commit 5d7857984220f928aaaa0e836a9e0d2a54acfdc0
author Paul Berry <paulberry@google.com> Thu Mar 20 09:08:53 2025 -0700
committer Commit Queue <dart-scoped@luci-project-accounts.iam.gserviceaccount.com> Thu Mar 20 09:08:53 2025 -0700
tree 284647a420d597aabad78b0a033a5f12a47e3edc
parent 5d1f4876ee033195c1f11eaa0cfd739ab81bfa6e

[analyzer] Fix dead code reporting for null-aware accesses.

A null-aware access can result in dead code if the target has static
type `Null`. The analyzer wasn't properly accounting for this,
resulting in some confusing ranges reported for the DEAD_CODE warning.

This change causes the following expressions to report dead code for
the code ranges indiced by `^`:

    Null myNullVar = null;
    myNullVar?[index];
    //         ^^^^^^ DEAD_CODE
    myNullVar?[index] = value;
    //         ^^^^^^^^^^^^^^ DEAD_CODE
    myNullVar?.method();
    //         ^^^^^^^^ DEAD_CODE
    myNullVar?.property;
    //         ^^^^^^^^ DEAD_CODE
    myNullVar?.property = value;
    //         ^^^^^^^^^^^^^^^^ DEAD_CODE

Note that the bug was confined solely to the logic that reports the
DEAD_CODE warning; there is no change to the reachability inferred by
flow analysis (and hence, this is a non-breaking change).

Fixes https://github.com/dart-lang/sdk/issues/60364.

Bug: https://github.com/dart-lang/sdk/issues/60364
Change-Id: I068826282fba6b9057e9c27d1d9310c65714e203
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/416723
Auto-Submit: Paul Berry <paulberry@google.com>
Reviewed-by: Konstantin Shcheglov <scheglov@google.com>
Commit-Queue: Konstantin Shcheglov <scheglov@google.com>