ent/load: safely marshaling schema

Summary: more descriptive output on marshaling failures.

Reviewed By: alexsn

Differential Revision: D16782294

fbshipit-source-id: 4ac3fbb3ef152d59bada257a9f0d8ccde5e95ae9

entc/load/testdata/failure/user.go

@@ -0,0 +1,16 @@
+package failure
+
+import (
+	"fbc/ent"
+	"fbc/ent/schema/edge"
+)
+
+type User struct {
+	ent.Schema
+}
+
+func (User) Edges() []ent.Edge {
+	return []ent.Edge{
+		edge.To("panic", User{}.Type),
+	}
+}