fuzz findings [javascript]: undeclared disagreements (2026-08-24)

[zmaril]

Fuzzing derived programs the grammar and the reference parser disagree on.

• findings: 2 (2 undeclared)
• iterations: 5000
• we_accepted: 3334
• we_rejected: 1103
• agreed: 2719
• widenings: 615
• grammar coverage: 99.8% of alternatives

Undeclared programs the reference parser accepts but our grammar splits differently (2 distinct):

class { }

class { } ;

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Filed automatically by piecework.
lang: javascript · kind: fuzz · grammar: 2ace7ce · corpus depth: 1000 packages
ticket: fuzz-javascript-701089105 (exit 0)

job log tail

[piecework] start  2026-08-23T23:43:39Z  (timeout 7200s, project treebank)
note: checkout dirty; running as-is
fuzz: 5000 programs derived from the javascript grammar (seed 701089105), judged by the parser and compiler together
fuzz: 3334 accepted by us (1103 discarded as unfaithful), 2719 agreed, 615 widening(s) in 2 distinct program(s) — 2 undeclared, 0 declared
fuzz: coverage — 895/897 grammar alternatives (99.8%), 212 tape(s) kept
  unreached    2  in comment
  351x  class { } ⏎ 
  264x  class { } ; ⏎ 
fuzz: report at corpus/javascript/reports/fuzz.json