Given the following shader:

            @group(0) @binding(0) var inputTexture: texture_2d<f32>;
            @fragment fn main(@builtin(position) fragcoord : vec4<f32>) ->
              @builtin(frag_depth) f32 {
              var depthValue : vec4<f32> = textureLoad(inputTexture, vec2<i32>(fragcoord.xy), 0);
              return depthValue.x;
            }

@builtin(frag_depth) appears to be ignored when the metal code is generated:


[[fragment]] float function0(vec<float, 4> parameter0 [[position]], constant __ArgumentBufferT_0& __ArgumentBuffer_0 [[buffer(0)]])
{
    texture2d<float, access::sample> global0 = __ArgumentBuffer_0.global0;
    vec<float, 4> local0 = global0.read(uint2(vec<int, 2>(parameter0.xy)), 0);
    return local0.x;
}