Let-aliasing breaks flow inference for results of `class`

Description

The following code complains a NPE is possible from .isArray,
but clearly the assertion prevents that. This issue is related
to let-aliasing, probably related to core.typed not knowing how
to update the type of `c` with the information that it's class
is non-nil.

Environment

None

Assignee

Unassigned

Reporter

Ambrose Bonnaire-Sergeant

Approval

None

Patch

None

Components

Fix versions

Priority

Blocker
Configure