Subclasses of the _Function class are generated on the fly as fields
with function types are encountered. Therefore, this class must be early
in the initialization order.
Change-Id: Ia0b998c443af9f6bdb4af512f6da99e6e3767c1f
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/237681
Reviewed-by: Joshua Litt <joshualitt@google.com>
Commit-Queue: Aske Simon Christensen <askesc@google.com>
