moq: add flag to toggle GODEBUG=gotypealias=1

internal/typealias/typealias_older.go

@@ -9,5 +9,6 @@ import (
 )
 
 func ConfigureGoDebug() {
-	fmt.Fprintln(os.Stderr, "only partial generics and type alias support")
+	fmt.Fprintln(os.Stderr, "type alias inside generics support only available in Go 1.22+")
+	os.Exit(1)
 }

main.go

@@ -18,7 +18,6 @@ import (
 )
 
 func main() {
-	typealias.ConfigureGoDebug()
 	log.SetPrefix("moq: ")
 	log.SetFlags(0)
 	debugFlags := strings.Split(",", strings.ToLower(os.Getenv("MOQ_DEBUG")))
@@ -33,6 +32,7 @@ func main() {
 	flagset.BoolVar(&moqCfg.StubImpl, "stub", false, "return zero values when no mock implementation is provided, do not panic")
 	flagset.BoolVar(&moqCfg.SkipEnsure, "skip-ensure", false, "suppress check that confirms a mock implements an interface, avoid import cycle if mocks generated outside of the tested package")
 	remove := flagset.Bool("rm", false, "first remove output file, if it exists")
+	typeAlias := flagset.Bool("typealias", false, "enable type alias support inside generics. (gotypesalias=1)")
 	flagset.BoolVar(&moqCfg.WithResets, "with-resets", false, "generate functions to facilitate resetting calls made to a mock")
 	printVersion := flagset.Bool("version", false, "show the version for moq")
 
@@ -47,6 +47,10 @@ func main() {
 		log.Fatal("cannot parse flags")
 	}
 
+	if *typeAlias {
+		typealias.ConfigureGoDebug()
+	}
+
 	if *printVersion {
 		info, ok := debug.ReadBuildInfo()
 		if !ok {