src/rules/correctness/chars.bend checks

rule chars: a match with more than eight character-literal arms (case '.':). Char is Chr{code: U32}, so such an arm is a U32 literal inside a constructor pattern, and bend's C backend pays for each one out of all proportion to its size -- about 90 MB, and the cost compounds through every def downstream of the one holding them (eighteen arms cost 1.57 GB and 8.3 s here, 0.10 GB and 0.7 s once rewritten). It is the literals, not the arms: a match over eighteen constructors costs nothing measurable.

Compare Char.to_u32(c) instead. Bind the fallback above the comparisons so it is a value, not a call, or bolt's own eager rule fires on it; and give the def the reusable quantity (+c: Char), since the code point and the fallback both consume it. Where the arms carry linear values, leave the match alone: a cascade would break linearity and do every branch's work.

Only a case's first match column is read, and only an arm whose pattern opens with a character literal counts: case 'x': does, case Con{'x', t}: and a literal in a later column of match a b: do not.