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lean4/tests/elab_fail/partialSyntaxTraces.lean.out.expected
Kim Morrison e01cbf2b8f feat: add structured TraceResult to TraceData (#12698)
This PR adds a `result? : Option TraceResult` field to `TraceData` and
populates it in `withTraceNode` and `withTraceNodeBefore`, so that
metaprograms walking trace trees can determine success/failure
structurally instead of string-matching on emoji.

`TraceResult` has three cases: `.success` (checkEmoji), `.failure`
(crossEmoji), and `.error` (bombEmoji, exception thrown). An
`ExceptToTraceResult` typeclass converts `Except` results to
`TraceResult` directly, with instances for `Bool` and `Option`.
`TraceResult.toEmoji` converts back to emoji for display. This replaces
the previous `ExceptToEmoji` typeclass — `TraceResult` is now the
primary representation rather than being derived from emoji strings.

`withTraceNodeBefore` (used by `isDefEq`) uses
`ExceptToTraceResult.toTraceResult` directly, correctly handling `Bool`
(`.ok false` = failure) and `Option` (`.ok none` = failure), with
`Except.error` mapping to `.error`.

For `withTraceNode`, `result?` defaults to `none`. Callers can pass
`mkResult?` to provide structured results; when set, the corresponding
emoji is auto-prepended to the message.

Motivated by mathlib's `#defeq_abuse` diagnostic tactic
(https://github.com/leanprover-community/mathlib4/pull/35750) which
currently string-matches on emoji to determine trace node outcomes. See
https://leanprover.zulipchat.com/#narrow/channel/113488-general/topic/backward.2EisDefEq.2ErespectTransparency

🤖 Prepared with Claude Code

---------

Co-authored-by: Claude Opus 4.6 <noreply@anthropic.com>
2026-03-10 02:42:57 +00:00

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partialSyntaxTraces.lean:6:0: error: unexpected end of input; expected ':=', 'where' or '|'
[Elab.command] 💥️ [Error pretty printing syntax: parenthesize: uncaught backtrack exception. Falling back to raw printer.]
(Command.declaration
(Command.declModifiers [] [] [] [] [] [] [])
(Command.definition "def" (Command.declId `f []) (Command.optDeclSig [] []) (Command.whereStructInst <missing>)))
[Elab.command] ✅️