May a `&T` be stored in a struct field?

Decided

D-0003, settled by the language’s author: part of spec §18. Older text cites it as 18.3.

No — banned outright, with no escape hatch. References live only on the stack; context structs hold ^T (§5.2)

Refined by D-0093 (r89, r90): a view struct may hold references. It is itself placed only where a reference may be, so references still live only on the stack. Not yet implemented (T-0111).