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Commit | Line | Data |
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f035d41b XL |
1 | use rustc_middle::mir::visit::Visitor; |
2 | use rustc_middle::mir::{self, BasicBlock, Location}; | |
3 | use rustc_middle::ty::TyCtxt; | |
c295e0f8 | 4 | use rustc_span::{symbol::sym, Span}; |
f035d41b | 5 | |
94222f64 | 6 | use super::check::Qualifs; |
1b1a35ee | 7 | use super::ops::{self, NonConstOp}; |
c295e0f8 | 8 | use super::qualifs::{NeedsNonConstDrop, Qualif}; |
f035d41b XL |
9 | use super::ConstCx; |
10 | ||
11 | /// Returns `true` if we should use the more precise live drop checker that runs after drop | |
12 | /// elaboration. | |
1b1a35ee XL |
13 | pub fn checking_enabled(ccx: &ConstCx<'_, '_>) -> bool { |
14 | // Const-stable functions must always use the stable live drop checker. | |
15 | if ccx.is_const_stable_const_fn() { | |
16 | return false; | |
17 | } | |
18 | ||
19 | ccx.tcx.features().const_precise_live_drops | |
f035d41b XL |
20 | } |
21 | ||
22 | /// Look for live drops in a const context. | |
23 | /// | |
24 | /// This is separate from the rest of the const checking logic because it must run after drop | |
25 | /// elaboration. | |
29967ef6 XL |
26 | pub fn check_live_drops(tcx: TyCtxt<'tcx>, body: &mir::Body<'tcx>) { |
27 | let def_id = body.source.def_id().expect_local(); | |
f035d41b XL |
28 | let const_kind = tcx.hir().body_const_context(def_id); |
29 | if const_kind.is_none() { | |
30 | return; | |
31 | } | |
32 | ||
c295e0f8 XL |
33 | if tcx.has_attr(def_id.to_def_id(), sym::rustc_do_not_const_check) { |
34 | return; | |
35 | } | |
36 | ||
29967ef6 | 37 | let ccx = ConstCx { body, tcx, const_kind, param_env: tcx.param_env(def_id) }; |
1b1a35ee | 38 | if !checking_enabled(&ccx) { |
f035d41b XL |
39 | return; |
40 | } | |
41 | ||
f035d41b XL |
42 | let mut visitor = CheckLiveDrops { ccx: &ccx, qualifs: Qualifs::default() }; |
43 | ||
44 | visitor.visit_body(body); | |
45 | } | |
46 | ||
47 | struct CheckLiveDrops<'mir, 'tcx> { | |
48 | ccx: &'mir ConstCx<'mir, 'tcx>, | |
49 | qualifs: Qualifs<'mir, 'tcx>, | |
50 | } | |
51 | ||
52 | // So we can access `body` and `tcx`. | |
53 | impl std::ops::Deref for CheckLiveDrops<'mir, 'tcx> { | |
54 | type Target = ConstCx<'mir, 'tcx>; | |
55 | ||
56 | fn deref(&self) -> &Self::Target { | |
57 | &self.ccx | |
58 | } | |
59 | } | |
60 | ||
61 | impl CheckLiveDrops<'mir, 'tcx> { | |
62 | fn check_live_drop(&self, span: Span) { | |
1b1a35ee | 63 | ops::LiveDrop { dropped_at: None }.build_error(self.ccx, span).emit(); |
f035d41b XL |
64 | } |
65 | } | |
66 | ||
67 | impl Visitor<'tcx> for CheckLiveDrops<'mir, 'tcx> { | |
68 | fn visit_basic_block_data(&mut self, bb: BasicBlock, block: &mir::BasicBlockData<'tcx>) { | |
69 | trace!("visit_basic_block_data: bb={:?} is_cleanup={:?}", bb, block.is_cleanup); | |
70 | ||
71 | // Ignore drop terminators in cleanup blocks. | |
72 | if block.is_cleanup { | |
73 | return; | |
74 | } | |
75 | ||
76 | self.super_basic_block_data(bb, block); | |
77 | } | |
78 | ||
79 | fn visit_terminator(&mut self, terminator: &mir::Terminator<'tcx>, location: Location) { | |
80 | trace!("visit_terminator: terminator={:?} location={:?}", terminator, location); | |
81 | ||
82 | match &terminator.kind { | |
83 | mir::TerminatorKind::Drop { place: dropped_place, .. } => { | |
84 | let dropped_ty = dropped_place.ty(self.body, self.tcx).ty; | |
c295e0f8 XL |
85 | if !NeedsNonConstDrop::in_any_value_of_ty(self.ccx, dropped_ty) { |
86 | // Instead of throwing a bug, we just return here. This is because we have to | |
87 | // run custom `const Drop` impls. | |
88 | return; | |
f035d41b XL |
89 | } |
90 | ||
91 | if dropped_place.is_indirect() { | |
92 | self.check_live_drop(terminator.source_info.span); | |
93 | return; | |
94 | } | |
95 | ||
cdc7bbd5 XL |
96 | // Drop elaboration is not precise enough to accept code like |
97 | // `src/test/ui/consts/control-flow/drop-pass.rs`; e.g., when an `Option<Vec<T>>` is | |
98 | // initialized with `None` and never changed, it still emits drop glue. | |
99 | // Hence we additionally check the qualifs here to allow more code to pass. | |
f035d41b XL |
100 | if self.qualifs.needs_drop(self.ccx, dropped_place.local, location) { |
101 | // Use the span where the dropped local was declared for the error. | |
102 | let span = self.body.local_decls[dropped_place.local].source_info.span; | |
103 | self.check_live_drop(span); | |
104 | } | |
105 | } | |
106 | ||
107 | mir::TerminatorKind::DropAndReplace { .. } => span_bug!( | |
108 | terminator.source_info.span, | |
109 | "`DropAndReplace` should be removed by drop elaboration", | |
110 | ), | |
111 | ||
112 | mir::TerminatorKind::Abort | |
113 | | mir::TerminatorKind::Call { .. } | |
114 | | mir::TerminatorKind::Assert { .. } | |
115 | | mir::TerminatorKind::FalseEdge { .. } | |
116 | | mir::TerminatorKind::FalseUnwind { .. } | |
117 | | mir::TerminatorKind::GeneratorDrop | |
118 | | mir::TerminatorKind::Goto { .. } | |
119 | | mir::TerminatorKind::InlineAsm { .. } | |
120 | | mir::TerminatorKind::Resume | |
121 | | mir::TerminatorKind::Return | |
122 | | mir::TerminatorKind::SwitchInt { .. } | |
123 | | mir::TerminatorKind::Unreachable | |
124 | | mir::TerminatorKind::Yield { .. } => {} | |
125 | } | |
126 | } | |
127 | } |