pub fn frontier_reason(op: &Op) -> Option<&'static str>Expand description
Why the fabric has no realization of an op on the interpreter-fallback frontier — None for every
realized op, and None for a frontier op nobody has explained, which the coverage locks refuse: an op
is tiled or it states its reason, there is no third state. A lane that meets one of these ops refuses
the program with this sentence, never a silently dropped op.