Alexander Markov
cbb5305f78
Add a kernel transformation which removes redundant casts and reduces some casts to null checks. This transformation assumes that type system is sound and subtyping relation is transitive. So in NNBD weak mode this transformation is always correct. In NNBD strong mode this transformation is correct only if opted-out libraries are not allowed. The following patterns are handled: If S <: T (this includes S <: T? in weak mode) S x; x as T => x If S <: T? in strong mode S x; x as T => (x == null) ? x as T : x This kernel transformation is not specific to the VM and can be reused by other back-ends such as dart2js and DDC. Fixes https://github.com/dart-lang/sdk/issues/40892 Issue https://github.com/dart-lang/sdk/issues/40893 Change-Id: I466ba96d763d5358011c768400c5225fa7bf5e67 Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/139314 Commit-Queue: Alexander Markov <alexmarkov@google.com> Reviewed-by: Johnni Winther <johnniwinther@google.com> Reviewed-by: Martin Kustermann <kustermann@google.com> Reviewed-by: Sigmund Cherem <sigmund@google.com>