Add Result type

Makefile

@@ -375,7 +375,7 @@ test-rts:
 test-rts-db:
 	$(MAKE) -C test
 
-test-stdlib: dist/bin/acton
+test-stdlib: distribution
 	cd compiler && stack test acton --ta '-p "stdlib"'
 	$(MAKE) -C test tls-test-server
 	cd test/stdlib_tests && "$(ACTON)" test

base/src/result.act

@@ -0,0 +1,71 @@
+
+
+class Result[T,E] (value):
+    def is_ok(self) -> bool:
+        raise NotImplementedError("Result.is_ok")
+    def is_err(self) -> bool:
+        return not self.is_ok()
+    def ok(self) -> ?T:
+        raise NotImplementedError("Result.ok")
+    def err(self) -> ?E:
+        raise NotImplementedError("Result.err")
+    def unwrap(self) -> T:
+        raise NotImplementedError("Result.unwrap")
+    def unwrap_err(self) -> E:
+        raise NotImplementedError("Result.unwrap_err")
+    def __bool__(self) -> bool:
+        return self.is_ok()
+
+class Ok[T,E] (Result[T,E]):
+    value: T
+
+    def __init__(self, value: T) -> None:
+        self.value = value
+
+    def is_ok(self) -> bool:
+        return True
+
+    def ok(self) -> ?T:
+        return self.value
+
+    def err(self) -> ?E:
+        return None
+
+    def unwrap(self) -> T:
+        return self.value
+
+    def unwrap_err(self) -> E:
+        raise ValueError("Called unwrap_err on {repr(self)}")
+
+    def __str__(self) -> str:
+        return "Ok({self.value})"
+
+    def __repr__(self) -> str:
+        return "Ok({repr(self.value)})"
+
+class Err[T,E] (Result[T,E]):
+    error: E
+
+    def __init__(self, error: E) -> None:
+        self.error = error
+
+    def is_ok(self) -> bool:
+        return False
+
+    def ok(self) -> ?T:
+        return None
+
+    def err(self) -> ?E:
+        return self.error
+
+    def unwrap(self) -> T:
+        raise ValueError("Called unwrap on {repr(self)}")
+
+    def unwrap_err(self) -> E:
+        return self.error
+
+    def __str__(self) -> str:
+        return "Err({self.error})"
+
+    def __repr__(self) -> str:
+        return "Err({repr(self.error)})"

test/stdlib_tests/src/test_result.act

@@ -0,0 +1,44 @@
+import result
+import testing
+
+def _test_result_ok():
+    ok = result.Ok(7)
+
+    testing.assertTrue(ok.is_ok())
+    testing.assertFalse(ok.is_err())
+    testing.assertTrue(bool(ok))
+    testing.assertEqual(ok.ok(), 7)
+    testing.assertEqual(ok.err(), None)
+    testing.assertEqual(ok.unwrap(), 7)
+    testing.assertEqual(str(ok), "Ok(7)")
+    testing.assertEqual(repr(ok), "Ok(7)")
+
+
+def _test_result_err():
+    err = result.Err("boom")
+
+    testing.assertFalse(err.is_ok())
+    testing.assertTrue(err.is_err())
+    testing.assertFalse(bool(err))
+    testing.assertEqual(err.ok(), None)
+    testing.assertEqual(err.err(), "boom")
+    testing.assertEqual(err.unwrap_err(), "boom")
+    testing.assertEqual(str(err), "Err(boom)")
+    testing.assertEqual(repr(err), "Err('boom')")
+
+
+def _test_result_unwrap_errors():
+    ok = result.Ok(7)
+    err = result.Err("boom")
+
+    try:
+        ok.unwrap_err()
+        raise testing.NotRaisesError("Ok.unwrap_err() should raise ValueError")
+    except ValueError:
+        pass
+
+    try:
+        err.unwrap()
+        raise testing.NotRaisesError("Err.unwrap() should raise ValueError")
+    except ValueError:
+        pass