shaderc internal error: ID <11> (OpVariable) Scalar boolean must be in a Block. %gl_PrimitiveID = OpVariable %_ptr_Input_int Input

[StefanPoelloth]

Compilation of the following shader fails with this error:

shaderc: internal error: compilation succeeded but failed to optimize: According to the Vulkan spec BuiltIn PrimitiveId variable needs to be a either a boolean or an array of booleans.ID <11> (OpVariable) Scalar boolean must be in a Block.
  %gl_PrimitiveID = OpVariable %_ptr_Input_int Input

To reproduce use this shader:

#version 460
#pragma shader_stage(fragment)
#extension GL_EXT_mesh_shader : require

layout(location = 0) out float TestOut;
layout(location = 0) perprimitiveEXT flat in float Test;

void main()
{
    TestOut = gl_PrimitiveID;
}

and compile with glslc --target-env=vulkan1.4 -O shader.glsl

Additional Info:

~$ glslc --version
shaderc v2023.8 v2025.3
spirv-tools v2025.3 v2022.4-833-g33e02568
glslang 11.1.0-1253-gefd24d75

Target: SPIR-V 1.0