fix: normalize instance argument in getStuckMVar? for class projections#12778
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leodemoura merged 1 commit intomasterfrom Mar 3, 2026
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fix: normalize instance argument in getStuckMVar? for class projections#12778leodemoura merged 1 commit intomasterfrom
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…ns (#12778) This PR fixes an inconsistency in `getStuckMVar?` where the instance argument to class projection functions and auxiliary parent projections was not whnf-normalized before checking for stuck metavariables. Every other case in `getStuckMVar?` (recursors, quotient recursors, `.proj` nodes) normalizes the major argument via `whnf` before recursing — class projection functions and aux parent projections were the exception. This bug was identified by Matthew Jasper. When the instance parameter to a class projection is not normalized, `getStuckMVar?` may fail to detect stuck metavariables that would be revealed by whnf, or conversely may report stuckness for expressions that would reduce to constructors. This caused issues with `OfNat` and `Zero` at `with_reducible_and_instances` transparency. Note: PR #12701 (already merged) is also required to fix the original Mathlib examples.
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This PR fixes an inconsistency in
getStuckMVar?where the instance argument to class projection functions and auxiliary parent projections was not whnf-normalized before checking for stuck metavariables. Every other case ingetStuckMVar?(recursors, quotient recursors,.projnodes) normalizes the major argument viawhnfbefore recursing — class projection functions and aux parent projections were the exception.This bug was identified by Matthew Jasper. When the instance parameter to a class projection is not normalized,
getStuckMVar?may fail to detect stuck metavariables that would be revealed by whnf, or conversely may report stuckness for expressions that would reduce to constructors. This caused issues withOfNatandZeroatwith_reducible_and_instancestransparency.Note: PR #12701 (already merged) is also required to fix the original Mathlib examples.