DIP Proposal: @manualScoped to prevent automatic field destruction

[FeepingCreature]

A new UDA is introduced: @manualScoped. It is valid for fields in 
structs and classes, as well as variables and parameters. Fields 
marked with @manualScoped are not automatically destructed on 
scope end.

For instance, a function taking a struct as a @manualScoped value 
will lead to a copy constructor call, but no destructor call. It 
is assumed the passed value will be moved into another field via 
move() or moveEmplace().

In @safe, only @manualScoped fields may be initialized with 
.init. This is to indicate that init represents a hole in the 
typesystem, and using it forces you to engage in manual lifecycle 
management.

The goal of this DIP is to make the union hack unnecessary and 
resolve the value/variable problem with .init initialized struct 
destruction, where { S s = S.init; } led to a destructor call but 
no corresponding constructor call.

Opinions?