reflect: Type interface is unimplemented comparable (generics)

[Code-Hex]

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

$ gotip version
go version devel go1.18-e50f0f372b Fri Feb 11 05:11:58 2022 +0000 darwin/arm64

What did you do?

The document for reflect.Type interface has described is comparable.

Type values are comparable, such as with the == operator, so they can be used as map keys.

However, I tried to compare with a function using generics comparable, and I get a compilation error.

What did you expect to see?

compilable

What did you see instead?

compilation error.

https://go.dev/play/p/vPcBpD86rST?v=gotip

[hopehook]

I find it is work fine at the my local go source code, which is failed on the go playground.

• my local version success: go version devel go1.18-a991d9dc27 Thu Jan 27 05:30:27 2022 +0000 darwin/amd64
• playground version failed: devel go1.18-5bd734839d Sun Feb 13 02:11:11 2022 +0000

So i compiled a new one, it failed also.

• latest source code of master branch failed: go version devel go1.18-badbc52d82 Mon Feb 14 05:18:03 2022 +0000 darwin/amd64

[hopehook]

@griesemer

[dmitshur]

Also CC @findleyr.

Placing it in 1.18 milestone to at least investigate whether something about this needs to be done for 1.18.

[ianlancetaylor]

It's true that reflect.Type is not treated as a comparable type, and it's true that that may be problematic in some cases. That said, we aren't going to do anything here for 1.18.

[ianlancetaylor]

See discussion at #51338 for a way to fix this.

[ianlancetaylor]

Rolling forward to 1.20.