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Sword 0.2.2 — Fold

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@PedroTessaro PedroTessaro released this 20 Oct 19:05
· 283 commits to main since this release
v0.2.2
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Learn about vigilant mode.

2026-10-20. A patch to Fold: what a server needs to authenticate, sign, stamp
and cache, a second name for a type, the grammar written down, and three bugs
in the runtime and its tests that had been showing up as flakes.

What changes for existing programs

Nothing that compiled before stops compiling. type is not a keyword: it is
special only at the start of a top-level declaration followed by a name, so a
field or a variable called type is still a name.

The language

  • type Name = T gives a type a second name. A Name is a T — values
    pass between them without a conversion — and an alias of a struct can write
    a literal or declare a method. It takes no type parameters, though it may
    name an instance: type Set = collections.Map[string, bool]. The language
    server and the editors' own colouring know it.
  • An array's length may be another package's constant:
    [crypto.Sha256Size]u8.
  • The grammar, in EBNF: the lexical rules, including when
    a newline ends a statement, and every production of the syntax.

Standard library

  • std/crypto: HMAC-SHA-256, crypto.Equal (a comparison that takes the
    same time wherever the bytes differ), PBKDF2-HMAC-SHA-256, and
    crypto.Random, bytes from the kernel's random source. Under
    SWORD_SIM_SEED the random bytes come from the seed, so a simulated run that
    makes a token makes the same one again.
  • std/encoding: hex, base64 and base64url into the caller's buffer.
    Decoding is strict, so each byte string has one spelling.
  • std/time: Rfc3339, HttpDate, ParseRfc3339 and ParseHttpDate,
    which reads all three forms RFC 9110 requires a recipient to accept.
  • std/http: static files carry Last-Modified and a weak ETag, and
    Files answers If-None-Match and If-Modified-Since with 304.

Nothing in any of them allocates.

Fixes

  • A dial whose connect failed closed its socket outside the poller; on macOS
    that is the close beside kqueue that can hang in the kernel until reboot
    (#41).
  • tests/dialreuse.sword lost dials on macOS because it could fill the listen
    queue, which there answers with a reset (#53).
  • Under ThreadSanitizer, a signal could be held in a task that parked and never
    came back; graceful hung about once in three hundred runs (#48).
  • shield test -sim on a standard library package warned about the runtime's
    own calls.
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