Constant not supported in GLSL shader binding style declaration

[theblackunknown]

Hi team,

I am trying to compile some of our GLSL shaders using slangc and I am running into issues because we are using constant in shader bindings declaration.
Currently we are using google/shaderc to compile our shader and we do not run into this compiler issue.

See below for a minimal repro case.
If you can point me to how to port it as a Slang test I would gladly contribute it if that helps.

Given the following constant-in-layout.slang file

#version 450 core

const uint DescriptorSet = 0;

const uint BindingPoint_Sampler = 0;
const uint BindingPoint_Scale = 1;
const uint BindingPoint_Bias = 2;

layout(location = 0) out mediump vec4 o_color;
layout(location = 0) in highp vec2 v_texCoord;
layout(location = 1) in highp float v_lodBias;
layout(set = DescriptorSet, binding = BindingPoint_Sampler) uniform highp usampler2D u_sampler;
layout(set = DescriptorSet, binding = BindingPoint_Scale) uniform buf0
{
    highp vec4 u_scale;
};
layout(set = DescriptorSet, binding = BindingPoint_Bias) uniform buf1
{
    highp vec4 u_bias;
};

void main()
{
    o_color = vec4(texelFetch(u_sampler, ivec2(v_texCoord), int(v_lodBias))) * u_scale + u_bias;
}

compiling the above file using the following command line
slangc.exe -target spirv -stage fragment -entry main constant-in-layout.slang

Will produce the following errors

tests\glsl\constant-in-layout.slang(15): error 20001: unexpected identifier, expected integer literal
layout(set = DescriptorSet, binding = BindingPoint_Sampler) uniform highp usampler2D u_sampler;
             ^~~~~~~~~~~~~
tests\glsl\constant-in-layout.slang(15): error 20001: unexpected identifier, expected integer literal
layout(set = DescriptorSet, binding = BindingPoint_Sampler) uniform highp usampler2D u_sampler;
                                      ^~~~~~~~~~~~~~~~~~~~
tests\glsl\constant-in-layout.slang(16): error 20001: unexpected identifier, expected integer literal
layout(set = DescriptorSet, binding = BindingPoint_Scale) uniform buf0
             ^~~~~~~~~~~~~
tests\glsl\constant-in-layout.slang(16): error 20001: unexpected identifier, expected integer literal
layout(set = DescriptorSet, binding = BindingPoint_Scale) uniform buf0
                                      ^~~~~~~~~~~~~~~~~~
tests\glsl\constant-in-layout.slang(20): error 20001: unexpected identifier, expected integer literal
layout(set = DescriptorSet, binding = BindingPoint_Bias) uniform buf1
             ^~~~~~~~~~~~~
tests\glsl\constant-in-layout.slang(20): error 20001: unexpected identifier, expected integer literal
layout(set = DescriptorSet, binding = BindingPoint_Bias) uniform buf1
                                      ^~~~~~~~~~~~~~~~~

[jkwak-work]

This appears to be a missing feature support for GLSL.
Slang doesn't support this way of using const variables at the moment.

[theblackunknown]

Thanks @jkwak-work, would you be able to point me at few places if I want to contribute to add this feature ?