spec: comma-ok expressions should return an untyped bool rather than a bool

[griesemer]

All comma-ok expressions return an ok value of type bool at the moment:

- map index: http://tip.golang.org/ref/spec#Index_expressions
- type assertion: http://tip.golang.org/ref/spec#Type_assertions
- channel receive: http://tip.golang.org/ref/spec#Receive_operator

There is no reason for them to not return an untyped bool instead:

- an untyped bool can be assigned to any bool variable
- an untyped bool will default to a bool type in a declaration (var _, ok = ... ; or _,
ok := ...)
- an untyped bool will default to a bool type in an assignment to an interface

This would be a completely backward-compatible language change.

[gopherbot]

Comment 1:

CL https://golang.org/cl/112320045 mentions this issue.

[griesemer]

Comment 2:

This issue was closed by revision c0fca13.

Status changed to Fixed.

[gopherbot]

CL https://golang.org/cl/27310 mentions this issue.