rustc_middle/ty/print/
mod.rs

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1use std::path::PathBuf;
2
3use hir::def::Namespace;
4use rustc_data_structures::fx::FxHashSet;
5use rustc_data_structures::sso::SsoHashSet;
6use rustc_hir as hir;
7use rustc_hir::def_id::{CrateNum, DefId, LocalDefId};
8use rustc_hir::definitions::{DefPathData, DisambiguatedDefPathData};
9use tracing::{debug, instrument, trace};
10
11use crate::ty::{self, GenericArg, ShortInstance, Ty, TyCtxt};
12
13// `pretty` is a separate module only for organization.
14mod pretty;
15pub use self::pretty::*;
16use super::Lift;
17
18pub type PrintError = std::fmt::Error;
19
20pub trait Print<'tcx, P> {
21    fn print(&self, cx: &mut P) -> Result<(), PrintError>;
22}
23
24/// Interface for outputting user-facing "type-system entities"
25/// (paths, types, lifetimes, constants, etc.) as a side-effect
26/// (e.g. formatting, like `PrettyPrinter` implementors do) or by
27/// constructing some alternative representation (e.g. an AST),
28/// which the associated types allow passing through the methods.
29///
30/// For pretty-printing/formatting in particular, see `PrettyPrinter`.
31//
32// FIXME(eddyb) find a better name; this is more general than "printing".
33pub trait Printer<'tcx>: Sized {
34    fn tcx<'a>(&'a self) -> TyCtxt<'tcx>;
35
36    fn print_def_path(
37        &mut self,
38        def_id: DefId,
39        args: &'tcx [GenericArg<'tcx>],
40    ) -> Result<(), PrintError> {
41        self.default_print_def_path(def_id, args)
42    }
43
44    fn print_impl_path(
45        &mut self,
46        impl_def_id: DefId,
47        args: &'tcx [GenericArg<'tcx>],
48    ) -> Result<(), PrintError> {
49        let tcx = self.tcx();
50        let self_ty = tcx.type_of(impl_def_id);
51        let impl_trait_ref = tcx.impl_trait_ref(impl_def_id);
52        let (self_ty, impl_trait_ref) = if tcx.generics_of(impl_def_id).count() <= args.len() {
53            (
54                self_ty.instantiate(tcx, args),
55                impl_trait_ref.map(|impl_trait_ref| impl_trait_ref.instantiate(tcx, args)),
56            )
57        } else {
58            // We are probably printing a nested item inside of an impl.
59            // Use the identity substitutions for the impl.
60            (
61                self_ty.instantiate_identity(),
62                impl_trait_ref.map(|impl_trait_ref| impl_trait_ref.instantiate_identity()),
63            )
64        };
65
66        self.default_print_impl_path(impl_def_id, self_ty, impl_trait_ref)
67    }
68
69    fn print_region(&mut self, region: ty::Region<'tcx>) -> Result<(), PrintError>;
70
71    fn print_type(&mut self, ty: Ty<'tcx>) -> Result<(), PrintError>;
72
73    fn print_dyn_existential(
74        &mut self,
75        predicates: &'tcx ty::List<ty::PolyExistentialPredicate<'tcx>>,
76    ) -> Result<(), PrintError>;
77
78    fn print_const(&mut self, ct: ty::Const<'tcx>) -> Result<(), PrintError>;
79
80    fn path_crate(&mut self, cnum: CrateNum) -> Result<(), PrintError>;
81
82    fn path_qualified(
83        &mut self,
84        self_ty: Ty<'tcx>,
85        trait_ref: Option<ty::TraitRef<'tcx>>,
86    ) -> Result<(), PrintError>;
87
88    fn path_append_impl(
89        &mut self,
90        print_prefix: impl FnOnce(&mut Self) -> Result<(), PrintError>,
91        disambiguated_data: &DisambiguatedDefPathData,
92        self_ty: Ty<'tcx>,
93        trait_ref: Option<ty::TraitRef<'tcx>>,
94    ) -> Result<(), PrintError>;
95
96    fn path_append(
97        &mut self,
98        print_prefix: impl FnOnce(&mut Self) -> Result<(), PrintError>,
99        disambiguated_data: &DisambiguatedDefPathData,
100    ) -> Result<(), PrintError>;
101
102    fn path_generic_args(
103        &mut self,
104        print_prefix: impl FnOnce(&mut Self) -> Result<(), PrintError>,
105        args: &[GenericArg<'tcx>],
106    ) -> Result<(), PrintError>;
107
108    fn should_truncate(&mut self) -> bool {
109        false
110    }
111
112    // Defaults (should not be overridden):
113
114    #[instrument(skip(self), level = "debug")]
115    fn default_print_def_path(
116        &mut self,
117        def_id: DefId,
118        args: &'tcx [GenericArg<'tcx>],
119    ) -> Result<(), PrintError> {
120        let key = self.tcx().def_key(def_id);
121        debug!(?key);
122
123        match key.disambiguated_data.data {
124            DefPathData::CrateRoot => {
125                assert!(key.parent.is_none());
126                self.path_crate(def_id.krate)
127            }
128
129            DefPathData::Impl => self.print_impl_path(def_id, args),
130
131            _ => {
132                let parent_def_id = DefId { index: key.parent.unwrap(), ..def_id };
133
134                let mut parent_args = args;
135                let mut trait_qualify_parent = false;
136                if !args.is_empty() {
137                    let generics = self.tcx().generics_of(def_id);
138                    parent_args = &args[..generics.parent_count.min(args.len())];
139
140                    match key.disambiguated_data.data {
141                        DefPathData::Closure => {
142                            // FIXME(async_closures): This is somewhat ugly.
143                            // We need to additionally print the `kind` field of a closure if
144                            // it is desugared from a coroutine-closure.
145                            if let Some(hir::CoroutineKind::Desugared(
146                                _,
147                                hir::CoroutineSource::Closure,
148                            )) = self.tcx().coroutine_kind(def_id)
149                                && args.len() > parent_args.len()
150                            {
151                                return self.path_generic_args(
152                                    |cx| cx.print_def_path(def_id, parent_args),
153                                    &args[..parent_args.len() + 1][..1],
154                                );
155                            } else {
156                                // Closures' own generics are only captures, don't print them.
157                            }
158                        }
159                        // This covers both `DefKind::AnonConst` and `DefKind::InlineConst`.
160                        // Anon consts doesn't have their own generics, and inline consts' own
161                        // generics are their inferred types, so don't print them.
162                        DefPathData::AnonConst => {}
163
164                        // If we have any generic arguments to print, we do that
165                        // on top of the same path, but without its own generics.
166                        _ => {
167                            if !generics.is_own_empty() && args.len() >= generics.count() {
168                                let args = generics.own_args_no_defaults(self.tcx(), args);
169                                return self.path_generic_args(
170                                    |cx| cx.print_def_path(def_id, parent_args),
171                                    args,
172                                );
173                            }
174                        }
175                    }
176
177                    // FIXME(eddyb) try to move this into the parent's printing
178                    // logic, instead of doing it when printing the child.
179                    trait_qualify_parent = generics.has_self
180                        && generics.parent == Some(parent_def_id)
181                        && parent_args.len() == generics.parent_count
182                        && self.tcx().generics_of(parent_def_id).parent_count == 0;
183                }
184
185                self.path_append(
186                    |cx: &mut Self| {
187                        if trait_qualify_parent {
188                            let trait_ref = ty::TraitRef::new(
189                                cx.tcx(),
190                                parent_def_id,
191                                parent_args.iter().copied(),
192                            );
193                            cx.path_qualified(trait_ref.self_ty(), Some(trait_ref))
194                        } else {
195                            cx.print_def_path(parent_def_id, parent_args)
196                        }
197                    },
198                    &key.disambiguated_data,
199                )
200            }
201        }
202    }
203
204    fn default_print_impl_path(
205        &mut self,
206        impl_def_id: DefId,
207        self_ty: Ty<'tcx>,
208        impl_trait_ref: Option<ty::TraitRef<'tcx>>,
209    ) -> Result<(), PrintError> {
210        debug!(
211            "default_print_impl_path: impl_def_id={:?}, self_ty={}, impl_trait_ref={:?}",
212            impl_def_id, self_ty, impl_trait_ref
213        );
214
215        let key = self.tcx().def_key(impl_def_id);
216        let parent_def_id = DefId { index: key.parent.unwrap(), ..impl_def_id };
217
218        // Decide whether to print the parent path for the impl.
219        // Logically, since impls are global, it's never needed, but
220        // users may find it useful. Currently, we omit the parent if
221        // the impl is either in the same module as the self-type or
222        // as the trait.
223        let in_self_mod = match characteristic_def_id_of_type(self_ty) {
224            None => false,
225            Some(ty_def_id) => self.tcx().parent(ty_def_id) == parent_def_id,
226        };
227        let in_trait_mod = match impl_trait_ref {
228            None => false,
229            Some(trait_ref) => self.tcx().parent(trait_ref.def_id) == parent_def_id,
230        };
231
232        if !in_self_mod && !in_trait_mod {
233            // If the impl is not co-located with either self-type or
234            // trait-type, then fallback to a format that identifies
235            // the module more clearly.
236            self.path_append_impl(
237                |cx| cx.print_def_path(parent_def_id, &[]),
238                &key.disambiguated_data,
239                self_ty,
240                impl_trait_ref,
241            )
242        } else {
243            // Otherwise, try to give a good form that would be valid language
244            // syntax. Preferably using associated item notation.
245            self.path_qualified(self_ty, impl_trait_ref)
246        }
247    }
248}
249
250/// As a heuristic, when we see an impl, if we see that the
251/// 'self type' is a type defined in the same module as the impl,
252/// we can omit including the path to the impl itself. This
253/// function tries to find a "characteristic `DefId`" for a
254/// type. It's just a heuristic so it makes some questionable
255/// decisions and we may want to adjust it later.
256///
257/// Visited set is needed to avoid full iteration over
258/// deeply nested tuples that have no DefId.
259fn characteristic_def_id_of_type_cached<'a>(
260    ty: Ty<'a>,
261    visited: &mut SsoHashSet<Ty<'a>>,
262) -> Option<DefId> {
263    match *ty.kind() {
264        ty::Adt(adt_def, _) => Some(adt_def.did()),
265
266        ty::Dynamic(data, ..) => data.principal_def_id(),
267
268        ty::Pat(subty, _) | ty::Array(subty, _) | ty::Slice(subty) => {
269            characteristic_def_id_of_type_cached(subty, visited)
270        }
271
272        ty::RawPtr(ty, _) => characteristic_def_id_of_type_cached(ty, visited),
273
274        ty::Ref(_, ty, _) => characteristic_def_id_of_type_cached(ty, visited),
275
276        ty::Tuple(tys) => tys.iter().find_map(|ty| {
277            if visited.insert(ty) {
278                return characteristic_def_id_of_type_cached(ty, visited);
279            }
280            return None;
281        }),
282
283        ty::FnDef(def_id, _)
284        | ty::Closure(def_id, _)
285        | ty::CoroutineClosure(def_id, _)
286        | ty::Coroutine(def_id, _)
287        | ty::CoroutineWitness(def_id, _)
288        | ty::Foreign(def_id) => Some(def_id),
289
290        ty::Bool
291        | ty::Char
292        | ty::Int(_)
293        | ty::Uint(_)
294        | ty::Str
295        | ty::FnPtr(..)
296        | ty::UnsafeBinder(_)
297        | ty::Alias(..)
298        | ty::Placeholder(..)
299        | ty::Param(_)
300        | ty::Infer(_)
301        | ty::Bound(..)
302        | ty::Error(_)
303        | ty::Never
304        | ty::Float(_) => None,
305    }
306}
307pub fn characteristic_def_id_of_type(ty: Ty<'_>) -> Option<DefId> {
308    characteristic_def_id_of_type_cached(ty, &mut SsoHashSet::new())
309}
310
311impl<'tcx, P: Printer<'tcx>> Print<'tcx, P> for ty::Region<'tcx> {
312    fn print(&self, cx: &mut P) -> Result<(), PrintError> {
313        cx.print_region(*self)
314    }
315}
316
317impl<'tcx, P: Printer<'tcx>> Print<'tcx, P> for Ty<'tcx> {
318    fn print(&self, cx: &mut P) -> Result<(), PrintError> {
319        cx.print_type(*self)
320    }
321}
322
323impl<'tcx, P: Printer<'tcx>> Print<'tcx, P> for &'tcx ty::List<ty::PolyExistentialPredicate<'tcx>> {
324    fn print(&self, cx: &mut P) -> Result<(), PrintError> {
325        cx.print_dyn_existential(self)
326    }
327}
328
329impl<'tcx, P: Printer<'tcx>> Print<'tcx, P> for ty::Const<'tcx> {
330    fn print(&self, cx: &mut P) -> Result<(), PrintError> {
331        cx.print_const(*self)
332    }
333}
334
335// This is only used by query descriptions
336pub fn describe_as_module(def_id: impl Into<LocalDefId>, tcx: TyCtxt<'_>) -> String {
337    let def_id = def_id.into();
338    if def_id.is_top_level_module() {
339        "top-level module".to_string()
340    } else {
341        format!("module `{}`", tcx.def_path_str(def_id))
342    }
343}
344
345impl<T> rustc_type_ir::ir_print::IrPrint<T> for TyCtxt<'_>
346where
347    T: Copy + for<'a, 'tcx> Lift<TyCtxt<'tcx>, Lifted: Print<'tcx, FmtPrinter<'a, 'tcx>>>,
348{
349    fn print(t: &T, fmt: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
350        ty::tls::with(|tcx| {
351            let mut cx = FmtPrinter::new(tcx, Namespace::TypeNS);
352            tcx.lift(*t).expect("could not lift for printing").print(&mut cx)?;
353            fmt.write_str(&cx.into_buffer())?;
354            Ok(())
355        })
356    }
357
358    fn print_debug(t: &T, fmt: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
359        with_no_trimmed_paths!(Self::print(t, fmt))
360    }
361}
362
363/// Format instance name that is already known to be too long for rustc.
364/// Show only the first 2 types if it is longer than 32 characters to avoid blasting
365/// the user's terminal with thousands of lines of type-name.
366///
367/// If the type name is longer than before+after, it will be written to a file.
368pub fn shrunk_instance_name<'tcx>(
369    tcx: TyCtxt<'tcx>,
370    instance: ty::Instance<'tcx>,
371) -> (String, Option<PathBuf>) {
372    let s = instance.to_string();
373
374    // Only use the shrunk version if it's really shorter.
375    // This also avoids the case where before and after slices overlap.
376    if s.chars().nth(33).is_some() {
377        let shrunk = format!("{}", ShortInstance(instance, 4));
378        if shrunk == s {
379            return (s, None);
380        }
381
382        let path = tcx.output_filenames(()).temp_path_ext("long-type.txt", None);
383        let written_to_path = std::fs::write(&path, s).ok().map(|_| path);
384
385        (shrunk, written_to_path)
386    } else {
387        (s, None)
388    }
389}
rustc_middle/ty/print/mod.rs

rustc_middle/ty/print/
mod.rs
