fieldGenerator: add top-level Generate method

This just calls all other generate methods for the fieldGenerator

gen/field.go

@@ -28,6 +28,26 @@ type fieldGroupGenerator struct {
 	Fields compile.FieldGroup
 }
 
+func (f fieldGroupGenerator) Generate(g Generator) error {
+	if err := f.DefineStruct(g); err != nil {
+		return err
+	}
+
+	if err := f.ToWire(g); err != nil {
+		return err
+	}
+
+	if err := f.FromWire(g); err != nil {
+		return err
+	}
+
+	if err := f.String(g); err != nil {
+		return err
+	}
+
+	return nil
+}
+
 func (f fieldGroupGenerator) DefineStruct(g Generator) error {
 	return g.DeclareFromTemplate(
 		`type <.Name> struct {

gen/struct.go

@@ -63,19 +63,7 @@ func structure(g Generator, spec *compile.StructSpec) error {
 		Fields: spec.Fields,
 	}
 
-	if err := fg.DefineStruct(g); err != nil {
-		return wrapGenerateError(spec.ThriftName(), err)
-	}
-
-	if err := fg.ToWire(g); err != nil {
-		return wrapGenerateError(spec.ThriftName(), err)
-	}
-
-	if err := fg.FromWire(g); err != nil {
-		return wrapGenerateError(spec.ThriftName(), err)
-	}
-
-	if err := fg.String(g); err != nil {
+	if err := fg.Generate(g); err != nil {
 		return wrapGenerateError(spec.ThriftName(), err)
 	}