Change ast::Array to use an ast::Expression for its `size` field. The
WGSL frontend now parses the array size as an `primary_expression`,
and the Resolver is responsible for validating the expression is a
signed or unsigned integer, and either a literal or a non-overridable
module-scope constant.
The Resolver evaluates the constant value of the size expression, and
so the resolved sem::Array type still has a constant size as before.
Fixed: tint:1068
Fixed: tint:1117
Change-Id: Icfa141482ea1e47ea8c21a25e9eb48221f176e9a
Reviewed-on: https://dawn-review.googlesource.com/c/tint/+/63061
Auto-Submit: James Price <jrprice@google.com>
Kokoro: Kokoro <noreply+kokoro@google.com>
Commit-Queue: James Price <jrprice@google.com>
Reviewed-by: Ben Clayton <bclayton@google.com>