056f589fb8
two-phase borrows: support multiple activations in one statement The need for this has arisen since the introduction of two-phase borrows on method autorefs in #49348. r'ing @pnkfelix to keep things off Niko's plate so he can make this redundant, and @pnkfelix is familiar with the code. Fixes #49635 Fixes #49662 r? @pnkfelix