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
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
|
use crate::ty::query::Providers;
use crate::hir::def_id::DefId;
use crate::hir;
use crate::ty::TyCtxt;
use syntax_pos::symbol::Symbol;
use crate::hir::map::blocks::FnLikeNode;
use syntax::attr;
impl<'tcx> TyCtxt<'tcx> {
/// Whether the `def_id` counts as const fn in your current crate, considering all active
/// feature gates
pub fn is_const_fn(self, def_id: DefId) -> bool {
self.is_const_fn_raw(def_id) && match self.is_unstable_const_fn(def_id) {
Some(feature_name) => {
// has a `rustc_const_unstable` attribute, check whether the user enabled the
// corresponding feature gate.
self.features()
.declared_lib_features
.iter()
.any(|&(sym, _)| sym == feature_name)
},
// functions without const stability are either stable user written
// const fn or the user is using feature gates and we thus don't
// care what they do
None => true,
}
}
/// Whether the `def_id` is an unstable const fn and what feature gate is necessary to enable it
pub fn is_unstable_const_fn(self, def_id: DefId) -> Option<Symbol> {
if self.is_const_fn_raw(def_id) {
self.lookup_stability(def_id)?.const_stability
} else {
None
}
}
/// Returns `true` if this function must conform to `min_const_fn`
pub fn is_min_const_fn(self, def_id: DefId) -> bool {
// Bail out if the signature doesn't contain `const`
if !self.is_const_fn_raw(def_id) {
return false;
}
if self.features().staged_api {
// in order for a libstd function to be considered min_const_fn
// it needs to be stable and have no `rustc_const_unstable` attribute
match self.lookup_stability(def_id) {
// stable functions with unstable const fn aren't `min_const_fn`
Some(&attr::Stability { const_stability: Some(_), .. }) => false,
// unstable functions don't need to conform
Some(&attr::Stability { ref level, .. }) if level.is_unstable() => false,
// everything else needs to conform, because it would be callable from
// other `min_const_fn` functions
_ => true,
}
} else {
// users enabling the `const_fn` feature gate can do what they want
!self.features().const_fn
}
}
}
pub fn provide(providers: &mut Providers<'_>) {
/// only checks whether the function has a `const` modifier
fn is_const_fn_raw(tcx: TyCtxt<'_>, def_id: DefId) -> bool {
let hir_id = tcx.hir().as_local_hir_id(def_id)
.expect("Non-local call to local provider is_const_fn");
let node = tcx.hir().get(hir_id);
if let Some(fn_like) = FnLikeNode::from_node(node) {
fn_like.constness() == hir::Constness::Const
} else if let hir::Node::Ctor(_) = node {
true
} else {
false
}
}
fn is_promotable_const_fn(tcx: TyCtxt<'_>, def_id: DefId) -> bool {
tcx.is_const_fn(def_id) && match tcx.lookup_stability(def_id) {
Some(stab) => {
if cfg!(debug_assertions) && stab.promotable {
let sig = tcx.fn_sig(def_id);
assert_eq!(
sig.unsafety(),
hir::Unsafety::Normal,
"don't mark const unsafe fns as promotable",
// https://github.com/rust-lang/rust/pull/53851#issuecomment-418760682
);
}
stab.promotable
},
None => false,
}
}
fn const_fn_is_allowed_fn_ptr(tcx: TyCtxt<'_>, def_id: DefId) -> bool {
tcx.is_const_fn(def_id) &&
tcx.lookup_stability(def_id)
.map(|stab| stab.allow_const_fn_ptr).unwrap_or(false)
}
*providers = Providers {
is_const_fn_raw,
is_promotable_const_fn,
const_fn_is_allowed_fn_ptr,
..*providers
};
}
|
