ANGLE/Metal bug. Fails to compile: On Apple M1 device and iPads. col.r += col.a = 1.0; Example: https://www.shadertoy.com/view/stjBRd
Thank you for the report. I think this one has been fixed already. If you have time, please retry with macOS 12.3 and/or iOS 15.3. Most likely duplicate of bug 230472
This is still broken on iOS 15.4.1
This is fixed in iOS 15.5
<rdar://problem/93727663>
*** This bug has been marked as a duplicate of bug 230472 ***