1 files changed, 89 insertions, 0 deletions
diff --git a/v_windows/v/vlib/builtin/option.v b/v_windows/v/vlib/builtin/option.v
new file mode 100644
index 0000000..1f1bdd9
--- /dev/null
+++ b/v_windows/v/vlib/builtin/option.v
@@ -0,0 +1,89 @@
+// Copyright (c) 2019-2021 Alexander Medvednikov. All rights reserved.
+// Use of this source code is governed by an MIT license
+// that can be found in the LICENSE file.
+module builtin
+
+// IError holds information about an error instance
+pub interface IError {
+	msg string
+	code int
+}
+
+// Error is the default implementation of IError, that is returned by e.g. `error()`
+pub struct Error {
+pub:
+	msg  string
+	code int
+}
+
+pub fn (err IError) str() string {
+	return match err {
+		None__ { 'none' }
+		Error { err.msg }
+		else { '$err.type_name(): $err.msg' }
+	}
+}
+
+const none__ = IError(&None__{})
+
+struct None__ {
+	msg  string
+	code int
+}
+
+fn (_ None__) str() string {
+	return 'none'
+}
+
+[if trace_error ?]
+fn trace_error(x string) {
+	eprintln('> ${@FN} | $x')
+}
+
+// error returns a default error instance containing the error given in `message`.
+// Example: `if ouch { return error('an error occurred') }`
+[inline]
+pub fn error(message string) IError {
+	trace_error(message)
+	return &Error{
+		msg: message
+	}
+}
+
+// error_with_code returns a default error instance containing the given `message` and error `code`.
+// `if ouch { return error_with_code('an error occurred', 1) }`
+[inline]
+pub fn error_with_code(message string, code int) IError {
+	trace_error('$message | code: $code')
+	return &Error{
+		msg: message
+		code: code
+	}
+}
+
+// Option is the base of V's internal optional return system.
+struct Option {
+	state byte
+	err   IError = none__
+	// Data is trailing after err
+	// and is not included in here but in the
+	// derived Option_xxx types
+}
+
+fn opt_ok(data voidptr, mut option Option, size int) {
+	unsafe {
+		*option = Option{}
+		// use err to get the end of OptionBase and then memcpy into it
+		vmemcpy(&byte(&option.err) + sizeof(IError), data, size)
+	}
+}
+
+[unsafe]
+pub fn (e &Error) free() {
+	unsafe { e.msg.free() }
+}
+
+[unsafe]
+pub fn (n &None__) free() {
+	unsafe { n.msg.free() }
+}