mathlib4 fix(to_fun): fix the `@[to_fun]` attribute when the proof is not by reflexivity

This PR fixes the bug in @[to_fun] reported in https://leanprover.zulipchat.com/#narrow/channel/287929-mathlib4/topic/.60to_fun.60.20tactic/with/563623809

Dec 14 '25 03:12 JovanGerb

PR summary e182c0d3c4

Import changes for modified files

No significant changes to the import graph

Import changes for all files

Files	Import difference

Declarations diff

+ Function.mul_comm' + Pi.mul_def'

You can run this locally as follows

## summary with just the declaration names:
./scripts/declarations_diff.sh <optional_commit>

## more verbose report:
./scripts/declarations_diff.sh long <optional_commit>

The doc-module for script/declarations_diff.sh contains some details about this script.

No changes to technical debt.

You can run this locally as

./scripts/technical-debt-metrics.sh pr_summary

The relative value is the weighted sum of the differences with weight given by the inverse of the current value of the statistic.
The absolute value is the relative value divided by the total sum of the inverses of the current values (i.e. the weighted average of the differences).