`Conditional` resource declaration based on link-time specialization constant fails to compile

[karel-tomanec]

Issue Description

When using link-time specialization constants to conditionally declare resources, Slang fails to compile. The use case is transitioning from #ifdef-guarded shader code to link-time specialization constants for conditionally including/excluding resource declarations whose types may be unsupported on certain targets (e.g. RWTexture2DMSArray<uint> on GPUs without multisampled storage image support).

Confirmed as a bug by @csyonghe on Discord.

Reproducer Code

extern static const bool kVariantMSSupported;

Conditional<RWTexture2DMSArray<uint>, kVariantMSSupported> headIndexImageMs;

Expected Behavior

When the specialization constant is false, the resource declaration (and its descriptor binding) should be completely omitted from the final SPIR-V output, since the underlying type may be unsupported on the target. The code should compile successfully regardless of the constant's value.

Actual Behavior

Compilation fails.