lean-ja / lean-ja/lean-by-example
エラーの位置を変更する例
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コード例
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Description
metaprogramming in lean より
open Lean
-- エラーの位置を細かく指定する例
syntax "error_position" ident : term
macro_rules
| `(error_position all) => Macro.throwError "Ahhh"
-- the `%$tk` syntax gives us the Syntax of the thing before the %,
-- in this case `error_position`, giving it the name `tk`
| `(error_position%$tk first) => withRef tk (Macro.throwError "Ahhh")
#check_failure error_position all -- the error is indicated at `error_position all`
#check_failure error_position first -- the error is only indicated at `error_position`
Contributor guide
First steps
- Read the whole issue, then the project's contributing guide.
- Comment on the issue to say you are picking it up — it saves two people doing the same work.
- Fork the repository and make your change on a branch.
- Open a pull request that references the issue number.
Research direction
No source file or test is named. Start by locating the existing Lean metaprogramming documentation and checking how code examples are organized; confirm whether this error-position example is missing or needs correction, then verify that the documented example renders and demonstrates the stated error locations.
Written by the indexing model from the issue text.
Assessment
- Domain
- documentation
- Issue type
- Documentation
- Difficulty
- 2/5
- Estimated time
- 1-3 hours
- Activity status
- Stale
- Clarity
- Needs clarification
- Newbie friendliness
- 35/100