spec: "representability" is not well defined in the spec

[griesemer]

We define other terms such as assignability, type identity, etc. Representability (as in "representable as a value of type T") is not explicitly defined. Yet it is a crucial concept: type checkers typically have a function implementing this predicate.

[griesemer]

See also #15384 as an example of where "representability" plays a role.

[odeke-em]

How's it going @griesemer? Just a gentle reminder about this issue.

[griesemer]

@odeke-em Not urgent but I'm aware of it.

[gopherbot]

Change https://golang.org/cl/57530 mentions this issue: spec: explicitly define notion of "representability" (clarification)