If an abstract-vector or abstract-matrix is indexed with a non-constant index expression, then the resulting value is non-constant, and so cannot be abstract.
In this situation the materialization cannot be done post-index, so materialization must happen on the object before indexing.
Bug: chromium:1345468
Change-Id: I9f29dc40301779a7ff8f173724374bd845a3a5b9
Reviewed-on: https://dawn-review.googlesource.com/c/dawn/+/96684
Reviewed-by: Antonio Maiorano <amaiorano@google.com>
Kokoro: Kokoro <noreply+kokoro@google.com>
Commit-Queue: Ben Clayton <bclayton@chromium.org>