go/types, types2: type checker accepts import of package called "init"

[griesemer]

Given two packages (for convenience represented via single files both stored in the same directory):

a.go: package init
b.go: package b; import "./a"

the compiler reports "cannot import package as init - init must be a func", but the go/types and types2 accept this (though they correctly don't accept a local rename to init).

cc: @findleyr

[gopherbot]

Change https://golang.org/cl/287494 mentions this issue: [dev.typeparams] cmd/compile/internal/types2: must not import a package called "init"

[findleyr]

The above CL was ported to dev.regabi in https://golang.org/cl/290570 (forgot to tag this issue). I think we can close this once dev.regabi becomes master.

[griesemer]

With the merge of dev.typeparams into master, this is now fixed.