Function mz_transform::typecheck::is_subtype_of

pub fn is_subtype_of(sub: &[ColumnType], sup: &[ColumnType]) -> bool

Returns true when it is safe to treat a sub row as an sup row

In particular, the core types must be equal, and if a column in sup is nullable, that column should also be nullable in sub Conversely, it is okay to treat a known non-nullable column as nullable: sub may be nullable when sup is not