Change the validator to enforce WGSL's requirement that all variables
in the `function` and `private` address spaces must have constructible
types.
Mark the `RayQuery` type as `CONSTRUCTIBLE`, since it is intended to
be used for local variables.
Add a regression test.
If an `Emit` statement covers an `Expression` that is not otherwise
used by any `Statement`, remove it from the `Arena` anyway. An `Emit`
statement controls when `Expression`s are evaluated, but it doesn't
have any side effects, so unless an expression is used by some other
statement, it's not necessary to the program.
Change printlns in the backend functions to say "generating" instead
of "writing" before calling the Naga backends. "Writing" suggests
writing output to a file; "generating" seems more accurate for calling
a backend.
Add a new type, `Input`, representing a particular Naga input file,
with methods to generate related paths - output files with a
particular extension, parameter files, and the input file itself.
Use this throughout `snapshots.rs` to generate paths.
Give `Input` utility methods for reading and writing files.
Rather than adding a `-glsl` suffix to the name, just rely on
`check_targets`' standard naming behavior, treating
`tests/in/variations.glsl` like any other snapshot input.
Remove the call to `Validator::validate` in `convert_spv`, since it
directly follows the call to `check_targets`, which also called
`Validator::validate`.
The only difference between the two is whether `Parameters::god_mode`
is respected, but this difference doesn't seem to have been
deliberate: at the time the call to `check_targets` was added to
`convert_spv` (5f21cf360, 2021-02-17), the two calls were exactly the
same.
Use `FastIndexSet`, rather than `FastHashSet`, for tracking global
declarations' dependencies, so that the order in which functions are
inserted into the `Module` is not dependent on the hash function.
Add a new Naga feature, `"compact"`, which adds a new function
`naga::compact::compact`, which removes unused expressions, types, and
constants from a `Module`.
The `front::wgsl::lowerer::RuntimeExpressionContext::local_table`
field does not need to be a mutable reference, as expressions never
introduce new local bindings.
