The forms the first slice answers now lower: x.toLocaleString() (and an
explicit undefined locale) to icu.numFormatDefault, the argument-free
Date#toLocaleString/toLocaleTimeString to the ICU date formatters, and
Intl.Segmenter({ granularity: "word" }) to the ICU word iterator (a
literal language tag is the locale; the empty string is the default).
Sentence segmentation keeps its refusing construction in JavaScript
dependencies, the grapheme segmenter stays the engine-free fast path,
and the code notes the deletion I4 schedules.
The refusals that named these forms follow: the four stdlib hints, the
Intl identifier hint, the Date method hint and the Segmenter option
messages list what lowers and what still does not (locale negotiation,
options bags, toLocaleDateString, formatter values). The library mode
refuses the icu.* libCalls, whose ambient locale state and data file a
library archive cannot carry, and the ambient process.config comment says
what a compiled binary can honestly answer.
An argument that IS undefined (exactly undefined, or void) means the
absent form and lowers; one whose type merely includes undefined may hold
a locale or an options bag at run time, and the constructor cannot read
either, so it is refused rather than silently treated as absent.
Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
string-width's `character.codePointAt(0)`, camelcase's
`string.toLocaleLowerCase(locale)`, toml's `input.substr(...)` and
pretty-bytes' `number.toPrecision(3)` threw "x.y is not a function": the
dynamic method dispatch had no answer for these names on strings and
numbers.
A checked-dynamic receiver calling a String or Number method the runtime
dispatch cannot answer (codePointAt, substr, toLocaleLowerCase,
toLocaleUpperCase, isWellFormed, toWellFormed, trimLeft, trimRight,
toPrecision, toExponential(digits)) now evaluates the receiver and
arguments once and dispatches on the runtime kind: a string or number runs
the typed lowering, every other kind keeps the runtime dispatch's answer.
Names other dyn kinds share (at, concat, slice) and the Annex B HTML names
chalk-style builders define (bold, link, ...) keep their existing
dispatch.
Typed receivers gain substr, the locale case pair, the HTML methods,
toPrecision and toExponential(fractionDigits), all previously compile-time
refusals. toPrecision/toExponential digits come from exact big-integer
arithmetic over the double (ties up on the exact binary value). Locale
case mapping follows V8: the first requested locale decides, Turkic
dotted/dotless I is implemented, and Lithuanian, Greek uppercasing,
objects and malformed tags throw a 'not supported yet' Error.
A checker-untyped JS binding holding `string | undefined` boxes into the
dyn receiver path for String methods (string-width's baseVisible result).
tests/diagnostics/retired-engine-1112-number-methods.ts compiles now and
moves back to tests/corpus/1112-number-methods.ts.
New runtime functions are reached only from the new lowerings; the
existing runtime objects' sections are unchanged.
Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
- Keep generic bindings and short-circuit writes scoped to their native execution context.
- Compile Map and Set copies, tuple callbacks and searches, and string-pattern replacement.
- Exercise production frontend registries without Node and preserve mutation, identity, and evaluation order.
- Lower Number.prototype.toFixed through the compiler IR and native backends.
- Match JavaScript rounding, range errors, and numeric edge cases in the runtime.
- Add differential coverage and update surface metadata and diagnostics.
- library-int suite snapshots SC4021/SC4022/SC4023 rendered end to end (slot path, evidence, span, fix) — the diagnostics-corpus discipline for codes the executable lane cannot reach
- dynamic-surface diagnostics fixture swaps Math.ceil for Math.sqrt (trunc/ceil compile statically now) and its snapshot regenerates
