leanprover / leanprover/lean4

Regression in whitespace-insensitive tactic parsing

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Description

example : True := by { skip;
  trivial }

fails with a parse error unless the indentation of trivial is greater or equal to the column of skip. cc: @gebner (since this is almost certainly fallout of #1612 and #1622)

Contributor guide

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First steps

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  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 reproducing the Lean example and inspect the tactic parser behavior around whitespace and indentation. Review the fallout referenced from #1612 and #1622, then verify that trivial parses regardless of whether its indentation is less than skip.

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
Mostly clear
Newbie friendliness
45/100

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