leanprover / leanprover/lean4

`elab_rules : tactic` patterns require redundant information

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#1,348 2 comments 0 reactions 0 assignees View on GitHub

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enhancement P-medium
Dominant language
Lean
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Description

import Lean

syntax "foo " str : tactic

open Lean Elab
elab_rules : tactic
  | `(foo $x:str) => logInfo x.getString

example : True := by
 foo "hello"  -- Error `tacticFoo_` has not been implemented

One has to write the elab_rules above as

elab_rules : tactic
  | `(tactic| foo $x:str) => logInfo x.getString

Contributor guide

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First steps

  1. Read the whole issue, then the project's contributing guide.
  2. Comment on the issue to say you are picking it up — it saves two people doing the same work.
  3. Fork the repository and make your change on a branch.
  4. Open a pull request that references the issue number.

Research direction

Start by running the minimal Lean reproduction in the issue and compare the two elab_rules : tactic patterns. Investigate how tactic syntax patterns are matched, then confirm the version without the redundant tactic| prefix allows foo "hello" to elaborate successfully.

Written by the indexing model from the issue text.

Assessment

Domain
compilers
Issue type
Bug
Difficulty
3/5
Estimated time
1-2 days
Activity status
Stale
Clarity
Clearly specified
Newbie friendliness
35/100

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