| // Copyright 2012-2013 The Rust Project Developers. See the COPYRIGHT |
| // file at the top-level directory of this distribution and at |
| // http://rust-lang.org/COPYRIGHT. |
| // |
| // Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or |
| // http://www.apache.org/licenses/LICENSE-2.0> or the MIT license |
| // <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your |
| // option. This file may not be copied, modified, or distributed |
| // except according to those terms. |
| |
| //! Error Reporting Code for the inference engine |
| //! |
| //! Because of the way inference, and in particular region inference, |
| //! works, it often happens that errors are not detected until far after |
| //! the relevant line of code has been type-checked. Therefore, there is |
| //! an elaborate system to track why a particular constraint in the |
| //! inference graph arose so that we can explain to the user what gave |
| //! rise to a particular error. |
| //! |
| //! The basis of the system are the "origin" types. An "origin" is the |
| //! reason that a constraint or inference variable arose. There are |
| //! different "origin" enums for different kinds of constraints/variables |
| //! (e.g., `TypeOrigin`, `RegionVariableOrigin`). An origin always has |
| //! a span, but also more information so that we can generate a meaningful |
| //! error message. |
| //! |
| //! Having a catalog of all the different reasons an error can arise is |
| //! also useful for other reasons, like cross-referencing FAQs etc, though |
| //! we are not really taking advantage of this yet. |
| //! |
| //! # Region Inference |
| //! |
| //! Region inference is particularly tricky because it always succeeds "in |
| //! the moment" and simply registers a constraint. Then, at the end, we |
| //! can compute the full graph and report errors, so we need to be able to |
| //! store and later report what gave rise to the conflicting constraints. |
| //! |
| //! # Subtype Trace |
| //! |
| //! Determining whether `T1 <: T2` often involves a number of subtypes and |
| //! subconstraints along the way. A "TypeTrace" is an extended version |
| //! of an origin that traces the types and other values that were being |
| //! compared. It is not necessarily comprehensive (in fact, at the time of |
| //! this writing it only tracks the root values being compared) but I'd |
| //! like to extend it to include significant "waypoints". For example, if |
| //! you are comparing `(T1, T2) <: (T3, T4)`, and the problem is that `T2 |
| //! <: T4` fails, I'd like the trace to include enough information to say |
| //! "in the 2nd element of the tuple". Similarly, failures when comparing |
| //! arguments or return types in fn types should be able to cite the |
| //! specific position, etc. |
| //! |
| //! # Reality vs plan |
| //! |
| //! Of course, there is still a LOT of code in typeck that has yet to be |
| //! ported to this system, and which relies on string concatenation at the |
| //! time of error detection. |
| |
| use infer; |
| use super::{InferCtxt, TypeTrace, SubregionOrigin, RegionVariableOrigin, ValuePairs}; |
| use super::region_constraints::GenericKind; |
| use super::lexical_region_resolve::RegionResolutionError; |
| |
| use std::fmt; |
| use hir; |
| use hir::map as hir_map; |
| use hir::def_id::DefId; |
| use middle::region; |
| use traits::{ObligationCause, ObligationCauseCode}; |
| use ty::{self, Region, Ty, TyCtxt, TypeFoldable, TypeVariants}; |
| use ty::error::TypeError; |
| use syntax::ast::DUMMY_NODE_ID; |
| use syntax_pos::{Pos, Span}; |
| use errors::{DiagnosticBuilder, DiagnosticStyledString}; |
| |
| use rustc_data_structures::indexed_vec::Idx; |
| |
| mod note; |
| |
| mod need_type_info; |
| |
| pub mod nice_region_error; |
| |
| impl<'a, 'gcx, 'tcx> TyCtxt<'a, 'gcx, 'tcx> { |
| pub fn note_and_explain_region(self, |
| region_scope_tree: ®ion::ScopeTree, |
| err: &mut DiagnosticBuilder, |
| prefix: &str, |
| region: ty::Region<'tcx>, |
| suffix: &str) { |
| fn item_scope_tag(item: &hir::Item) -> &'static str { |
| match item.node { |
| hir::ItemImpl(..) => "impl", |
| hir::ItemStruct(..) => "struct", |
| hir::ItemUnion(..) => "union", |
| hir::ItemEnum(..) => "enum", |
| hir::ItemTrait(..) => "trait", |
| hir::ItemFn(..) => "function body", |
| _ => "item" |
| } |
| } |
| |
| fn trait_item_scope_tag(item: &hir::TraitItem) -> &'static str { |
| match item.node { |
| hir::TraitItemKind::Method(..) => "method body", |
| hir::TraitItemKind::Const(..) | |
| hir::TraitItemKind::Type(..) => "associated item" |
| } |
| } |
| |
| fn impl_item_scope_tag(item: &hir::ImplItem) -> &'static str { |
| match item.node { |
| hir::ImplItemKind::Method(..) => "method body", |
| hir::ImplItemKind::Const(..) | |
| hir::ImplItemKind::Type(_) => "associated item" |
| } |
| } |
| |
| fn explain_span<'a, 'gcx, 'tcx>(tcx: TyCtxt<'a, 'gcx, 'tcx>, |
| heading: &str, span: Span) |
| -> (String, Option<Span>) { |
| let lo = tcx.sess.codemap().lookup_char_pos_adj(span.lo()); |
| (format!("the {} at {}:{}", heading, lo.line, lo.col.to_usize() + 1), |
| Some(span)) |
| } |
| |
| let (description, span) = match *region { |
| ty::ReScope(scope) => { |
| let new_string; |
| let unknown_scope = || { |
| format!("{}unknown scope: {:?}{}. Please report a bug.", |
| prefix, scope, suffix) |
| }; |
| let span = scope.span(self, region_scope_tree); |
| let tag = match self.hir.find(scope.node_id(self, region_scope_tree)) { |
| Some(hir_map::NodeBlock(_)) => "block", |
| Some(hir_map::NodeExpr(expr)) => match expr.node { |
| hir::ExprCall(..) => "call", |
| hir::ExprMethodCall(..) => "method call", |
| hir::ExprMatch(.., hir::MatchSource::IfLetDesugar { .. }) => "if let", |
| hir::ExprMatch(.., hir::MatchSource::WhileLetDesugar) => "while let", |
| hir::ExprMatch(.., hir::MatchSource::ForLoopDesugar) => "for", |
| hir::ExprMatch(..) => "match", |
| _ => "expression", |
| }, |
| Some(hir_map::NodeStmt(_)) => "statement", |
| Some(hir_map::NodeItem(it)) => item_scope_tag(&it), |
| Some(hir_map::NodeTraitItem(it)) => trait_item_scope_tag(&it), |
| Some(hir_map::NodeImplItem(it)) => impl_item_scope_tag(&it), |
| Some(_) | None => { |
| err.span_note(span, &unknown_scope()); |
| return; |
| } |
| }; |
| let scope_decorated_tag = match scope.data() { |
| region::ScopeData::Node(_) => tag, |
| region::ScopeData::CallSite(_) => { |
| "scope of call-site for function" |
| } |
| region::ScopeData::Arguments(_) => { |
| "scope of function body" |
| } |
| region::ScopeData::Destruction(_) => { |
| new_string = format!("destruction scope surrounding {}", tag); |
| &new_string[..] |
| } |
| region::ScopeData::Remainder(r) => { |
| new_string = format!("block suffix following statement {}", |
| r.first_statement_index.index()); |
| &new_string[..] |
| } |
| }; |
| explain_span(self, scope_decorated_tag, span) |
| } |
| |
| ty::ReEarlyBound(_) | |
| ty::ReFree(_) => { |
| let scope = region.free_region_binding_scope(self); |
| let prefix = match *region { |
| ty::ReEarlyBound(ref br) => { |
| format!("the lifetime {} as defined on", br.name) |
| } |
| ty::ReFree(ref fr) => { |
| match fr.bound_region { |
| ty::BrAnon(idx) => { |
| format!("the anonymous lifetime #{} defined on", idx + 1) |
| } |
| ty::BrFresh(_) => "an anonymous lifetime defined on".to_owned(), |
| _ => { |
| format!("the lifetime {} as defined on", |
| fr.bound_region) |
| } |
| } |
| } |
| _ => bug!() |
| }; |
| |
| let node = self.hir.as_local_node_id(scope) |
| .unwrap_or(DUMMY_NODE_ID); |
| let unknown; |
| let tag = match self.hir.find(node) { |
| Some(hir_map::NodeBlock(_)) | |
| Some(hir_map::NodeExpr(_)) => "body", |
| Some(hir_map::NodeItem(it)) => item_scope_tag(&it), |
| Some(hir_map::NodeTraitItem(it)) => trait_item_scope_tag(&it), |
| Some(hir_map::NodeImplItem(it)) => impl_item_scope_tag(&it), |
| |
| // this really should not happen, but it does: |
| // FIXME(#27942) |
| Some(_) => { |
| unknown = format!("unexpected node ({}) for scope {:?}. \ |
| Please report a bug.", |
| self.hir.node_to_string(node), scope); |
| &unknown |
| } |
| None => { |
| unknown = format!("unknown node for scope {:?}. \ |
| Please report a bug.", scope); |
| &unknown |
| } |
| }; |
| let (msg, opt_span) = explain_span(self, tag, self.hir.span(node)); |
| (format!("{} {}", prefix, msg), opt_span) |
| } |
| |
| ty::ReStatic => ("the static lifetime".to_owned(), None), |
| |
| ty::ReEmpty => ("the empty lifetime".to_owned(), None), |
| |
| // FIXME(#13998) ReSkolemized should probably print like |
| // ReFree rather than dumping Debug output on the user. |
| // |
| // We shouldn't really be having unification failures with ReVar |
| // and ReLateBound though. |
| ty::ReSkolemized(..) | |
| ty::ReVar(_) | |
| ty::ReLateBound(..) | |
| ty::ReErased => { |
| (format!("lifetime {:?}", region), None) |
| } |
| |
| // We shouldn't encounter an error message with ReClosureBound. |
| ty::ReClosureBound(..) => { |
| bug!( |
| "encountered unexpected ReClosureBound: {:?}", |
| region, |
| ); |
| } |
| }; |
| let message = format!("{}{}{}", prefix, description, suffix); |
| if let Some(span) = span { |
| err.span_note(span, &message); |
| } else { |
| err.note(&message); |
| } |
| } |
| } |
| |
| impl<'a, 'gcx, 'tcx> InferCtxt<'a, 'gcx, 'tcx> { |
| pub fn report_region_errors(&self, |
| region_scope_tree: ®ion::ScopeTree, |
| errors: &Vec<RegionResolutionError<'tcx>>, |
| will_later_be_reported_by_nll: bool) { |
| debug!("report_region_errors(): {} errors to start", errors.len()); |
| |
| if will_later_be_reported_by_nll && self.tcx.sess.nll() { |
| // With `#![feature(nll)]`, we want to present a nice user |
| // experience, so don't even mention the errors from the |
| // AST checker. |
| if self.tcx.sess.features.borrow().nll { |
| return; |
| } |
| |
| // But with -Znll, it's nice to have some note for later. |
| for error in errors { |
| match *error { |
| RegionResolutionError::ConcreteFailure(ref origin, ..) | |
| RegionResolutionError::GenericBoundFailure(ref origin, ..) => { |
| self.tcx.sess.span_warn( |
| origin.span(), |
| "not reporting region error due to -Znll"); |
| } |
| |
| RegionResolutionError::SubSupConflict(ref rvo, ..) => { |
| self.tcx.sess.span_warn( |
| rvo.span(), |
| "not reporting region error due to -Znll"); |
| } |
| } |
| } |
| |
| return; |
| } |
| |
| // try to pre-process the errors, which will group some of them |
| // together into a `ProcessedErrors` group: |
| let errors = self.process_errors(errors); |
| |
| debug!("report_region_errors: {} errors after preprocessing", errors.len()); |
| |
| for error in errors { |
| debug!("report_region_errors: error = {:?}", error); |
| |
| if !self.try_report_nice_region_error(&error) { |
| match error.clone() { |
| // These errors could indicate all manner of different |
| // problems with many different solutions. Rather |
| // than generate a "one size fits all" error, what we |
| // attempt to do is go through a number of specific |
| // scenarios and try to find the best way to present |
| // the error. If all of these fails, we fall back to a rather |
| // general bit of code that displays the error information |
| RegionResolutionError::ConcreteFailure(origin, sub, sup) => { |
| self.report_concrete_failure(region_scope_tree, origin, sub, sup).emit(); |
| } |
| |
| RegionResolutionError::GenericBoundFailure(origin, param_ty, sub) => { |
| self.report_generic_bound_failure( |
| region_scope_tree, |
| origin.span(), |
| Some(origin), |
| param_ty, |
| sub, |
| ); |
| } |
| |
| RegionResolutionError::SubSupConflict(var_origin, |
| sub_origin, |
| sub_r, |
| sup_origin, |
| sup_r) => { |
| self.report_sub_sup_conflict(region_scope_tree, |
| var_origin, |
| sub_origin, |
| sub_r, |
| sup_origin, |
| sup_r); |
| } |
| } |
| } |
| } |
| } |
| |
| // This method goes through all the errors and try to group certain types |
| // of error together, for the purpose of suggesting explicit lifetime |
| // parameters to the user. This is done so that we can have a more |
| // complete view of what lifetimes should be the same. |
| // If the return value is an empty vector, it means that processing |
| // failed (so the return value of this method should not be used). |
| // |
| // The method also attempts to weed out messages that seem like |
| // duplicates that will be unhelpful to the end-user. But |
| // obviously it never weeds out ALL errors. |
| fn process_errors(&self, errors: &Vec<RegionResolutionError<'tcx>>) |
| -> Vec<RegionResolutionError<'tcx>> { |
| debug!("process_errors()"); |
| |
| // We want to avoid reporting generic-bound failures if we can |
| // avoid it: these have a very high rate of being unhelpful in |
| // practice. This is because they are basically secondary |
| // checks that test the state of the region graph after the |
| // rest of inference is done, and the other kinds of errors |
| // indicate that the region constraint graph is internally |
| // inconsistent, so these test results are likely to be |
| // meaningless. |
| // |
| // Therefore, we filter them out of the list unless they are |
| // the only thing in the list. |
| |
| let is_bound_failure = |e: &RegionResolutionError<'tcx>| match *e { |
| RegionResolutionError::GenericBoundFailure(..) => true, |
| RegionResolutionError::ConcreteFailure(..) | |
| RegionResolutionError::SubSupConflict(..) => false, |
| }; |
| |
| |
| let mut errors = if errors.iter().all(|e| is_bound_failure(e)) { |
| errors.clone() |
| } else { |
| errors.iter().filter(|&e| !is_bound_failure(e)).cloned().collect() |
| }; |
| |
| // sort the errors by span, for better error message stability. |
| errors.sort_by_key(|u| match *u { |
| RegionResolutionError::ConcreteFailure(ref sro, _, _) => sro.span(), |
| RegionResolutionError::GenericBoundFailure(ref sro, _, _) => sro.span(), |
| RegionResolutionError::SubSupConflict(ref rvo, _, _, _, _) => rvo.span(), |
| }); |
| errors |
| } |
| |
| /// Adds a note if the types come from similarly named crates |
| fn check_and_note_conflicting_crates(&self, |
| err: &mut DiagnosticBuilder, |
| terr: &TypeError<'tcx>, |
| sp: Span) { |
| let report_path_match = |err: &mut DiagnosticBuilder, did1: DefId, did2: DefId| { |
| // Only external crates, if either is from a local |
| // module we could have false positives |
| if !(did1.is_local() || did2.is_local()) && did1.krate != did2.krate { |
| let exp_path = self.tcx.item_path_str(did1); |
| let found_path = self.tcx.item_path_str(did2); |
| let exp_abs_path = self.tcx.absolute_item_path_str(did1); |
| let found_abs_path = self.tcx.absolute_item_path_str(did2); |
| // We compare strings because DefPath can be different |
| // for imported and non-imported crates |
| if exp_path == found_path |
| || exp_abs_path == found_abs_path { |
| let crate_name = self.tcx.crate_name(did1.krate); |
| err.span_note(sp, &format!("Perhaps two different versions \ |
| of crate `{}` are being used?", |
| crate_name)); |
| } |
| } |
| }; |
| match *terr { |
| TypeError::Sorts(ref exp_found) => { |
| // if they are both "path types", there's a chance of ambiguity |
| // due to different versions of the same crate |
| match (&exp_found.expected.sty, &exp_found.found.sty) { |
| (&ty::TyAdt(exp_adt, _), &ty::TyAdt(found_adt, _)) => { |
| report_path_match(err, exp_adt.did, found_adt.did); |
| }, |
| _ => () |
| } |
| }, |
| TypeError::Traits(ref exp_found) => { |
| report_path_match(err, exp_found.expected, exp_found.found); |
| }, |
| _ => () // FIXME(#22750) handle traits and stuff |
| } |
| } |
| |
| fn note_error_origin(&self, |
| err: &mut DiagnosticBuilder<'tcx>, |
| cause: &ObligationCause<'tcx>) |
| { |
| match cause.code { |
| ObligationCauseCode::MatchExpressionArm { arm_span, source } => match source { |
| hir::MatchSource::IfLetDesugar {..} => { |
| err.span_note(arm_span, "`if let` arm with an incompatible type"); |
| } |
| _ => { |
| err.span_note(arm_span, "match arm with an incompatible type"); |
| } |
| }, |
| _ => () |
| } |
| } |
| |
| /// Given that `other_ty` is the same as a type argument for `name` in `sub`, populate `value` |
| /// highlighting `name` and every type argument that isn't at `pos` (which is `other_ty`), and |
| /// populate `other_value` with `other_ty`. |
| /// |
| /// ```text |
| /// Foo<Bar<Qux>> |
| /// ^^^^--------^ this is highlighted |
| /// | | |
| /// | this type argument is exactly the same as the other type, not highlighted |
| /// this is highlighted |
| /// Bar<Qux> |
| /// -------- this type is the same as a type argument in the other type, not highlighted |
| /// ``` |
| fn highlight_outer(&self, |
| value: &mut DiagnosticStyledString, |
| other_value: &mut DiagnosticStyledString, |
| name: String, |
| sub: &ty::subst::Substs<'tcx>, |
| pos: usize, |
| other_ty: &Ty<'tcx>) { |
| // `value` and `other_value` hold two incomplete type representation for display. |
| // `name` is the path of both types being compared. `sub` |
| value.push_highlighted(name); |
| let len = sub.len(); |
| if len > 0 { |
| value.push_highlighted("<"); |
| } |
| |
| // Output the lifetimes fot the first type |
| let lifetimes = sub.regions().map(|lifetime| { |
| let s = format!("{}", lifetime); |
| if s.is_empty() { |
| "'_".to_string() |
| } else { |
| s |
| } |
| }).collect::<Vec<_>>().join(", "); |
| if !lifetimes.is_empty() { |
| if sub.regions().count() < len { |
| value.push_normal(lifetimes + &", "); |
| } else { |
| value.push_normal(lifetimes); |
| } |
| } |
| |
| // Highlight all the type arguments that aren't at `pos` and compare the type argument at |
| // `pos` and `other_ty`. |
| for (i, type_arg) in sub.types().enumerate() { |
| if i == pos { |
| let values = self.cmp(type_arg, other_ty); |
| value.0.extend((values.0).0); |
| other_value.0.extend((values.1).0); |
| } else { |
| value.push_highlighted(format!("{}", type_arg)); |
| } |
| |
| if len > 0 && i != len - 1 { |
| value.push_normal(", "); |
| } |
| //self.push_comma(&mut value, &mut other_value, len, i); |
| } |
| if len > 0 { |
| value.push_highlighted(">"); |
| } |
| } |
| |
| /// If `other_ty` is the same as a type argument present in `sub`, highlight `path` in `t1_out`, |
| /// as that is the difference to the other type. |
| /// |
| /// For the following code: |
| /// |
| /// ```norun |
| /// let x: Foo<Bar<Qux>> = foo::<Bar<Qux>>(); |
| /// ``` |
| /// |
| /// The type error output will behave in the following way: |
| /// |
| /// ```text |
| /// Foo<Bar<Qux>> |
| /// ^^^^--------^ this is highlighted |
| /// | | |
| /// | this type argument is exactly the same as the other type, not highlighted |
| /// this is highlighted |
| /// Bar<Qux> |
| /// -------- this type is the same as a type argument in the other type, not highlighted |
| /// ``` |
| fn cmp_type_arg(&self, |
| mut t1_out: &mut DiagnosticStyledString, |
| mut t2_out: &mut DiagnosticStyledString, |
| path: String, |
| sub: &ty::subst::Substs<'tcx>, |
| other_path: String, |
| other_ty: &Ty<'tcx>) -> Option<()> { |
| for (i, ta) in sub.types().enumerate() { |
| if &ta == other_ty { |
| self.highlight_outer(&mut t1_out, &mut t2_out, path, sub, i, &other_ty); |
| return Some(()); |
| } |
| if let &ty::TyAdt(def, _) = &ta.sty { |
| let path_ = self.tcx.item_path_str(def.did.clone()); |
| if path_ == other_path { |
| self.highlight_outer(&mut t1_out, &mut t2_out, path, sub, i, &other_ty); |
| return Some(()); |
| } |
| } |
| } |
| None |
| } |
| |
| /// Add a `,` to the type representation only if it is appropriate. |
| fn push_comma(&self, |
| value: &mut DiagnosticStyledString, |
| other_value: &mut DiagnosticStyledString, |
| len: usize, |
| pos: usize) { |
| if len > 0 && pos != len - 1 { |
| value.push_normal(", "); |
| other_value.push_normal(", "); |
| } |
| } |
| |
| /// Compare two given types, eliding parts that are the same between them and highlighting |
| /// relevant differences, and return two representation of those types for highlighted printing. |
| fn cmp(&self, t1: Ty<'tcx>, t2: Ty<'tcx>) |
| -> (DiagnosticStyledString, DiagnosticStyledString) |
| { |
| fn equals<'tcx>(a: &Ty<'tcx>, b: &Ty<'tcx>) -> bool { |
| match (&a.sty, &b.sty) { |
| (a, b) if *a == *b => true, |
| (&ty::TyInt(_), &ty::TyInfer(ty::InferTy::IntVar(_))) | |
| (&ty::TyInfer(ty::InferTy::IntVar(_)), &ty::TyInt(_)) | |
| (&ty::TyInfer(ty::InferTy::IntVar(_)), &ty::TyInfer(ty::InferTy::IntVar(_))) | |
| (&ty::TyFloat(_), &ty::TyInfer(ty::InferTy::FloatVar(_))) | |
| (&ty::TyInfer(ty::InferTy::FloatVar(_)), &ty::TyFloat(_)) | |
| (&ty::TyInfer(ty::InferTy::FloatVar(_)), |
| &ty::TyInfer(ty::InferTy::FloatVar(_))) => true, |
| _ => false, |
| } |
| } |
| |
| fn push_ty_ref<'tcx>(r: &ty::Region<'tcx>, |
| tnm: &ty::TypeAndMut<'tcx>, |
| s: &mut DiagnosticStyledString) { |
| let r = &format!("{}", r); |
| s.push_highlighted(format!("&{}{}{}", |
| r, |
| if r == "" { |
| "" |
| } else { |
| " " |
| }, |
| if tnm.mutbl == hir::MutMutable { |
| "mut " |
| } else { |
| "" |
| })); |
| s.push_normal(format!("{}", tnm.ty)); |
| } |
| |
| match (&t1.sty, &t2.sty) { |
| (&ty::TyAdt(def1, sub1), &ty::TyAdt(def2, sub2)) => { |
| let mut values = (DiagnosticStyledString::new(), DiagnosticStyledString::new()); |
| let path1 = self.tcx.item_path_str(def1.did.clone()); |
| let path2 = self.tcx.item_path_str(def2.did.clone()); |
| if def1.did == def2.did { |
| // Easy case. Replace same types with `_` to shorten the output and highlight |
| // the differing ones. |
| // let x: Foo<Bar, Qux> = y::<Foo<Quz, Qux>>(); |
| // Foo<Bar, _> |
| // Foo<Quz, _> |
| // --- ^ type argument elided |
| // | |
| // highlighted in output |
| values.0.push_normal(path1); |
| values.1.push_normal(path2); |
| |
| // Only draw `<...>` if there're lifetime/type arguments. |
| let len = sub1.len(); |
| if len > 0 { |
| values.0.push_normal("<"); |
| values.1.push_normal("<"); |
| } |
| |
| fn lifetime_display(lifetime: Region) -> String { |
| let s = format!("{}", lifetime); |
| if s.is_empty() { |
| "'_".to_string() |
| } else { |
| s |
| } |
| } |
| // At one point we'd like to elide all lifetimes here, they are irrelevant for |
| // all diagnostics that use this output |
| // |
| // Foo<'x, '_, Bar> |
| // Foo<'y, '_, Qux> |
| // ^^ ^^ --- type arguments are not elided |
| // | | |
| // | elided as they were the same |
| // not elided, they were different, but irrelevant |
| let lifetimes = sub1.regions().zip(sub2.regions()); |
| for (i, lifetimes) in lifetimes.enumerate() { |
| let l1 = lifetime_display(lifetimes.0); |
| let l2 = lifetime_display(lifetimes.1); |
| if l1 == l2 { |
| values.0.push_normal("'_"); |
| values.1.push_normal("'_"); |
| } else { |
| values.0.push_highlighted(l1); |
| values.1.push_highlighted(l2); |
| } |
| self.push_comma(&mut values.0, &mut values.1, len, i); |
| } |
| |
| // We're comparing two types with the same path, so we compare the type |
| // arguments for both. If they are the same, do not highlight and elide from the |
| // output. |
| // Foo<_, Bar> |
| // Foo<_, Qux> |
| // ^ elided type as this type argument was the same in both sides |
| let type_arguments = sub1.types().zip(sub2.types()); |
| let regions_len = sub1.regions().collect::<Vec<_>>().len(); |
| for (i, (ta1, ta2)) in type_arguments.enumerate() { |
| let i = i + regions_len; |
| if ta1 == ta2 { |
| values.0.push_normal("_"); |
| values.1.push_normal("_"); |
| } else { |
| let (x1, x2) = self.cmp(ta1, ta2); |
| (values.0).0.extend(x1.0); |
| (values.1).0.extend(x2.0); |
| } |
| self.push_comma(&mut values.0, &mut values.1, len, i); |
| } |
| |
| // Close the type argument bracket. |
| // Only draw `<...>` if there're lifetime/type arguments. |
| if len > 0 { |
| values.0.push_normal(">"); |
| values.1.push_normal(">"); |
| } |
| values |
| } else { |
| // Check for case: |
| // let x: Foo<Bar<Qux> = foo::<Bar<Qux>>(); |
| // Foo<Bar<Qux> |
| // ------- this type argument is exactly the same as the other type |
| // Bar<Qux> |
| if self.cmp_type_arg(&mut values.0, |
| &mut values.1, |
| path1.clone(), |
| sub1, |
| path2.clone(), |
| &t2).is_some() { |
| return values; |
| } |
| // Check for case: |
| // let x: Bar<Qux> = y:<Foo<Bar<Qux>>>(); |
| // Bar<Qux> |
| // Foo<Bar<Qux>> |
| // ------- this type argument is exactly the same as the other type |
| if self.cmp_type_arg(&mut values.1, |
| &mut values.0, |
| path2, |
| sub2, |
| path1, |
| &t1).is_some() { |
| return values; |
| } |
| |
| // We couldn't find anything in common, highlight everything. |
| // let x: Bar<Qux> = y::<Foo<Zar>>(); |
| (DiagnosticStyledString::highlighted(format!("{}", t1)), |
| DiagnosticStyledString::highlighted(format!("{}", t2))) |
| } |
| } |
| |
| // When finding T != &T, hightlight only the borrow |
| (&ty::TyRef(r1, ref tnm1), _) if equals(&tnm1.ty, &t2) => { |
| let mut values = (DiagnosticStyledString::new(), DiagnosticStyledString::new()); |
| push_ty_ref(&r1, tnm1, &mut values.0); |
| values.1.push_normal(format!("{}", t2)); |
| values |
| } |
| (_, &ty::TyRef(r2, ref tnm2)) if equals(&t1, &tnm2.ty) => { |
| let mut values = (DiagnosticStyledString::new(), DiagnosticStyledString::new()); |
| values.0.push_normal(format!("{}", t1)); |
| push_ty_ref(&r2, tnm2, &mut values.1); |
| values |
| } |
| |
| // When encountering &T != &mut T, highlight only the borrow |
| (&ty::TyRef(r1, ref tnm1), &ty::TyRef(r2, ref tnm2)) if equals(&tnm1.ty, &tnm2.ty) => { |
| let mut values = (DiagnosticStyledString::new(), DiagnosticStyledString::new()); |
| push_ty_ref(&r1, tnm1, &mut values.0); |
| push_ty_ref(&r2, tnm2, &mut values.1); |
| values |
| } |
| |
| _ => { |
| if t1 == t2 { |
| // The two types are the same, elide and don't highlight. |
| (DiagnosticStyledString::normal("_"), DiagnosticStyledString::normal("_")) |
| } else { |
| // We couldn't find anything in common, highlight everything. |
| (DiagnosticStyledString::highlighted(format!("{}", t1)), |
| DiagnosticStyledString::highlighted(format!("{}", t2))) |
| } |
| } |
| } |
| } |
| |
| pub fn note_type_err(&self, |
| diag: &mut DiagnosticBuilder<'tcx>, |
| cause: &ObligationCause<'tcx>, |
| secondary_span: Option<(Span, String)>, |
| mut values: Option<ValuePairs<'tcx>>, |
| terr: &TypeError<'tcx>) |
| { |
| // For some types of errors, expected-found does not make |
| // sense, so just ignore the values we were given. |
| match terr { |
| TypeError::CyclicTy(_) => { values = None; } |
| _ => { } |
| } |
| |
| let (expected_found, exp_found, is_simple_error) = match values { |
| None => (None, None, false), |
| Some(values) => { |
| let (is_simple_error, exp_found) = match values { |
| ValuePairs::Types(exp_found) => { |
| let is_simple_err = exp_found.expected.is_primitive() |
| && exp_found.found.is_primitive(); |
| |
| (is_simple_err, Some(exp_found)) |
| } |
| _ => (false, None), |
| }; |
| let vals = match self.values_str(&values) { |
| Some((expected, found)) => Some((expected, found)), |
| None => { |
| // Derived error. Cancel the emitter. |
| self.tcx.sess.diagnostic().cancel(diag); |
| return |
| } |
| }; |
| (vals, exp_found, is_simple_error) |
| } |
| }; |
| |
| let span = cause.span; |
| |
| diag.span_label(span, terr.to_string()); |
| if let Some((sp, msg)) = secondary_span { |
| diag.span_label(sp, msg); |
| } |
| |
| if let Some((expected, found)) = expected_found { |
| match (terr, is_simple_error, expected == found) { |
| (&TypeError::Sorts(ref values), false, true) => { |
| diag.note_expected_found_extra( |
| &"type", expected, found, |
| &format!(" ({})", values.expected.sort_string(self.tcx)), |
| &format!(" ({})", values.found.sort_string(self.tcx))); |
| } |
| (_, false, _) => { |
| if let Some(exp_found) = exp_found { |
| let (def_id, ret_ty) = match exp_found.found.sty { |
| TypeVariants::TyFnDef(def, _) => { |
| (Some(def), Some(self.tcx.fn_sig(def).output())) |
| } |
| _ => (None, None) |
| }; |
| |
| let exp_is_struct = match exp_found.expected.sty { |
| TypeVariants::TyAdt(def, _) => def.is_struct(), |
| _ => false |
| }; |
| |
| if let (Some(def_id), Some(ret_ty)) = (def_id, ret_ty) { |
| if exp_is_struct && exp_found.expected == ret_ty.0 { |
| let message = format!( |
| "did you mean `{}(/* fields */)`?", |
| self.tcx.item_path_str(def_id) |
| ); |
| diag.span_label(cause.span, message); |
| } |
| } |
| } |
| |
| diag.note_expected_found(&"type", expected, found); |
| } |
| _ => (), |
| } |
| } |
| |
| self.check_and_note_conflicting_crates(diag, terr, span); |
| self.tcx.note_and_explain_type_err(diag, terr, span); |
| |
| // It reads better to have the error origin as the final |
| // thing. |
| self.note_error_origin(diag, &cause); |
| } |
| |
| pub fn report_and_explain_type_error(&self, |
| trace: TypeTrace<'tcx>, |
| terr: &TypeError<'tcx>) |
| -> DiagnosticBuilder<'tcx> |
| { |
| debug!("report_and_explain_type_error(trace={:?}, terr={:?})", |
| trace, |
| terr); |
| |
| let span = trace.cause.span; |
| let failure_code = trace.cause.as_failure_code(terr); |
| let mut diag = match failure_code { |
| FailureCode::Error0317(failure_str) => { |
| struct_span_err!(self.tcx.sess, span, E0317, "{}", failure_str) |
| } |
| FailureCode::Error0580(failure_str) => { |
| struct_span_err!(self.tcx.sess, span, E0580, "{}", failure_str) |
| } |
| FailureCode::Error0308(failure_str) => { |
| struct_span_err!(self.tcx.sess, span, E0308, "{}", failure_str) |
| } |
| FailureCode::Error0644(failure_str) => { |
| struct_span_err!(self.tcx.sess, span, E0644, "{}", failure_str) |
| } |
| }; |
| self.note_type_err(&mut diag, &trace.cause, None, Some(trace.values), terr); |
| diag |
| } |
| |
| fn values_str(&self, values: &ValuePairs<'tcx>) |
| -> Option<(DiagnosticStyledString, DiagnosticStyledString)> |
| { |
| match *values { |
| infer::Types(ref exp_found) => self.expected_found_str_ty(exp_found), |
| infer::TraitRefs(ref exp_found) => self.expected_found_str(exp_found), |
| infer::PolyTraitRefs(ref exp_found) => self.expected_found_str(exp_found), |
| } |
| } |
| |
| fn expected_found_str_ty(&self, |
| exp_found: &ty::error::ExpectedFound<Ty<'tcx>>) |
| -> Option<(DiagnosticStyledString, DiagnosticStyledString)> { |
| let exp_found = self.resolve_type_vars_if_possible(exp_found); |
| if exp_found.references_error() { |
| return None; |
| } |
| |
| Some(self.cmp(exp_found.expected, exp_found.found)) |
| } |
| |
| /// Returns a string of the form "expected `{}`, found `{}`". |
| fn expected_found_str<T: fmt::Display + TypeFoldable<'tcx>>( |
| &self, |
| exp_found: &ty::error::ExpectedFound<T>) |
| -> Option<(DiagnosticStyledString, DiagnosticStyledString)> |
| { |
| let exp_found = self.resolve_type_vars_if_possible(exp_found); |
| if exp_found.references_error() { |
| return None; |
| } |
| |
| Some((DiagnosticStyledString::highlighted(format!("{}", exp_found.expected)), |
| DiagnosticStyledString::highlighted(format!("{}", exp_found.found)))) |
| } |
| |
| pub fn report_generic_bound_failure(&self, |
| region_scope_tree: ®ion::ScopeTree, |
| span: Span, |
| origin: Option<SubregionOrigin<'tcx>>, |
| bound_kind: GenericKind<'tcx>, |
| sub: Region<'tcx>) |
| { |
| // Attempt to obtain the span of the parameter so we can |
| // suggest adding an explicit lifetime bound to it. |
| let type_param_span = match (self.in_progress_tables, bound_kind) { |
| (Some(ref table), GenericKind::Param(ref param)) => { |
| let table = table.borrow(); |
| table.local_id_root.and_then(|did| { |
| let generics = self.tcx.generics_of(did); |
| // Account for the case where `did` corresponds to `Self`, which doesn't have |
| // the expected type argument. |
| if !param.is_self() { |
| let type_param = generics.type_param(param, self.tcx); |
| let hir = &self.tcx.hir; |
| hir.as_local_node_id(type_param.def_id).map(|id| { |
| // Get the `hir::TyParam` to verify wether it already has any bounds. |
| // We do this to avoid suggesting code that ends up as `T: 'a'b`, |
| // instead we suggest `T: 'a + 'b` in that case. |
| let has_lifetimes = if let hir_map::NodeTyParam(ref p) = hir.get(id) { |
| p.bounds.len() > 0 |
| } else { |
| false |
| }; |
| let sp = hir.span(id); |
| // `sp` only covers `T`, change it so that it covers |
| // `T:` when appropriate |
| let sp = if has_lifetimes { |
| sp.to(sp.next_point().next_point()) |
| } else { |
| sp |
| }; |
| (sp, has_lifetimes) |
| }) |
| } else { |
| None |
| } |
| }) |
| } |
| _ => None, |
| }; |
| |
| let labeled_user_string = match bound_kind { |
| GenericKind::Param(ref p) => |
| format!("the parameter type `{}`", p), |
| GenericKind::Projection(ref p) => |
| format!("the associated type `{}`", p), |
| }; |
| |
| if let Some(SubregionOrigin::CompareImplMethodObligation { |
| span, item_name, impl_item_def_id, trait_item_def_id, |
| }) = origin { |
| self.report_extra_impl_obligation(span, |
| item_name, |
| impl_item_def_id, |
| trait_item_def_id, |
| &format!("`{}: {}`", bound_kind, sub)) |
| .emit(); |
| return; |
| } |
| |
| fn binding_suggestion<'tcx, S: fmt::Display>(err: &mut DiagnosticBuilder<'tcx>, |
| type_param_span: Option<(Span, bool)>, |
| bound_kind: GenericKind<'tcx>, |
| sub: S) { |
| let consider = &format!("consider adding an explicit lifetime bound `{}: {}`...", |
| bound_kind, |
| sub); |
| if let Some((sp, has_lifetimes)) = type_param_span { |
| let tail = if has_lifetimes { |
| " + " |
| } else { |
| "" |
| }; |
| let suggestion = format!("{}: {}{}", bound_kind, sub, tail); |
| err.span_suggestion_short(sp, consider, suggestion); |
| } else { |
| err.help(consider); |
| } |
| } |
| |
| let mut err = match *sub { |
| ty::ReEarlyBound(_) | |
| ty::ReFree(ty::FreeRegion {bound_region: ty::BrNamed(..), ..}) => { |
| // Does the required lifetime have a nice name we can print? |
| let mut err = struct_span_err!(self.tcx.sess, |
| span, |
| E0309, |
| "{} may not live long enough", |
| labeled_user_string); |
| binding_suggestion(&mut err, type_param_span, bound_kind, sub); |
| err |
| } |
| |
| ty::ReStatic => { |
| // Does the required lifetime have a nice name we can print? |
| let mut err = struct_span_err!(self.tcx.sess, |
| span, |
| E0310, |
| "{} may not live long enough", |
| labeled_user_string); |
| binding_suggestion(&mut err, type_param_span, bound_kind, "'static"); |
| err |
| } |
| |
| _ => { |
| // If not, be less specific. |
| let mut err = struct_span_err!(self.tcx.sess, |
| span, |
| E0311, |
| "{} may not live long enough", |
| labeled_user_string); |
| err.help(&format!("consider adding an explicit lifetime bound for `{}`", |
| bound_kind)); |
| self.tcx.note_and_explain_region( |
| region_scope_tree, |
| &mut err, |
| &format!("{} must be valid for ", labeled_user_string), |
| sub, |
| "..."); |
| err |
| } |
| }; |
| |
| if let Some(origin) = origin { |
| self.note_region_origin(&mut err, &origin); |
| } |
| err.emit(); |
| } |
| |
| fn report_sub_sup_conflict(&self, |
| region_scope_tree: ®ion::ScopeTree, |
| var_origin: RegionVariableOrigin, |
| sub_origin: SubregionOrigin<'tcx>, |
| sub_region: Region<'tcx>, |
| sup_origin: SubregionOrigin<'tcx>, |
| sup_region: Region<'tcx>) { |
| let mut err = self.report_inference_failure(var_origin); |
| |
| self.tcx.note_and_explain_region(region_scope_tree, &mut err, |
| "first, the lifetime cannot outlive ", |
| sup_region, |
| "..."); |
| |
| self.note_region_origin(&mut err, &sup_origin); |
| |
| self.tcx.note_and_explain_region(region_scope_tree, &mut err, |
| "but, the lifetime must be valid for ", |
| sub_region, |
| "..."); |
| |
| self.note_region_origin(&mut err, &sub_origin); |
| err.emit(); |
| } |
| } |
| |
| impl<'a, 'gcx, 'tcx> InferCtxt<'a, 'gcx, 'tcx> { |
| fn report_inference_failure(&self, |
| var_origin: RegionVariableOrigin) |
| -> DiagnosticBuilder<'tcx> { |
| let br_string = |br: ty::BoundRegion| { |
| let mut s = br.to_string(); |
| if !s.is_empty() { |
| s.push_str(" "); |
| } |
| s |
| }; |
| let var_description = match var_origin { |
| infer::MiscVariable(_) => "".to_string(), |
| infer::PatternRegion(_) => " for pattern".to_string(), |
| infer::AddrOfRegion(_) => " for borrow expression".to_string(), |
| infer::Autoref(_) => " for autoref".to_string(), |
| infer::Coercion(_) => " for automatic coercion".to_string(), |
| infer::LateBoundRegion(_, br, infer::FnCall) => { |
| format!(" for lifetime parameter {}in function call", |
| br_string(br)) |
| } |
| infer::LateBoundRegion(_, br, infer::HigherRankedType) => { |
| format!(" for lifetime parameter {}in generic type", br_string(br)) |
| } |
| infer::LateBoundRegion(_, br, infer::AssocTypeProjection(def_id)) => { |
| format!(" for lifetime parameter {}in trait containing associated type `{}`", |
| br_string(br), self.tcx.associated_item(def_id).name) |
| } |
| infer::EarlyBoundRegion(_, name) => { |
| format!(" for lifetime parameter `{}`", |
| name) |
| } |
| infer::BoundRegionInCoherence(name) => { |
| format!(" for lifetime parameter `{}` in coherence check", |
| name) |
| } |
| infer::UpvarRegion(ref upvar_id, _) => { |
| let var_node_id = self.tcx.hir.hir_to_node_id(upvar_id.var_id); |
| let var_name = self.tcx.hir.name(var_node_id); |
| format!(" for capture of `{}` by closure", var_name) |
| } |
| infer::NLL(..) => bug!("NLL variable found in lexical phase"), |
| }; |
| |
| struct_span_err!(self.tcx.sess, var_origin.span(), E0495, |
| "cannot infer an appropriate lifetime{} \ |
| due to conflicting requirements", |
| var_description) |
| } |
| } |
| |
| enum FailureCode { |
| Error0317(&'static str), |
| Error0580(&'static str), |
| Error0308(&'static str), |
| Error0644(&'static str), |
| } |
| |
| impl<'tcx> ObligationCause<'tcx> { |
| fn as_failure_code(&self, terr: &TypeError<'tcx>) -> FailureCode { |
| use self::FailureCode::*; |
| use traits::ObligationCauseCode::*; |
| match self.code { |
| CompareImplMethodObligation { .. } => Error0308("method not compatible with trait"), |
| MatchExpressionArm { source, .. } => Error0308(match source { |
| hir::MatchSource::IfLetDesugar{..} => "`if let` arms have incompatible types", |
| _ => "match arms have incompatible types", |
| }), |
| IfExpression => Error0308("if and else have incompatible types"), |
| IfExpressionWithNoElse => Error0317("if may be missing an else clause"), |
| EquatePredicate => Error0308("equality predicate not satisfied"), |
| MainFunctionType => Error0580("main function has wrong type"), |
| StartFunctionType => Error0308("start function has wrong type"), |
| IntrinsicType => Error0308("intrinsic has wrong type"), |
| MethodReceiver => Error0308("mismatched method receiver"), |
| |
| // In the case where we have no more specific thing to |
| // say, also take a look at the error code, maybe we can |
| // tailor to that. |
| _ => match terr { |
| TypeError::CyclicTy(ty) if ty.is_closure() || ty.is_generator() => |
| Error0644("closure/generator type that references itself"), |
| _ => |
| Error0308("mismatched types"), |
| } |
| } |
| } |
| |
| fn as_requirement_str(&self) -> &'static str { |
| use traits::ObligationCauseCode::*; |
| match self.code { |
| CompareImplMethodObligation { .. } => "method type is compatible with trait", |
| ExprAssignable => "expression is assignable", |
| MatchExpressionArm { source, .. } => match source { |
| hir::MatchSource::IfLetDesugar{..} => "`if let` arms have compatible types", |
| _ => "match arms have compatible types", |
| }, |
| IfExpression => "if and else have compatible types", |
| IfExpressionWithNoElse => "if missing an else returns ()", |
| EquatePredicate => "equality where clause is satisfied", |
| MainFunctionType => "`main` function has the correct type", |
| StartFunctionType => "`start` function has the correct type", |
| IntrinsicType => "intrinsic has the correct type", |
| MethodReceiver => "method receiver has the correct type", |
| _ => "types are compatible", |
| } |
| } |
| } |
