better error msg

pkg/codegen/pcl/binder_schema.go

@@ -499,10 +499,11 @@ func getDiscriminatedUnionObjectItem(t model.Type) (string, model.Type) {
 // no member if found, (nil, true) returned. If the query is nonsensical, either
 // because no schema is associated with the EnumMember or if the type of value
 // mismatches the type of the schema, (nil, false) is returned.
-func EnumMember(t *model.EnumType, value cty.Value) (*schema.Enum, bool) {
+func EnumMember(t *model.EnumType, value cty.Value) (*schema.Enum, []interface{}, bool) {
 	srcBase, ok := GetSchemaForType(t)
+	validMembers := make([]interface{}, 0)
 	if !ok {
-		return nil, false
+		return nil, validMembers, false
 	}
 	src := srcBase.(*schema.EnumType)
 
@@ -512,28 +513,31 @@ func EnumMember(t *model.EnumType, value cty.Value) (*schema.Enum, bool) {
 		for _, el := range src.Elements {
 			v := el.Value.(string)
 			if v == s {
-				return el, true
+				return el, validMembers, true
 			}
+			validMembers = append(validMembers, v)
 		}
-		return nil, true
+		return nil, validMembers, true
 	case t.Type.Equals(model.NumberType):
 		f, _ := value.AsBigFloat().Float64()
 		for _, el := range src.Elements {
 			if el.Value.(float64) == f {
-				return el, true
+				return el, validMembers, true
 			}
+			validMembers = append(validMembers, f)
 		}
-		return nil, true
+		return nil, validMembers, true
 	case t.Type.Equals(model.IntType):
 		f, _ := value.AsBigFloat().Int64()
 		for _, el := range src.Elements {
 			if el.Value.(int64) == f {
-				return el, true
+				return el, validMembers, true
 			}
+			validMembers = append(validMembers, f)
 		}
-		return nil, true
+		return nil, validMembers, true
 	default:
-		return nil, false
+		return nil, validMembers, false
 	}
 }
 
@@ -562,10 +566,13 @@ func GenEnum(
 	if known != cty.NilVal {
 		// If the value is known, but we can't find a member, we should have
 		// indicated a conversion is impossible when type checking.
-		member, ok := EnumMember(t, known)
+		member, validMembers, ok := EnumMember(t, known)
 		contract.Assertf(ok,
 			"We have determined %s is a safe enum, which we define as "+
 				"being able to calculate a member for", t)
+		if member == nil {
+			contract.Failf("Invalid enum provided: valid values are %v", validMembers)
+		}
 		safeEnum(member)
 	} else {
 		unsafeEnum(from)