[Impeller] impellerc will blow up if you specify a layout(location= on a sampler2D. #141219
Description
Error looks like
Compilation failed.
/Users/dnfield/src/flutter_shaders/lib/shaders/pixelation.frag: GLSL to SPIRV failed; Compilation error. 0 error(s) and 2 warning(s).
/Users/dnfield/src/flutter_shaders/lib/shaders/pixelation.frag:10: warning: 'uPixels' : ignoring layout qualifier for uniform location
/Users/dnfield/src/flutter_shaders/lib/shaders/pixelation.frag:11: warning: 'uSize' : ignoring layout qualifier for uniform location
shaderc: internal error: compilation succeeded but failed to optimize: [VUID-StandaloneSpirv-Location-06672] Location decoration must not be applied to this storage class
%uTexture = OpVariable %_ptr_UniformConstant_44 UniformConstant
Target debug_android_application failed: ShaderCompilerException: Shader compilation of "/Users/dnfield/src/flutter_shaders/lib/shaders/pixelation.frag" to "/Users/dnfield/src/flutter_shaders/example/build/app/intermediates/flutter/debug/flutter_assets/packages/flutter_shaders/shaders/pixelation.frag" failed with exit code 1.
impellerc stdout:
impellerc stderr:
Compilation failed.
/Users/dnfield/src/flutter_shaders/lib/shaders/pixelation.frag: GLSL to SPIRV failed; Compilation error. 0 error(s) and 2 warning(s).
/Users/dnfield/src/flutter_shaders/lib/shaders/pixelation.frag:10: warning: 'uPixels' : ignoring layout qualifier for uniform location
/Users/dnfield/src/flutter_shaders/lib/shaders/pixelation.frag:11: warning: 'uSize' : ignoring layout qualifier for uniform location
shaderc: internal error: compilation succeeded but failed to optimize: [VUID-StandaloneSpirv-Location-06672] Location decoration must not be applied to this storage class
%uTexture = OpVariable %_ptr_UniformConstant_44 UniformConstant
The solution is to remove the location directive (or even just remove the whole layout specifier).
The error is probably going to be hard for users to understand, but I think it's also probably not super commonly used and maybe the users who do come across it will just know what to do.
I don't know if there's any way to get shaderc to be more permissive of such errors, but I'm also not sure how much more we want shaderc to accept weird input data. The path forward is probably flutter_gpu for this kind of thing anyway?