Paul Berry
6c5c9d384f
This change updates the flow analysis logic for `is` and `as`
expressions so that when the language feature `sound-flow-analysis` is
enabled, the static type of the operand is compared to the type to the
right of the `is` or `as` keyword. If one of the types is non-nullable
and the other type is `Null`, then the type test is known to fail. For
an `as` expression, this means that the code path following the
expression will be marked as unreachable. For an `is` expression, this
means that any code paths that assume it evaluates to `true` will be
marked as unreachable.
Note that these new behaviors break assumptions made by three
pre-existing flow analysis tests. I was able to adjust one of the
tests ("equalityOp_end does not set reachability for `this`") to
preserve its old behavior. The other two tests became redundant, so I
removed them.
There is no behavioral change if the feature `sound-flow-analysis` is
disabled.
Bug: https://github.com/dart-lang/sdk/issues/60438
Change-Id: Ib3a9e96bd39cf7df4c6c297568763c0f25bc9e39
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/420164
Reviewed-by: Konstantin Shcheglov <scheglov@google.com>
Reviewed-by: Chloe Stefantsova <cstefantsova@google.com>
Commit-Queue: Paul Berry <paulberry@google.com>
FE/analyzer shared code
This package contains logic that is shared between the front_end and analyzer packages. It is intended solely to facilitate development of the Dart SDK, and is not intended for use by end users. In particular, this package has no public API, so no guarantee is made of compatibility between one version of the package and the next.
End users should consider using the analyzer package to analyze Dart source code.