Module placeholders 

Positional-placeholder scan over a query block’s raw SQL body.

This is a lexical scan, not a SQL parser — deliberately, and the design (docs/design/declarative-custom-query.md §2) prices the alternative: knowing a $N’s type requires preparing the statement against a live catalogue, which would make cratestack-macros need a database connection at macro-expansion time for the first time ever. Knowing a $N’s position needs none of that, and position is all the two checks in cratestack-parser’s validate/queries.rs need: no reference beyond the declared parameter count, and no declared parameter left unreferenced.

It does step over the spans Postgres itself reads as text — string literals, dollar-quoted bodies, quoted identifiers and comments (see [skip]) — because not doing so does not merely miss checks, it falsely rejects valid SQL. That regression was real and measured in cratestack#867’s review; [skip]’s module doc has the numbers and the reasoning for why a lexer is on the right side of the line design §3 draws.

Functions

scan_sql_placeholders

Every distinct N in a $N token appearing in sql as an actual parameter reference, ascending.