Fixes #899

main.go

@@ -1713,7 +1713,11 @@ func recordType(used, origin types.Type, done map[*types.Named]bool, fieldToStru
 		// Ensure we record the original generic struct, if there is one.
 		recordType(used.Underlying(), used.Origin().Underlying(), done, fieldToStruct)
 	case *types.Struct:
-		origin := origin.(*types.Struct)
+		origin, ok := origin.(*types.Struct)
+		if !ok {
+			return
+		}
+
 		for i := range used.NumFields() {
 			field := used.Field(i)
 			fieldToStruct[field] = origin

testdata/script/typeparams.txtar

@@ -24,7 +24,7 @@ type GenericVector[GenericParamT any] []GenericParamT
 
 type GenericGraph[T any] struct {
 	Content T
-	Edges []GenericGraph[T]
+	Edges   []GenericGraph[T]
 }
 
 type PredeclaredSignedInteger interface {
@@ -40,7 +40,7 @@ type StringableSignedInteger interface {
 type CombineEmbeds interface {
 	string | int
 
-	interface { EmbeddedMethod() }
+	interface{ EmbeddedMethod() }
 	RegularMethod()
 }
 
@@ -49,3 +49,7 @@ type Slice[T any] []T
 func sliceOfPointer() Slice[*any] {
 	return []*any{}
 }
+
+type Map[K, V comparable] map[K]V
+
+var _ = Map[string, struct{}]{}