rustc_middle/ty/
region.rs

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
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
use std::ops::Deref;

use rustc_data_structures::intern::Interned;
use rustc_errors::MultiSpan;
use rustc_hir::def_id::DefId;
use rustc_macros::{HashStable, TyDecodable, TyEncodable};
use rustc_span::symbol::{Symbol, kw, sym};
use rustc_span::{DUMMY_SP, ErrorGuaranteed};
use rustc_type_ir::RegionKind as IrRegionKind;
pub use rustc_type_ir::RegionVid;
use tracing::debug;

use crate::ty::{self, BoundVar, TyCtxt, TypeFlags};

pub type RegionKind<'tcx> = IrRegionKind<TyCtxt<'tcx>>;

/// Use this rather than `RegionKind`, whenever possible.
#[derive(Copy, Clone, PartialEq, Eq, Hash, HashStable)]
#[rustc_pass_by_value]
pub struct Region<'tcx>(pub Interned<'tcx, RegionKind<'tcx>>);

impl<'tcx> rustc_type_ir::inherent::IntoKind for Region<'tcx> {
    type Kind = RegionKind<'tcx>;

    fn kind(self) -> RegionKind<'tcx> {
        *self
    }
}

impl<'tcx> rustc_type_ir::visit::Flags for Region<'tcx> {
    fn flags(&self) -> TypeFlags {
        self.type_flags()
    }

    fn outer_exclusive_binder(&self) -> ty::DebruijnIndex {
        match **self {
            ty::ReBound(debruijn, _) => debruijn.shifted_in(1),
            _ => ty::INNERMOST,
        }
    }
}

impl<'tcx> Region<'tcx> {
    #[inline]
    pub fn new_early_param(
        tcx: TyCtxt<'tcx>,
        early_bound_region: ty::EarlyParamRegion,
    ) -> Region<'tcx> {
        tcx.intern_region(ty::ReEarlyParam(early_bound_region))
    }

    #[inline]
    pub fn new_bound(
        tcx: TyCtxt<'tcx>,
        debruijn: ty::DebruijnIndex,
        bound_region: ty::BoundRegion,
    ) -> Region<'tcx> {
        // Use a pre-interned one when possible.
        if let ty::BoundRegion { var, kind: ty::BoundRegionKind::Anon } = bound_region
            && let Some(inner) = tcx.lifetimes.re_late_bounds.get(debruijn.as_usize())
            && let Some(re) = inner.get(var.as_usize()).copied()
        {
            re
        } else {
            tcx.intern_region(ty::ReBound(debruijn, bound_region))
        }
    }

    #[inline]
    pub fn new_late_param(
        tcx: TyCtxt<'tcx>,
        scope: DefId,
        bound_region: ty::BoundRegionKind,
    ) -> Region<'tcx> {
        tcx.intern_region(ty::ReLateParam(ty::LateParamRegion { scope, bound_region }))
    }

    #[inline]
    pub fn new_var(tcx: TyCtxt<'tcx>, v: ty::RegionVid) -> Region<'tcx> {
        // Use a pre-interned one when possible.
        tcx.lifetimes
            .re_vars
            .get(v.as_usize())
            .copied()
            .unwrap_or_else(|| tcx.intern_region(ty::ReVar(v)))
    }

    #[inline]
    pub fn new_placeholder(tcx: TyCtxt<'tcx>, placeholder: ty::PlaceholderRegion) -> Region<'tcx> {
        tcx.intern_region(ty::RePlaceholder(placeholder))
    }

    /// Constructs a `RegionKind::ReError` region.
    #[track_caller]
    pub fn new_error(tcx: TyCtxt<'tcx>, guar: ErrorGuaranteed) -> Region<'tcx> {
        tcx.intern_region(ty::ReError(guar))
    }

    /// Constructs a `RegionKind::ReError` region and registers a delayed bug to ensure it gets
    /// used.
    #[track_caller]
    pub fn new_error_misc(tcx: TyCtxt<'tcx>) -> Region<'tcx> {
        Region::new_error_with_message(
            tcx,
            DUMMY_SP,
            "RegionKind::ReError constructed but no error reported",
        )
    }

    /// Constructs a `RegionKind::ReError` region and registers a delayed bug with the given `msg`
    /// to ensure it gets used.
    #[track_caller]
    pub fn new_error_with_message<S: Into<MultiSpan>>(
        tcx: TyCtxt<'tcx>,
        span: S,
        msg: &'static str,
    ) -> Region<'tcx> {
        let reported = tcx.dcx().span_delayed_bug(span, msg);
        Region::new_error(tcx, reported)
    }

    /// Avoid this in favour of more specific `new_*` methods, where possible,
    /// to avoid the cost of the `match`.
    pub fn new_from_kind(tcx: TyCtxt<'tcx>, kind: RegionKind<'tcx>) -> Region<'tcx> {
        match kind {
            ty::ReEarlyParam(region) => Region::new_early_param(tcx, region),
            ty::ReBound(debruijn, region) => Region::new_bound(tcx, debruijn, region),
            ty::ReLateParam(ty::LateParamRegion { scope, bound_region }) => {
                Region::new_late_param(tcx, scope, bound_region)
            }
            ty::ReStatic => tcx.lifetimes.re_static,
            ty::ReVar(vid) => Region::new_var(tcx, vid),
            ty::RePlaceholder(region) => Region::new_placeholder(tcx, region),
            ty::ReErased => tcx.lifetimes.re_erased,
            ty::ReError(reported) => Region::new_error(tcx, reported),
        }
    }
}

impl<'tcx> rustc_type_ir::inherent::Region<TyCtxt<'tcx>> for Region<'tcx> {
    fn new_bound(
        interner: TyCtxt<'tcx>,
        debruijn: ty::DebruijnIndex,
        var: ty::BoundRegion,
    ) -> Self {
        Region::new_bound(interner, debruijn, var)
    }

    fn new_anon_bound(tcx: TyCtxt<'tcx>, debruijn: ty::DebruijnIndex, var: ty::BoundVar) -> Self {
        Region::new_bound(tcx, debruijn, ty::BoundRegion { var, kind: ty::BoundRegionKind::Anon })
    }

    fn new_static(tcx: TyCtxt<'tcx>) -> Self {
        tcx.lifetimes.re_static
    }
}

/// Region utilities
impl<'tcx> Region<'tcx> {
    pub fn kind(self) -> RegionKind<'tcx> {
        *self.0.0
    }

    pub fn get_name(self) -> Option<Symbol> {
        if self.has_name() {
            match *self {
                ty::ReEarlyParam(ebr) => Some(ebr.name),
                ty::ReBound(_, br) => br.kind.get_name(),
                ty::ReLateParam(fr) => fr.bound_region.get_name(),
                ty::ReStatic => Some(kw::StaticLifetime),
                ty::RePlaceholder(placeholder) => placeholder.bound.kind.get_name(),
                _ => None,
            }
        } else {
            None
        }
    }

    pub fn get_name_or_anon(self) -> Symbol {
        match self.get_name() {
            Some(name) => name,
            None => sym::anon,
        }
    }

    /// Is this region named by the user?
    pub fn has_name(self) -> bool {
        match *self {
            ty::ReEarlyParam(ebr) => ebr.has_name(),
            ty::ReBound(_, br) => br.kind.is_named(),
            ty::ReLateParam(fr) => fr.bound_region.is_named(),
            ty::ReStatic => true,
            ty::ReVar(..) => false,
            ty::RePlaceholder(placeholder) => placeholder.bound.kind.is_named(),
            ty::ReErased => false,
            ty::ReError(_) => false,
        }
    }

    #[inline]
    pub fn is_error(self) -> bool {
        matches!(*self, ty::ReError(_))
    }

    #[inline]
    pub fn is_static(self) -> bool {
        matches!(*self, ty::ReStatic)
    }

    #[inline]
    pub fn is_erased(self) -> bool {
        matches!(*self, ty::ReErased)
    }

    #[inline]
    pub fn is_bound(self) -> bool {
        matches!(*self, ty::ReBound(..))
    }

    #[inline]
    pub fn is_placeholder(self) -> bool {
        matches!(*self, ty::RePlaceholder(..))
    }

    #[inline]
    pub fn bound_at_or_above_binder(self, index: ty::DebruijnIndex) -> bool {
        match *self {
            ty::ReBound(debruijn, _) => debruijn >= index,
            _ => false,
        }
    }

    pub fn type_flags(self) -> TypeFlags {
        let mut flags = TypeFlags::empty();

        match *self {
            ty::ReVar(..) => {
                flags = flags | TypeFlags::HAS_FREE_REGIONS;
                flags = flags | TypeFlags::HAS_FREE_LOCAL_REGIONS;
                flags = flags | TypeFlags::HAS_RE_INFER;
            }
            ty::RePlaceholder(..) => {
                flags = flags | TypeFlags::HAS_FREE_REGIONS;
                flags = flags | TypeFlags::HAS_FREE_LOCAL_REGIONS;
                flags = flags | TypeFlags::HAS_RE_PLACEHOLDER;
            }
            ty::ReEarlyParam(..) => {
                flags = flags | TypeFlags::HAS_FREE_REGIONS;
                flags = flags | TypeFlags::HAS_FREE_LOCAL_REGIONS;
                flags = flags | TypeFlags::HAS_RE_PARAM;
            }
            ty::ReLateParam { .. } => {
                flags = flags | TypeFlags::HAS_FREE_REGIONS;
                flags = flags | TypeFlags::HAS_FREE_LOCAL_REGIONS;
            }
            ty::ReStatic => {
                flags = flags | TypeFlags::HAS_FREE_REGIONS;
            }
            ty::ReBound(..) => {
                flags = flags | TypeFlags::HAS_RE_BOUND;
            }
            ty::ReErased => {
                flags = flags | TypeFlags::HAS_RE_ERASED;
            }
            ty::ReError(_) => {
                flags = flags | TypeFlags::HAS_FREE_REGIONS;
                flags = flags | TypeFlags::HAS_ERROR;
            }
        }

        debug!("type_flags({:?}) = {:?}", self, flags);

        flags
    }

    /// True for free regions other than `'static`.
    pub fn is_param(self) -> bool {
        matches!(*self, ty::ReEarlyParam(_) | ty::ReLateParam(_))
    }

    /// True for free region in the current context.
    ///
    /// This is the case for `'static` and param regions.
    pub fn is_free(self) -> bool {
        match *self {
            ty::ReStatic | ty::ReEarlyParam(..) | ty::ReLateParam(..) => true,
            ty::ReVar(..)
            | ty::RePlaceholder(..)
            | ty::ReBound(..)
            | ty::ReErased
            | ty::ReError(..) => false,
        }
    }

    pub fn is_var(self) -> bool {
        matches!(self.kind(), ty::ReVar(_))
    }

    pub fn as_var(self) -> RegionVid {
        match self.kind() {
            ty::ReVar(vid) => vid,
            _ => bug!("expected region {:?} to be of kind ReVar", self),
        }
    }

    /// Given some item `binding_item`, check if this region is a generic parameter introduced by it
    /// or one of the parent generics. Returns the `DefId` of the parameter definition if so.
    pub fn opt_param_def_id(self, tcx: TyCtxt<'tcx>, binding_item: DefId) -> Option<DefId> {
        match self.kind() {
            ty::ReEarlyParam(ebr) => {
                Some(tcx.generics_of(binding_item).region_param(ebr, tcx).def_id)
            }
            ty::ReLateParam(ty::LateParamRegion {
                bound_region: ty::BoundRegionKind::Named(def_id, _),
                ..
            }) => Some(def_id),
            _ => None,
        }
    }
}

impl<'tcx> Deref for Region<'tcx> {
    type Target = RegionKind<'tcx>;

    #[inline]
    fn deref(&self) -> &RegionKind<'tcx> {
        self.0.0
    }
}

#[derive(Copy, Clone, PartialEq, Eq, Hash, TyEncodable, TyDecodable)]
#[derive(HashStable)]
pub struct EarlyParamRegion {
    pub index: u32,
    pub name: Symbol,
}

impl rustc_type_ir::inherent::ParamLike for EarlyParamRegion {
    fn index(self) -> u32 {
        self.index
    }
}

impl std::fmt::Debug for EarlyParamRegion {
    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
        write!(f, "{}/#{}", self.name, self.index)
    }
}

#[derive(Clone, PartialEq, Eq, Hash, TyEncodable, TyDecodable, Copy)]
#[derive(HashStable)]
/// The parameter representation of late-bound function parameters, "some region
/// at least as big as the scope `fr.scope`".
///
/// Similar to a placeholder region as we create `LateParam` regions when entering a binder
/// except they are always in the root universe and instead of using a boundvar to distinguish
/// between others we use the `DefId` of the parameter. For this reason the `bound_region` field
/// should basically always be `BoundRegionKind::Named` as otherwise there is no way of telling
/// different parameters apart.
pub struct LateParamRegion {
    pub scope: DefId,
    pub bound_region: BoundRegionKind,
}

#[derive(Clone, PartialEq, Eq, Hash, TyEncodable, TyDecodable, Copy)]
#[derive(HashStable)]
pub enum BoundRegionKind {
    /// An anonymous region parameter for a given fn (&T)
    Anon,

    /// Named region parameters for functions (a in &'a T)
    ///
    /// The `DefId` is needed to distinguish free regions in
    /// the event of shadowing.
    Named(DefId, Symbol),

    /// Anonymous region for the implicit env pointer parameter
    /// to a closure
    ClosureEnv,
}

#[derive(Copy, Clone, PartialEq, Eq, Hash, TyEncodable, TyDecodable)]
#[derive(HashStable)]
pub struct BoundRegion {
    pub var: BoundVar,
    pub kind: BoundRegionKind,
}

impl<'tcx> rustc_type_ir::inherent::BoundVarLike<TyCtxt<'tcx>> for BoundRegion {
    fn var(self) -> BoundVar {
        self.var
    }

    fn assert_eq(self, var: ty::BoundVariableKind) {
        assert_eq!(self.kind, var.expect_region())
    }
}

impl core::fmt::Debug for BoundRegion {
    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
        match self.kind {
            BoundRegionKind::Anon => write!(f, "{:?}", self.var),
            BoundRegionKind::ClosureEnv => write!(f, "{:?}.Env", self.var),
            BoundRegionKind::Named(def, symbol) => {
                write!(f, "{:?}.Named({:?}, {:?})", self.var, def, symbol)
            }
        }
    }
}

impl BoundRegionKind {
    pub fn is_named(&self) -> bool {
        match *self {
            BoundRegionKind::Named(_, name) => name != kw::UnderscoreLifetime && name != kw::Empty,
            _ => false,
        }
    }

    pub fn get_name(&self) -> Option<Symbol> {
        if self.is_named() {
            match *self {
                BoundRegionKind::Named(_, name) => return Some(name),
                _ => unreachable!(),
            }
        }

        None
    }

    pub fn get_id(&self) -> Option<DefId> {
        match *self {
            BoundRegionKind::Named(id, _) => Some(id),
            _ => None,
        }
    }
}