Commit 2024-01-18 09:44 158d8524

feat: construct Haar measure in locally compact non-Hausdorff groups (#9746) The construction we have is given in T2 spaces, but it works in non-Hausdorff spaces modulo a few modifications. For this, we introduce an ad hoc class T2OrLocallyCompactRegularSpace, which is just enough to unify the arguments, as a replacement for the class ClosableCompactSubsetOpenSpace (which is not strong enough). In the file Separation.lean, we move some material that was only available on T2 spaces to this new class. The construction is needed for a forthcoming improvement of uniqueness results for Haar measures, based on https://mathoverflow.net/questions/456670/uniqueness-of-left-invariant-borel-probability-measure-on-compact-groups.