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 for item in ty::get_attrs(infcx.tcx, def_id).iter() {
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());
145 pub fn report_selection_error<'a, 'tcx>(infcx: &InferCtxt<'a, 'tcx>,
146 obligation: &PredicateObligation<'tcx>,
147 error: &SelectionError<'tcx>)
150 SelectionError::Overflow => {
151 // We could track the stack here more precisely if we wanted, I imagine.
153 infcx.resolve_type_vars_if_possible(&obligation.predicate);
154 infcx.tcx.sess.span_err(
155 obligation.cause.span,
157 "overflow evaluating the requirement `{}`",
158 predicate.user_string(infcx.tcx)).as_slice());
160 suggest_new_overflow_limit(infcx.tcx, obligation.cause.span);
162 note_obligation_cause(infcx, obligation);
165 SelectionError::Unimplemented => {
166 match &obligation.cause.code {
167 &ObligationCauseCode::CompareImplMethodObligation => {
168 infcx.tcx.sess.span_err(
169 obligation.cause.span,
171 "the requirement `{}` appears on the impl \
172 method but not on the corresponding trait method",
173 obligation.predicate.user_string(infcx.tcx)).as_slice());
176 match obligation.predicate {
177 ty::Predicate::Trait(ref trait_predicate) => {
178 let trait_predicate =
179 infcx.resolve_type_vars_if_possible(trait_predicate);
181 if !trait_predicate.references_error() {
182 let trait_ref = trait_predicate.to_poly_trait_ref();
183 infcx.tcx.sess.span_err(
184 obligation.cause.span,
186 "the trait `{}` is not implemented for the type `{}`",
187 trait_ref.user_string(infcx.tcx),
188 trait_ref.self_ty().user_string(infcx.tcx)).as_slice());
189 // Check if it has a custom "#[rustc_on_unimplemented]"
190 // error message, report with that message if it does
191 let custom_note = report_on_unimplemented(infcx, &*trait_ref.0,
192 obligation.cause.span);
193 if let Some(s) = custom_note {
194 infcx.tcx.sess.span_note(obligation.cause.span,
200 ty::Predicate::Equate(ref predicate) => {
201 let predicate = infcx.resolve_type_vars_if_possible(predicate);
202 let err = infcx.equality_predicate(obligation.cause.span,
203 &predicate).unwrap_err();
204 infcx.tcx.sess.span_err(
205 obligation.cause.span,
207 "the requirement `{}` is not satisfied (`{}`)",
208 predicate.user_string(infcx.tcx),
209 ty::type_err_to_str(infcx.tcx, &err)).as_slice());
212 ty::Predicate::RegionOutlives(ref predicate) => {
213 let predicate = infcx.resolve_type_vars_if_possible(predicate);
214 let err = infcx.region_outlives_predicate(obligation.cause.span,
215 &predicate).unwrap_err();
216 infcx.tcx.sess.span_err(
217 obligation.cause.span,
219 "the requirement `{}` is not satisfied (`{}`)",
220 predicate.user_string(infcx.tcx),
221 ty::type_err_to_str(infcx.tcx, &err)).as_slice());
224 ty::Predicate::Projection(..) | ty::Predicate::TypeOutlives(..) => {
226 infcx.resolve_type_vars_if_possible(&obligation.predicate);
227 infcx.tcx.sess.span_err(
228 obligation.cause.span,
230 "the requirement `{}` is not satisfied",
231 predicate.user_string(infcx.tcx)).as_slice());
238 OutputTypeParameterMismatch(ref expected_trait_ref, ref actual_trait_ref, ref e) => {
239 let expected_trait_ref = infcx.resolve_type_vars_if_possible(&*expected_trait_ref);
240 let actual_trait_ref = infcx.resolve_type_vars_if_possible(&*actual_trait_ref);
241 if !ty::type_is_error(actual_trait_ref.self_ty()) {
242 infcx.tcx.sess.span_err(
243 obligation.cause.span,
245 "type mismatch: the type `{}` implements the trait `{}`, \
246 but the trait `{}` is required ({})",
247 expected_trait_ref.self_ty().user_string(infcx.tcx),
248 expected_trait_ref.user_string(infcx.tcx),
249 actual_trait_ref.user_string(infcx.tcx),
250 ty::type_err_to_str(infcx.tcx, e)).as_slice());
251 note_obligation_cause(infcx, obligation);
257 pub fn maybe_report_ambiguity<'a, 'tcx>(infcx: &InferCtxt<'a, 'tcx>,
258 obligation: &PredicateObligation<'tcx>) {
259 // Unable to successfully determine, probably means
260 // insufficient type information, but could mean
261 // ambiguous impls. The latter *ought* to be a
262 // coherence violation, so we don't report it here.
264 let predicate = infcx.resolve_type_vars_if_possible(&obligation.predicate);
266 debug!("maybe_report_ambiguity(predicate={}, obligation={})",
267 predicate.repr(infcx.tcx),
268 obligation.repr(infcx.tcx));
271 ty::Predicate::Trait(ref data) => {
272 let trait_ref = data.to_poly_trait_ref();
273 let self_ty = trait_ref.self_ty();
274 let all_types = &trait_ref.substs().types;
275 if all_types.iter().any(|&t| ty::type_is_error(t)) {
276 } else if all_types.iter().any(|&t| ty::type_needs_infer(t)) {
277 // This is kind of a hack: it frequently happens that some earlier
278 // error prevents types from being fully inferred, and then we get
279 // a bunch of uninteresting errors saying something like "<generic
280 // #0> doesn't implement Sized". It may even be true that we
281 // could just skip over all checks where the self-ty is an
282 // inference variable, but I was afraid that there might be an
283 // inference variable created, registered as an obligation, and
284 // then never forced by writeback, and hence by skipping here we'd
285 // be ignoring the fact that we don't KNOW the type works
286 // out. Though even that would probably be harmless, given that
287 // we're only talking about builtin traits, which are known to be
288 // inhabited. But in any case I just threw in this check for
289 // has_errors() to be sure that compilation isn't happening
290 // anyway. In that case, why inundate the user.
291 if !infcx.tcx.sess.has_errors() {
293 infcx.tcx.lang_items.sized_trait()
294 .map_or(false, |sized_id| sized_id == trait_ref.def_id())
296 infcx.tcx.sess.span_err(
297 obligation.cause.span,
299 "unable to infer enough type information about `{}`; \
300 type annotations required",
301 self_ty.user_string(infcx.tcx)).as_slice());
303 infcx.tcx.sess.span_err(
304 obligation.cause.span,
306 "type annotations required: cannot resolve `{}`",
307 predicate.user_string(infcx.tcx)).as_slice());
308 note_obligation_cause(infcx, obligation);
311 } else if !infcx.tcx.sess.has_errors() {
312 // Ambiguity. Coherence should have reported an error.
313 infcx.tcx.sess.span_bug(
314 obligation.cause.span,
316 "coherence failed to report ambiguity: \
317 cannot locate the impl of the trait `{}` for \
319 trait_ref.user_string(infcx.tcx),
320 self_ty.user_string(infcx.tcx)).as_slice());
325 if !infcx.tcx.sess.has_errors() {
326 infcx.tcx.sess.span_err(
327 obligation.cause.span,
329 "type annotations required: cannot resolve `{}`",
330 predicate.user_string(infcx.tcx)).as_slice());
331 note_obligation_cause(infcx, obligation);
337 fn note_obligation_cause<'a, 'tcx>(infcx: &InferCtxt<'a, 'tcx>,
338 obligation: &PredicateObligation<'tcx>)
340 note_obligation_cause_code(infcx,
341 &obligation.predicate,
342 obligation.cause.span,
343 &obligation.cause.code);
346 fn note_obligation_cause_code<'a, 'tcx>(infcx: &InferCtxt<'a, 'tcx>,
347 predicate: &ty::Predicate<'tcx>,
349 cause_code: &ObligationCauseCode<'tcx>)
353 ObligationCauseCode::MiscObligation => { }
354 ObligationCauseCode::ItemObligation(item_def_id) => {
355 let item_name = ty::item_path_str(tcx, item_def_id);
358 format!("required by `{}`", item_name).as_slice());
360 ObligationCauseCode::ObjectCastObligation(object_ty) => {
364 "required for the cast to the object type `{}`",
365 infcx.ty_to_string(object_ty)).as_slice());
367 ObligationCauseCode::RepeatVec => {
370 "the `Copy` trait is required because the \
371 repeated element will be copied");
373 ObligationCauseCode::VariableType(_) => {
376 "all local variables must have a statically known size");
378 ObligationCauseCode::ReturnType => {
381 "the return type of a function must have a \
382 statically known size");
384 ObligationCauseCode::AssignmentLhsSized => {
387 "the left-hand-side of an assignment must have a statically known size");
389 ObligationCauseCode::StructInitializerSized => {
392 "structs must have a statically known size to be initialized");
394 ObligationCauseCode::ClosureCapture(var_id, closure_span, builtin_bound) => {
395 let def_id = tcx.lang_items.from_builtin_kind(builtin_bound).unwrap();
396 let trait_name = ty::item_path_str(tcx, def_id);
397 let name = ty::local_var_name_str(tcx, var_id);
398 span_note!(tcx.sess, closure_span,
399 "the closure that captures `{}` requires that all captured variables \
400 implement the trait `{}`",
404 ObligationCauseCode::FieldSized => {
405 span_note!(tcx.sess, cause_span,
406 "only the last field of a struct or enum variant \
407 may have a dynamically sized type")
409 ObligationCauseCode::ObjectSized => {
410 span_note!(tcx.sess, cause_span,
411 "only sized types can be made into objects");
413 ObligationCauseCode::SharedStatic => {
414 span_note!(tcx.sess, cause_span,
415 "shared static variables must have a type that implements `Sync`");
417 ObligationCauseCode::BuiltinDerivedObligation(ref data) => {
418 let parent_trait_ref = infcx.resolve_type_vars_if_possible(&data.parent_trait_ref);
419 span_note!(tcx.sess, cause_span,
420 "required because it appears within the type `{}`",
421 parent_trait_ref.0.self_ty().user_string(infcx.tcx));
422 let parent_predicate = parent_trait_ref.as_predicate();
423 note_obligation_cause_code(infcx, &parent_predicate, cause_span, &*data.parent_code);
425 ObligationCauseCode::ImplDerivedObligation(ref data) => {
426 let parent_trait_ref = infcx.resolve_type_vars_if_possible(&data.parent_trait_ref);
427 span_note!(tcx.sess, cause_span,
428 "required because of the requirements on the impl of `{}` for `{}`",
429 parent_trait_ref.user_string(infcx.tcx),
430 parent_trait_ref.0.self_ty().user_string(infcx.tcx));
431 let parent_predicate = parent_trait_ref.as_predicate();
432 note_obligation_cause_code(infcx, &parent_predicate, cause_span, &*data.parent_code);
434 ObligationCauseCode::CompareImplMethodObligation => {
435 span_note!(tcx.sess, cause_span,
436 "the requirement `{}` appears on the impl method\
437 but not on the corresponding trait method",
438 predicate.user_string(infcx.tcx));
443 pub fn suggest_new_overflow_limit(tcx: &ty::ctxt, span: Span) {
444 let current_limit = tcx.sess.recursion_limit.get();
445 let suggested_limit = current_limit * 2;
449 "consider adding a `#![recursion_limit=\"{}\"]` attribute to your crate",