fields.generated.ts reads IR nodes' fields by name, so a field ir.ts gains
after the last `pnpm generate:ir-fields` is skipped by the walkers until
someone regenerates the file; `--check` in CI reports it, but only on the
run that looks.
The generator now ends the file with type-level checks, one per node kind
and per nested record the walkers enumerate: a field outside the list the
file was generated from fails type checking with the field's name, and so
does a field read as a scalar (no string, no object) that can now hold a
string or an object. Fields the file reads already fail type checking when
they are removed or change type. The checks are types only and emit no
code.
Chris Tate
07f159accd