fuzz findings [zig]: undeclared disagreements (2026-08-22)

[zmaril]

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

• findings: 111 (111 undeclared)
• iterations: 5000
• we_accepted: 2883
• we_rejected: 1815
• agreed: 1535
• widenings: 1348
• grammar coverage: 99.6% of alternatives

Undeclared programs the reference parser accepts but our grammar splits differently (111 distinct):

. { .. }

. { AA . * }

. { anytype }

test AA : { }

. { async AA }

---

Filed automatically by piecework.
lang: zig · kind: fuzz · grammar: 80fdf0e · corpus depth: 0 packages
ticket: fuzz-zig-675206893 (exit 0)

job log tail

[piecework] start  2026-08-22T22:38:09Z  (timeout 7200s, project treebank)
note: pull failed; running current checkout
fuzz: 5000 programs derived from the zig grammar (seed 675206893), judged by the parser and compiler together
fuzz: 2883 accepted by us (1815 discarded as unfaithful), 1535 agreed, 1348 widening(s) in 111 distinct program(s) — 111 undeclared, 0 declared
fuzz: coverage — 465/467 grammar alternatives (99.6%), 95 tape(s) kept
  unreached    2  in line_comment
   52x  . { .. } ⏎ 
    1x  . { AA . * } ⏎ 
    1x  . { anytype } ⏎ 
   71x  test AA : { } ⏎ 
   34x  . { async AA } ⏎ 
  236x  struct ( ) { } ⏎ 
   18x  . { . AA = .. } ⏎ 
    2x  comptime ( .. ) ⏎ 
   12x  comptime anytype ⏎ 
    1x  . { anytype { } } ⏎ 
   36x  test " " AA : { } ⏎ 
   74x  test AA : { } AA , ⏎ 
    1x  comptime ( AA . * ) ⏎ 
    1x  . { . AA = anytype } ⏎ 
    3x  comptime AA . * . AA ⏎ 
    3x  comptime AA : AA . * ⏎ 
    1x  comptime [ * AA ] AA ⏎ 
    8x  . { . AA = async AA } ⏎ 
    2x  comptime ( async AA ) ⏎ 
  116x  extern struct ( ) { } ⏎ 
fuzz: report at corpus/zig/reports/fuzz.json