summaryrefslogtreecommitdiffstats
path: root/compiler/rustc_middle/src/ty/generics.rs
blob: 48329da3e63326049a5878ba502c28f0b1c73a19 (plain)
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
use crate::ty;
use crate::ty::{EarlyBinder, SubstsRef};
use rustc_ast as ast;
use rustc_data_structures::fx::FxHashMap;
use rustc_hir::def_id::DefId;
use rustc_span::symbol::{kw, Symbol};
use rustc_span::Span;

use super::{EarlyBoundRegion, InstantiatedPredicates, ParamConst, ParamTy, Predicate, TyCtxt};

#[derive(Clone, Debug, TyEncodable, TyDecodable, HashStable)]
pub enum GenericParamDefKind {
    Lifetime,
    Type { has_default: bool, synthetic: bool },
    Const { has_default: bool },
}

impl GenericParamDefKind {
    pub fn descr(&self) -> &'static str {
        match self {
            GenericParamDefKind::Lifetime => "lifetime",
            GenericParamDefKind::Type { .. } => "type",
            GenericParamDefKind::Const { .. } => "constant",
        }
    }
    pub fn to_ord(&self) -> ast::ParamKindOrd {
        match self {
            GenericParamDefKind::Lifetime => ast::ParamKindOrd::Lifetime,
            GenericParamDefKind::Type { .. } | GenericParamDefKind::Const { .. } => {
                ast::ParamKindOrd::TypeOrConst
            }
        }
    }

    pub fn is_ty_or_const(&self) -> bool {
        match self {
            GenericParamDefKind::Lifetime => false,
            GenericParamDefKind::Type { .. } | GenericParamDefKind::Const { .. } => true,
        }
    }

    pub fn is_synthetic(&self) -> bool {
        match self {
            GenericParamDefKind::Type { synthetic, .. } => *synthetic,
            _ => false,
        }
    }
}

#[derive(Clone, Debug, TyEncodable, TyDecodable, HashStable)]
pub struct GenericParamDef {
    pub name: Symbol,
    pub def_id: DefId,
    pub index: u32,

    /// `pure_wrt_drop`, set by the (unsafe) `#[may_dangle]` attribute
    /// on generic parameter `'a`/`T`, asserts data behind the parameter
    /// `'a`/`T` won't be accessed during the parent type's `Drop` impl.
    pub pure_wrt_drop: bool,

    pub kind: GenericParamDefKind,
}

impl GenericParamDef {
    pub fn to_early_bound_region_data(&self) -> ty::EarlyBoundRegion {
        if let GenericParamDefKind::Lifetime = self.kind {
            ty::EarlyBoundRegion { def_id: self.def_id, index: self.index, name: self.name }
        } else {
            bug!("cannot convert a non-lifetime parameter def to an early bound region")
        }
    }

    pub fn has_default(&self) -> bool {
        match self.kind {
            GenericParamDefKind::Type { has_default, .. }
            | GenericParamDefKind::Const { has_default } => has_default,
            GenericParamDefKind::Lifetime => false,
        }
    }

    pub fn is_anonymous_lifetime(&self) -> bool {
        match self.kind {
            GenericParamDefKind::Lifetime => {
                self.name == kw::UnderscoreLifetime || self.name == kw::Empty
            }
            _ => false,
        }
    }

    pub fn default_value<'tcx>(
        &self,
        tcx: TyCtxt<'tcx>,
    ) -> Option<EarlyBinder<ty::GenericArg<'tcx>>> {
        match self.kind {
            GenericParamDefKind::Type { has_default, .. } if has_default => {
                Some(tcx.bound_type_of(self.def_id).map_bound(|t| t.into()))
            }
            GenericParamDefKind::Const { has_default } if has_default => {
                Some(tcx.bound_const_param_default(self.def_id).map_bound(|c| c.into()))
            }
            _ => None,
        }
    }

    pub fn to_error<'tcx>(
        &self,
        tcx: TyCtxt<'tcx>,
        preceding_substs: &[ty::GenericArg<'tcx>],
    ) -> ty::GenericArg<'tcx> {
        match &self.kind {
            ty::GenericParamDefKind::Lifetime => tcx.lifetimes.re_static.into(),
            ty::GenericParamDefKind::Type { .. } => tcx.ty_error().into(),
            ty::GenericParamDefKind::Const { .. } => {
                tcx.const_error(tcx.bound_type_of(self.def_id).subst(tcx, preceding_substs)).into()
            }
        }
    }
}

#[derive(Default)]
pub struct GenericParamCount {
    pub lifetimes: usize,
    pub types: usize,
    pub consts: usize,
}

/// Information about the formal type/lifetime parameters associated
/// with an item or method. Analogous to `hir::Generics`.
///
/// The ordering of parameters is the same as in `Subst` (excluding child generics):
/// `Self` (optionally), `Lifetime` params..., `Type` params...
#[derive(Clone, Debug, TyEncodable, TyDecodable, HashStable)]
pub struct Generics {
    pub parent: Option<DefId>,
    pub parent_count: usize,
    pub params: Vec<GenericParamDef>,

    /// Reverse map to the `index` field of each `GenericParamDef`.
    #[stable_hasher(ignore)]
    pub param_def_id_to_index: FxHashMap<DefId, u32>,

    pub has_self: bool,
    pub has_late_bound_regions: Option<Span>,
}

impl<'tcx> Generics {
    /// Looks through the generics and all parents to find the index of the
    /// given param def-id. This is in comparison to the `param_def_id_to_index`
    /// struct member, which only stores information about this item's own
    /// generics.
    pub fn param_def_id_to_index(&self, tcx: TyCtxt<'tcx>, def_id: DefId) -> Option<u32> {
        if let Some(idx) = self.param_def_id_to_index.get(&def_id) {
            Some(*idx)
        } else if let Some(parent) = self.parent {
            let parent = tcx.generics_of(parent);
            parent.param_def_id_to_index(tcx, def_id)
        } else {
            None
        }
    }

    #[inline]
    pub fn count(&self) -> usize {
        self.parent_count + self.params.len()
    }

    pub fn own_counts(&self) -> GenericParamCount {
        // We could cache this as a property of `GenericParamCount`, but
        // the aim is to refactor this away entirely eventually and the
        // presence of this method will be a constant reminder.
        let mut own_counts = GenericParamCount::default();

        for param in &self.params {
            match param.kind {
                GenericParamDefKind::Lifetime => own_counts.lifetimes += 1,
                GenericParamDefKind::Type { .. } => own_counts.types += 1,
                GenericParamDefKind::Const { .. } => own_counts.consts += 1,
            }
        }

        own_counts
    }

    pub fn own_defaults(&self) -> GenericParamCount {
        let mut own_defaults = GenericParamCount::default();

        for param in &self.params {
            match param.kind {
                GenericParamDefKind::Lifetime => (),
                GenericParamDefKind::Type { has_default, .. } => {
                    own_defaults.types += has_default as usize;
                }
                GenericParamDefKind::Const { has_default } => {
                    own_defaults.consts += has_default as usize;
                }
            }
        }

        own_defaults
    }

    pub fn requires_monomorphization(&self, tcx: TyCtxt<'tcx>) -> bool {
        if self.own_requires_monomorphization() {
            return true;
        }

        if let Some(parent_def_id) = self.parent {
            let parent = tcx.generics_of(parent_def_id);
            parent.requires_monomorphization(tcx)
        } else {
            false
        }
    }

    pub fn own_requires_monomorphization(&self) -> bool {
        for param in &self.params {
            match param.kind {
                GenericParamDefKind::Type { .. } | GenericParamDefKind::Const { .. } => {
                    return true;
                }
                GenericParamDefKind::Lifetime => {}
            }
        }
        false
    }

    /// Returns the `GenericParamDef` with the given index.
    pub fn param_at(&'tcx self, param_index: usize, tcx: TyCtxt<'tcx>) -> &'tcx GenericParamDef {
        if let Some(index) = param_index.checked_sub(self.parent_count) {
            &self.params[index]
        } else {
            tcx.generics_of(self.parent.expect("parent_count > 0 but no parent?"))
                .param_at(param_index, tcx)
        }
    }

    /// Returns the `GenericParamDef` associated with this `EarlyBoundRegion`.
    pub fn region_param(
        &'tcx self,
        param: &EarlyBoundRegion,
        tcx: TyCtxt<'tcx>,
    ) -> &'tcx GenericParamDef {
        let param = self.param_at(param.index as usize, tcx);
        match param.kind {
            GenericParamDefKind::Lifetime => param,
            _ => bug!("expected lifetime parameter, but found another generic parameter"),
        }
    }

    /// Returns the `GenericParamDef` associated with this `ParamTy`.
    pub fn type_param(&'tcx self, param: &ParamTy, tcx: TyCtxt<'tcx>) -> &'tcx GenericParamDef {
        let param = self.param_at(param.index as usize, tcx);
        match param.kind {
            GenericParamDefKind::Type { .. } => param,
            _ => bug!("expected type parameter, but found another generic parameter"),
        }
    }

    /// Returns the `GenericParamDef` associated with this `ParamConst`.
    pub fn const_param(&'tcx self, param: &ParamConst, tcx: TyCtxt<'tcx>) -> &GenericParamDef {
        let param = self.param_at(param.index as usize, tcx);
        match param.kind {
            GenericParamDefKind::Const { .. } => param,
            _ => bug!("expected const parameter, but found another generic parameter"),
        }
    }

    /// Returns `true` if `params` has `impl Trait`.
    pub fn has_impl_trait(&'tcx self) -> bool {
        self.params.iter().any(|param| {
            matches!(param.kind, ty::GenericParamDefKind::Type { synthetic: true, .. })
        })
    }

    /// Returns the substs corresponding to the generic parameters
    /// of this item, excluding `Self`.
    ///
    /// **This should only be used for diagnostics purposes.**
    pub fn own_substs_no_defaults(
        &'tcx self,
        tcx: TyCtxt<'tcx>,
        substs: &'tcx [ty::GenericArg<'tcx>],
    ) -> &'tcx [ty::GenericArg<'tcx>] {
        let mut own_params = self.parent_count..self.count();
        if self.has_self && self.parent.is_none() {
            own_params.start = 1;
        }

        // Filter the default arguments.
        //
        // This currently uses structural equality instead
        // of semantic equivalence. While not ideal, that's
        // good enough for now as this should only be used
        // for diagnostics anyways.
        own_params.end -= self
            .params
            .iter()
            .rev()
            .take_while(|param| {
                param.default_value(tcx).map_or(false, |default| {
                    default.subst(tcx, substs) == substs[param.index as usize]
                })
            })
            .count();

        &substs[own_params]
    }

    /// Returns the substs corresponding to the generic parameters of this item, excluding `Self`.
    ///
    /// **This should only be used for diagnostics purposes.**
    pub fn own_substs(
        &'tcx self,
        substs: &'tcx [ty::GenericArg<'tcx>],
    ) -> &'tcx [ty::GenericArg<'tcx>] {
        let own = &substs[self.parent_count..][..self.params.len()];
        if self.has_self && self.parent.is_none() { &own[1..] } else { &own }
    }
}

/// Bounds on generics.
#[derive(Copy, Clone, Default, Debug, TyEncodable, TyDecodable, HashStable)]
pub struct GenericPredicates<'tcx> {
    pub parent: Option<DefId>,
    pub predicates: &'tcx [(Predicate<'tcx>, Span)],
}

impl<'tcx> GenericPredicates<'tcx> {
    pub fn instantiate(
        &self,
        tcx: TyCtxt<'tcx>,
        substs: SubstsRef<'tcx>,
    ) -> InstantiatedPredicates<'tcx> {
        let mut instantiated = InstantiatedPredicates::empty();
        self.instantiate_into(tcx, &mut instantiated, substs);
        instantiated
    }

    pub fn instantiate_own(
        &self,
        tcx: TyCtxt<'tcx>,
        substs: SubstsRef<'tcx>,
    ) -> InstantiatedPredicates<'tcx> {
        InstantiatedPredicates {
            predicates: self
                .predicates
                .iter()
                .map(|(p, _)| EarlyBinder(*p).subst(tcx, substs))
                .collect(),
            spans: self.predicates.iter().map(|(_, sp)| *sp).collect(),
        }
    }

    #[instrument(level = "debug", skip(self, tcx))]
    fn instantiate_into(
        &self,
        tcx: TyCtxt<'tcx>,
        instantiated: &mut InstantiatedPredicates<'tcx>,
        substs: SubstsRef<'tcx>,
    ) {
        if let Some(def_id) = self.parent {
            tcx.predicates_of(def_id).instantiate_into(tcx, instantiated, substs);
        }
        instantiated
            .predicates
            .extend(self.predicates.iter().map(|(p, _)| EarlyBinder(*p).subst(tcx, substs)));
        instantiated.spans.extend(self.predicates.iter().map(|(_, sp)| *sp));
    }

    pub fn instantiate_identity(&self, tcx: TyCtxt<'tcx>) -> InstantiatedPredicates<'tcx> {
        let mut instantiated = InstantiatedPredicates::empty();
        self.instantiate_identity_into(tcx, &mut instantiated);
        instantiated
    }

    fn instantiate_identity_into(
        &self,
        tcx: TyCtxt<'tcx>,
        instantiated: &mut InstantiatedPredicates<'tcx>,
    ) {
        if let Some(def_id) = self.parent {
            tcx.predicates_of(def_id).instantiate_identity_into(tcx, instantiated);
        }
        instantiated.predicates.extend(self.predicates.iter().map(|(p, _)| p));
        instantiated.spans.extend(self.predicates.iter().map(|(_, s)| s));
    }
}