rustc_middle/mir/
query.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
//! Values computed by queries that use MIR.

use std::cell::Cell;
use std::fmt::{self, Debug};

use derive_where::derive_where;
use rustc_abi::{FieldIdx, VariantIdx};
use rustc_data_structures::fx::FxIndexMap;
use rustc_errors::ErrorGuaranteed;
use rustc_hir::def_id::LocalDefId;
use rustc_index::bit_set::{BitMatrix, BitSet};
use rustc_index::{Idx, IndexVec};
use rustc_macros::{HashStable, TyDecodable, TyEncodable, TypeFoldable, TypeVisitable};
use rustc_span::Span;
use rustc_span::symbol::Symbol;
use smallvec::SmallVec;

use super::{ConstValue, SourceInfo};
use crate::mir;
use crate::ty::fold::fold_regions;
use crate::ty::{self, CoroutineArgsExt, OpaqueHiddenType, Ty, TyCtxt};

rustc_index::newtype_index! {
    #[derive(HashStable)]
    #[encodable]
    #[debug_format = "_{}"]
    pub struct CoroutineSavedLocal {}
}

#[derive(Clone, Debug, PartialEq, Eq)]
#[derive(TyEncodable, TyDecodable, HashStable, TypeFoldable, TypeVisitable)]
pub struct CoroutineSavedTy<'tcx> {
    pub ty: Ty<'tcx>,
    /// Source info corresponding to the local in the original MIR body.
    pub source_info: SourceInfo,
    /// Whether the local should be ignored for trait bound computations.
    pub ignore_for_traits: bool,
}

/// The layout of coroutine state.
#[derive(Clone, PartialEq, Eq)]
#[derive(TyEncodable, TyDecodable, HashStable, TypeFoldable, TypeVisitable)]
pub struct CoroutineLayout<'tcx> {
    /// The type of every local stored inside the coroutine.
    pub field_tys: IndexVec<CoroutineSavedLocal, CoroutineSavedTy<'tcx>>,

    /// The name for debuginfo.
    pub field_names: IndexVec<CoroutineSavedLocal, Option<Symbol>>,

    /// Which of the above fields are in each variant. Note that one field may
    /// be stored in multiple variants.
    pub variant_fields: IndexVec<VariantIdx, IndexVec<FieldIdx, CoroutineSavedLocal>>,

    /// The source that led to each variant being created (usually, a yield or
    /// await).
    pub variant_source_info: IndexVec<VariantIdx, SourceInfo>,

    /// Which saved locals are storage-live at the same time. Locals that do not
    /// have conflicts with each other are allowed to overlap in the computed
    /// layout.
    #[type_foldable(identity)]
    #[type_visitable(ignore)]
    pub storage_conflicts: BitMatrix<CoroutineSavedLocal, CoroutineSavedLocal>,
}

impl Debug for CoroutineLayout<'_> {
    fn fmt(&self, fmt: &mut fmt::Formatter<'_>) -> fmt::Result {
        /// Prints an iterator of (key, value) tuples as a map.
        struct MapPrinter<'a, K, V>(Cell<Option<Box<dyn Iterator<Item = (K, V)> + 'a>>>);
        impl<'a, K, V> MapPrinter<'a, K, V> {
            fn new(iter: impl Iterator<Item = (K, V)> + 'a) -> Self {
                Self(Cell::new(Some(Box::new(iter))))
            }
        }
        impl<'a, K: Debug, V: Debug> Debug for MapPrinter<'a, K, V> {
            fn fmt(&self, fmt: &mut fmt::Formatter<'_>) -> fmt::Result {
                fmt.debug_map().entries(self.0.take().unwrap()).finish()
            }
        }

        /// Prints the coroutine variant name.
        struct GenVariantPrinter(VariantIdx);
        impl From<VariantIdx> for GenVariantPrinter {
            fn from(idx: VariantIdx) -> Self {
                GenVariantPrinter(idx)
            }
        }
        impl Debug for GenVariantPrinter {
            fn fmt(&self, fmt: &mut fmt::Formatter<'_>) -> fmt::Result {
                let variant_name = ty::CoroutineArgs::variant_name(self.0);
                if fmt.alternate() {
                    write!(fmt, "{:9}({:?})", variant_name, self.0)
                } else {
                    write!(fmt, "{variant_name}")
                }
            }
        }

        /// Forces its contents to print in regular mode instead of alternate mode.
        struct OneLinePrinter<T>(T);
        impl<T: Debug> Debug for OneLinePrinter<T> {
            fn fmt(&self, fmt: &mut fmt::Formatter<'_>) -> fmt::Result {
                write!(fmt, "{:?}", self.0)
            }
        }

        fmt.debug_struct("CoroutineLayout")
            .field("field_tys", &MapPrinter::new(self.field_tys.iter_enumerated()))
            .field(
                "variant_fields",
                &MapPrinter::new(
                    self.variant_fields
                        .iter_enumerated()
                        .map(|(k, v)| (GenVariantPrinter(k), OneLinePrinter(v))),
                ),
            )
            .field("storage_conflicts", &self.storage_conflicts)
            .finish()
    }
}

#[derive(Debug, TyEncodable, TyDecodable, HashStable)]
pub struct BorrowCheckResult<'tcx> {
    /// All the opaque types that are restricted to concrete types
    /// by this function. Unlike the value in `TypeckResults`, this has
    /// unerased regions.
    pub concrete_opaque_types: FxIndexMap<LocalDefId, OpaqueHiddenType<'tcx>>,
    pub closure_requirements: Option<ClosureRegionRequirements<'tcx>>,
    pub used_mut_upvars: SmallVec<[FieldIdx; 8]>,
    pub tainted_by_errors: Option<ErrorGuaranteed>,
}

/// The result of the `mir_const_qualif` query.
///
/// Each field (except `tainted_by_errors`) corresponds to an implementer of the `Qualif` trait in
/// `rustc_const_eval/src/transform/check_consts/qualifs.rs`. See that file for more information on each
/// `Qualif`.
#[derive(Clone, Copy, Debug, Default, TyEncodable, TyDecodable, HashStable)]
pub struct ConstQualifs {
    pub has_mut_interior: bool,
    pub needs_drop: bool,
    pub needs_non_const_drop: bool,
    pub tainted_by_errors: Option<ErrorGuaranteed>,
}

/// After we borrow check a closure, we are left with various
/// requirements that we have inferred between the free regions that
/// appear in the closure's signature or on its field types. These
/// requirements are then verified and proved by the closure's
/// creating function. This struct encodes those requirements.
///
/// The requirements are listed as being between various `RegionVid`. The 0th
/// region refers to `'static`; subsequent region vids refer to the free
/// regions that appear in the closure (or coroutine's) type, in order of
/// appearance. (This numbering is actually defined by the `UniversalRegions`
/// struct in the NLL region checker. See for example
/// `UniversalRegions::closure_mapping`.) Note the free regions in the
/// closure's signature and captures are erased.
///
/// Example: If type check produces a closure with the closure args:
///
/// ```text
/// ClosureArgs = [
///     'a,                                         // From the parent.
///     'b,
///     i8,                                         // the "closure kind"
///     for<'x> fn(&'<erased> &'x u32) -> &'x u32,  // the "closure signature"
///     &'<erased> String,                          // some upvar
/// ]
/// ```
///
/// We would "renumber" each free region to a unique vid, as follows:
///
/// ```text
/// ClosureArgs = [
///     '1,                                         // From the parent.
///     '2,
///     i8,                                         // the "closure kind"
///     for<'x> fn(&'3 &'x u32) -> &'x u32,         // the "closure signature"
///     &'4 String,                                 // some upvar
/// ]
/// ```
///
/// Now the code might impose a requirement like `'1: '2`. When an
/// instance of the closure is created, the corresponding free regions
/// can be extracted from its type and constrained to have the given
/// outlives relationship.
#[derive(Clone, Debug, TyEncodable, TyDecodable, HashStable)]
pub struct ClosureRegionRequirements<'tcx> {
    /// The number of external regions defined on the closure. In our
    /// example above, it would be 3 -- one for `'static`, then `'1`
    /// and `'2`. This is just used for a sanity check later on, to
    /// make sure that the number of regions we see at the callsite
    /// matches.
    pub num_external_vids: usize,

    /// Requirements between the various free regions defined in
    /// indices.
    pub outlives_requirements: Vec<ClosureOutlivesRequirement<'tcx>>,
}

/// Indicates an outlives-constraint between a type or between two
/// free regions declared on the closure.
#[derive(Copy, Clone, Debug, TyEncodable, TyDecodable, HashStable)]
pub struct ClosureOutlivesRequirement<'tcx> {
    // This region or type ...
    pub subject: ClosureOutlivesSubject<'tcx>,

    // ... must outlive this one.
    pub outlived_free_region: ty::RegionVid,

    // If not, report an error here ...
    pub blame_span: Span,

    // ... due to this reason.
    pub category: ConstraintCategory<'tcx>,
}

// Make sure this enum doesn't unintentionally grow
#[cfg(target_pointer_width = "64")]
rustc_data_structures::static_assert_size!(ConstraintCategory<'_>, 16);

/// Outlives-constraints can be categorized to determine whether and why they
/// are interesting (for error reporting). Order of variants indicates sort
/// order of the category, thereby influencing diagnostic output.
///
/// See also `rustc_const_eval::borrow_check::constraints`.
#[derive(Copy, Clone, Debug, Eq, PartialEq, Hash)]
#[derive(TyEncodable, TyDecodable, HashStable, TypeVisitable, TypeFoldable)]
#[derive_where(PartialOrd, Ord)]
pub enum ConstraintCategory<'tcx> {
    Return(ReturnConstraint),
    Yield,
    UseAsConst,
    UseAsStatic,
    TypeAnnotation,
    Cast {
        /// Whether this cast is a coercion that was automatically inserted by the compiler.
        is_implicit_coercion: bool,
        /// Whether this is an unsizing coercion and if yes, this contains the target type.
        /// Region variables are erased to ReErased.
        #[derive_where(skip)]
        unsize_to: Option<Ty<'tcx>>,
    },

    /// A constraint that came from checking the body of a closure.
    ///
    /// We try to get the category that the closure used when reporting this.
    ClosureBounds,

    /// Contains the function type if available.
    CallArgument(#[derive_where(skip)] Option<Ty<'tcx>>),
    CopyBound,
    SizedBound,
    Assignment,
    /// A constraint that came from a usage of a variable (e.g. in an ADT expression
    /// like `Foo { field: my_val }`)
    Usage,
    OpaqueType,
    ClosureUpvar(FieldIdx),

    /// A constraint from a user-written predicate
    /// with the provided span, written on the item
    /// with the given `DefId`
    Predicate(Span),

    /// A "boring" constraint (caused by the given location) is one that
    /// the user probably doesn't want to see described in diagnostics,
    /// because it is kind of an artifact of the type system setup.
    Boring,
    // Boring and applicable everywhere.
    BoringNoLocation,

    /// A constraint that doesn't correspond to anything the user sees.
    Internal,

    /// An internal constraint derived from an illegal universe relation.
    IllegalUniverse,
}

#[derive(Copy, Clone, Debug, Eq, PartialEq, PartialOrd, Ord, Hash)]
#[derive(TyEncodable, TyDecodable, HashStable, TypeVisitable, TypeFoldable)]
pub enum ReturnConstraint {
    Normal,
    ClosureUpvar(FieldIdx),
}

/// The subject of a `ClosureOutlivesRequirement` -- that is, the thing
/// that must outlive some region.
#[derive(Copy, Clone, Debug, TyEncodable, TyDecodable, HashStable)]
pub enum ClosureOutlivesSubject<'tcx> {
    /// Subject is a type, typically a type parameter, but could also
    /// be a projection. Indicates a requirement like `T: 'a` being
    /// passed to the caller, where the type here is `T`.
    Ty(ClosureOutlivesSubjectTy<'tcx>),

    /// Subject is a free region from the closure. Indicates a requirement
    /// like `'a: 'b` being passed to the caller; the region here is `'a`.
    Region(ty::RegionVid),
}

/// Represents a `ty::Ty` for use in [`ClosureOutlivesSubject`].
///
/// This abstraction is necessary because the type may include `ReVar` regions,
/// which is what we use internally within NLL code, and they can't be used in
/// a query response.
///
/// DO NOT implement `TypeVisitable` or `TypeFoldable` traits, because this
/// type is not recognized as a binder for late-bound region.
#[derive(Copy, Clone, Debug, TyEncodable, TyDecodable, HashStable)]
pub struct ClosureOutlivesSubjectTy<'tcx> {
    inner: Ty<'tcx>,
}

impl<'tcx> ClosureOutlivesSubjectTy<'tcx> {
    /// All regions of `ty` must be of kind `ReVar` and must represent
    /// universal regions *external* to the closure.
    pub fn bind(tcx: TyCtxt<'tcx>, ty: Ty<'tcx>) -> Self {
        let inner = fold_regions(tcx, ty, |r, depth| match r.kind() {
            ty::ReVar(vid) => {
                let br = ty::BoundRegion {
                    var: ty::BoundVar::new(vid.index()),
                    kind: ty::BoundRegionKind::Anon,
                };
                ty::Region::new_bound(tcx, depth, br)
            }
            _ => bug!("unexpected region in ClosureOutlivesSubjectTy: {r:?}"),
        });

        Self { inner }
    }

    pub fn instantiate(
        self,
        tcx: TyCtxt<'tcx>,
        mut map: impl FnMut(ty::RegionVid) -> ty::Region<'tcx>,
    ) -> Ty<'tcx> {
        fold_regions(tcx, self.inner, |r, depth| match r.kind() {
            ty::ReBound(debruijn, br) => {
                debug_assert_eq!(debruijn, depth);
                map(ty::RegionVid::new(br.var.index()))
            }
            _ => bug!("unexpected region {r:?}"),
        })
    }
}

/// The constituent parts of a mir constant of kind ADT or array.
#[derive(Copy, Clone, Debug, HashStable)]
pub struct DestructuredConstant<'tcx> {
    pub variant: Option<VariantIdx>,
    pub fields: &'tcx [(ConstValue<'tcx>, Ty<'tcx>)],
}

/// Summarizes coverage IDs inserted by the `InstrumentCoverage` MIR pass
/// (for compiler option `-Cinstrument-coverage`), after MIR optimizations
/// have had a chance to potentially remove some of them.
///
/// Used by the `coverage_ids_info` query.
#[derive(Clone, TyEncodable, TyDecodable, Debug, HashStable)]
pub struct CoverageIdsInfo {
    pub counters_seen: BitSet<mir::coverage::CounterId>,
    pub expressions_seen: BitSet<mir::coverage::ExpressionId>,
}

impl CoverageIdsInfo {
    /// Coverage codegen needs to know how many coverage counters are ever
    /// incremented within a function, so that it can set the `num-counters`
    /// argument of the `llvm.instrprof.increment` intrinsic.
    ///
    /// This may be less than the highest counter ID emitted by the
    /// InstrumentCoverage MIR pass, if the highest-numbered counter increments
    /// were removed by MIR optimizations.
    pub fn num_counters_after_mir_opts(&self) -> u32 {
        // FIXME(Zalathar): Currently this treats an unused counter as "used"
        // if its ID is less than that of the highest counter that really is
        // used. Fixing this would require adding a renumbering step somewhere.
        self.counters_seen.last_set_in(..).map_or(0, |max| max.as_u32() + 1)
    }
}