1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
|
use rustc_middle::ty::{self, Ty, TyCtxt};
pub use rustc_middle::traits::query::{DropckConstraint, DropckOutlivesResult};
/// This returns true if the type `ty` is "trivial" for
/// dropck-outlives -- that is, if it doesn't require any types to
/// outlive. This is similar but not *quite* the same as the
/// `needs_drop` test in the compiler already -- that is, for every
/// type T for which this function return true, needs-drop would
/// return `false`. But the reverse does not hold: in particular,
/// `needs_drop` returns false for `PhantomData`, but it is not
/// trivial for dropck-outlives.
///
/// Note also that `needs_drop` requires a "global" type (i.e., one
/// with erased regions), but this function does not.
///
// FIXME(@lcnr): remove this module and move this function somewhere else.
pub fn trivial_dropck_outlives<'tcx>(tcx: TyCtxt<'tcx>, ty: Ty<'tcx>) -> bool {
match ty.kind() {
// None of these types have a destructor and hence they do not
// require anything in particular to outlive the dtor's
// execution.
ty::Infer(ty::FreshIntTy(_))
| ty::Infer(ty::FreshFloatTy(_))
| ty::Bool
| ty::Int(_)
| ty::Uint(_)
| ty::Float(_)
| ty::Never
| ty::FnDef(..)
| ty::FnPtr(_)
| ty::Char
| ty::GeneratorWitness(..)
| ty::RawPtr(_)
| ty::Ref(..)
| ty::Str
| ty::Foreign(..)
| ty::Error(_) => true,
// [T; N] and [T] have same properties as T.
ty::Array(ty, _) | ty::Slice(ty) => trivial_dropck_outlives(tcx, *ty),
// (T1..Tn) and closures have same properties as T1..Tn --
// check if *all* of them are trivial.
ty::Tuple(tys) => tys.iter().all(|t| trivial_dropck_outlives(tcx, t)),
ty::Closure(_, ref substs) => {
trivial_dropck_outlives(tcx, substs.as_closure().tupled_upvars_ty())
}
ty::Adt(def, _) => {
if Some(def.did()) == tcx.lang_items().manually_drop() {
// `ManuallyDrop` never has a dtor.
true
} else {
// Other types might. Moreover, PhantomData doesn't
// have a dtor, but it is considered to own its
// content, so it is non-trivial. Unions can have `impl Drop`,
// and hence are non-trivial as well.
false
}
}
// The following *might* require a destructor: needs deeper inspection.
ty::Dynamic(..)
| ty::Alias(..)
| ty::Param(_)
| ty::Placeholder(..)
| ty::Infer(_)
| ty::Bound(..)
| ty::Generator(..) => false,
}
}
|
