Lean 4 fork for HoTT-compatible kernel extensions (Path types, transport, HITs). Maintained against upstream leanprover/lean4.
490c79502b
This PR fixes #12846, where the new do elaborator produced confusing errors when a do element's continuation had a mismatched monadic result type. The errors were misleading both in location (e.g., pointing at the value of `let x ← value` rather than the `let` keyword) and in content (e.g., mentioning `PUnit.unit` which the user never wrote). The fix introduces `DoElemCont.ensureUnitAt`/`ensureHasTypeAt`, which check the continuation result type early and report mismatches with a clear message ("The `do` element has monadic result type ... but the rest of the `do` block has monadic result type ..."). Each do-element elaborator (`let`, `have`, `let rec`, `for`, `unless`, `dbg_trace`, `assert!`, `idbg`, etc.) now captures its keyword token via `%$tk` and passes it to `ensureUnitAt` so that the error points at the do element rather than at an internal elaboration artifact. The old ad-hoc type check in `for` and the confusing `ensureHasType` call in `continueWithUnit` are replaced by this uniform mechanism. Additionally, `extractMonadInfo` now calls `instantiateMVars` on the expected type, and `While.lean`/`If.lean` macros propagate token info through their expansions. Closes #12846 --------- Co-authored-by: Rob23oba <robin.arnez@web.de> |
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