0ead4ff72b
When mixin applications introduce forwarding stubs with covariant checks they can contain uses of type parameters that belong to the synthetic mixin application class. The type environment needs to be updated to contain those type parameters. Also cleanup some comments, variable names, and the code to avoid an assertion failure. Methods can contain covariant checks on the arguments, not just setters. Issue: https://github.com/dart-lang/sdk/issues/52688 Change-Id: Ifd91f76de85cb2092b0a3a0c4a808f2660eb5c17 Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/308460 Reviewed-by: Sigmund Cherem <sigmund@google.com> Commit-Queue: Nicholas Shahan <nshahan@google.com>