revset: make generatorset.__nonzero__ lazy The 'for r in self:' call could trigger full consumption of the generator while we only need a single value. We also fast path if a single value got already computed. See inline comment for more details. This provide massive speedup for lazy operation using boolean testing. max(::tip) e5b507efb36e) wall 0.055609 comb 0.060000 user 0.060000 sys 0.000000 (best of 100) after change) wall 0.000109 comb 0.000000 user 0.000000 sys 0.000000 (best of 19146)