var_store.fresh(), no_region(Pattern::Underscore))],
+        };
+
+        let true_expr = Tag {
+            variant_var: var_store.fresh(),
+            ext_var: var_store.fresh(),
+            name: TagName::Global("True".into()),
+            arguments: vec![],
+        };
+
+        let branch = WhenBranch {
+            patterns: vec![no_region(pattern)],
+            value: no_region(true_expr),
+            guard: None,
+        };
+
+        branches.push(branch);
+    }
+
+    let body = When {
+        cond_var: result_var,
+        expr_var: ret_var,
+        region: Region::zero(),
+        loc_cond: Box::new(no_region(Var(Symbol::ARG_1))),
+        branches,
+    };
+
+    defn(
+        symbol,
+        vec![(result_var, Symbol::ARG_1)],
+        var_store,
+        body,
+        ret_var,
+    )
+}
+
 fn result_is_ok(symbol: Symbol, var_store: &mut VarStore) -> Def {
     let ret_var = var_store.fresh();
     let result_var = var_store.fresh();