https://github.com/xialvjun/ts-sql-plugin is an interesting project that uses a TS plugin to typecheck sql query strings.
https://github.com/mmkal/slonik-tools/tree/master/packages/typegen#readme is also an interesting project that uses runtime tracing to detect query types on first run.

Both should allow you to do something roughly like this:

const notDeleted = (asOf = null) => sql`
  deleted_at is null or deleted_at > ${asOf || sql`now()`}
`

const myQuery = (bar) => sql`
  select * from mytable
  where ${notDeleted()}
  and foo = ${bar}
`

// result is fully typed
const result = await db.query(myQuery(bar))

Is pgTyped interested in experimenting with such techniques to enable query composition, for convenient sharing of common conditions etc?