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
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
486
487
488
489
490
491
492
493
494
495
496
497
498
499
500
501
502
503
504
505
506
507
508
509
510
511
512
513
514
515
516
517
518
519
520
521
522
523
524
525
526
527
//! This module contains some shared code for encoding and decoding various
//! things from the `ty` module, and in particular implements support for
//! "shorthands" which allow to have pointers back into the already encoded
//! stream instead of re-encoding the same thing twice.
//!
//! The functionality in here is shared between persisting to crate metadata and
//! persisting to incr. comp. caches.

use crate::arena::ArenaAllocatable;
use crate::infer::canonical::{CanonicalVarInfo, CanonicalVarInfos};
use crate::mir::{
    self,
    interpret::{AllocId, ConstAllocation},
};
use crate::traits;
use crate::ty::subst::SubstsRef;
use crate::ty::{self, AdtDef, Ty};
use rustc_data_structures::fx::FxHashMap;
use rustc_middle::ty::TyCtxt;
use rustc_serialize::{Decodable, Encodable};
use rustc_span::Span;
pub use rustc_type_ir::{TyDecoder, TyEncoder};
use std::hash::Hash;
use std::intrinsics;
use std::marker::DiscriminantKind;

/// The shorthand encoding uses an enum's variant index `usize`
/// and is offset by this value so it never matches a real variant.
/// This offset is also chosen so that the first byte is never < 0x80.
pub const SHORTHAND_OFFSET: usize = 0x80;

pub trait EncodableWithShorthand<E: TyEncoder>: Copy + Eq + Hash {
    type Variant: Encodable<E>;
    fn variant(&self) -> &Self::Variant;
}

#[allow(rustc::usage_of_ty_tykind)]
impl<'tcx, E: TyEncoder<I = TyCtxt<'tcx>>> EncodableWithShorthand<E> for Ty<'tcx> {
    type Variant = ty::TyKind<'tcx>;

    #[inline]
    fn variant(&self) -> &Self::Variant {
        self.kind()
    }
}

impl<'tcx, E: TyEncoder<I = TyCtxt<'tcx>>> EncodableWithShorthand<E> for ty::PredicateKind<'tcx> {
    type Variant = ty::PredicateKind<'tcx>;

    #[inline]
    fn variant(&self) -> &Self::Variant {
        self
    }
}

/// Trait for decoding to a reference.
///
/// This is a separate trait from `Decodable` so that we can implement it for
/// upstream types, such as `FxHashSet`.
///
/// The `TyDecodable` derive macro will use this trait for fields that are
/// references (and don't use a type alias to hide that).
///
/// `Decodable` can still be implemented in cases where `Decodable` is required
/// by a trait bound.
pub trait RefDecodable<'tcx, D: TyDecoder<I = TyCtxt<'tcx>>> {
    fn decode(d: &mut D) -> &'tcx Self;
}

/// Encode the given value or a previously cached shorthand.
pub fn encode_with_shorthand<'tcx, E, T, M>(encoder: &mut E, value: &T, cache: M)
where
    E: TyEncoder<I = TyCtxt<'tcx>>,
    M: for<'b> Fn(&'b mut E) -> &'b mut FxHashMap<T, usize>,
    T: EncodableWithShorthand<E>,
    // The discriminant and shorthand must have the same size.
    T::Variant: DiscriminantKind<Discriminant = isize>,
{
    let existing_shorthand = cache(encoder).get(value).copied();
    if let Some(shorthand) = existing_shorthand {
        encoder.emit_usize(shorthand);
        return;
    }

    let variant = value.variant();

    let start = encoder.position();
    variant.encode(encoder);
    let len = encoder.position() - start;

    // The shorthand encoding uses the same usize as the
    // discriminant, with an offset so they can't conflict.
    let discriminant = intrinsics::discriminant_value(variant);
    assert!(SHORTHAND_OFFSET > discriminant as usize);

    let shorthand = start + SHORTHAND_OFFSET;

    // Get the number of bits that leb128 could fit
    // in the same space as the fully encoded type.
    let leb128_bits = len * 7;

    // Check that the shorthand is a not longer than the
    // full encoding itself, i.e., it's an obvious win.
    if leb128_bits >= 64 || (shorthand as u64) < (1 << leb128_bits) {
        cache(encoder).insert(*value, shorthand);
    }
}

impl<'tcx, E: TyEncoder<I = TyCtxt<'tcx>>> Encodable<E> for Ty<'tcx> {
    fn encode(&self, e: &mut E) {
        encode_with_shorthand(e, self, TyEncoder::type_shorthands);
    }
}

impl<'tcx, E: TyEncoder<I = TyCtxt<'tcx>>> Encodable<E>
    for ty::Binder<'tcx, ty::PredicateKind<'tcx>>
{
    fn encode(&self, e: &mut E) {
        self.bound_vars().encode(e);
        encode_with_shorthand(e, &self.skip_binder(), TyEncoder::predicate_shorthands);
    }
}

impl<'tcx, E: TyEncoder<I = TyCtxt<'tcx>>> Encodable<E> for ty::Predicate<'tcx> {
    fn encode(&self, e: &mut E) {
        self.kind().encode(e);
    }
}

impl<'tcx, E: TyEncoder<I = TyCtxt<'tcx>>> Encodable<E> for ty::Region<'tcx> {
    fn encode(&self, e: &mut E) {
        self.kind().encode(e);
    }
}

impl<'tcx, E: TyEncoder<I = TyCtxt<'tcx>>> Encodable<E> for ty::Const<'tcx> {
    fn encode(&self, e: &mut E) {
        self.0.0.encode(e);
    }
}

impl<'tcx, E: TyEncoder<I = TyCtxt<'tcx>>> Encodable<E> for ConstAllocation<'tcx> {
    fn encode(&self, e: &mut E) {
        self.inner().encode(e)
    }
}

impl<'tcx, E: TyEncoder<I = TyCtxt<'tcx>>> Encodable<E> for AdtDef<'tcx> {
    fn encode(&self, e: &mut E) {
        self.0.0.encode(e)
    }
}

impl<'tcx, E: TyEncoder<I = TyCtxt<'tcx>>> Encodable<E> for AllocId {
    fn encode(&self, e: &mut E) {
        e.encode_alloc_id(self)
    }
}

#[inline]
fn decode_arena_allocable<
    'tcx,
    D: TyDecoder<I = TyCtxt<'tcx>>,
    T: ArenaAllocatable<'tcx> + Decodable<D>,
>(
    decoder: &mut D,
) -> &'tcx T
where
    D: TyDecoder,
{
    decoder.interner().arena.alloc(Decodable::decode(decoder))
}

#[inline]
fn decode_arena_allocable_slice<
    'tcx,
    D: TyDecoder<I = TyCtxt<'tcx>>,
    T: ArenaAllocatable<'tcx> + Decodable<D>,
>(
    decoder: &mut D,
) -> &'tcx [T]
where
    D: TyDecoder,
{
    decoder.interner().arena.alloc_from_iter(<Vec<T> as Decodable<D>>::decode(decoder))
}

impl<'tcx, D: TyDecoder<I = TyCtxt<'tcx>>> Decodable<D> for Ty<'tcx> {
    #[allow(rustc::usage_of_ty_tykind)]
    fn decode(decoder: &mut D) -> Ty<'tcx> {
        // Handle shorthands first, if we have a usize > 0x80.
        if decoder.positioned_at_shorthand() {
            let pos = decoder.read_usize();
            assert!(pos >= SHORTHAND_OFFSET);
            let shorthand = pos - SHORTHAND_OFFSET;

            decoder.cached_ty_for_shorthand(shorthand, |decoder| {
                decoder.with_position(shorthand, Ty::decode)
            })
        } else {
            let tcx = decoder.interner();
            tcx.mk_ty(rustc_type_ir::TyKind::decode(decoder))
        }
    }
}

impl<'tcx, D: TyDecoder<I = TyCtxt<'tcx>>> Decodable<D>
    for ty::Binder<'tcx, ty::PredicateKind<'tcx>>
{
    fn decode(decoder: &mut D) -> ty::Binder<'tcx, ty::PredicateKind<'tcx>> {
        let bound_vars = Decodable::decode(decoder);
        // Handle shorthands first, if we have a usize > 0x80.
        ty::Binder::bind_with_vars(
            if decoder.positioned_at_shorthand() {
                let pos = decoder.read_usize();
                assert!(pos >= SHORTHAND_OFFSET);
                let shorthand = pos - SHORTHAND_OFFSET;

                decoder.with_position(shorthand, ty::PredicateKind::decode)
            } else {
                ty::PredicateKind::decode(decoder)
            },
            bound_vars,
        )
    }
}

impl<'tcx, D: TyDecoder<I = TyCtxt<'tcx>>> Decodable<D> for ty::Predicate<'tcx> {
    fn decode(decoder: &mut D) -> ty::Predicate<'tcx> {
        let predicate_kind = Decodable::decode(decoder);
        decoder.interner().mk_predicate(predicate_kind)
    }
}

impl<'tcx, D: TyDecoder<I = TyCtxt<'tcx>>> Decodable<D> for SubstsRef<'tcx> {
    fn decode(decoder: &mut D) -> Self {
        let len = decoder.read_usize();
        let tcx = decoder.interner();
        tcx.mk_substs(
            (0..len).map::<ty::subst::GenericArg<'tcx>, _>(|_| Decodable::decode(decoder)),
        )
    }
}

impl<'tcx, D: TyDecoder<I = TyCtxt<'tcx>>> Decodable<D> for mir::Place<'tcx> {
    fn decode(decoder: &mut D) -> Self {
        let local: mir::Local = Decodable::decode(decoder);
        let len = decoder.read_usize();
        let projection = decoder.interner().mk_place_elems(
            (0..len).map::<mir::PlaceElem<'tcx>, _>(|_| Decodable::decode(decoder)),
        );
        mir::Place { local, projection }
    }
}

impl<'tcx, D: TyDecoder<I = TyCtxt<'tcx>>> Decodable<D> for ty::Region<'tcx> {
    fn decode(decoder: &mut D) -> Self {
        decoder.interner().mk_region(Decodable::decode(decoder))
    }
}

impl<'tcx, D: TyDecoder<I = TyCtxt<'tcx>>> Decodable<D> for CanonicalVarInfos<'tcx> {
    fn decode(decoder: &mut D) -> Self {
        let len = decoder.read_usize();
        let interned: Vec<CanonicalVarInfo<'tcx>> =
            (0..len).map(|_| Decodable::decode(decoder)).collect();
        decoder.interner().intern_canonical_var_infos(interned.as_slice())
    }
}

impl<'tcx, D: TyDecoder<I = TyCtxt<'tcx>>> Decodable<D> for AllocId {
    fn decode(decoder: &mut D) -> Self {
        decoder.decode_alloc_id()
    }
}

impl<'tcx, D: TyDecoder<I = TyCtxt<'tcx>>> Decodable<D> for ty::SymbolName<'tcx> {
    fn decode(decoder: &mut D) -> Self {
        ty::SymbolName::new(decoder.interner(), &decoder.read_str())
    }
}

macro_rules! impl_decodable_via_ref {
    ($($t:ty),+) => {
        $(impl<'tcx, D: TyDecoder<I = TyCtxt<'tcx>>> Decodable<D> for $t {
            fn decode(decoder: &mut D) -> Self {
                RefDecodable::decode(decoder)
            }
        })*
    }
}

impl<'tcx, D: TyDecoder<I = TyCtxt<'tcx>>> RefDecodable<'tcx, D> for ty::List<Ty<'tcx>> {
    fn decode(decoder: &mut D) -> &'tcx Self {
        let len = decoder.read_usize();
        decoder.interner().mk_type_list((0..len).map::<Ty<'tcx>, _>(|_| Decodable::decode(decoder)))
    }
}

impl<'tcx, D: TyDecoder<I = TyCtxt<'tcx>>> RefDecodable<'tcx, D>
    for ty::List<ty::Binder<'tcx, ty::ExistentialPredicate<'tcx>>>
{
    fn decode(decoder: &mut D) -> &'tcx Self {
        let len = decoder.read_usize();
        decoder.interner().mk_poly_existential_predicates(
            (0..len).map::<ty::Binder<'tcx, _>, _>(|_| Decodable::decode(decoder)),
        )
    }
}

impl<'tcx, D: TyDecoder<I = TyCtxt<'tcx>>> Decodable<D> for ty::Const<'tcx> {
    fn decode(decoder: &mut D) -> Self {
        decoder.interner().mk_const(Decodable::decode(decoder))
    }
}

impl<'tcx, D: TyDecoder<I = TyCtxt<'tcx>>> RefDecodable<'tcx, D> for [ty::ValTree<'tcx>] {
    fn decode(decoder: &mut D) -> &'tcx Self {
        decoder.interner().arena.alloc_from_iter(
            (0..decoder.read_usize()).map(|_| Decodable::decode(decoder)).collect::<Vec<_>>(),
        )
    }
}

impl<'tcx, D: TyDecoder<I = TyCtxt<'tcx>>> Decodable<D> for ConstAllocation<'tcx> {
    fn decode(decoder: &mut D) -> Self {
        decoder.interner().intern_const_alloc(Decodable::decode(decoder))
    }
}

impl<'tcx, D: TyDecoder<I = TyCtxt<'tcx>>> Decodable<D> for AdtDef<'tcx> {
    fn decode(decoder: &mut D) -> Self {
        decoder.interner().intern_adt_def(Decodable::decode(decoder))
    }
}

impl<'tcx, D: TyDecoder<I = TyCtxt<'tcx>>> RefDecodable<'tcx, D>
    for [(ty::Predicate<'tcx>, Span)]
{
    fn decode(decoder: &mut D) -> &'tcx Self {
        decoder.interner().arena.alloc_from_iter(
            (0..decoder.read_usize()).map(|_| Decodable::decode(decoder)).collect::<Vec<_>>(),
        )
    }
}

impl<'tcx, D: TyDecoder<I = TyCtxt<'tcx>>> RefDecodable<'tcx, D>
    for [ty::abstract_const::Node<'tcx>]
{
    fn decode(decoder: &mut D) -> &'tcx Self {
        decoder.interner().arena.alloc_from_iter(
            (0..decoder.read_usize()).map(|_| Decodable::decode(decoder)).collect::<Vec<_>>(),
        )
    }
}

impl<'tcx, D: TyDecoder<I = TyCtxt<'tcx>>> RefDecodable<'tcx, D>
    for [ty::abstract_const::NodeId]
{
    fn decode(decoder: &mut D) -> &'tcx Self {
        decoder.interner().arena.alloc_from_iter(
            (0..decoder.read_usize()).map(|_| Decodable::decode(decoder)).collect::<Vec<_>>(),
        )
    }
}

impl<'tcx, D: TyDecoder<I = TyCtxt<'tcx>>> RefDecodable<'tcx, D>
    for ty::List<ty::BoundVariableKind>
{
    fn decode(decoder: &mut D) -> &'tcx Self {
        let len = decoder.read_usize();
        decoder.interner().mk_bound_variable_kinds(
            (0..len).map::<ty::BoundVariableKind, _>(|_| Decodable::decode(decoder)),
        )
    }
}

impl_decodable_via_ref! {
    &'tcx ty::TypeckResults<'tcx>,
    &'tcx ty::List<Ty<'tcx>>,
    &'tcx ty::List<ty::Binder<'tcx, ty::ExistentialPredicate<'tcx>>>,
    &'tcx traits::ImplSource<'tcx, ()>,
    &'tcx mir::Body<'tcx>,
    &'tcx mir::UnsafetyCheckResult,
    &'tcx mir::BorrowCheckResult<'tcx>,
    &'tcx mir::coverage::CodeRegion,
    &'tcx ty::List<ty::BoundVariableKind>
}

#[macro_export]
macro_rules! __impl_decoder_methods {
    ($($name:ident -> $ty:ty;)*) => {
        $(
            #[inline]
            fn $name(&mut self) -> $ty {
                self.opaque.$name()
            }
        )*
    }
}

macro_rules! impl_arena_allocatable_decoder {
    ([]$args:tt) => {};
    ([decode $(, $attrs:ident)*]
     [$name:ident: $ty:ty]) => {
        impl<'tcx, D: TyDecoder<I = TyCtxt<'tcx>>> RefDecodable<'tcx, D> for $ty {
            #[inline]
            fn decode(decoder: &mut D) -> &'tcx Self {
                decode_arena_allocable(decoder)
            }
        }

        impl<'tcx, D: TyDecoder<I = TyCtxt<'tcx>>> RefDecodable<'tcx, D> for [$ty] {
            #[inline]
            fn decode(decoder: &mut D) -> &'tcx Self {
                decode_arena_allocable_slice(decoder)
            }
        }
    };
}

macro_rules! impl_arena_allocatable_decoders {
    ([$($a:tt $name:ident: $ty:ty,)*]) => {
        $(
            impl_arena_allocatable_decoder!($a [$name: $ty]);
        )*
    }
}

rustc_hir::arena_types!(impl_arena_allocatable_decoders);
arena_types!(impl_arena_allocatable_decoders);

macro_rules! impl_arena_copy_decoder {
    (<$tcx:tt> $($ty:ty,)*) => {
        $(impl<'tcx, D: TyDecoder<I = TyCtxt<'tcx>>> RefDecodable<'tcx, D> for $ty {
            #[inline]
            fn decode(decoder: &mut D) -> &'tcx Self {
                decoder.interner().arena.alloc(Decodable::decode(decoder))
            }
        }

        impl<'tcx, D: TyDecoder<I = TyCtxt<'tcx>>> RefDecodable<'tcx, D> for [$ty] {
            #[inline]
            fn decode(decoder: &mut D) -> &'tcx Self {
                decoder.interner().arena.alloc_from_iter(<Vec<_> as Decodable<D>>::decode(decoder))
            }
        })*
    };
}

impl_arena_copy_decoder! {<'tcx>
    Span,
    rustc_span::symbol::Ident,
    ty::Variance,
    rustc_span::def_id::DefId,
    rustc_span::def_id::LocalDefId,
    (rustc_middle::middle::exported_symbols::ExportedSymbol<'tcx>, rustc_middle::middle::exported_symbols::SymbolExportInfo),
}

#[macro_export]
macro_rules! implement_ty_decoder {
    ($DecoderName:ident <$($typaram:tt),*>) => {
        mod __ty_decoder_impl {
            use std::borrow::Cow;
            use rustc_serialize::Decoder;

            use super::$DecoderName;

            impl<$($typaram ),*> Decoder for $DecoderName<$($typaram),*> {
                $crate::__impl_decoder_methods! {
                    read_u128 -> u128;
                    read_u64 -> u64;
                    read_u32 -> u32;
                    read_u16 -> u16;
                    read_u8 -> u8;
                    read_usize -> usize;

                    read_i128 -> i128;
                    read_i64 -> i64;
                    read_i32 -> i32;
                    read_i16 -> i16;
                    read_i8 -> i8;
                    read_isize -> isize;

                    read_bool -> bool;
                    read_f64 -> f64;
                    read_f32 -> f32;
                    read_char -> char;
                    read_str -> &str;
                }

                #[inline]
                fn read_raw_bytes(&mut self, len: usize) -> &[u8] {
                    self.opaque.read_raw_bytes(len)
                }
            }
        }
    }
}

macro_rules! impl_binder_encode_decode {
    ($($t:ty),+ $(,)?) => {
        $(
            impl<'tcx, E: TyEncoder<I = TyCtxt<'tcx>>> Encodable<E> for ty::Binder<'tcx, $t> {
                fn encode(&self, e: &mut E) {
                    self.bound_vars().encode(e);
                    self.as_ref().skip_binder().encode(e);
                }
            }
            impl<'tcx, D: TyDecoder<I = TyCtxt<'tcx>>> Decodable<D> for ty::Binder<'tcx, $t> {
                fn decode(decoder: &mut D) -> Self {
                    let bound_vars = Decodable::decode(decoder);
                    ty::Binder::bind_with_vars(Decodable::decode(decoder), bound_vars)
                }
            }
        )*
    }
}

impl_binder_encode_decode! {
    &'tcx ty::List<Ty<'tcx>>,
    ty::FnSig<'tcx>,
    ty::ExistentialPredicate<'tcx>,
    ty::TraitRef<'tcx>,
    Vec<ty::GeneratorInteriorTypeCause<'tcx>>,
    ty::ExistentialTraitRef<'tcx>,
}