[Bug Report] Metadata() is not reflected when setting the Default() in goa design.

[nao1215]

Goa design can use user-specific types as payload parameters through the use of Metadata(). However, the type specified in Metadata() is not reflected in the Default() setting.

Example (goa design)

var PagingType = Type("PagingType", func() {
	Param("limit", Integer, func() {
		Metadata("struct:field:type", "model.PagingLimit", "github.com/sample/model")
		Minimum(1)
		Default(20)
	})
})

Example (auto generated code, actual behavior)

// Finalize sets the default values for pagingType type instance.
func (ut *pagingType) Finalize() {
	var defaultLimit = 20
	if ut.Limit == nil {
		ut.Limit = &defaultLimit   // ⭐️ Bug. type mismatch.
	}
}

Expected behavior

Goa generates the following code:

func (ut *pagingType) Finalize() {
	var defaultLimit model.PagingLimit = 20
	if ut.Limit == nil {
		ut.Limit = &defaultLimit
	}
}