From Copilot's twelfth pass of #1962. A `/// <reference types="x" />` pulls in
a package's declarations exactly like an import does, but TypeScript reports
it in `preProcessFile`'s `typeReferenceDirectives`, not `importedFiles` — and
only the latter was read. A shared source using one could therefore load the
root's copy of a package alongside a client's without it ever entering the
candidate set, so its skew would pass. Same silent-miss direction as the
earlier syntax gaps, through a channel the parser switch didn't cover because
I only read one of its two outputs.
`typeReferencePackageNames` maps a directive to both candidates, since the
name is the *type* name and not the package: `node` resolves to `@types/node`,
while a package shipping its own declarations resolves to itself. Returning
both over-approximates, the safe direction — whichever isn't installed drops
out downstream. Scoped names mangle `@scope/pkg` → `@types/scope__pkg`,
TypeScript's convention. `path` references name a file, not a package, and are
ignored.
The real candidate set is unchanged at 17: no shared source uses a triple-slash
reference today. As with the other syntax fixes, this closes the channel
against the one that arrives later.
Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01HDdo1rNRVQnVRRdsqSrvG3
87c1e05420