RFC 0006 error reporting wanted file:line:col but IR nodes carried no
position, so diagnostics read only "type error in <ns>: <msg>". Now:
type error /tmp/scene.clj:5:5: `inc` requires a number, but argument 1 is a string
The reader records each LIST form's absolute start offset in a table keyed
by form identity (lists are fresh arrays, never interned), gated behind a
flag the loaders enable only when JOLT_TYPE_CHECK is on — zero cost off.
Keying by identity makes positions survive macroexpansion exactly when the
user's own sub-form is spliced through, and absent for macro-synthesized
structure: a `(inc :k)` written inside `(when c ...)` reports at its own
line, never at the expansion's generated if/do.
The analyzer stamps the offset onto :invoke nodes (form-position host
contract fn); the checker carries it into each diagnostic as :pos; the
loaders stash the file's source + path on the env (save/restored across
nested requires); backend/type-check! converts offset -> line:col via the
reader's line-col and renders the RFC format. Falls back to the ns when no
position is available (synthetic forms), so it is never worse than before.
Gate green, conformance 335/335, suite 4718, runtime bench even (positions
are compile-time only; off by default).
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