Reverse generics so that inference can handle the type arguments on c…

…all sites

internal/jobserver/buildid/version.go

@@ -35,13 +35,10 @@ type (
 	VersionSuffixResponse string
 )
 
-func (*VersionSuffixRequest) Subject() string {
-	return versionSubject
-}
-
-func (VersionSuffixResponse) IsResponseTo(*VersionSuffixRequest) {}
+func (VersionSuffixRequest) Subject() string                  { return versionSubject }
+func (VersionSuffixRequest) ResponseIs(VersionSuffixResponse) {}
 
-func (s *service) versionSuffix(ctx context.Context, _ *VersionSuffixRequest) (VersionSuffixResponse, error) {
+func (s *service) versionSuffix(ctx context.Context, _ VersionSuffixRequest) (VersionSuffixResponse, error) {
 	log := zerolog.Ctx(ctx)
 
 	s.mu.Lock()

internal/jobserver/client/client.go

@@ -43,12 +43,13 @@ func (c *Client) Close() {
 }
 
 type (
-	request interface {
+	request[Res any] interface {
 		Subject() string
+		common.Request[Res]
 	}
 )
 
-func Request[Req request, Res common.ResponseTo[Req]](ctx context.Context, client *Client, req Req) (Res, error) {
+func Request[Res any, Req request[Res]](ctx context.Context, client *Client, req Req) (Res, error) {
 	reqData, err := json.Marshal(req)
 	if err != nil {
 		var zero Res

internal/jobserver/common/handler.go

@@ -16,19 +16,19 @@ import (
 )
 
 type (
-	ResponseTo[Request any] interface {
-		IsResponseTo(Request)
+	Request[Res any] interface {
+		ResponseIs(Res)
 	}
 	// RequestHandler is a function that processes a request of a given type, and returns a response or an error to be
 	// sent back to the client.
-	RequestHandler[Request any, Response ResponseTo[Request]] func(context.Context, Request) (Response, error)
+	RequestHandler[Res any, Req Request[Res]] func(context.Context, Req) (Res, error)
 )
 
 // HandleRequest returns a NATS subscription target that calls the provided request handler in a new goroutine if the
 // NATS message payload can be parsed into the specified request type, and responds to the client appropriately.
-func HandleRequest[Request any, Response ResponseTo[Request]](ctx context.Context, handler RequestHandler[Request, Response]) func(*nats.Msg) {
+func HandleRequest[Res any, Req Request[Res]](ctx context.Context, handler RequestHandler[Res, Req]) func(*nats.Msg) {
 	return func(msg *nats.Msg) {
-		var req Request
+		var req Req
 		if err := json.Unmarshal(msg.Data, &req); err != nil {
 			respond(ctx, msg, errorResponse{Error: err.Error()})
 			return
@@ -41,7 +41,7 @@ func HandleRequest[Request any, Response ResponseTo[Request]](ctx context.Contex
 				respond(ctx, msg, errorResponse{Error: err.Error()})
 				return
 			}
-			respond(ctx, msg, successResponse[Response]{Result: resp})
+			respond(ctx, msg, successResponse[Res]{Result: resp})
 		}()
 	}
 }

internal/jobserver/nbt/nbt.go

@@ -117,8 +117,8 @@ const (
 	LabelAsmhdr  Label = "go_asm.h"
 )
 
-func (StartRequest) Subject() string             { return startSubject }
-func (*StartResponse) IsResponseTo(StartRequest) {}
+func (StartRequest) Subject() string           { return startSubject }
+func (StartRequest) ResponseIs(*StartResponse) {}
 
 func (s *service) start(ctx context.Context, req StartRequest) (*StartResponse, error) {
 	if req.ImportPath == "" || req.BuildID == "" {
@@ -183,8 +183,8 @@ type (
 	}
 )
 
-func (FinishRequest) Subject() string              { return finishSubject }
-func (*FinishResponse) IsResponseTo(FinishRequest) {}
+func (FinishRequest) Subject() string            { return finishSubject }
+func (FinishRequest) ResponseIs(*FinishResponse) {}
 
 var errNoFilesNorError = errors.New("missing files, and no error reported")
 
@@ -214,7 +214,7 @@ func (s *service) finish(ctx context.Context, req FinishRequest) (*FinishRespons
 
 	if !state.isDone.CompareAndSwap(false, true) {
 		log.Info().Msg("Task was already completed (concurrent retry?)")
-		return &FinishResponse{}, nil
+		return nil, nil
 	}
 
 	defer state.onDone()

internal/jobserver/pkgs/resolve.go

@@ -60,19 +60,16 @@ type (
 	ResolveResponse map[string]string
 )
 
-func NewResolveRequest(dir string, pattern string) *ResolveRequest {
-	return &ResolveRequest{
+func NewResolveRequest(dir string, pattern string) ResolveRequest {
+	return ResolveRequest{
 		Dir:     dir,
 		Env:     os.Environ(),
 		Pattern: pattern,
 	}
 }
 
-func (*ResolveRequest) Subject() string {
-	return resolveSubject
-}
-
-func (ResolveResponse) IsResponseTo(*ResolveRequest) {}
+func (ResolveRequest) Subject() string            { return resolveSubject }
+func (ResolveRequest) ResponseIs(ResolveResponse) {}
 
 func (r *ResolveRequest) canonicalizeEnviron() {
 	named := make(map[string]string, len(r.Env))

internal/jobserver/pkgs/resolve_test.go

@@ -39,7 +39,7 @@ func Test(t *testing.T) {
 		env := os.Environ()
 
 		// First request is expected to always be a cache miss
-		resp, err := client.Request[*pkgs.ResolveRequest, pkgs.ResolveResponse](
+		resp, err := client.Request(
 			context.Background(),
 			conn,
 			&pkgs.ResolveRequest{
@@ -56,7 +56,7 @@ func Test(t *testing.T) {
 		// of entries in `env` is also shuffled, which should have no impact on the
 		// cache hitting or missing.
 		rand.Shuffle(len(env), func(i, j int) { env[i], env[j] = env[j], env[i] })
-		resp, err = client.Request[*pkgs.ResolveRequest, pkgs.ResolveResponse](
+		resp, err = client.Request(
 			context.Background(),
 			conn,
 			&pkgs.ResolveRequest{
@@ -70,7 +70,7 @@ func Test(t *testing.T) {
 		assert.EqualValues(t, 1, server.CacheStats.Hits())
 
 		// Third request is different, should result in a cache miss again
-		resp, err = client.Request[*pkgs.ResolveRequest, pkgs.ResolveResponse](
+		resp, err = client.Request(
 			context.Background(),
 			conn,
 			&pkgs.ResolveRequest{
@@ -93,7 +93,7 @@ func Test(t *testing.T) {
 		require.NoError(t, err)
 		defer conn.Close()
 
-		resp, err := client.Request[*pkgs.ResolveRequest, pkgs.ResolveResponse](
+		resp, err := client.Request(
 			context.Background(),
 			conn,
 			&pkgs.ResolveRequest{Pattern: "definitely.not/a@valid\x01package"},

internal/toolexec/aspect/oncompile.go

@@ -76,7 +76,7 @@ func (w Weaver) OnCompile(ctx context.Context, cmd *proxy.CompileCommand) (resEr
 	if js, err := client.FromEnvironment(ctx, cmd.WorkDir); err != nil {
 		log.Debug().Str("work-dir", cmd.WorkDir).Err(err).Msg("Failed to obtain job server client")
 	} else {
-		res, err := client.Request[nbt.StartRequest, *nbt.StartResponse](ctx, js, nbt.StartRequest{ImportPath: w.ImportPath, BuildID: cmd.Flags.BuildID})
+		res, err := client.Request(ctx, js, nbt.StartRequest{ImportPath: w.ImportPath, BuildID: cmd.Flags.BuildID})
 		if err != nil {
 			log.Error().Err(err).Msg("Never-build-twice start request failed")
 			js.Close()
@@ -133,7 +133,7 @@ func (w Weaver) OnCompile(ctx context.Context, cmd *proxy.CompileCommand) (resEr
 					files[nbt.LabelAsmhdr] = asmhdr
 				}
 			}
-			_, err := client.Request[nbt.FinishRequest, *nbt.FinishResponse](ctx, js, nbt.FinishRequest{
+			_, err := client.Request(ctx, js, nbt.FinishRequest{
 				ImportPath:  w.ImportPath,
 				FinishToken: res.FinishToken,
 				Files:       files,

internal/toolexec/aspect/resolve.go

@@ -35,7 +35,7 @@ func resolvePackageFiles(ctx context.Context, importPath string, workDir string)
 		// and the root work tree contains all child work trees involved in resolutions.
 		req.TempDir = filepath.Join(workDir, "__tmp__")
 	}
-	archives, err := client.Request[*pkgs.ResolveRequest, pkgs.ResolveResponse](
+	archives, err := client.Request(
 		context.Background(),
 		conn,
 		req,

internal/toolexec/version.go

@@ -53,7 +53,7 @@ func ComputeVersion(ctx context.Context, cmd proxy.Command) (string, error) {
 	}
 	defer conn.Close()
 
-	res, err := client.Request[*buildid.VersionSuffixRequest, buildid.VersionSuffixResponse](context.Background(), conn, nil)
+	res, err := client.Request(context.Background(), conn, buildid.VersionSuffixRequest{})
 	if err != nil {
 		return "", err
 	}