go.tools/ssa: ssa panics on blank "ok" in comma-ok select clause

[axw]

Steps to reproduce:

     1. Run ssadump -build=F repro.go[0]
     2. There is no step 2.

    [0] http://play.golang.org/p/H3T_pwRTzg

What is the expected output?

    Not a panic.

What do you see instead?

    "panic: blank.typ is unimplemented"

[robpike]

Comment 1:

Labels changed: added priority-later, toolbug, removed priority-triage.

Owner changed to @adonovan.

Status changed to Accepted.

[adonovan]

Comment 2:

This issue was closed by revision golang/tools@cf7368c.

Status changed to Fixed.

[axw]

Comment 3:

Thanks! llgo now implements select on the ssa branch, passing the existing tests.