Fix value receivers for unions too

fixes 42

codegen/interface_build.go

@@ -37,7 +37,11 @@ func buildInterface(types NamedTypes, typ schema.NamedType, prog *loader.Program
 
 		for _, implementor := range typ.PossibleTypes {
 			t := types[implementor.TypeName()]
-			i.Implementors = append(i.Implementors, InterfaceImplementor{NamedType: t, ValueReceiver: true})
+
+			i.Implementors = append(i.Implementors, InterfaceImplementor{
+				NamedType:     t,
+				ValueReceiver: isValueReceiver(types[typ.Name], t, prog),
+			})
 		}
 
 		return i

test/generated.go

@@ -876,6 +876,19 @@ func (ec *executionContext) _Shape(sel []query.Selection, obj *Shape) graphql.Ma
 	}
 }
 
+func (ec *executionContext) _ShapeUnion(sel []query.Selection, obj *ShapeUnion) graphql.Marshaler {
+	switch obj := (*obj).(type) {
+	case nil:
+		return graphql.Null
+	case *Circle:
+		return ec._Circle(sel, obj)
+	case *Rectangle:
+		return ec._Rectangle(sel, obj)
+	default:
+		panic(fmt.Errorf("unexpected type %T", obj))
+	}
+}
+
 func UnmarshalInnerInput(v interface{}) (InnerInput, error) {
 	var it InnerInput
 
@@ -912,7 +925,7 @@ func UnmarshalOuterInput(v interface{}) (OuterInput, error) {
 	return it, nil
 }
 
-var parsedSchema = schema.MustParse("input InnerInput {\n    id:Int!\n}\n\ninput OuterInput {\n    inner: InnerInput!\n}\n\ntype OuterObject {\n    inner: InnerObject!\n}\n\ntype InnerObject {\n    id: Int!\n}\n\ninterface Shape {\n    area: Float\n}\n\ntype Circle implements Shape {\n    radius: Float\n    area: Float\n}\n\ntype Rectangle implements Shape {\n    length: Float\n    width: Float\n    area: Float\n}\n\ntype Query {\n    nestedInputs(input: [[OuterInput]] = [[{inner: {id: 1}}]]): Boolean\n    nestedOutputs: [[OuterObject]]\n    shapes: [Shape]\n}\n")
+var parsedSchema = schema.MustParse("input InnerInput {\n    id:Int!\n}\n\ninput OuterInput {\n    inner: InnerInput!\n}\n\ntype OuterObject {\n    inner: InnerObject!\n}\n\ntype InnerObject {\n    id: Int!\n}\n\ninterface Shape {\n    area: Float\n}\n\ntype Circle implements Shape {\n    radius: Float\n    area: Float\n}\n\ntype Rectangle implements Shape {\n    length: Float\n    width: Float\n    area: Float\n}\n\nunion ShapeUnion = Circle | Rectangle\n\ntype Query {\n    nestedInputs(input: [[OuterInput]] = [[{inner: {id: 1}}]]): Boolean\n    nestedOutputs: [[OuterObject]]\n    shapes: [Shape]\n}\n")
 
 func (ec *executionContext) introspectSchema() *introspection.Schema {
 	return introspection.WrapSchema(parsedSchema)

test/models.go

@@ -6,6 +6,10 @@ type Shape interface {
 	Area() float64
 }
 
+type ShapeUnion interface {
+	Area() float64
+}
+
 type Circle struct {
 	Radius float64
 }

test/schema.graphql

@@ -29,6 +29,8 @@ type Rectangle implements Shape {
     area: Float
 }
 
+union ShapeUnion = Circle | Rectangle
+
 type Query {
     nestedInputs(input: [[OuterInput]] = [[{inner: {id: 1}}]]): Boolean
     nestedOutputs: [[OuterObject]]

test/types.json

@@ -1,5 +1,6 @@
 {
     "Shape": "github.com/vektah/gqlgen/test.Shape",
+    "ShapeUnion": "github.com/vektah/gqlgen/test.ShapeUnion",
     "Circle": "github.com/vektah/gqlgen/test.Circle",
     "Rectangle": "github.com/vektah/gqlgen/test.Rectangle"
 }