As part of the on-going build-out of recursive types in newt, complex types have been re-worked such that every complex type is a dictionary of type declarations (previously, record types were a dictionary of values, with special logic to generate modified copies of this dictionary). In this new model, type declarations that reference existing types are implemented as type aliases. Thus, in the following type declaration, person.age is an alias for int, is an un-aliased record type, and and both alias the built-in type string.

person {
   name {

For purposes of assignment and conversion, a type alias is directly equivalent to the type it aliases.

The struct keyword is noteworthily absent from the previous record type definition, and there are now commas separating type members. These are not accidents, as the re-worked type declarations allow for arbitrarily nested type definitions, and repeated use of the struct and sum keywords felt heavy and inelegant. For this (primarily aesthetic) reason, the keywords are omitted from the nested types, and to maintain a uniform, non-astonishing grammar, the keyword is omitted from the top-level complex type declarations as well.

Omission of the keywords requires another mechanism for differentiating sum and product types, however, so members of record types must now be comma-delimited, while sum type variants are delimited by a vertical bar (that is, a pipe). In this new syntax, a linked list of integers might be expressed as follows:

list {
        | item {

The new syntax very closely matches the proposed syntax for map literals, which is a nice isomorphism, but does raise concerns about legibility issues. Time will tell.