Lean 4 fork for HoTT-compatible kernel extensions (Path types, transport, HITs). Maintained against upstream leanprover/lean4.
74e7886ce7
Adds a simple error-recovery mechanism to Lean's parser, similar to those used in other combinator parsing libraries. Lean itself isn't very amenable to error recovery with this mechanism, as it requires global knowledge of the grammar in question to write recovery rules that don't break backtracking or `<|>`. I only found a few opportunities. But for DSLs, this is really important. In particular, Verso parse errors interacted very badly with Lean parse errors in a way that required frequent "restart file" commands, but this mechanism allows me to both recover from Verso parse errors and to have Lean skip the rest of the file rather than repeatedly trying to parse it as Lean commands. |
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This is the repository for Lean 4.
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