cryptic error from Metal on Mac with Nvidia GPU

What does it means when -[MTLDevice newRenderPipelineStateWithDescriptor:options:reflection:error:] returns the error "No primitive topology specified for layer selection program generation"? We've seen this after Ogre has compiled a vertex shader that uses [[viewport_array_index]] on a Mac with Nvidia graphics.

cryptic error from Metal on Mac with Nvidia GPU
 
 
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