When specifying explicit precision and scale for numerics, Postgres allows the ranges 0..=1000 for precision and -1000..=1000 for scale. Currently, ExactNumberInfo uses u64 to represent scale, and the parser fails on the - when trying to parse DDL with a negative scale:

create table t (x numeric(1000,-10));

Error during parsing: ParserError("Expected: literal int, found: - at Line: 1, Column: 32")