Nightly Dotty workflow of 2022-06-04 failed

[github-actions]

See https://github.com/lampepfl/dotty/actions/runs/2438246396

[griggt]

We probably need to disable tests/neg/i12640.scala again. It's resumed its flakiness since #15343.

[info] Test dotty.tools.dotc.CompilationTests.negAll started
Wrong number of errors encountered when compiling out/compileNeg/neg/i12640
expected: 2, actual: 1
Unfulfilled expectations:
tests/neg/i12640.scala:15
Unexpected errors:
-> following the errors:
 at 15: Recursion limit exceeded.
Maybe there is an illegal cyclic reference?
If that's not the case, you could also try to increase the stacksize using the -Xss JVM option.
A recurring operation is (inner to outer):
  type parameters of [_$5]
  type parameters of F

Previous failure #12693, subsequent removal #12720 and reinstatement #14873.

[som-snytt]

Maybe vulpix needs // error{1,2} where you can give it a range.