Merge pull request #333 from bytecodealliance/ydnar/result-dx

Author: ydnar

cm/CHANGELOG.md

@@ -2,6 +2,12 @@
 
 The format is based on [Keep a Changelog](https://keepachangelog.com/en/1.1.0/), and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0.html).
 
+## [Unreleased]
+
+### Added
+
+- Mutating methods `SetOK` and `SetErr` on `result` types (`Result[Shape, OK, Err]`).
+
 ## [v0.2.2] — 2025-03-16
 
 ### Fixed

cm/result.go

@@ -39,6 +39,40 @@ type result[Shape, OK, Err any] struct {
 	data  Shape // [unsafe.Sizeof(*(*Shape)(unsafe.Pointer(nil)))]byte
 }
 
+// OK returns an OK result with shape Shape and type OK and Err.
+// Pass Result[OK, OK, Err] or Result[Err, OK, Err] as the first type argument.
+func OK[R AnyResult[Shape, OK, Err], Shape, OK, Err any](ok OK) R {
+	var r Result[Shape, OK, Err]
+	r.validate()
+	r.isErr = ResultOK
+	*((*OK)(unsafe.Pointer(&r.data))) = ok
+	return R(r)
+}
+
+// Err returns an error result with shape Shape and type OK and Err.
+// Pass Result[OK, OK, Err] or Result[Err, OK, Err] as the first type argument.
+func Err[R AnyResult[Shape, OK, Err], Shape, OK, Err any](err Err) R {
+	var r Result[Shape, OK, Err]
+	r.validate()
+	r.isErr = ResultErr
+	*((*Err)(unsafe.Pointer(&r.data))) = err
+	return R(r)
+}
+
+// SetOK sets r to an OK result.
+func (r *result[Shape, OK, Err]) SetOK(ok OK) {
+	r.validate()
+	r.isErr = ResultOK
+	*((*OK)(unsafe.Pointer(&r.data))) = ok
+}
+
+// SetErr sets r to an error result.
+func (r *result[Shape, OK, Err]) SetErr(err Err) {
+	r.validate()
+	r.isErr = ResultErr
+	*((*Err)(unsafe.Pointer(&r.data))) = err
+}
+
 // IsOK returns true if r represents the OK case.
 func (r *result[Shape, OK, Err]) IsOK() bool {
 	r.validate()
@@ -107,23 +141,3 @@ func (r *result[Shape, OK, Err]) validate() {
 		panic("result: size of data type == 0, but result size != 1")
 	}
 }
-
-// OK returns an OK result with shape Shape and type OK and Err.
-// Pass Result[OK, OK, Err] or Result[Err, OK, Err] as the first type argument.
-func OK[R AnyResult[Shape, OK, Err], Shape, OK, Err any](ok OK) R {
-	var r Result[Shape, OK, Err]
-	r.validate()
-	r.isErr = ResultOK
-	*((*OK)(unsafe.Pointer(&r.data))) = ok
-	return R(r)
-}
-
-// Err returns an error result with shape Shape and type OK and Err.
-// Pass Result[OK, OK, Err] or Result[Err, OK, Err] as the first type argument.
-func Err[R AnyResult[Shape, OK, Err], Shape, OK, Err any](err Err) R {
-	var r Result[Shape, OK, Err]
-	r.validate()
-	r.isErr = ResultErr
-	*((*Err)(unsafe.Pointer(&r.data))) = err
-	return R(r)
-}

cm/result_test.go

@@ -13,13 +13,29 @@ var (
 )
 
 type resulter[OK, Err any] interface {
+	SetOK(OK)
+	SetErr(Err)
 	IsOK() bool
 	IsErr() bool
 	OK() *OK
 	Err() *Err
 	Result() (OK, Err, bool)
 }
 
+func TestResultSetOKSetErr(t *testing.T) {
+	var r Result[string, int32, string]
+
+	r.SetOK(12345)
+	if want, got := int32(12345), r.OK(); *got != want {
+		t.Errorf("OK(): %v, expected %v", got, want)
+	}
+
+	r.SetErr("error")
+	if want, got := "error", r.Err(); *got != want {
+		t.Errorf("Err(): %v, expected %v", got, want)
+	}
+}
+
 func TestResultOKOrErr(t *testing.T) {
 	r1 := OK[Result[string, string, struct{}]]("hello")
 	if ok := r1.OK(); ok == nil {