In `naga::valid::expression::validate_expression`, use a let-else
statement so that the outermost control flow follows the success path,
and errors are close to the conditions that trigger them.
Properly apply WGSL's automatic conversions to the arguments
to texture sampling functions.
Introduce helper function `Lowerer::expression_with_leaf_scalar`.
Although this can't affect behavior, use
`Lowerer::expression_for_abstract` for the `image` and `sampler`
arguments, simply because we want to move away from
`Lower::expression`'s automatic concretization, and move towards
having callers say explicitly what sort of conversions they need.
Although this can't affect behavior, use
`Lowerer::expression_with_leaf_scalar` for the `offset` argument, so
that the code spells out that this requires an `i32` value, rather
than depending on blind concretization giving it that.
Continue to use `Lowerer::expression` for `gather` and `array_index`,
since those happen to behave correctly with blind concretization, and
can be cleaned up later.
Fixes#7427.
Change `naga::front::wgsl::lower` to `use` `ir` and `proc`,
and then qualify identifiers with that instead of `crate`.
This is strictly fiddling with `use` directives and name
qualification, with the concomitant formatting changes; there should
be no change to the module's behavior or meaning.
Closes#7481.
This implementation roughly follows approach 2 outlined in #7481, i.e.,
it adds a polyfill for the signed and unsigned dot product of packed
vectors for each platform. It doesn't use the specialized instructions
that are available for this operation on SPIR-V (with capability
DotProductInput4x8BitPacked).
Have constant evaluator use `wrapping_abs` instead of `abs` when
applying `MathFunction::Abs` to AbstractInt values. WGSL says that
applying `abs` to the most negative AbstractInt value must return it
unchanged, which is what Rust's `i64::wrapping_abs` does.
