leanprover / leanprover/lean4

doc comment error message is confusing

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#7,591 2 comments 1 reaction 0 assignees View on GitHub

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Description

Say I do something like

/-- illegal -/
namespace A
end A

That gives error:

unexpected token 'namespace'; expected '#guard_msgs', 'abbrev', 'add_decl_doc', 'axiom', 'binder_predicate', ..

This is a bit confusing, and maybe there should be something mentioning that namespace (and import etc) can't have doc comments on them.

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First steps

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  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 snippet in the issue and inspect how the parser reports an illegal doc comment before a namespace. Determine the intended diagnostic for namespace and import declarations, then add or update focused parser tests so the resulting message clearly explains that these declarations cannot have doc comments.

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
35/100

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