summaryrefslogtreecommitdiffstats
path: root/compiler/rustc_hir_analysis/src/lib.rs
blob: 525cd24190a4c920db4a1fc0030ba56c31c54f18 (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
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
528
529
530
531
532
533
534
535
536
537
538
539
540
541
542
543
544
545
546
547
548
549
550
551
552
/*!

# typeck

The type checker is responsible for:

1. Determining the type of each expression.
2. Resolving methods and traits.
3. Guaranteeing that most type rules are met. ("Most?", you say, "why most?"
   Well, dear reader, read on.)

The main entry point is [`check_crate()`]. Type checking operates in
several major phases:

1. The collect phase first passes over all items and determines their
   type, without examining their "innards".

2. Variance inference then runs to compute the variance of each parameter.

3. Coherence checks for overlapping or orphaned impls.

4. Finally, the check phase then checks function bodies and so forth.
   Within the check phase, we check each function body one at a time
   (bodies of function expressions are checked as part of the
   containing function).  Inference is used to supply types wherever
   they are unknown. The actual checking of a function itself has
   several phases (check, regionck, writeback), as discussed in the
   documentation for the [`check`] module.

The type checker is defined into various submodules which are documented
independently:

- astconv: converts the AST representation of types
  into the `ty` representation.

- collect: computes the types of each top-level item and enters them into
  the `tcx.types` table for later use.

- coherence: enforces coherence rules, builds some tables.

- variance: variance inference

- outlives: outlives inference

- check: walks over function bodies and type checks them, inferring types for
  local variables, type parameters, etc as necessary.

- infer: finds the types to use for each type variable such that
  all subtyping and assignment constraints are met.  In essence, the check
  module specifies the constraints, and the infer module solves them.

## Note

This API is completely unstable and subject to change.

*/

#![allow(rustc::potential_query_instability)]
#![doc(html_root_url = "https://doc.rust-lang.org/nightly/nightly-rustc/")]
#![feature(box_patterns)]
#![feature(control_flow_enum)]
#![feature(drain_filter)]
#![feature(hash_drain_filter)]
#![feature(if_let_guard)]
#![feature(is_sorted)]
#![feature(iter_intersperse)]
#![feature(let_chains)]
#![feature(min_specialization)]
#![feature(never_type)]
#![feature(once_cell)]
#![feature(slice_partition_dedup)]
#![feature(try_blocks)]
#![feature(is_some_and)]
#![feature(type_alias_impl_trait)]
#![recursion_limit = "256"]

#[macro_use]
extern crate tracing;

#[macro_use]
extern crate rustc_middle;

// These are used by Clippy.
pub mod check;

pub mod astconv;
mod bounds;
mod check_unused;
mod coherence;
// FIXME: This module shouldn't be public.
pub mod collect;
mod constrained_generic_params;
mod errors;
pub mod hir_wf_check;
mod impl_wf_check;
mod outlives;
pub mod structured_errors;
mod variance;

use rustc_errors::{struct_span_err, ErrorGuaranteed};
use rustc_hir as hir;
use rustc_hir::def_id::DefId;
use rustc_hir::{Node, CRATE_HIR_ID};
use rustc_infer::infer::{InferOk, TyCtxtInferExt};
use rustc_middle::middle;
use rustc_middle::ty::query::Providers;
use rustc_middle::ty::{self, Ty, TyCtxt};
use rustc_middle::util;
use rustc_session::config::EntryFnType;
use rustc_span::{symbol::sym, Span, DUMMY_SP};
use rustc_target::spec::abi::Abi;
use rustc_trait_selection::traits::error_reporting::TypeErrCtxtExt as _;
use rustc_trait_selection::traits::{self, ObligationCause, ObligationCauseCode};

use std::iter;

use astconv::AstConv;
use bounds::Bounds;

fn require_c_abi_if_c_variadic(tcx: TyCtxt<'_>, decl: &hir::FnDecl<'_>, abi: Abi, span: Span) {
    match (decl.c_variadic, abi) {
        // The function has the correct calling convention, or isn't a "C-variadic" function.
        (false, _) | (true, Abi::C { .. }) | (true, Abi::Cdecl { .. }) => {}
        // The function is a "C-variadic" function with an incorrect calling convention.
        (true, _) => {
            let mut err = struct_span_err!(
                tcx.sess,
                span,
                E0045,
                "C-variadic function must have C or cdecl calling convention"
            );
            err.span_label(span, "C-variadics require C or cdecl calling convention").emit();
        }
    }
}

fn require_same_types<'tcx>(
    tcx: TyCtxt<'tcx>,
    cause: &ObligationCause<'tcx>,
    expected: Ty<'tcx>,
    actual: Ty<'tcx>,
) -> bool {
    let infcx = &tcx.infer_ctxt().build();
    let param_env = ty::ParamEnv::empty();
    let errors = match infcx.at(cause, param_env).eq(expected, actual) {
        Ok(InferOk { obligations, .. }) => traits::fully_solve_obligations(infcx, obligations),
        Err(err) => {
            infcx.err_ctxt().report_mismatched_types(cause, expected, actual, err).emit();
            return false;
        }
    };

    match &errors[..] {
        [] => true,
        errors => {
            infcx.err_ctxt().report_fulfillment_errors(errors, None, false);
            false
        }
    }
}

fn check_main_fn_ty(tcx: TyCtxt<'_>, main_def_id: DefId) {
    let main_fnsig = tcx.fn_sig(main_def_id);
    let main_span = tcx.def_span(main_def_id);

    fn main_fn_diagnostics_hir_id(tcx: TyCtxt<'_>, def_id: DefId, sp: Span) -> hir::HirId {
        if let Some(local_def_id) = def_id.as_local() {
            let hir_id = tcx.hir().local_def_id_to_hir_id(local_def_id);
            let hir_type = tcx.type_of(local_def_id);
            if !matches!(hir_type.kind(), ty::FnDef(..)) {
                span_bug!(sp, "main has a non-function type: found `{}`", hir_type);
            }
            hir_id
        } else {
            CRATE_HIR_ID
        }
    }

    fn main_fn_generics_params_span(tcx: TyCtxt<'_>, def_id: DefId) -> Option<Span> {
        if !def_id.is_local() {
            return None;
        }
        let hir_id = tcx.hir().local_def_id_to_hir_id(def_id.expect_local());
        match tcx.hir().find(hir_id) {
            Some(Node::Item(hir::Item { kind: hir::ItemKind::Fn(_, ref generics, _), .. })) => {
                if !generics.params.is_empty() {
                    Some(generics.span)
                } else {
                    None
                }
            }
            _ => {
                span_bug!(tcx.def_span(def_id), "main has a non-function type");
            }
        }
    }

    fn main_fn_where_clauses_span(tcx: TyCtxt<'_>, def_id: DefId) -> Option<Span> {
        if !def_id.is_local() {
            return None;
        }
        let hir_id = tcx.hir().local_def_id_to_hir_id(def_id.expect_local());
        match tcx.hir().find(hir_id) {
            Some(Node::Item(hir::Item { kind: hir::ItemKind::Fn(_, ref generics, _), .. })) => {
                Some(generics.where_clause_span)
            }
            _ => {
                span_bug!(tcx.def_span(def_id), "main has a non-function type");
            }
        }
    }

    fn main_fn_asyncness_span(tcx: TyCtxt<'_>, def_id: DefId) -> Option<Span> {
        if !def_id.is_local() {
            return None;
        }
        Some(tcx.def_span(def_id))
    }

    fn main_fn_return_type_span(tcx: TyCtxt<'_>, def_id: DefId) -> Option<Span> {
        if !def_id.is_local() {
            return None;
        }
        let hir_id = tcx.hir().local_def_id_to_hir_id(def_id.expect_local());
        match tcx.hir().find(hir_id) {
            Some(Node::Item(hir::Item { kind: hir::ItemKind::Fn(ref fn_sig, _, _), .. })) => {
                Some(fn_sig.decl.output.span())
            }
            _ => {
                span_bug!(tcx.def_span(def_id), "main has a non-function type");
            }
        }
    }

    let mut error = false;
    let main_diagnostics_hir_id = main_fn_diagnostics_hir_id(tcx, main_def_id, main_span);
    let main_fn_generics = tcx.generics_of(main_def_id);
    let main_fn_predicates = tcx.predicates_of(main_def_id);
    if main_fn_generics.count() != 0 || !main_fnsig.bound_vars().is_empty() {
        let generics_param_span = main_fn_generics_params_span(tcx, main_def_id);
        let msg = "`main` function is not allowed to have generic \
            parameters";
        let mut diag =
            struct_span_err!(tcx.sess, generics_param_span.unwrap_or(main_span), E0131, "{}", msg);
        if let Some(generics_param_span) = generics_param_span {
            let label = "`main` cannot have generic parameters";
            diag.span_label(generics_param_span, label);
        }
        diag.emit();
        error = true;
    } else if !main_fn_predicates.predicates.is_empty() {
        // generics may bring in implicit predicates, so we skip this check if generics is present.
        let generics_where_clauses_span = main_fn_where_clauses_span(tcx, main_def_id);
        let mut diag = struct_span_err!(
            tcx.sess,
            generics_where_clauses_span.unwrap_or(main_span),
            E0646,
            "`main` function is not allowed to have a `where` clause"
        );
        if let Some(generics_where_clauses_span) = generics_where_clauses_span {
            diag.span_label(generics_where_clauses_span, "`main` cannot have a `where` clause");
        }
        diag.emit();
        error = true;
    }

    let main_asyncness = tcx.asyncness(main_def_id);
    if let hir::IsAsync::Async = main_asyncness {
        let mut diag = struct_span_err!(
            tcx.sess,
            main_span,
            E0752,
            "`main` function is not allowed to be `async`"
        );
        let asyncness_span = main_fn_asyncness_span(tcx, main_def_id);
        if let Some(asyncness_span) = asyncness_span {
            diag.span_label(asyncness_span, "`main` function is not allowed to be `async`");
        }
        diag.emit();
        error = true;
    }

    for attr in tcx.get_attrs(main_def_id, sym::track_caller) {
        tcx.sess
            .struct_span_err(attr.span, "`main` function is not allowed to be `#[track_caller]`")
            .span_label(main_span, "`main` function is not allowed to be `#[track_caller]`")
            .emit();
        error = true;
    }

    if error {
        return;
    }

    let expected_return_type;
    if let Some(term_did) = tcx.lang_items().termination() {
        let return_ty = main_fnsig.output();
        let return_ty_span = main_fn_return_type_span(tcx, main_def_id).unwrap_or(main_span);
        if !return_ty.bound_vars().is_empty() {
            let msg = "`main` function return type is not allowed to have generic \
                    parameters";
            struct_span_err!(tcx.sess, return_ty_span, E0131, "{}", msg).emit();
            error = true;
        }
        let return_ty = return_ty.skip_binder();
        let infcx = tcx.infer_ctxt().build();
        // Main should have no WC, so empty param env is OK here.
        let param_env = ty::ParamEnv::empty();
        let cause = traits::ObligationCause::new(
            return_ty_span,
            main_diagnostics_hir_id,
            ObligationCauseCode::MainFunctionType,
        );
        let ocx = traits::ObligationCtxt::new(&infcx);
        let norm_return_ty = ocx.normalize(cause.clone(), param_env, return_ty);
        ocx.register_bound(cause, param_env, norm_return_ty, term_did);
        let errors = ocx.select_all_or_error();
        if !errors.is_empty() {
            infcx.err_ctxt().report_fulfillment_errors(&errors, None, false);
            error = true;
        }
        // now we can take the return type of the given main function
        expected_return_type = main_fnsig.output();
    } else {
        // standard () main return type
        expected_return_type = ty::Binder::dummy(tcx.mk_unit());
    }

    if error {
        return;
    }

    let se_ty = tcx.mk_fn_ptr(expected_return_type.map_bound(|expected_return_type| {
        tcx.mk_fn_sig(iter::empty(), expected_return_type, false, hir::Unsafety::Normal, Abi::Rust)
    }));

    require_same_types(
        tcx,
        &ObligationCause::new(
            main_span,
            main_diagnostics_hir_id,
            ObligationCauseCode::MainFunctionType,
        ),
        se_ty,
        tcx.mk_fn_ptr(main_fnsig),
    );
}
fn check_start_fn_ty(tcx: TyCtxt<'_>, start_def_id: DefId) {
    let start_def_id = start_def_id.expect_local();
    let start_id = tcx.hir().local_def_id_to_hir_id(start_def_id);
    let start_span = tcx.def_span(start_def_id);
    let start_t = tcx.type_of(start_def_id);
    match start_t.kind() {
        ty::FnDef(..) => {
            if let Some(Node::Item(it)) = tcx.hir().find(start_id) {
                if let hir::ItemKind::Fn(ref sig, ref generics, _) = it.kind {
                    let mut error = false;
                    if !generics.params.is_empty() {
                        struct_span_err!(
                            tcx.sess,
                            generics.span,
                            E0132,
                            "start function is not allowed to have type parameters"
                        )
                        .span_label(generics.span, "start function cannot have type parameters")
                        .emit();
                        error = true;
                    }
                    if generics.has_where_clause_predicates {
                        struct_span_err!(
                            tcx.sess,
                            generics.where_clause_span,
                            E0647,
                            "start function is not allowed to have a `where` clause"
                        )
                        .span_label(
                            generics.where_clause_span,
                            "start function cannot have a `where` clause",
                        )
                        .emit();
                        error = true;
                    }
                    if let hir::IsAsync::Async = sig.header.asyncness {
                        let span = tcx.def_span(it.owner_id);
                        struct_span_err!(
                            tcx.sess,
                            span,
                            E0752,
                            "`start` is not allowed to be `async`"
                        )
                        .span_label(span, "`start` is not allowed to be `async`")
                        .emit();
                        error = true;
                    }

                    let attrs = tcx.hir().attrs(start_id);
                    for attr in attrs {
                        if attr.has_name(sym::track_caller) {
                            tcx.sess
                                .struct_span_err(
                                    attr.span,
                                    "`start` is not allowed to be `#[track_caller]`",
                                )
                                .span_label(
                                    start_span,
                                    "`start` is not allowed to be `#[track_caller]`",
                                )
                                .emit();
                            error = true;
                        }
                    }

                    if error {
                        return;
                    }
                }
            }

            let se_ty = tcx.mk_fn_ptr(ty::Binder::dummy(tcx.mk_fn_sig(
                [tcx.types.isize, tcx.mk_imm_ptr(tcx.mk_imm_ptr(tcx.types.u8))].iter().cloned(),
                tcx.types.isize,
                false,
                hir::Unsafety::Normal,
                Abi::Rust,
            )));

            require_same_types(
                tcx,
                &ObligationCause::new(start_span, start_id, ObligationCauseCode::StartFunctionType),
                se_ty,
                tcx.mk_fn_ptr(tcx.fn_sig(start_def_id)),
            );
        }
        _ => {
            span_bug!(start_span, "start has a non-function type: found `{}`", start_t);
        }
    }
}

fn check_for_entry_fn(tcx: TyCtxt<'_>) {
    match tcx.entry_fn(()) {
        Some((def_id, EntryFnType::Main { .. })) => check_main_fn_ty(tcx, def_id),
        Some((def_id, EntryFnType::Start)) => check_start_fn_ty(tcx, def_id),
        _ => {}
    }
}

pub fn provide(providers: &mut Providers) {
    collect::provide(providers);
    coherence::provide(providers);
    check::provide(providers);
    variance::provide(providers);
    outlives::provide(providers);
    impl_wf_check::provide(providers);
    hir_wf_check::provide(providers);
}

pub fn check_crate(tcx: TyCtxt<'_>) -> Result<(), ErrorGuaranteed> {
    let _prof_timer = tcx.sess.timer("type_check_crate");

    // this ensures that later parts of type checking can assume that items
    // have valid types and not error
    // FIXME(matthewjasper) We shouldn't need to use `track_errors`.
    tcx.sess.track_errors(|| {
        tcx.sess.time("type_collecting", || {
            tcx.hir().for_each_module(|module| tcx.ensure().collect_mod_item_types(module))
        });
    })?;

    if tcx.features().rustc_attrs {
        tcx.sess.track_errors(|| {
            tcx.sess.time("outlives_testing", || outlives::test::test_inferred_outlives(tcx));
        })?;
    }

    tcx.sess.track_errors(|| {
        tcx.sess.time("impl_wf_inference", || {
            tcx.hir().for_each_module(|module| tcx.ensure().check_mod_impl_wf(module))
        });
    })?;

    tcx.sess.track_errors(|| {
        tcx.sess.time("coherence_checking", || {
            for &trait_def_id in tcx.all_local_trait_impls(()).keys() {
                tcx.ensure().coherent_trait(trait_def_id);
            }

            // these queries are executed for side-effects (error reporting):
            tcx.ensure().crate_inherent_impls(());
            tcx.ensure().crate_inherent_impls_overlap_check(());
        });
    })?;

    if tcx.features().rustc_attrs {
        tcx.sess.track_errors(|| {
            tcx.sess.time("variance_testing", || variance::test::test_variance(tcx));
        })?;
    }

    tcx.sess.track_errors(|| {
        tcx.sess.time("wf_checking", || {
            tcx.hir().par_for_each_module(|module| tcx.ensure().check_mod_type_wf(module))
        });
    })?;

    // NOTE: This is copy/pasted in librustdoc/core.rs and should be kept in sync.
    tcx.sess.time("item_types_checking", || {
        tcx.hir().for_each_module(|module| tcx.ensure().check_mod_item_types(module))
    });

    tcx.sess.time("item_bodies_checking", || tcx.typeck_item_bodies(()));

    check_unused::check_crate(tcx);
    check_for_entry_fn(tcx);

    if let Some(reported) = tcx.sess.has_errors() { Err(reported) } else { Ok(()) }
}

/// A quasi-deprecated helper used in rustdoc and clippy to get
/// the type from a HIR node.
pub fn hir_ty_to_ty<'tcx>(tcx: TyCtxt<'tcx>, hir_ty: &hir::Ty<'_>) -> Ty<'tcx> {
    // In case there are any projections, etc., find the "environment"
    // def-ID that will be used to determine the traits/predicates in
    // scope.  This is derived from the enclosing item-like thing.
    let env_def_id = tcx.hir().get_parent_item(hir_ty.hir_id);
    let item_cx = self::collect::ItemCtxt::new(tcx, env_def_id.to_def_id());
    <dyn AstConv<'_>>::ast_ty_to_ty(&item_cx, hir_ty)
}

pub fn hir_trait_to_predicates<'tcx>(
    tcx: TyCtxt<'tcx>,
    hir_trait: &hir::TraitRef<'_>,
    self_ty: Ty<'tcx>,
) -> Bounds<'tcx> {
    // In case there are any projections, etc., find the "environment"
    // def-ID that will be used to determine the traits/predicates in
    // scope.  This is derived from the enclosing item-like thing.
    let env_def_id = tcx.hir().get_parent_item(hir_trait.hir_ref_id);
    let item_cx = self::collect::ItemCtxt::new(tcx, env_def_id.to_def_id());
    let mut bounds = Bounds::default();
    let _ = <dyn AstConv<'_>>::instantiate_poly_trait_ref(
        &item_cx,
        hir_trait,
        DUMMY_SP,
        ty::BoundConstness::NotConst,
        self_ty,
        &mut bounds,
        true,
    );

    bounds
}