c.f. https://wpt.fyi/results/css/CSS2/floats?label=master&product=chrome%5Bexperimental%5D&product=firefox%5Bexperimental%5D&product=safari-167%20preview%5Bexperimental%5D&product=safari-172%20preview&product=safari%5Bstable%5D&q=floats-rule3-outside%20%20001 bisect points at 262277@main as the culprit we don't have this imported in WebKit (bug 209735) see https://wpt.fyi/results/css/CSS2/floats/floats-rule3-outside-left-001.xht and https://wpt.fyi/results/css/CSS2/floats/floats-rule3-outside-right-001.xht
<rdar://problem/110903782>
While working on a test reduction I noticed that both Chrome and Firefox let floats overlap https://jsfiddle.net/65h4eykx/1/ very sus.
Created attachment 466764 [details] Patch
Comment on attachment 466764 [details] Patch Gallery quality ASCII art
(In reply to Antti Koivisto from comment #4) > Comment on attachment 466764 [details] > Patch > > Gallery quality ASCII art don't give me ideas
Created attachment 466767 [details] [fast-cq]Patch
Committed 265345@main (c03d0ac6e6db): <https://commits.webkit.org/265345@main> All reviewed patches have been landed. Closing bug and clearing flags on attachment 466767 [details].