rustc_middle/ty/print/
mod.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
use std::path::PathBuf;

use hir::def::Namespace;
use rustc_data_structures::fx::FxHashSet;
use rustc_data_structures::sso::SsoHashSet;
use rustc_hir as hir;
use rustc_hir::def_id::{CrateNum, DefId, LocalDefId};
use rustc_hir::definitions::{DefPathData, DisambiguatedDefPathData};
use tracing::{debug, instrument, trace};

use crate::ty::{self, GenericArg, ShortInstance, Ty, TyCtxt};

// `pretty` is a separate module only for organization.
mod pretty;
pub use self::pretty::*;
use super::Lift;

pub type PrintError = std::fmt::Error;

pub trait Print<'tcx, P> {
    fn print(&self, cx: &mut P) -> Result<(), PrintError>;
}

/// Interface for outputting user-facing "type-system entities"
/// (paths, types, lifetimes, constants, etc.) as a side-effect
/// (e.g. formatting, like `PrettyPrinter` implementors do) or by
/// constructing some alternative representation (e.g. an AST),
/// which the associated types allow passing through the methods.
///
/// For pretty-printing/formatting in particular, see `PrettyPrinter`.
//
// FIXME(eddyb) find a better name; this is more general than "printing".
pub trait Printer<'tcx>: Sized {
    fn tcx<'a>(&'a self) -> TyCtxt<'tcx>;

    fn print_def_path(
        &mut self,
        def_id: DefId,
        args: &'tcx [GenericArg<'tcx>],
    ) -> Result<(), PrintError> {
        self.default_print_def_path(def_id, args)
    }

    fn print_impl_path(
        &mut self,
        impl_def_id: DefId,
        args: &'tcx [GenericArg<'tcx>],
        self_ty: Ty<'tcx>,
        trait_ref: Option<ty::TraitRef<'tcx>>,
    ) -> Result<(), PrintError> {
        self.default_print_impl_path(impl_def_id, args, self_ty, trait_ref)
    }

    fn print_region(&mut self, region: ty::Region<'tcx>) -> Result<(), PrintError>;

    fn print_type(&mut self, ty: Ty<'tcx>) -> Result<(), PrintError>;

    fn print_dyn_existential(
        &mut self,
        predicates: &'tcx ty::List<ty::PolyExistentialPredicate<'tcx>>,
    ) -> Result<(), PrintError>;

    fn print_const(&mut self, ct: ty::Const<'tcx>) -> Result<(), PrintError>;

    fn path_crate(&mut self, cnum: CrateNum) -> Result<(), PrintError>;

    fn path_qualified(
        &mut self,
        self_ty: Ty<'tcx>,
        trait_ref: Option<ty::TraitRef<'tcx>>,
    ) -> Result<(), PrintError>;

    fn path_append_impl(
        &mut self,
        print_prefix: impl FnOnce(&mut Self) -> Result<(), PrintError>,
        disambiguated_data: &DisambiguatedDefPathData,
        self_ty: Ty<'tcx>,
        trait_ref: Option<ty::TraitRef<'tcx>>,
    ) -> Result<(), PrintError>;

    fn path_append(
        &mut self,
        print_prefix: impl FnOnce(&mut Self) -> Result<(), PrintError>,
        disambiguated_data: &DisambiguatedDefPathData,
    ) -> Result<(), PrintError>;

    fn path_generic_args(
        &mut self,
        print_prefix: impl FnOnce(&mut Self) -> Result<(), PrintError>,
        args: &[GenericArg<'tcx>],
    ) -> Result<(), PrintError>;

    // Defaults (should not be overridden):

    #[instrument(skip(self), level = "debug")]
    fn default_print_def_path(
        &mut self,
        def_id: DefId,
        args: &'tcx [GenericArg<'tcx>],
    ) -> Result<(), PrintError> {
        let key = self.tcx().def_key(def_id);
        debug!(?key);

        match key.disambiguated_data.data {
            DefPathData::CrateRoot => {
                assert!(key.parent.is_none());
                self.path_crate(def_id.krate)
            }

            DefPathData::Impl => {
                let generics = self.tcx().generics_of(def_id);
                let self_ty = self.tcx().type_of(def_id);
                let impl_trait_ref = self.tcx().impl_trait_ref(def_id);
                let (self_ty, impl_trait_ref) = if args.len() >= generics.count() {
                    (
                        self_ty.instantiate(self.tcx(), args),
                        impl_trait_ref.map(|i| i.instantiate(self.tcx(), args)),
                    )
                } else {
                    (
                        self_ty.instantiate_identity(),
                        impl_trait_ref.map(|i| i.instantiate_identity()),
                    )
                };
                self.print_impl_path(def_id, args, self_ty, impl_trait_ref)
            }

            _ => {
                let parent_def_id = DefId { index: key.parent.unwrap(), ..def_id };

                let mut parent_args = args;
                let mut trait_qualify_parent = false;
                if !args.is_empty() {
                    let generics = self.tcx().generics_of(def_id);
                    parent_args = &args[..generics.parent_count.min(args.len())];

                    match key.disambiguated_data.data {
                        DefPathData::Closure => {
                            // FIXME(async_closures): This is somewhat ugly.
                            // We need to additionally print the `kind` field of a closure if
                            // it is desugared from a coroutine-closure.
                            if let Some(hir::CoroutineKind::Desugared(
                                _,
                                hir::CoroutineSource::Closure,
                            )) = self.tcx().coroutine_kind(def_id)
                                && args.len() > parent_args.len()
                            {
                                return self.path_generic_args(
                                    |cx| cx.print_def_path(def_id, parent_args),
                                    &args[..parent_args.len() + 1][..1],
                                );
                            } else {
                                // Closures' own generics are only captures, don't print them.
                            }
                        }
                        // This covers both `DefKind::AnonConst` and `DefKind::InlineConst`.
                        // Anon consts doesn't have their own generics, and inline consts' own
                        // generics are their inferred types, so don't print them.
                        DefPathData::AnonConst => {}

                        // If we have any generic arguments to print, we do that
                        // on top of the same path, but without its own generics.
                        _ => {
                            if !generics.is_own_empty() && args.len() >= generics.count() {
                                let args = generics.own_args_no_defaults(self.tcx(), args);
                                return self.path_generic_args(
                                    |cx| cx.print_def_path(def_id, parent_args),
                                    args,
                                );
                            }
                        }
                    }

                    // FIXME(eddyb) try to move this into the parent's printing
                    // logic, instead of doing it when printing the child.
                    trait_qualify_parent = generics.has_self
                        && generics.parent == Some(parent_def_id)
                        && parent_args.len() == generics.parent_count
                        && self.tcx().generics_of(parent_def_id).parent_count == 0;
                }

                self.path_append(
                    |cx: &mut Self| {
                        if trait_qualify_parent {
                            let trait_ref = ty::TraitRef::new(
                                cx.tcx(),
                                parent_def_id,
                                parent_args.iter().copied(),
                            );
                            cx.path_qualified(trait_ref.self_ty(), Some(trait_ref))
                        } else {
                            cx.print_def_path(parent_def_id, parent_args)
                        }
                    },
                    &key.disambiguated_data,
                )
            }
        }
    }

    fn default_print_impl_path(
        &mut self,
        impl_def_id: DefId,
        _args: &'tcx [GenericArg<'tcx>],
        self_ty: Ty<'tcx>,
        impl_trait_ref: Option<ty::TraitRef<'tcx>>,
    ) -> Result<(), PrintError> {
        debug!(
            "default_print_impl_path: impl_def_id={:?}, self_ty={}, impl_trait_ref={:?}",
            impl_def_id, self_ty, impl_trait_ref
        );

        let key = self.tcx().def_key(impl_def_id);
        let parent_def_id = DefId { index: key.parent.unwrap(), ..impl_def_id };

        // Decide whether to print the parent path for the impl.
        // Logically, since impls are global, it's never needed, but
        // users may find it useful. Currently, we omit the parent if
        // the impl is either in the same module as the self-type or
        // as the trait.
        let in_self_mod = match characteristic_def_id_of_type(self_ty) {
            None => false,
            Some(ty_def_id) => self.tcx().parent(ty_def_id) == parent_def_id,
        };
        let in_trait_mod = match impl_trait_ref {
            None => false,
            Some(trait_ref) => self.tcx().parent(trait_ref.def_id) == parent_def_id,
        };

        if !in_self_mod && !in_trait_mod {
            // If the impl is not co-located with either self-type or
            // trait-type, then fallback to a format that identifies
            // the module more clearly.
            self.path_append_impl(
                |cx| cx.print_def_path(parent_def_id, &[]),
                &key.disambiguated_data,
                self_ty,
                impl_trait_ref,
            )
        } else {
            // Otherwise, try to give a good form that would be valid language
            // syntax. Preferably using associated item notation.
            self.path_qualified(self_ty, impl_trait_ref)
        }
    }
}

/// As a heuristic, when we see an impl, if we see that the
/// 'self type' is a type defined in the same module as the impl,
/// we can omit including the path to the impl itself. This
/// function tries to find a "characteristic `DefId`" for a
/// type. It's just a heuristic so it makes some questionable
/// decisions and we may want to adjust it later.
///
/// Visited set is needed to avoid full iteration over
/// deeply nested tuples that have no DefId.
fn characteristic_def_id_of_type_cached<'a>(
    ty: Ty<'a>,
    visited: &mut SsoHashSet<Ty<'a>>,
) -> Option<DefId> {
    match *ty.kind() {
        ty::Adt(adt_def, _) => Some(adt_def.did()),

        ty::Dynamic(data, ..) => data.principal_def_id(),

        ty::Pat(subty, _) | ty::Array(subty, _) | ty::Slice(subty) => {
            characteristic_def_id_of_type_cached(subty, visited)
        }

        ty::RawPtr(ty, _) => characteristic_def_id_of_type_cached(ty, visited),

        ty::Ref(_, ty, _) => characteristic_def_id_of_type_cached(ty, visited),

        ty::Tuple(tys) => tys.iter().find_map(|ty| {
            if visited.insert(ty) {
                return characteristic_def_id_of_type_cached(ty, visited);
            }
            return None;
        }),

        ty::FnDef(def_id, _)
        | ty::Closure(def_id, _)
        | ty::CoroutineClosure(def_id, _)
        | ty::Coroutine(def_id, _)
        | ty::CoroutineWitness(def_id, _)
        | ty::Foreign(def_id) => Some(def_id),

        ty::Bool
        | ty::Char
        | ty::Int(_)
        | ty::Uint(_)
        | ty::Str
        | ty::FnPtr(..)
        | ty::Alias(..)
        | ty::Placeholder(..)
        | ty::Param(_)
        | ty::Infer(_)
        | ty::Bound(..)
        | ty::Error(_)
        | ty::Never
        | ty::Float(_) => None,
    }
}
pub fn characteristic_def_id_of_type(ty: Ty<'_>) -> Option<DefId> {
    characteristic_def_id_of_type_cached(ty, &mut SsoHashSet::new())
}

impl<'tcx, P: Printer<'tcx>> Print<'tcx, P> for ty::Region<'tcx> {
    fn print(&self, cx: &mut P) -> Result<(), PrintError> {
        cx.print_region(*self)
    }
}

impl<'tcx, P: Printer<'tcx>> Print<'tcx, P> for Ty<'tcx> {
    fn print(&self, cx: &mut P) -> Result<(), PrintError> {
        cx.print_type(*self)
    }
}

impl<'tcx, P: Printer<'tcx>> Print<'tcx, P> for &'tcx ty::List<ty::PolyExistentialPredicate<'tcx>> {
    fn print(&self, cx: &mut P) -> Result<(), PrintError> {
        cx.print_dyn_existential(self)
    }
}

impl<'tcx, P: Printer<'tcx>> Print<'tcx, P> for ty::Const<'tcx> {
    fn print(&self, cx: &mut P) -> Result<(), PrintError> {
        cx.print_const(*self)
    }
}

// This is only used by query descriptions
pub fn describe_as_module(def_id: impl Into<LocalDefId>, tcx: TyCtxt<'_>) -> String {
    let def_id = def_id.into();
    if def_id.is_top_level_module() {
        "top-level module".to_string()
    } else {
        format!("module `{}`", tcx.def_path_str(def_id))
    }
}

impl<T> rustc_type_ir::ir_print::IrPrint<T> for TyCtxt<'_>
where
    T: Copy + for<'a, 'tcx> Lift<TyCtxt<'tcx>, Lifted: Print<'tcx, FmtPrinter<'a, 'tcx>>>,
{
    fn print(t: &T, fmt: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
        ty::tls::with(|tcx| {
            let mut cx = FmtPrinter::new(tcx, Namespace::TypeNS);
            tcx.lift(*t).expect("could not lift for printing").print(&mut cx)?;
            fmt.write_str(&cx.into_buffer())?;
            Ok(())
        })
    }

    fn print_debug(t: &T, fmt: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
        with_no_trimmed_paths!(Self::print(t, fmt))
    }
}

/// Format instance name that is already known to be too long for rustc.
/// Show only the first 2 types if it is longer than 32 characters to avoid blasting
/// the user's terminal with thousands of lines of type-name.
///
/// If the type name is longer than before+after, it will be written to a file.
pub fn shrunk_instance_name<'tcx>(
    tcx: TyCtxt<'tcx>,
    instance: ty::Instance<'tcx>,
) -> (String, Option<PathBuf>) {
    let s = instance.to_string();

    // Only use the shrunk version if it's really shorter.
    // This also avoids the case where before and after slices overlap.
    if s.chars().nth(33).is_some() {
        let shrunk = format!("{}", ShortInstance(instance, 4));
        if shrunk == s {
            return (s, None);
        }

        let path = tcx.output_filenames(()).temp_path_ext("long-type.txt", None);
        let written_to_path = std::fs::write(&path, s).ok().map(|_| path);

        (shrunk, written_to_path)
    } else {
        (s, None)
    }
}