proposal: Go 2: allow default values in methods

[furkilic]

Creating this proposal as I couldn't find any proposal regarding this enhancement.

We often use method overloading in our work :

func (m MyType) something(s string) {
  m.somethingWithI(s, 1)
}
func (m MyType) somethingWithI(s string, i int) {
  m.somethingWithIAndObjAndF(s, i, MyOtherType{}, 0.0)
}
func (m MyType) somethingWithIAndObjAndF(s string, i int, obj MyOtherType, f float64) {
	// s => dynamic
	// i => default 1
	// obj => default MyOtherType{}
	// f => default 0.0
}

// usage
m := MyType{}
m.something("Hello")
m.somethingWithI("Hello", 2)
m.somethingWithIAndObjAndF("Hello", 1, MyOtherType{}, 0.1)

It will be pleasent to have something as such :

func (m MyType) something(s string, i int:= 1, obj MyOtherType := MyOtherType{} , f float64 := 0.0) {
  	// s => dynamic
	// i => default 1
	// obj => default MyOtherType{}
	// f => default 0.0
}

// or make all the paremeters on the right by default once one of them is defaulted
func (m MyType) something(s string, i int:= 1, obj MyOtherType, f float64) {
  	// s => dynamic
	// i => default 1
	// obj => default MyOtherType{}
	// f => default 0.0
}

m:= MyType{}
m.something("Hello")
m.something("Hello", 2)
m.something("Hello", 1, MyOtherType{}, 0.1)

[ALTree]

Optional arguments were proposed and rejected here #1675.

It appears that the proposal was rejected for being fundamentally at odds with the foundational design goals of Go. I'm not sure much has changed in that regard.

[ghost]

this is against go's philosophy

[zigo101]

we can use variadic parameters to simulate default argument values, though which is not perfect.

[ianlancetaylor]

Thanks for the proposal. This does seem to be the same as #1675, which was declined. Closing as a dup.