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>
Front end for Dart
This package provides a low-level API for use by compiler back ends that wish to implement the Dart language. It is intended for eventual use by dev_compiler, dart2js, and the Dart VM. In addition, it will share implementation details with the analyzer package--this will be accomplished by having the analyzer package import (and re-export) parts of this package's private implementation.
End-users should use the dart analyze
command-line tool to analyze their Dart code.
Integrators that want to write tools that analyze Dart code should use the analyzer package.
Note: A previous version of this package was published on pub.dev. It has now been marked DISCONTINUED as it is not intended for direct consumption, as per the notes above.