lexer: yield* is delegation - #309
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A `*` directly after `yield` on the same line scans as the FROM token
that `yield from` produces, so `yield* other()`, `yield *other()` and
`yield * other()` all delegate, which is how JavaScript reads the same
spelling. They used to compile to a bare yield multiplied by the
operand, which yielded undefined and never delegated.
`(yield) * 2` and `yield ** 2` keep their meaning, `*{` still opens a
Map literal ahead of this branch, `yield *= x` still rejects, and a `*`
opening the next line stays multiplication because the retag requires
the yield's own line.
No grammar change: the parser is byte-identical and the corpus is
unchanged. The editor grammars already color yield as a keyword and *
as an operator. The browser bundle is regenerated under the pinned Bun.
Battery: eight rows in async.rip pin the three spellings, the return
value, a generator method, the parenthesized multiply, exponentiation,
the Map literal, and the emitted code.
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Summary
yield*now means delegation, the same thing asyield from. A*directly afteryieldon the same line scans as the delegation token, soyield* other(),yield *other()andyield * other()all emityield* other(). Until now they compiled to(yield) * other(): a bare yield multiplied by the operand, which yieldedundefinedand never delegated, with no error.Unchanged on purpose.
(yield) * 2andyield ** 2keep their meaning.yield *{a: 1}still yields a Map because*{is claimed first.yield *= xstill rejects. A*that opens the next line stays multiplication, since the retag requires the yield's own line.One meaning change.
yield * 3used to multiply the sent value by three and now delegates to3, which throws at runtime. JavaScript reads the spelling the same way.No grammar change.
src/parser.jsis byte-identical, the corpus is unchanged, and the three editor grammars already coloryieldas a keyword and*as an operator. Browser bundle regenerated under Bun 1.4.0.Test
Eight new rows in
async.rip. Language battery 3258 passing, toolchain gates 661 passing, fulltest:allsuite green across all 26 lanes.