go/types: ignore artificial cycles introduced via method declarations
At the moment, method declarations are type-checked together with
they receiver base types. This is a known problem (to be fixed early
for Go 1.12) but with the new cycle detection algorithm now also
introduced artifical type cycles.
This change pushes a special marker on the cycle path in those cases
so that these cycles can be ignored.
Fixes #26124.
Change-Id: I64da4ccc32d4ae293da48880c892154a1c6ac3fe
Reviewed-on: https://go-review.googlesource.com/121757
Run-TryBot: Robert Griesemer <gri@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org> Reviewed-by: Alan Donovan <adonovan@google.com>