Allow const func of named type

[earthboundkid]

What version of Go are you using (go version)?

Go 1.10

Does this issue reproduce with the latest release?

Yes

What did you do?

Play link:

package main

type funky func()

const g funky = func() {}

func main() {
}

What did you expect to see?

Succesful compilation.

What did you see instead?

prog.go:5:7: const initializer func literal is not a constant

Comment

Being able to make constant functions with a named type would be useful for http.HandlerFunc.

[earthboundkid]

This is also not allowed:

package main

type funky func()

func f() {}

const g funky = f

func main() {
}

[jimmyfrasche]

This isn't a bug: this is a proposal to change the language. As such, it needs to follow https://github.com/golang/proposal/blob/master/README.md I would recommend reading some existing issues with the Proposal label to get an idea of what sort of information you should include.

There needs to be a lot more information here. Are there differences in use between a const func and a var func? If you have a const func what can't you do with it. Is the only benefit http.Handlers or are there others? What are the downsides? Is const f = decorator(anotherFunc) legal?

I'm going to close this issue. Please create a new issue when you have a more fleshed out proposal or comment on one of the current issues for extending what can be const, such as #21130, and make an argument for including func as well.

[ianlancetaylor]

Related to #6386.