Lyric

What changed in v2.3.1 — 2026-08-21

The post-2.3.0 audit's patch wave: four measured bugs, none of them reachable from a program that was doing anything unusual. The bytecode format stays 3.3, and the language gains nothing — three of the four were valid programs the toolchain mishandled. Three conformance cases activate with this release (//! since: 2.3.1); the suite stands at 88.

Fixed

• A parent interface's default method works through a child-typed value. c.describe(), where describe is a default declared on the parent of c's interface, was an internal compiler error in Debug and a wrong receiver slot in Release — the optimizer had resolved the slot to the parent's function and called it directly with a child-typed value, which the language does not convert either. All three routes to such a default are fixed and pinned: through an interface-typed value, through a constraint naming the child, and through an element of an interface-typed array. The constraint route had a second gap of its own and reported "'C' has no 'describe'" from the lowering.
• An array literal gives its elements the element type. let xs: (?int)[] = [null, 5]; was accepted by the checker and refused by the lowering ("'null' in a position without an expected type"), and let xs: Shape[] = [Sq { }]; put class references where interface values were declared — an internal error in Debug, a wrong dispatch in Release. An element is a context position like every other now.
• A redirected stream carries UTF-8. On Windows the console's code page encoded redirected output too, and lyrrepl set that shared code page unconditionally — so a tool running beside a REPL could have its output best-fit-mapped, turning an em dash into a hyphen. Every tool now writes UTF-8 into a redirected stream and reads UTF-8 from a redirected stdin; the code page is set only for a console that really is one. This is what made individual process-spawning tests fail sporadically under load since M16.
• A float renders with a lowercase exponent. println(f"{1.0e21}") wrote 1E+21, where C, Go, Python, JavaScript and Rust all write 1e+21. std.string.fromFloat backs the f-string lowering, so its output is program behaviour: the shape is now specified (spec §11) and pinned — shortest round-trip, plain decimal while the decimal exponent lies in -4 .. 16 and scientific outside it, Infinity / -Infinity / NaN, -0 for negative zero. The disassembler, the IR printer and the debugger's variables panel render through the same one place.

The full changelog →