1 // Copyright 2014 The Rust Project Developers. See the COPYRIGHT
2 // file at the top-level directory of this distribution and at
3 // http://rust-lang.org/COPYRIGHT.
5 // Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
6 // http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
7 // <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
8 // option. This file may not be copied, modified, or distributed
9 // except according to those terms.
14 MismatchedProjectionTypes,
16 OutputTypeParameterMismatch,
21 use fmt_macros::{Parser, Piece, Position};
22 use middle::infer::InferCtxt;
23 use middle::ty::{self, AsPredicate, ReferencesError, ToPolyTraitRef, TraitRef};
24 use std::collections::HashMap;
25 use syntax::codemap::{DUMMY_SP, Span};
26 use syntax::attr::{AttributeMethods, AttrMetaMethods};
27 use util::ppaux::{Repr, UserString};
29 pub fn report_fulfillment_errors<'a, 'tcx>(infcx: &InferCtxt<'a, 'tcx>,
30 errors: &Vec<FulfillmentError<'tcx>>) {
31 for error in errors.iter() {
32 report_fulfillment_error(infcx, error);
36 fn report_fulfillment_error<'a, 'tcx>(infcx: &InferCtxt<'a, 'tcx>,
37 error: &FulfillmentError<'tcx>) {
39 FulfillmentErrorCode::CodeSelectionError(ref e) => {
40 report_selection_error(infcx, &error.obligation, e);
42 FulfillmentErrorCode::CodeProjectionError(ref e) => {
43 report_projection_error(infcx, &error.obligation, e);
45 FulfillmentErrorCode::CodeAmbiguity => {
46 maybe_report_ambiguity(infcx, &error.obligation);
51 pub fn report_projection_error<'a, 'tcx>(infcx: &InferCtxt<'a, 'tcx>,
52 obligation: &PredicateObligation<'tcx>,
53 error: &MismatchedProjectionTypes<'tcx>)
56 infcx.resolve_type_vars_if_possible(&obligation.predicate);
57 if !predicate.references_error() {
58 infcx.tcx.sess.span_err(
59 obligation.cause.span,
61 "type mismatch resolving `{}`: {}",
62 predicate.user_string(infcx.tcx),
63 ty::type_err_to_str(infcx.tcx, &error.err)).as_slice());
64 note_obligation_cause(infcx, obligation);
68 fn report_on_unimplemented<'a, 'tcx>(infcx: &InferCtxt<'a, 'tcx>,
69 trait_ref: &TraitRef<'tcx>,
70 span: Span) -> Option<String> {
71 let def_id = trait_ref.def_id;
72 let mut report = None;
73 ty::each_attr(infcx.tcx, def_id, |item| {
74 if item.check_name("rustc_on_unimplemented") {
75 let err_sp = if item.meta().span == DUMMY_SP {
80 let def = ty::lookup_trait_def(infcx.tcx, def_id);
81 let trait_str = def.trait_ref.user_string(infcx.tcx);
82 if let Some(ref istring) = item.value_str() {
83 let mut generic_map = def.generics.types.iter_enumerated()
84 .map(|(param, i, gen)| {
85 (gen.name.as_str().to_string(),
86 trait_ref.substs.types.get(param, i)
87 .user_string(infcx.tcx))
88 }).collect::<HashMap<String, String>>();
89 generic_map.insert("Self".to_string(),
90 trait_ref.self_ty().user_string(infcx.tcx));
91 let parser = Parser::new(istring.get());
92 let mut errored = false;
93 let err: String = parser.filter_map(|p| {
95 Piece::String(s) => Some(s),
96 Piece::NextArgument(a) => match a.position {
97 Position::ArgumentNamed(s) => match generic_map.get(s) {
98 Some(val) => Some(val.as_slice()),
102 format!("the #[rustc_on_unimplemented] \
104 trait definition for {} refers to \
105 non-existent type parameter {}",
115 format!("the #[rustc_on_unimplemented] \
117 trait definition for {} must have named \
119 eg `#[rustc_on_unimplemented = \
121 trait_str).as_slice());
128 // Report only if the format string checks out
133 infcx.tcx.sess.span_err(err_sp,
134 format!("the #[rustc_on_unimplemented] attribute on \
135 trait definition for {} must have a value, \
136 eg `#[rustc_on_unimplemented = \"foo\"]`",
137 trait_str).as_slice());
147 pub fn report_selection_error<'a, 'tcx>(infcx: &InferCtxt<'a, 'tcx>,
148 obligation: &PredicateObligation<'tcx>,
149 error: &SelectionError<'tcx>)
152 SelectionError::Overflow => {
153 // We could track the stack here more precisely if we wanted, I imagine.
155 infcx.resolve_type_vars_if_possible(&obligation.predicate);
156 infcx.tcx.sess.span_err(
157 obligation.cause.span,
159 "overflow evaluating the requirement `{}`",
160 predicate.user_string(infcx.tcx)).as_slice());
162 suggest_new_overflow_limit(infcx.tcx, obligation.cause.span);
164 note_obligation_cause(infcx, obligation);
166 SelectionError::Unimplemented => {
167 match obligation.predicate {
168 ty::Predicate::Trait(ref trait_predicate) => {
169 let trait_predicate =
170 infcx.resolve_type_vars_if_possible(trait_predicate);
171 if !trait_predicate.references_error() {
172 let trait_ref = trait_predicate.to_poly_trait_ref();
173 infcx.tcx.sess.span_err(
174 obligation.cause.span,
176 "the trait `{}` is not implemented for the type `{}`",
177 trait_ref.user_string(infcx.tcx),
178 trait_ref.self_ty().user_string(infcx.tcx)).as_slice());
179 // Check if it has a custom "#[rustc_on_unimplemented]" error message,
180 // report with that message if it does
181 let custom_note = report_on_unimplemented(infcx, &*trait_ref.0,
182 obligation.cause.span);
183 if let Some(s) = custom_note {
184 infcx.tcx.sess.span_note(obligation.cause.span,
190 ty::Predicate::Equate(ref predicate) => {
191 let predicate = infcx.resolve_type_vars_if_possible(predicate);
192 let err = infcx.equality_predicate(obligation.cause.span,
193 &predicate).unwrap_err();
194 infcx.tcx.sess.span_err(
195 obligation.cause.span,
197 "the requirement `{}` is not satisfied (`{}`)",
198 predicate.user_string(infcx.tcx),
199 ty::type_err_to_str(infcx.tcx, &err)).as_slice());
202 ty::Predicate::RegionOutlives(ref predicate) => {
203 let predicate = infcx.resolve_type_vars_if_possible(predicate);
204 let err = infcx.region_outlives_predicate(obligation.cause.span,
205 &predicate).unwrap_err();
206 infcx.tcx.sess.span_err(
207 obligation.cause.span,
209 "the requirement `{}` is not satisfied (`{}`)",
210 predicate.user_string(infcx.tcx),
211 ty::type_err_to_str(infcx.tcx, &err)).as_slice());
214 ty::Predicate::Projection(..) |
215 ty::Predicate::TypeOutlives(..) => {
217 infcx.resolve_type_vars_if_possible(&obligation.predicate);
218 infcx.tcx.sess.span_err(
219 obligation.cause.span,
221 "the requirement `{}` is not satisfied",
222 predicate.user_string(infcx.tcx)).as_slice());
226 OutputTypeParameterMismatch(ref expected_trait_ref, ref actual_trait_ref, ref e) => {
227 let expected_trait_ref = infcx.resolve_type_vars_if_possible(&*expected_trait_ref);
228 let actual_trait_ref = infcx.resolve_type_vars_if_possible(&*actual_trait_ref);
229 if !ty::type_is_error(actual_trait_ref.self_ty()) {
230 infcx.tcx.sess.span_err(
231 obligation.cause.span,
233 "type mismatch: the type `{}` implements the trait `{}`, \
234 but the trait `{}` is required ({})",
235 expected_trait_ref.self_ty().user_string(infcx.tcx),
236 expected_trait_ref.user_string(infcx.tcx),
237 actual_trait_ref.user_string(infcx.tcx),
238 ty::type_err_to_str(infcx.tcx, e)).as_slice());
239 note_obligation_cause(infcx, obligation);
245 pub fn maybe_report_ambiguity<'a, 'tcx>(infcx: &InferCtxt<'a, 'tcx>,
246 obligation: &PredicateObligation<'tcx>) {
247 // Unable to successfully determine, probably means
248 // insufficient type information, but could mean
249 // ambiguous impls. The latter *ought* to be a
250 // coherence violation, so we don't report it here.
252 let predicate = infcx.resolve_type_vars_if_possible(&obligation.predicate);
254 debug!("maybe_report_ambiguity(predicate={}, obligation={})",
255 predicate.repr(infcx.tcx),
256 obligation.repr(infcx.tcx));
259 ty::Predicate::Trait(ref data) => {
260 let trait_ref = data.to_poly_trait_ref();
261 let self_ty = trait_ref.self_ty();
262 let all_types = &trait_ref.substs().types;
263 if all_types.iter().any(|&t| ty::type_is_error(t)) {
264 } else if all_types.iter().any(|&t| ty::type_needs_infer(t)) {
265 // This is kind of a hack: it frequently happens that some earlier
266 // error prevents types from being fully inferred, and then we get
267 // a bunch of uninteresting errors saying something like "<generic
268 // #0> doesn't implement Sized". It may even be true that we
269 // could just skip over all checks where the self-ty is an
270 // inference variable, but I was afraid that there might be an
271 // inference variable created, registered as an obligation, and
272 // then never forced by writeback, and hence by skipping here we'd
273 // be ignoring the fact that we don't KNOW the type works
274 // out. Though even that would probably be harmless, given that
275 // we're only talking about builtin traits, which are known to be
276 // inhabited. But in any case I just threw in this check for
277 // has_errors() to be sure that compilation isn't happening
278 // anyway. In that case, why inundate the user.
279 if !infcx.tcx.sess.has_errors() {
281 infcx.tcx.lang_items.sized_trait()
282 .map_or(false, |sized_id| sized_id == trait_ref.def_id())
284 infcx.tcx.sess.span_err(
285 obligation.cause.span,
287 "unable to infer enough type information about `{}`; \
288 type annotations required",
289 self_ty.user_string(infcx.tcx)).as_slice());
291 infcx.tcx.sess.span_err(
292 obligation.cause.span,
294 "type annotations required: cannot resolve `{}`",
295 predicate.user_string(infcx.tcx)).as_slice());
296 note_obligation_cause(infcx, obligation);
299 } else if !infcx.tcx.sess.has_errors() {
300 // Ambiguity. Coherence should have reported an error.
301 infcx.tcx.sess.span_bug(
302 obligation.cause.span,
304 "coherence failed to report ambiguity: \
305 cannot locate the impl of the trait `{}` for \
307 trait_ref.user_string(infcx.tcx),
308 self_ty.user_string(infcx.tcx)).as_slice());
313 if !infcx.tcx.sess.has_errors() {
314 infcx.tcx.sess.span_err(
315 obligation.cause.span,
317 "type annotations required: cannot resolve `{}`",
318 predicate.user_string(infcx.tcx)).as_slice());
319 note_obligation_cause(infcx, obligation);
325 fn note_obligation_cause<'a, 'tcx>(infcx: &InferCtxt<'a, 'tcx>,
326 obligation: &PredicateObligation<'tcx>)
328 note_obligation_cause_code(infcx,
329 &obligation.predicate,
330 obligation.cause.span,
331 &obligation.cause.code);
334 fn note_obligation_cause_code<'a, 'tcx>(infcx: &InferCtxt<'a, 'tcx>,
335 _predicate: &ty::Predicate<'tcx>,
337 cause_code: &ObligationCauseCode<'tcx>)
341 ObligationCauseCode::MiscObligation => { }
342 ObligationCauseCode::ItemObligation(item_def_id) => {
343 let item_name = ty::item_path_str(tcx, item_def_id);
346 format!("required by `{}`", item_name).as_slice());
348 ObligationCauseCode::ObjectCastObligation(object_ty) => {
352 "required for the cast to the object type `{}`",
353 infcx.ty_to_string(object_ty)).as_slice());
355 ObligationCauseCode::RepeatVec => {
358 "the `Copy` trait is required because the \
359 repeated element will be copied");
361 ObligationCauseCode::VariableType(_) => {
364 "all local variables must have a statically known size");
366 ObligationCauseCode::ReturnType => {
369 "the return type of a function must have a \
370 statically known size");
372 ObligationCauseCode::AssignmentLhsSized => {
375 "the left-hand-side of an assignment must have a statically known size");
377 ObligationCauseCode::StructInitializerSized => {
380 "structs must have a statically known size to be initialized");
382 ObligationCauseCode::ClosureCapture(var_id, closure_span, builtin_bound) => {
383 let def_id = tcx.lang_items.from_builtin_kind(builtin_bound).unwrap();
384 let trait_name = ty::item_path_str(tcx, def_id);
385 let name = ty::local_var_name_str(tcx, var_id);
386 span_note!(tcx.sess, closure_span,
387 "the closure that captures `{}` requires that all captured variables \
388 implement the trait `{}`",
392 ObligationCauseCode::FieldSized => {
393 span_note!(tcx.sess, cause_span,
394 "only the last field of a struct or enum variant \
395 may have a dynamically sized type")
397 ObligationCauseCode::ObjectSized => {
398 span_note!(tcx.sess, cause_span,
399 "only sized types can be made into objects");
401 ObligationCauseCode::SharedStatic => {
402 span_note!(tcx.sess, cause_span,
403 "shared static variables must have a type that implements `Sync`");
405 ObligationCauseCode::BuiltinDerivedObligation(ref data) => {
406 let parent_trait_ref = infcx.resolve_type_vars_if_possible(&data.parent_trait_ref);
407 span_note!(tcx.sess, cause_span,
408 "required because it appears within the type `{}`",
409 parent_trait_ref.0.self_ty().user_string(infcx.tcx));
410 let parent_predicate = parent_trait_ref.as_predicate();
411 note_obligation_cause_code(infcx, &parent_predicate, cause_span, &*data.parent_code);
413 ObligationCauseCode::ImplDerivedObligation(ref data) => {
414 let parent_trait_ref = infcx.resolve_type_vars_if_possible(&data.parent_trait_ref);
415 span_note!(tcx.sess, cause_span,
416 "required because of the requirements on the impl of `{}` for `{}`",
417 parent_trait_ref.user_string(infcx.tcx),
418 parent_trait_ref.0.self_ty().user_string(infcx.tcx));
419 let parent_predicate = parent_trait_ref.as_predicate();
420 note_obligation_cause_code(infcx, &parent_predicate, cause_span, &*data.parent_code);
425 pub fn suggest_new_overflow_limit(tcx: &ty::ctxt, span: Span) {
426 let current_limit = tcx.sess.recursion_limit.get();
427 let suggested_limit = current_limit * 2;
431 "consider adding a `#![recursion_limit=\"{}\"]` attribute to your crate",