cmd/compile: panics with generic type alias and based-on constraint [1.23 backport]

[gopherbot]

@cuonglm requested issue #68580 to be considered for backport to the next 1.23 minor release.

@gopherbot please backport this issue to go1.23

[dmitshur]

@cuonglm Please note the second paragraph of https://groups.google.com/g/golang-dev/c/or4BmCu3LIE/m/a1Hv1yoxBAAJ, copied here:

Any CLs that land after CL 600176 ("internal/goversion: update Version to 1.24") but target go1.23.0 must be cherry-picked to release-branch.go1.23. Cherry-pick CLs can be created following the same steps as usual but do not need a backport issue or approval from the release team. Please continue to use your judgment about what should be included this late in the Go 1.23 release cycle.

Closing this. If you believe this fix should be included in Go 1.23 this late in the cycle, please directly create the backport CL, add a reviewer and then submit it. Thanks.

[cuonglm]

@dmitshur Ops, I missed that email. Thanks for noticing me.