simplify the typeparams test case added for #1027

The marshaler interface and some of the other types were unnecessary.
The remaining test still fails without the fix,
because the crux of the issue is the separate package
with the Result generic type having Data as a type parameter and field.

testdata/script/typeparams.txtar

@@ -9,13 +9,6 @@ package main
 
 import "test/main/lib"
 
-type Blob []byte
-
-func (b Blob) MarshalBinary() ([]byte, error)  { return b, nil }
-func (b *Blob) UnmarshalBinary(d []byte) error { *b = append((*b)[:0], d...); return nil }
-
-type Name string
-
 func main() {
 	GenericFunc[int, int](1, 2)
 	var _ GenericVector[int]
@@ -31,10 +24,9 @@ func main() {
 	var gan genericAliasNamed
 	gan.list = nil
 
-	e := lib.Entry[Name, Blob, *Blob]{Key: "k", Data: Blob("v")}
-	r := lib.Load[Name, Blob, *Blob](e)
-	_ = r.Data.Key
-	_ = r.Data.Value
+	e := lib.Entry[string, int]{Key: "foo", Data: 123}
+	r := lib.Load[string, int](e)
+	_ = r.Data
 }
 
 func GenericFunc[GenericParamA, B any](x GenericParamA, y B) {}
@@ -114,31 +106,15 @@ var _ = byKeys(map[string]int{"one": 1})
 -- lib/lib.go --
 package lib
 
-import "encoding"
-
-type Pair[Key, Value any] struct {
-	Key   Key
-	Value Value
+type Result[Data any] struct {
+	Data Data
 }
 
-type Result[TData any] struct {
-	Data TData
-	Err  error
+type Entry[Key ~string, Data any] struct {
+	Key  Key
+	Data Data
 }
 
-type Entry[TKey ~string, TData encoding.BinaryMarshaler, TPtr interface {
-	*TData
-	encoding.BinaryUnmarshaler
-}] struct {
-	Key  TKey
-	Data TData
-}
-
-func Load[TKey ~string, TData encoding.BinaryMarshaler, TPtr interface {
-	*TData
-	encoding.BinaryUnmarshaler
-}](e Entry[TKey, TData, TPtr]) Result[Pair[TKey, TData]] {
-	return Result[Pair[TKey, TData]]{
-		Data: Pair[TKey, TData]{Key: e.Key, Value: e.Data},
-	}
+func Load[Key ~string, Data any](e Entry[Key, Data]) Result[Data] {
+	return Result[Data]{Data: e.Data}
 }