From 698f8c2f01ea549d77d7dc3338a12e04c11057b9 Mon Sep 17 00:00:00 2001 From: Daniel Baumann Date: Wed, 17 Apr 2024 14:02:58 +0200 Subject: Adding upstream version 1.64.0+dfsg1. Signed-off-by: Daniel Baumann --- .../rustc_infer/src/infer/error_reporting/mod.rs | 3121 ++++++++++++++++++++ .../src/infer/error_reporting/need_type_info.rs | 1134 +++++++ .../nice_region_error/different_lifetimes.rs | 234 ++ .../nice_region_error/find_anon_type.rs | 234 ++ .../mismatched_static_lifetime.rs | 102 + .../infer/error_reporting/nice_region_error/mod.rs | 77 + .../nice_region_error/named_anon_conflict.rs | 116 + .../nice_region_error/placeholder_error.rs | 501 ++++ .../nice_region_error/static_impl_trait.rs | 577 ++++ .../nice_region_error/trait_impl_difference.rs | 176 ++ .../error_reporting/nice_region_error/util.rs | 167 ++ .../rustc_infer/src/infer/error_reporting/note.rs | 414 +++ 12 files changed, 6853 insertions(+) create mode 100644 compiler/rustc_infer/src/infer/error_reporting/mod.rs create mode 100644 compiler/rustc_infer/src/infer/error_reporting/need_type_info.rs create mode 100644 compiler/rustc_infer/src/infer/error_reporting/nice_region_error/different_lifetimes.rs create mode 100644 compiler/rustc_infer/src/infer/error_reporting/nice_region_error/find_anon_type.rs create mode 100644 compiler/rustc_infer/src/infer/error_reporting/nice_region_error/mismatched_static_lifetime.rs create mode 100644 compiler/rustc_infer/src/infer/error_reporting/nice_region_error/mod.rs create mode 100644 compiler/rustc_infer/src/infer/error_reporting/nice_region_error/named_anon_conflict.rs create mode 100644 compiler/rustc_infer/src/infer/error_reporting/nice_region_error/placeholder_error.rs create mode 100644 compiler/rustc_infer/src/infer/error_reporting/nice_region_error/static_impl_trait.rs create mode 100644 compiler/rustc_infer/src/infer/error_reporting/nice_region_error/trait_impl_difference.rs create mode 100644 compiler/rustc_infer/src/infer/error_reporting/nice_region_error/util.rs create mode 100644 compiler/rustc_infer/src/infer/error_reporting/note.rs (limited to 'compiler/rustc_infer/src/infer/error_reporting') diff --git a/compiler/rustc_infer/src/infer/error_reporting/mod.rs b/compiler/rustc_infer/src/infer/error_reporting/mod.rs new file mode 100644 index 000000000..20864c657 --- /dev/null +++ b/compiler/rustc_infer/src/infer/error_reporting/mod.rs @@ -0,0 +1,3121 @@ +//! 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 system is based around a set of "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 super::lexical_region_resolve::RegionResolutionError; +use super::region_constraints::GenericKind; +use super::{InferCtxt, RegionVariableOrigin, SubregionOrigin, TypeTrace, ValuePairs}; + +use crate::infer; +use crate::infer::error_reporting::nice_region_error::find_anon_type::find_anon_type; +use crate::traits::error_reporting::report_object_safety_error; +use crate::traits::{ + IfExpressionCause, MatchExpressionArmCause, ObligationCause, ObligationCauseCode, + StatementAsExpression, +}; + +use rustc_data_structures::fx::{FxHashMap, FxHashSet}; +use rustc_errors::{pluralize, struct_span_err, Diagnostic, ErrorGuaranteed}; +use rustc_errors::{Applicability, DiagnosticBuilder, DiagnosticStyledString, MultiSpan}; +use rustc_hir as hir; +use rustc_hir::def_id::{DefId, LocalDefId}; +use rustc_hir::lang_items::LangItem; +use rustc_hir::Node; +use rustc_middle::dep_graph::DepContext; +use rustc_middle::ty::print::with_no_trimmed_paths; +use rustc_middle::ty::{ + self, error::TypeError, Binder, List, Region, Subst, Ty, TyCtxt, TypeFoldable, + TypeSuperVisitable, TypeVisitable, +}; +use rustc_span::{sym, symbol::kw, BytePos, DesugaringKind, Pos, Span}; +use rustc_target::spec::abi; +use std::ops::ControlFlow; +use std::{cmp, fmt, iter}; + +mod note; + +mod need_type_info; +pub use need_type_info::TypeAnnotationNeeded; + +pub mod nice_region_error; + +pub(super) fn note_and_explain_region<'tcx>( + tcx: TyCtxt<'tcx>, + err: &mut Diagnostic, + prefix: &str, + region: ty::Region<'tcx>, + suffix: &str, + alt_span: Option, +) { + let (description, span) = match *region { + ty::ReEarlyBound(_) | ty::ReFree(_) | ty::ReStatic => { + msg_span_from_free_region(tcx, region, alt_span) + } + + ty::ReEmpty(ty::UniverseIndex::ROOT) => ("the empty lifetime".to_owned(), alt_span), + + // uh oh, hope no user ever sees THIS + ty::ReEmpty(ui) => (format!("the empty lifetime in universe {:?}", ui), alt_span), + + ty::RePlaceholder(_) => return, + + // FIXME(#13998) RePlaceholder 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::ReVar(_) | ty::ReLateBound(..) | ty::ReErased => { + (format!("lifetime {:?}", region), alt_span) + } + }; + + emit_msg_span(err, prefix, description, span, suffix); +} + +fn explain_free_region<'tcx>( + tcx: TyCtxt<'tcx>, + err: &mut Diagnostic, + prefix: &str, + region: ty::Region<'tcx>, + suffix: &str, +) { + let (description, span) = msg_span_from_free_region(tcx, region, None); + + label_msg_span(err, prefix, description, span, suffix); +} + +fn msg_span_from_free_region<'tcx>( + tcx: TyCtxt<'tcx>, + region: ty::Region<'tcx>, + alt_span: Option, +) -> (String, Option) { + match *region { + ty::ReEarlyBound(_) | ty::ReFree(_) => { + let (msg, span) = msg_span_from_early_bound_and_free_regions(tcx, region); + (msg, Some(span)) + } + ty::ReStatic => ("the static lifetime".to_owned(), alt_span), + ty::ReEmpty(ty::UniverseIndex::ROOT) => ("an empty lifetime".to_owned(), alt_span), + ty::ReEmpty(ui) => (format!("an empty lifetime in universe {:?}", ui), alt_span), + _ => bug!("{:?}", region), + } +} + +fn msg_span_from_early_bound_and_free_regions<'tcx>( + tcx: TyCtxt<'tcx>, + region: ty::Region<'tcx>, +) -> (String, Span) { + let scope = region.free_region_binding_scope(tcx).expect_local(); + match *region { + ty::ReEarlyBound(ref br) => { + let mut sp = tcx.def_span(scope); + if let Some(param) = + tcx.hir().get_generics(scope).and_then(|generics| generics.get_named(br.name)) + { + sp = param.span; + } + let text = if br.has_name() { + format!("the lifetime `{}` as defined here", br.name) + } else { + format!("the anonymous lifetime as defined here") + }; + (text, sp) + } + ty::ReFree(ref fr) => { + if !fr.bound_region.is_named() + && let Some((ty, _)) = find_anon_type(tcx, region, &fr.bound_region) + { + ("the anonymous lifetime defined here".to_string(), ty.span) + } else { + match fr.bound_region { + ty::BoundRegionKind::BrNamed(_, name) => { + let mut sp = tcx.def_span(scope); + if let Some(param) = + tcx.hir().get_generics(scope).and_then(|generics| generics.get_named(name)) + { + sp = param.span; + } + let text = if name == kw::UnderscoreLifetime { + format!("the anonymous lifetime as defined here") + } else { + format!("the lifetime `{}` as defined here", name) + }; + (text, sp) + } + ty::BrAnon(idx) => ( + format!("the anonymous lifetime #{} defined here", idx + 1), + tcx.def_span(scope) + ), + _ => ( + format!("the lifetime `{}` as defined here", region), + tcx.def_span(scope), + ), + } + } + } + _ => bug!(), + } +} + +fn emit_msg_span( + err: &mut Diagnostic, + prefix: &str, + description: String, + span: Option, + suffix: &str, +) { + let message = format!("{}{}{}", prefix, description, suffix); + + if let Some(span) = span { + err.span_note(span, &message); + } else { + err.note(&message); + } +} + +fn label_msg_span( + err: &mut Diagnostic, + prefix: &str, + description: String, + span: Option, + suffix: &str, +) { + let message = format!("{}{}{}", prefix, description, suffix); + + if let Some(span) = span { + err.span_label(span, &message); + } else { + err.note(&message); + } +} + +pub fn unexpected_hidden_region_diagnostic<'tcx>( + tcx: TyCtxt<'tcx>, + span: Span, + hidden_ty: Ty<'tcx>, + hidden_region: ty::Region<'tcx>, + opaque_ty: ty::OpaqueTypeKey<'tcx>, +) -> DiagnosticBuilder<'tcx, ErrorGuaranteed> { + let opaque_ty = tcx.mk_opaque(opaque_ty.def_id.to_def_id(), opaque_ty.substs); + let mut err = struct_span_err!( + tcx.sess, + span, + E0700, + "hidden type for `{opaque_ty}` captures lifetime that does not appear in bounds", + ); + + // Explain the region we are capturing. + match *hidden_region { + ty::ReEmpty(ty::UniverseIndex::ROOT) => { + // All lifetimes shorter than the function body are `empty` in + // lexical region resolution. The default explanation of "an empty + // lifetime" isn't really accurate here. + let message = format!( + "hidden type `{}` captures lifetime smaller than the function body", + hidden_ty + ); + err.span_note(span, &message); + } + ty::ReEarlyBound(_) | ty::ReFree(_) | ty::ReStatic | ty::ReEmpty(_) => { + // Assuming regionck succeeded (*), we ought to always be + // capturing *some* region from the fn header, and hence it + // ought to be free. So under normal circumstances, we will go + // down this path which gives a decent human readable + // explanation. + // + // (*) if not, the `tainted_by_errors` field would be set to + // `Some(ErrorGuaranteed)` in any case, so we wouldn't be here at all. + explain_free_region( + tcx, + &mut err, + &format!("hidden type `{}` captures ", hidden_ty), + hidden_region, + "", + ); + if let Some(reg_info) = tcx.is_suitable_region(hidden_region) { + let fn_returns = tcx.return_type_impl_or_dyn_traits(reg_info.def_id); + nice_region_error::suggest_new_region_bound( + tcx, + &mut err, + fn_returns, + hidden_region.to_string(), + None, + format!("captures `{}`", hidden_region), + None, + ) + } + } + _ => { + // Ugh. This is a painful case: the hidden region is not one + // that we can easily summarize or explain. This can happen + // in a case like + // `src/test/ui/multiple-lifetimes/ordinary-bounds-unsuited.rs`: + // + // ``` + // fn upper_bounds<'a, 'b>(a: Ordinary<'a>, b: Ordinary<'b>) -> impl Trait<'a, 'b> { + // if condition() { a } else { b } + // } + // ``` + // + // Here the captured lifetime is the intersection of `'a` and + // `'b`, which we can't quite express. + + // We can at least report a really cryptic error for now. + note_and_explain_region( + tcx, + &mut err, + &format!("hidden type `{}` captures ", hidden_ty), + hidden_region, + "", + None, + ); + } + } + + err +} + +impl<'a, 'tcx> InferCtxt<'a, 'tcx> { + pub fn report_region_errors( + &self, + generic_param_scope: LocalDefId, + errors: &[RegionResolutionError<'tcx>], + ) { + debug!("report_region_errors(): {} errors to start", errors.len()); + + // 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) => { + if sub.is_placeholder() || sup.is_placeholder() { + self.report_placeholder_failure(origin, sub, sup).emit(); + } else { + self.report_concrete_failure(origin, sub, sup).emit(); + } + } + + RegionResolutionError::GenericBoundFailure(origin, param_ty, sub) => { + self.report_generic_bound_failure( + generic_param_scope, + origin.span(), + Some(origin), + param_ty, + sub, + ); + } + + RegionResolutionError::SubSupConflict( + _, + var_origin, + sub_origin, + sub_r, + sup_origin, + sup_r, + _, + ) => { + if sub_r.is_placeholder() { + self.report_placeholder_failure(sub_origin, sub_r, sup_r).emit(); + } else if sup_r.is_placeholder() { + self.report_placeholder_failure(sup_origin, sub_r, sup_r).emit(); + } else { + self.report_sub_sup_conflict( + var_origin, sub_origin, sub_r, sup_origin, sup_r, + ); + } + } + + RegionResolutionError::UpperBoundUniverseConflict( + _, + _, + var_universe, + sup_origin, + sup_r, + ) => { + assert!(sup_r.is_placeholder()); + + // Make a dummy value for the "sub region" -- + // this is the initial value of the + // placeholder. In practice, we expect more + // tailored errors that don't really use this + // value. + let sub_r = self.tcx.mk_region(ty::ReEmpty(var_universe)); + + self.report_placeholder_failure(sup_origin, sub_r, sup_r).emit(); + } + } + } + } + } + + // 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: &[RegionResolutionError<'tcx>], + ) -> Vec> { + 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(..) + | RegionResolutionError::UpperBoundUniverseConflict(..) => false, + }; + + let mut errors = if errors.iter().all(|e| is_bound_failure(e)) { + errors.to_owned() + } 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(), + RegionResolutionError::UpperBoundUniverseConflict(_, 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 Diagnostic, terr: &TypeError<'tcx>) { + use hir::def_id::CrateNum; + use rustc_hir::definitions::DisambiguatedDefPathData; + use ty::print::Printer; + use ty::subst::GenericArg; + + struct AbsolutePathPrinter<'tcx> { + tcx: TyCtxt<'tcx>, + } + + struct NonTrivialPath; + + impl<'tcx> Printer<'tcx> for AbsolutePathPrinter<'tcx> { + type Error = NonTrivialPath; + + type Path = Vec; + type Region = !; + type Type = !; + type DynExistential = !; + type Const = !; + + fn tcx<'a>(&'a self) -> TyCtxt<'tcx> { + self.tcx + } + + fn print_region(self, _region: ty::Region<'_>) -> Result { + Err(NonTrivialPath) + } + + fn print_type(self, _ty: Ty<'tcx>) -> Result { + Err(NonTrivialPath) + } + + fn print_dyn_existential( + self, + _predicates: &'tcx ty::List>>, + ) -> Result { + Err(NonTrivialPath) + } + + fn print_const(self, _ct: ty::Const<'tcx>) -> Result { + Err(NonTrivialPath) + } + + fn path_crate(self, cnum: CrateNum) -> Result { + Ok(vec![self.tcx.crate_name(cnum).to_string()]) + } + fn path_qualified( + self, + _self_ty: Ty<'tcx>, + _trait_ref: Option>, + ) -> Result { + Err(NonTrivialPath) + } + + fn path_append_impl( + self, + _print_prefix: impl FnOnce(Self) -> Result, + _disambiguated_data: &DisambiguatedDefPathData, + _self_ty: Ty<'tcx>, + _trait_ref: Option>, + ) -> Result { + Err(NonTrivialPath) + } + fn path_append( + self, + print_prefix: impl FnOnce(Self) -> Result, + disambiguated_data: &DisambiguatedDefPathData, + ) -> Result { + let mut path = print_prefix(self)?; + path.push(disambiguated_data.to_string()); + Ok(path) + } + fn path_generic_args( + self, + print_prefix: impl FnOnce(Self) -> Result, + _args: &[GenericArg<'tcx>], + ) -> Result { + print_prefix(self) + } + } + + let report_path_match = |err: &mut Diagnostic, 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 abs_path = + |def_id| AbsolutePathPrinter { tcx: self.tcx }.print_def_path(def_id, &[]); + + // We compare strings because DefPath can be different + // for imported and non-imported crates + let same_path = || -> Result<_, NonTrivialPath> { + Ok(self.tcx.def_path_str(did1) == self.tcx.def_path_str(did2) + || abs_path(did1)? == abs_path(did2)?) + }; + if same_path().unwrap_or(false) { + let crate_name = self.tcx.crate_name(did1.krate); + err.note(&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 + if let (&ty::Adt(exp_adt, _), &ty::Adt(found_adt, _)) = + (exp_found.expected.kind(), exp_found.found.kind()) + { + 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 Diagnostic, + cause: &ObligationCause<'tcx>, + exp_found: Option>>, + terr: &TypeError<'tcx>, + ) { + match *cause.code() { + ObligationCauseCode::Pattern { origin_expr: true, span: Some(span), root_ty } => { + let ty = self.resolve_vars_if_possible(root_ty); + if !matches!(ty.kind(), ty::Infer(ty::InferTy::TyVar(_) | ty::InferTy::FreshTy(_))) + { + // don't show type `_` + if span.desugaring_kind() == Some(DesugaringKind::ForLoop) + && let ty::Adt(def, substs) = ty.kind() + && Some(def.did()) == self.tcx.get_diagnostic_item(sym::Option) + { + err.span_label(span, format!("this is an iterator with items of type `{}`", substs.type_at(0))); + } else { + err.span_label(span, format!("this expression has type `{}`", ty)); + } + } + if let Some(ty::error::ExpectedFound { found, .. }) = exp_found + && ty.is_box() && ty.boxed_ty() == found + && let Ok(snippet) = self.tcx.sess.source_map().span_to_snippet(span) + { + err.span_suggestion( + span, + "consider dereferencing the boxed value", + format!("*{}", snippet), + Applicability::MachineApplicable, + ); + } + } + ObligationCauseCode::Pattern { origin_expr: false, span: Some(span), .. } => { + err.span_label(span, "expected due to this"); + } + ObligationCauseCode::MatchExpressionArm(box MatchExpressionArmCause { + arm_block_id, + arm_span, + arm_ty, + prior_arm_block_id, + prior_arm_span, + prior_arm_ty, + source, + ref prior_arms, + scrut_hir_id, + opt_suggest_box_span, + scrut_span, + .. + }) => match source { + hir::MatchSource::TryDesugar => { + if let Some(ty::error::ExpectedFound { expected, .. }) = exp_found { + let scrut_expr = self.tcx.hir().expect_expr(scrut_hir_id); + let scrut_ty = if let hir::ExprKind::Call(_, args) = &scrut_expr.kind { + let arg_expr = args.first().expect("try desugaring call w/out arg"); + self.in_progress_typeck_results.and_then(|typeck_results| { + typeck_results.borrow().expr_ty_opt(arg_expr) + }) + } else { + bug!("try desugaring w/out call expr as scrutinee"); + }; + + match scrut_ty { + Some(ty) if expected == ty => { + let source_map = self.tcx.sess.source_map(); + err.span_suggestion( + source_map.end_point(cause.span), + "try removing this `?`", + "", + Applicability::MachineApplicable, + ); + } + _ => {} + } + } + } + _ => { + // `prior_arm_ty` can be `!`, `expected` will have better info when present. + let t = self.resolve_vars_if_possible(match exp_found { + Some(ty::error::ExpectedFound { expected, .. }) => expected, + _ => prior_arm_ty, + }); + let source_map = self.tcx.sess.source_map(); + let mut any_multiline_arm = source_map.is_multiline(arm_span); + if prior_arms.len() <= 4 { + for sp in prior_arms { + any_multiline_arm |= source_map.is_multiline(*sp); + err.span_label(*sp, format!("this is found to be of type `{}`", t)); + } + } else if let Some(sp) = prior_arms.last() { + any_multiline_arm |= source_map.is_multiline(*sp); + err.span_label( + *sp, + format!("this and all prior arms are found to be of type `{}`", t), + ); + } + let outer_error_span = if any_multiline_arm { + // Cover just `match` and the scrutinee expression, not + // the entire match body, to reduce diagram noise. + cause.span.shrink_to_lo().to(scrut_span) + } else { + cause.span + }; + let msg = "`match` arms have incompatible types"; + err.span_label(outer_error_span, msg); + self.suggest_remove_semi_or_return_binding( + err, + prior_arm_block_id, + prior_arm_ty, + prior_arm_span, + arm_block_id, + arm_ty, + arm_span, + ); + if let Some(ret_sp) = opt_suggest_box_span { + // Get return type span and point to it. + self.suggest_boxing_for_return_impl_trait( + err, + ret_sp, + prior_arms.iter().chain(std::iter::once(&arm_span)).map(|s| *s), + ); + } + } + }, + ObligationCauseCode::IfExpression(box IfExpressionCause { + then_id, + else_id, + then_ty, + else_ty, + outer_span, + opt_suggest_box_span, + }) => { + let then_span = self.find_block_span_from_hir_id(then_id); + let else_span = self.find_block_span_from_hir_id(else_id); + err.span_label(then_span, "expected because of this"); + if let Some(sp) = outer_span { + err.span_label(sp, "`if` and `else` have incompatible types"); + } + self.suggest_remove_semi_or_return_binding( + err, + Some(then_id), + then_ty, + then_span, + Some(else_id), + else_ty, + else_span, + ); + if let Some(ret_sp) = opt_suggest_box_span { + self.suggest_boxing_for_return_impl_trait( + err, + ret_sp, + [then_span, else_span].into_iter(), + ); + } + } + ObligationCauseCode::LetElse => { + err.help("try adding a diverging expression, such as `return` or `panic!(..)`"); + err.help("...or use `match` instead of `let...else`"); + } + _ => { + if let ObligationCauseCode::BindingObligation(_, binding_span) = + cause.code().peel_derives() + { + if matches!(terr, TypeError::RegionsPlaceholderMismatch) { + err.span_note(*binding_span, "the lifetime requirement is introduced here"); + } + } + } + } + } + + fn suggest_remove_semi_or_return_binding( + &self, + err: &mut Diagnostic, + first_id: Option, + first_ty: Ty<'tcx>, + first_span: Span, + second_id: Option, + second_ty: Ty<'tcx>, + second_span: Span, + ) { + let remove_semicolon = [ + (first_id, self.resolve_vars_if_possible(second_ty)), + (second_id, self.resolve_vars_if_possible(first_ty)), + ] + .into_iter() + .find_map(|(id, ty)| { + let hir::Node::Block(blk) = self.tcx.hir().get(id?) else { return None }; + self.could_remove_semicolon(blk, ty) + }); + match remove_semicolon { + Some((sp, StatementAsExpression::NeedsBoxing)) => { + err.multipart_suggestion( + "consider removing this semicolon and boxing the expressions", + vec![ + (first_span.shrink_to_lo(), "Box::new(".to_string()), + (first_span.shrink_to_hi(), ")".to_string()), + (second_span.shrink_to_lo(), "Box::new(".to_string()), + (second_span.shrink_to_hi(), ")".to_string()), + (sp, String::new()), + ], + Applicability::MachineApplicable, + ); + } + Some((sp, StatementAsExpression::CorrectType)) => { + err.span_suggestion_short( + sp, + "consider removing this semicolon", + "", + Applicability::MachineApplicable, + ); + } + None => { + for (id, ty) in [(first_id, second_ty), (second_id, first_ty)] { + if let Some(id) = id + && let hir::Node::Block(blk) = self.tcx.hir().get(id) + && self.consider_returning_binding(blk, ty, err) + { + break; + } + } + } + } + } + + fn suggest_boxing_for_return_impl_trait( + &self, + err: &mut Diagnostic, + return_sp: Span, + arm_spans: impl Iterator, + ) { + err.multipart_suggestion( + "you could change the return type to be a boxed trait object", + vec![ + (return_sp.with_hi(return_sp.lo() + BytePos(4)), "Box".to_string()), + ], + Applicability::MaybeIncorrect, + ); + let sugg = arm_spans + .flat_map(|sp| { + [(sp.shrink_to_lo(), "Box::new(".to_string()), (sp.shrink_to_hi(), ")".to_string())] + .into_iter() + }) + .collect::>(); + err.multipart_suggestion( + "if you change the return type to expect trait objects, box the returned expressions", + sugg, + Applicability::MaybeIncorrect, + ); + } + + /// 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> + /// ^^^^--------^ this is highlighted + /// | | + /// | this type argument is exactly the same as the other type, not highlighted + /// this is highlighted + /// Bar + /// -------- 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::SubstsRef<'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 for the first type + let lifetimes = sub + .regions() + .map(|lifetime| { + let s = lifetime.to_string(); + if s.is_empty() { "'_".to_string() } else { s } + }) + .collect::>() + .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(type_arg.to_string()); + } + + if len > 0 && i != len - 1 { + value.push_normal(", "); + } + } + 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: + /// + /// ```ignore (illustrative) + /// let x: Foo> = foo::>(); + /// ``` + /// + /// The type error output will behave in the following way: + /// + /// ```text + /// Foo> + /// ^^^^--------^ this is highlighted + /// | | + /// | this type argument is exactly the same as the other type, not highlighted + /// this is highlighted + /// Bar + /// -------- 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: &'tcx [ty::GenericArg<'tcx>], + other_path: String, + other_ty: Ty<'tcx>, + ) -> Option<()> { + // FIXME/HACK: Go back to `SubstsRef` to use its inherent methods, + // ideally that shouldn't be necessary. + let sub = self.tcx.intern_substs(sub); + 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::Adt(def, _) = ta.kind() { + let path_ = self.tcx.def_path_str(def.did()); + if path_ == other_path { + self.highlight_outer(&mut t1_out, &mut t2_out, path, sub, i, other_ty); + return Some(()); + } + } + } + None + } + + /// Adds 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(", "); + } + } + + /// Given two `fn` signatures highlight only sub-parts that are different. + fn cmp_fn_sig( + &self, + sig1: &ty::PolyFnSig<'tcx>, + sig2: &ty::PolyFnSig<'tcx>, + ) -> (DiagnosticStyledString, DiagnosticStyledString) { + let get_lifetimes = |sig| { + use rustc_hir::def::Namespace; + let (_, sig, reg) = ty::print::FmtPrinter::new(self.tcx, Namespace::TypeNS) + .name_all_regions(sig) + .unwrap(); + let lts: Vec = reg.into_iter().map(|(_, kind)| kind.to_string()).collect(); + (if lts.is_empty() { String::new() } else { format!("for<{}> ", lts.join(", ")) }, sig) + }; + + let (lt1, sig1) = get_lifetimes(sig1); + let (lt2, sig2) = get_lifetimes(sig2); + + // unsafe extern "C" for<'a> fn(&'a T) -> &'a T + let mut values = ( + DiagnosticStyledString::normal("".to_string()), + DiagnosticStyledString::normal("".to_string()), + ); + + // unsafe extern "C" for<'a> fn(&'a T) -> &'a T + // ^^^^^^ + values.0.push(sig1.unsafety.prefix_str(), sig1.unsafety != sig2.unsafety); + values.1.push(sig2.unsafety.prefix_str(), sig1.unsafety != sig2.unsafety); + + // unsafe extern "C" for<'a> fn(&'a T) -> &'a T + // ^^^^^^^^^^ + if sig1.abi != abi::Abi::Rust { + values.0.push(format!("extern {} ", sig1.abi), sig1.abi != sig2.abi); + } + if sig2.abi != abi::Abi::Rust { + values.1.push(format!("extern {} ", sig2.abi), sig1.abi != sig2.abi); + } + + // unsafe extern "C" for<'a> fn(&'a T) -> &'a T + // ^^^^^^^^ + let lifetime_diff = lt1 != lt2; + values.0.push(lt1, lifetime_diff); + values.1.push(lt2, lifetime_diff); + + // unsafe extern "C" for<'a> fn(&'a T) -> &'a T + // ^^^ + values.0.push_normal("fn("); + values.1.push_normal("fn("); + + // unsafe extern "C" for<'a> fn(&'a T) -> &'a T + // ^^^^^ + let len1 = sig1.inputs().len(); + let len2 = sig2.inputs().len(); + if len1 == len2 { + for (i, (l, r)) in iter::zip(sig1.inputs(), sig2.inputs()).enumerate() { + let (x1, x2) = self.cmp(*l, *r); + (values.0).0.extend(x1.0); + (values.1).0.extend(x2.0); + self.push_comma(&mut values.0, &mut values.1, len1, i); + } + } else { + for (i, l) in sig1.inputs().iter().enumerate() { + values.0.push_highlighted(l.to_string()); + if i != len1 - 1 { + values.0.push_highlighted(", "); + } + } + for (i, r) in sig2.inputs().iter().enumerate() { + values.1.push_highlighted(r.to_string()); + if i != len2 - 1 { + values.1.push_highlighted(", "); + } + } + } + + if sig1.c_variadic { + if len1 > 0 { + values.0.push_normal(", "); + } + values.0.push("...", !sig2.c_variadic); + } + if sig2.c_variadic { + if len2 > 0 { + values.1.push_normal(", "); + } + values.1.push("...", !sig1.c_variadic); + } + + // unsafe extern "C" for<'a> fn(&'a T) -> &'a T + // ^ + values.0.push_normal(")"); + values.1.push_normal(")"); + + // unsafe extern "C" for<'a> fn(&'a T) -> &'a T + // ^^^^^^^^ + let output1 = sig1.output(); + let output2 = sig2.output(); + let (x1, x2) = self.cmp(output1, output2); + if !output1.is_unit() { + values.0.push_normal(" -> "); + (values.0).0.extend(x1.0); + } + if !output2.is_unit() { + values.1.push_normal(" -> "); + (values.1).0.extend(x2.0); + } + values + } + + /// Compares 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. + pub fn cmp( + &self, + t1: Ty<'tcx>, + t2: Ty<'tcx>, + ) -> (DiagnosticStyledString, DiagnosticStyledString) { + debug!("cmp(t1={}, t1.kind={:?}, t2={}, t2.kind={:?})", t1, t1.kind(), t2, t2.kind()); + + // helper functions + fn equals<'tcx>(a: Ty<'tcx>, b: Ty<'tcx>) -> bool { + match (a.kind(), b.kind()) { + (a, b) if *a == *b => true, + (&ty::Int(_), &ty::Infer(ty::InferTy::IntVar(_))) + | ( + &ty::Infer(ty::InferTy::IntVar(_)), + &ty::Int(_) | &ty::Infer(ty::InferTy::IntVar(_)), + ) + | (&ty::Float(_), &ty::Infer(ty::InferTy::FloatVar(_))) + | ( + &ty::Infer(ty::InferTy::FloatVar(_)), + &ty::Float(_) | &ty::Infer(ty::InferTy::FloatVar(_)), + ) => true, + _ => false, + } + } + + fn push_ty_ref<'tcx>( + region: ty::Region<'tcx>, + ty: Ty<'tcx>, + mutbl: hir::Mutability, + s: &mut DiagnosticStyledString, + ) { + let mut r = region.to_string(); + if r == "'_" { + r.clear(); + } else { + r.push(' '); + } + s.push_highlighted(format!("&{}{}", r, mutbl.prefix_str())); + s.push_normal(ty.to_string()); + } + + // process starts here + match (t1.kind(), t2.kind()) { + (&ty::Adt(def1, sub1), &ty::Adt(def2, sub2)) => { + let did1 = def1.did(); + let did2 = def2.did(); + let sub_no_defaults_1 = + self.tcx.generics_of(did1).own_substs_no_defaults(self.tcx, sub1); + let sub_no_defaults_2 = + self.tcx.generics_of(did2).own_substs_no_defaults(self.tcx, sub2); + let mut values = (DiagnosticStyledString::new(), DiagnosticStyledString::new()); + let path1 = self.tcx.def_path_str(did1); + let path2 = self.tcx.def_path_str(did2); + if did1 == did2 { + // Easy case. Replace same types with `_` to shorten the output and highlight + // the differing ones. + // let x: Foo = y::>(); + // Foo + // Foo + // --- ^ type argument elided + // | + // highlighted in output + values.0.push_normal(path1); + values.1.push_normal(path2); + + // Avoid printing out default generic parameters that are common to both + // types. + let len1 = sub_no_defaults_1.len(); + let len2 = sub_no_defaults_2.len(); + let common_len = cmp::min(len1, len2); + let remainder1: Vec<_> = sub1.types().skip(common_len).collect(); + let remainder2: Vec<_> = sub2.types().skip(common_len).collect(); + let common_default_params = + iter::zip(remainder1.iter().rev(), remainder2.iter().rev()) + .filter(|(a, b)| a == b) + .count(); + let len = sub1.len() - common_default_params; + let consts_offset = len - sub1.consts().count(); + + // Only draw `<...>` if there are lifetime/type arguments. + if len > 0 { + values.0.push_normal("<"); + values.1.push_normal("<"); + } + + fn lifetime_display(lifetime: Region<'_>) -> String { + let s = lifetime.to_string(); + 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 + // + // For bound lifetimes, keep the names of the lifetimes, + // even if they are the same so that it's clear what's happening + // if we have something like + // + // for<'r, 's> fn(Inv<'r>, Inv<'s>) + // for<'r> fn(Inv<'r>, Inv<'r>) + 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 lifetimes.0 != lifetimes.1 { + values.0.push_highlighted(l1); + values.1.push_highlighted(l2); + } else if lifetimes.0.is_late_bound() { + values.0.push_normal(l1); + values.1.push_normal(l2); + } else { + values.0.push_normal("'_"); + values.1.push_normal("'_"); + } + 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().count(); + let num_display_types = consts_offset - regions_len; + for (i, (ta1, ta2)) in type_arguments.take(num_display_types).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); + } + + // Do the same for const arguments, if they are equal, do not highlight and + // elide them from the output. + let const_arguments = sub1.consts().zip(sub2.consts()); + for (i, (ca1, ca2)) in const_arguments.enumerate() { + let i = i + consts_offset; + if ca1 == ca2 { + values.0.push_normal("_"); + values.1.push_normal("_"); + } else { + values.0.push_highlighted(ca1.to_string()); + values.1.push_highlighted(ca2.to_string()); + } + self.push_comma(&mut values.0, &mut values.1, len, i); + } + + // Close the type argument bracket. + // Only draw `<...>` if there are lifetime/type arguments. + if len > 0 { + values.0.push_normal(">"); + values.1.push_normal(">"); + } + values + } else { + // Check for case: + // let x: Foo = foo::>(); + // Foo + // ------- this type argument is exactly the same as the other type + // Bar + if self + .cmp_type_arg( + &mut values.0, + &mut values.1, + path1.clone(), + sub_no_defaults_1, + path2.clone(), + t2, + ) + .is_some() + { + return values; + } + // Check for case: + // let x: Bar = y:>>(); + // Bar + // Foo> + // ------- this type argument is exactly the same as the other type + if self + .cmp_type_arg( + &mut values.1, + &mut values.0, + path2, + sub_no_defaults_2, + path1, + t1, + ) + .is_some() + { + return values; + } + + // We can't find anything in common, highlight relevant part of type path. + // let x: foo::bar::Baz = y:>(); + // foo::bar::Baz + // foo::bar::Bar + // -------- this part of the path is different + + let t1_str = t1.to_string(); + let t2_str = t2.to_string(); + let min_len = t1_str.len().min(t2_str.len()); + + const SEPARATOR: &str = "::"; + let separator_len = SEPARATOR.len(); + let split_idx: usize = + iter::zip(t1_str.split(SEPARATOR), t2_str.split(SEPARATOR)) + .take_while(|(mod1_str, mod2_str)| mod1_str == mod2_str) + .map(|(mod_str, _)| mod_str.len() + separator_len) + .sum(); + + debug!( + "cmp: separator_len={}, split_idx={}, min_len={}", + separator_len, split_idx, min_len + ); + + if split_idx >= min_len { + // paths are identical, highlight everything + ( + DiagnosticStyledString::highlighted(t1_str), + DiagnosticStyledString::highlighted(t2_str), + ) + } else { + let (common, uniq1) = t1_str.split_at(split_idx); + let (_, uniq2) = t2_str.split_at(split_idx); + debug!("cmp: common={}, uniq1={}, uniq2={}", common, uniq1, uniq2); + + values.0.push_normal(common); + values.0.push_highlighted(uniq1); + values.1.push_normal(common); + values.1.push_highlighted(uniq2); + + values + } + } + } + + // When finding T != &T, highlight only the borrow + (&ty::Ref(r1, ref_ty1, mutbl1), _) if equals(ref_ty1, t2) => { + let mut values = (DiagnosticStyledString::new(), DiagnosticStyledString::new()); + push_ty_ref(r1, ref_ty1, mutbl1, &mut values.0); + values.1.push_normal(t2.to_string()); + values + } + (_, &ty::Ref(r2, ref_ty2, mutbl2)) if equals(t1, ref_ty2) => { + let mut values = (DiagnosticStyledString::new(), DiagnosticStyledString::new()); + values.0.push_normal(t1.to_string()); + push_ty_ref(r2, ref_ty2, mutbl2, &mut values.1); + values + } + + // When encountering &T != &mut T, highlight only the borrow + (&ty::Ref(r1, ref_ty1, mutbl1), &ty::Ref(r2, ref_ty2, mutbl2)) + if equals(ref_ty1, ref_ty2) => + { + let mut values = (DiagnosticStyledString::new(), DiagnosticStyledString::new()); + push_ty_ref(r1, ref_ty1, mutbl1, &mut values.0); + push_ty_ref(r2, ref_ty2, mutbl2, &mut values.1); + values + } + + // When encountering tuples of the same size, highlight only the differing types + (&ty::Tuple(substs1), &ty::Tuple(substs2)) if substs1.len() == substs2.len() => { + let mut values = + (DiagnosticStyledString::normal("("), DiagnosticStyledString::normal("(")); + let len = substs1.len(); + for (i, (left, right)) in substs1.iter().zip(substs2).enumerate() { + let (x1, x2) = self.cmp(left, right); + (values.0).0.extend(x1.0); + (values.1).0.extend(x2.0); + self.push_comma(&mut values.0, &mut values.1, len, i); + } + if len == 1 { + // Keep the output for single element tuples as `(ty,)`. + values.0.push_normal(","); + values.1.push_normal(","); + } + values.0.push_normal(")"); + values.1.push_normal(")"); + values + } + + (ty::FnDef(did1, substs1), ty::FnDef(did2, substs2)) => { + let sig1 = self.tcx.bound_fn_sig(*did1).subst(self.tcx, substs1); + let sig2 = self.tcx.bound_fn_sig(*did2).subst(self.tcx, substs2); + let mut values = self.cmp_fn_sig(&sig1, &sig2); + let path1 = format!(" {{{}}}", self.tcx.def_path_str_with_substs(*did1, substs1)); + let path2 = format!(" {{{}}}", self.tcx.def_path_str_with_substs(*did2, substs2)); + let same_path = path1 == path2; + values.0.push(path1, !same_path); + values.1.push(path2, !same_path); + values + } + + (ty::FnDef(did1, substs1), ty::FnPtr(sig2)) => { + let sig1 = self.tcx.bound_fn_sig(*did1).subst(self.tcx, substs1); + let mut values = self.cmp_fn_sig(&sig1, sig2); + values.0.push_highlighted(format!( + " {{{}}}", + self.tcx.def_path_str_with_substs(*did1, substs1) + )); + values + } + + (ty::FnPtr(sig1), ty::FnDef(did2, substs2)) => { + let sig2 = self.tcx.bound_fn_sig(*did2).subst(self.tcx, substs2); + let mut values = self.cmp_fn_sig(sig1, &sig2); + values.1.push_normal(format!( + " {{{}}}", + self.tcx.def_path_str_with_substs(*did2, substs2) + )); + values + } + + (ty::FnPtr(sig1), ty::FnPtr(sig2)) => self.cmp_fn_sig(sig1, sig2), + + _ => { + 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(t1.to_string()), + DiagnosticStyledString::highlighted(t2.to_string()), + ) + } + } + } + } + + /// Extend a type error with extra labels pointing at "non-trivial" types, like closures and + /// the return type of `async fn`s. + /// + /// `secondary_span` gives the caller the opportunity to expand `diag` with a `span_label`. + /// + /// `swap_secondary_and_primary` is used to make projection errors in particular nicer by using + /// the message in `secondary_span` as the primary label, and apply the message that would + /// otherwise be used for the primary label on the `secondary_span` `Span`. This applies on + /// E0271, like `src/test/ui/issues/issue-39970.stderr`. + #[tracing::instrument( + level = "debug", + skip(self, diag, secondary_span, swap_secondary_and_primary, force_label) + )] + pub fn note_type_err( + &self, + diag: &mut Diagnostic, + cause: &ObligationCause<'tcx>, + secondary_span: Option<(Span, String)>, + mut values: Option>, + terr: &TypeError<'tcx>, + swap_secondary_and_primary: bool, + force_label: bool, + ) { + let span = cause.span(); + + // For some types of errors, expected-found does not make + // sense, so just ignore the values we were given. + if let TypeError::CyclicTy(_) = terr { + values = None; + } + struct OpaqueTypesVisitor<'tcx> { + types: FxHashMap>, + expected: FxHashMap>, + found: FxHashMap>, + ignore_span: Span, + tcx: TyCtxt<'tcx>, + } + + impl<'tcx> OpaqueTypesVisitor<'tcx> { + fn visit_expected_found( + tcx: TyCtxt<'tcx>, + expected: Ty<'tcx>, + found: Ty<'tcx>, + ignore_span: Span, + ) -> Self { + let mut types_visitor = OpaqueTypesVisitor { + types: Default::default(), + expected: Default::default(), + found: Default::default(), + ignore_span, + tcx, + }; + // The visitor puts all the relevant encountered types in `self.types`, but in + // here we want to visit two separate types with no relation to each other, so we + // move the results from `types` to `expected` or `found` as appropriate. + expected.visit_with(&mut types_visitor); + std::mem::swap(&mut types_visitor.expected, &mut types_visitor.types); + found.visit_with(&mut types_visitor); + std::mem::swap(&mut types_visitor.found, &mut types_visitor.types); + types_visitor + } + + fn report(&self, err: &mut Diagnostic) { + self.add_labels_for_types(err, "expected", &self.expected); + self.add_labels_for_types(err, "found", &self.found); + } + + fn add_labels_for_types( + &self, + err: &mut Diagnostic, + target: &str, + types: &FxHashMap>, + ) { + for (key, values) in types.iter() { + let count = values.len(); + let kind = key.descr(); + let mut returned_async_output_error = false; + for &sp in values { + if sp.is_desugaring(DesugaringKind::Async) && !returned_async_output_error { + if [sp] != err.span.primary_spans() { + let mut span: MultiSpan = sp.into(); + span.push_span_label( + sp, + format!( + "checked the `Output` of this `async fn`, {}{} {}{}", + if count > 1 { "one of the " } else { "" }, + target, + kind, + pluralize!(count), + ), + ); + err.span_note( + span, + "while checking the return type of the `async fn`", + ); + } else { + err.span_label( + sp, + format!( + "checked the `Output` of this `async fn`, {}{} {}{}", + if count > 1 { "one of the " } else { "" }, + target, + kind, + pluralize!(count), + ), + ); + err.note("while checking the return type of the `async fn`"); + } + returned_async_output_error = true; + } else { + err.span_label( + sp, + format!( + "{}{} {}{}", + if count == 1 { "the " } else { "one of the " }, + target, + kind, + pluralize!(count), + ), + ); + } + } + } + } + } + + impl<'tcx> ty::visit::TypeVisitor<'tcx> for OpaqueTypesVisitor<'tcx> { + fn visit_ty(&mut self, t: Ty<'tcx>) -> ControlFlow { + if let Some((kind, def_id)) = TyCategory::from_ty(self.tcx, t) { + let span = self.tcx.def_span(def_id); + // Avoid cluttering the output when the "found" and error span overlap: + // + // error[E0308]: mismatched types + // --> $DIR/issue-20862.rs:2:5 + // | + // LL | |y| x + y + // | ^^^^^^^^^ + // | | + // | the found closure + // | expected `()`, found closure + // | + // = note: expected unit type `()` + // found closure `[closure@$DIR/issue-20862.rs:2:5: 2:14 x:_]` + if !self.ignore_span.overlaps(span) { + self.types.entry(kind).or_default().insert(span); + } + } + t.super_visit_with(self) + } + } + + debug!("note_type_err(diag={:?})", diag); + enum Mismatch<'a> { + Variable(ty::error::ExpectedFound>), + Fixed(&'static str), + } + let (expected_found, exp_found, is_simple_error, values) = match values { + None => (None, Mismatch::Fixed("type"), false, None), + Some(values) => { + let values = self.resolve_vars_if_possible(values); + let (is_simple_error, exp_found) = match values { + ValuePairs::Terms(infer::ExpectedFound { + expected: ty::Term::Ty(expected), + found: ty::Term::Ty(found), + }) => { + let is_simple_err = expected.is_simple_text() && found.is_simple_text(); + OpaqueTypesVisitor::visit_expected_found(self.tcx, expected, found, span) + .report(diag); + + ( + is_simple_err, + Mismatch::Variable(infer::ExpectedFound { expected, found }), + ) + } + ValuePairs::TraitRefs(_) | ValuePairs::PolyTraitRefs(_) => { + (false, Mismatch::Fixed("trait")) + } + _ => (false, Mismatch::Fixed("type")), + }; + let vals = match self.values_str(values) { + Some((expected, found)) => Some((expected, found)), + None => { + // Derived error. Cancel the emitter. + // NOTE(eddyb) this was `.cancel()`, but `diag` + // is borrowed, so we can't fully defuse it. + diag.downgrade_to_delayed_bug(); + return; + } + }; + (vals, exp_found, is_simple_error, Some(values)) + } + }; + + match terr { + // Ignore msg for object safe coercion + // since E0038 message will be printed + TypeError::ObjectUnsafeCoercion(_) => {} + _ => { + let mut label_or_note = |span: Span, msg: &str| { + if force_label || &[span] == diag.span.primary_spans() { + diag.span_label(span, msg); + } else { + diag.span_note(span, msg); + } + }; + if let Some((sp, msg)) = secondary_span { + if swap_secondary_and_primary { + let terr = if let Some(infer::ValuePairs::Terms(infer::ExpectedFound { + expected, + .. + })) = values + { + format!("expected this to be `{}`", expected) + } else { + terr.to_string() + }; + label_or_note(sp, &terr); + label_or_note(span, &msg); + } else { + label_or_note(span, &terr.to_string()); + label_or_note(sp, &msg); + } + } else { + label_or_note(span, &terr.to_string()); + } + } + }; + if let Some((expected, found)) = expected_found { + let (expected_label, found_label, exp_found) = match exp_found { + Mismatch::Variable(ef) => ( + ef.expected.prefix_string(self.tcx), + ef.found.prefix_string(self.tcx), + Some(ef), + ), + Mismatch::Fixed(s) => (s.into(), s.into(), None), + }; + match (&terr, expected == found) { + (TypeError::Sorts(values), extra) => { + let sort_string = |ty: Ty<'tcx>| match (extra, ty.kind()) { + (true, ty::Opaque(def_id, _)) => { + let sm = self.tcx.sess.source_map(); + let pos = sm.lookup_char_pos(self.tcx.def_span(*def_id).lo()); + format!( + " (opaque type at <{}:{}:{}>)", + sm.filename_for_diagnostics(&pos.file.name), + pos.line, + pos.col.to_usize() + 1, + ) + } + (true, _) => format!(" ({})", ty.sort_string(self.tcx)), + (false, _) => "".to_string(), + }; + if !(values.expected.is_simple_text() && values.found.is_simple_text()) + || (exp_found.map_or(false, |ef| { + // This happens when the type error is a subset of the expectation, + // like when you have two references but one is `usize` and the other + // is `f32`. In those cases we still want to show the `note`. If the + // value from `ef` is `Infer(_)`, then we ignore it. + if !ef.expected.is_ty_infer() { + ef.expected != values.expected + } else if !ef.found.is_ty_infer() { + ef.found != values.found + } else { + false + } + })) + { + diag.note_expected_found_extra( + &expected_label, + expected, + &found_label, + found, + &sort_string(values.expected), + &sort_string(values.found), + ); + } + } + (TypeError::ObjectUnsafeCoercion(_), _) => { + diag.note_unsuccessful_coercion(found, expected); + } + (_, _) => { + debug!( + "note_type_err: exp_found={:?}, expected={:?} found={:?}", + exp_found, expected, found + ); + if !is_simple_error || terr.must_include_note() { + diag.note_expected_found(&expected_label, expected, &found_label, found); + } + } + } + } + let exp_found = match exp_found { + Mismatch::Variable(exp_found) => Some(exp_found), + Mismatch::Fixed(_) => None, + }; + let exp_found = match terr { + // `terr` has more accurate type information than `exp_found` in match expressions. + ty::error::TypeError::Sorts(terr) + if exp_found.map_or(false, |ef| terr.found == ef.found) => + { + Some(*terr) + } + _ => exp_found, + }; + debug!("exp_found {:?} terr {:?} cause.code {:?}", exp_found, terr, cause.code()); + if let Some(exp_found) = exp_found { + let should_suggest_fixes = + if let ObligationCauseCode::Pattern { root_ty, .. } = cause.code() { + // Skip if the root_ty of the pattern is not the same as the expected_ty. + // If these types aren't equal then we've probably peeled off a layer of arrays. + self.same_type_modulo_infer(*root_ty, exp_found.expected) + } else { + true + }; + + if should_suggest_fixes { + self.suggest_tuple_pattern(cause, &exp_found, diag); + self.suggest_as_ref_where_appropriate(span, &exp_found, diag); + self.suggest_accessing_field_where_appropriate(cause, &exp_found, diag); + self.suggest_await_on_expect_found(cause, span, &exp_found, diag); + } + } + + // In some (most?) cases cause.body_id points to actual body, but in some cases + // it's an actual definition. According to the comments (e.g. in + // librustc_typeck/check/compare_method.rs:compare_predicate_entailment) the latter + // is relied upon by some other code. This might (or might not) need cleanup. + let body_owner_def_id = + self.tcx.hir().opt_local_def_id(cause.body_id).unwrap_or_else(|| { + self.tcx.hir().body_owner_def_id(hir::BodyId { hir_id: cause.body_id }) + }); + self.check_and_note_conflicting_crates(diag, terr); + self.tcx.note_and_explain_type_err(diag, terr, cause, span, body_owner_def_id.to_def_id()); + + if let Some(ValuePairs::PolyTraitRefs(exp_found)) = values + && let ty::Closure(def_id, _) = exp_found.expected.skip_binder().self_ty().kind() + && let Some(def_id) = def_id.as_local() + { + let span = self.tcx.def_span(def_id); + diag.span_note(span, "this closure does not fulfill the lifetime requirements"); + } + + // It reads better to have the error origin as the final + // thing. + self.note_error_origin(diag, cause, exp_found, terr); + + debug!(?diag); + } + + fn suggest_tuple_pattern( + &self, + cause: &ObligationCause<'tcx>, + exp_found: &ty::error::ExpectedFound>, + diag: &mut Diagnostic, + ) { + // Heavily inspired by `FnCtxt::suggest_compatible_variants`, with + // some modifications due to that being in typeck and this being in infer. + if let ObligationCauseCode::Pattern { .. } = cause.code() { + if let ty::Adt(expected_adt, substs) = exp_found.expected.kind() { + let compatible_variants: Vec<_> = expected_adt + .variants() + .iter() + .filter(|variant| { + variant.fields.len() == 1 && variant.ctor_kind == hir::def::CtorKind::Fn + }) + .filter_map(|variant| { + let sole_field = &variant.fields[0]; + let sole_field_ty = sole_field.ty(self.tcx, substs); + if self.same_type_modulo_infer(sole_field_ty, exp_found.found) { + let variant_path = + with_no_trimmed_paths!(self.tcx.def_path_str(variant.def_id)); + // FIXME #56861: DRYer prelude filtering + if let Some(path) = variant_path.strip_prefix("std::prelude::") { + if let Some((_, path)) = path.split_once("::") { + return Some(path.to_string()); + } + } + Some(variant_path) + } else { + None + } + }) + .collect(); + match &compatible_variants[..] { + [] => {} + [variant] => { + diag.multipart_suggestion_verbose( + &format!("try wrapping the pattern in `{}`", variant), + vec![ + (cause.span.shrink_to_lo(), format!("{}(", variant)), + (cause.span.shrink_to_hi(), ")".to_string()), + ], + Applicability::MaybeIncorrect, + ); + } + _ => { + // More than one matching variant. + diag.multipart_suggestions( + &format!( + "try wrapping the pattern in a variant of `{}`", + self.tcx.def_path_str(expected_adt.did()) + ), + compatible_variants.into_iter().map(|variant| { + vec![ + (cause.span.shrink_to_lo(), format!("{}(", variant)), + (cause.span.shrink_to_hi(), ")".to_string()), + ] + }), + Applicability::MaybeIncorrect, + ); + } + } + } + } + } + + pub fn get_impl_future_output_ty(&self, ty: Ty<'tcx>) -> Option>> { + if let ty::Opaque(def_id, substs) = ty.kind() { + let future_trait = self.tcx.require_lang_item(LangItem::Future, None); + // Future::Output + let item_def_id = self.tcx.associated_item_def_ids(future_trait)[0]; + + let bounds = self.tcx.bound_explicit_item_bounds(*def_id); + + for predicate in bounds.transpose_iter().map(|e| e.map_bound(|(p, _)| *p)) { + let predicate = predicate.subst(self.tcx, substs); + let output = predicate + .kind() + .map_bound(|kind| match kind { + ty::PredicateKind::Projection(projection_predicate) + if projection_predicate.projection_ty.item_def_id == item_def_id => + { + projection_predicate.term.ty() + } + _ => None, + }) + .transpose(); + if output.is_some() { + // We don't account for multiple `Future::Output = Ty` constraints. + return output; + } + } + } + None + } + + /// A possible error is to forget to add `.await` when using futures: + /// + /// ```compile_fail,E0308 + /// async fn make_u32() -> u32 { + /// 22 + /// } + /// + /// fn take_u32(x: u32) {} + /// + /// async fn foo() { + /// let x = make_u32(); + /// take_u32(x); + /// } + /// ``` + /// + /// This routine checks if the found type `T` implements `Future` where `U` is the + /// expected type. If this is the case, and we are inside of an async body, it suggests adding + /// `.await` to the tail of the expression. + fn suggest_await_on_expect_found( + &self, + cause: &ObligationCause<'tcx>, + exp_span: Span, + exp_found: &ty::error::ExpectedFound>, + diag: &mut Diagnostic, + ) { + debug!( + "suggest_await_on_expect_found: exp_span={:?}, expected_ty={:?}, found_ty={:?}", + exp_span, exp_found.expected, exp_found.found, + ); + + if let ObligationCauseCode::CompareImplItemObligation { .. } = cause.code() { + return; + } + + match ( + self.get_impl_future_output_ty(exp_found.expected).map(Binder::skip_binder), + self.get_impl_future_output_ty(exp_found.found).map(Binder::skip_binder), + ) { + (Some(exp), Some(found)) if self.same_type_modulo_infer(exp, found) => match cause + .code() + { + ObligationCauseCode::IfExpression(box IfExpressionCause { then_id, .. }) => { + let then_span = self.find_block_span_from_hir_id(*then_id); + diag.multipart_suggestion( + "consider `await`ing on both `Future`s", + vec![ + (then_span.shrink_to_hi(), ".await".to_string()), + (exp_span.shrink_to_hi(), ".await".to_string()), + ], + Applicability::MaybeIncorrect, + ); + } + ObligationCauseCode::MatchExpressionArm(box MatchExpressionArmCause { + prior_arms, + .. + }) => { + if let [.., arm_span] = &prior_arms[..] { + diag.multipart_suggestion( + "consider `await`ing on both `Future`s", + vec![ + (arm_span.shrink_to_hi(), ".await".to_string()), + (exp_span.shrink_to_hi(), ".await".to_string()), + ], + Applicability::MaybeIncorrect, + ); + } else { + diag.help("consider `await`ing on both `Future`s"); + } + } + _ => { + diag.help("consider `await`ing on both `Future`s"); + } + }, + (_, Some(ty)) if self.same_type_modulo_infer(exp_found.expected, ty) => { + diag.span_suggestion_verbose( + exp_span.shrink_to_hi(), + "consider `await`ing on the `Future`", + ".await", + Applicability::MaybeIncorrect, + ); + } + (Some(ty), _) if self.same_type_modulo_infer(ty, exp_found.found) => match cause.code() + { + ObligationCauseCode::Pattern { span: Some(then_span), .. } => { + diag.span_suggestion_verbose( + then_span.shrink_to_hi(), + "consider `await`ing on the `Future`", + ".await", + Applicability::MaybeIncorrect, + ); + } + ObligationCauseCode::IfExpression(box IfExpressionCause { then_id, .. }) => { + let then_span = self.find_block_span_from_hir_id(*then_id); + diag.span_suggestion_verbose( + then_span.shrink_to_hi(), + "consider `await`ing on the `Future`", + ".await", + Applicability::MaybeIncorrect, + ); + } + ObligationCauseCode::MatchExpressionArm(box MatchExpressionArmCause { + ref prior_arms, + .. + }) => { + diag.multipart_suggestion_verbose( + "consider `await`ing on the `Future`", + prior_arms + .iter() + .map(|arm| (arm.shrink_to_hi(), ".await".to_string())) + .collect(), + Applicability::MaybeIncorrect, + ); + } + _ => {} + }, + _ => {} + } + } + + fn suggest_accessing_field_where_appropriate( + &self, + cause: &ObligationCause<'tcx>, + exp_found: &ty::error::ExpectedFound>, + diag: &mut Diagnostic, + ) { + debug!( + "suggest_accessing_field_where_appropriate(cause={:?}, exp_found={:?})", + cause, exp_found + ); + if let ty::Adt(expected_def, expected_substs) = exp_found.expected.kind() { + if expected_def.is_enum() { + return; + } + + if let Some((name, ty)) = expected_def + .non_enum_variant() + .fields + .iter() + .filter(|field| field.vis.is_accessible_from(field.did, self.tcx)) + .map(|field| (field.name, field.ty(self.tcx, expected_substs))) + .find(|(_, ty)| self.same_type_modulo_infer(*ty, exp_found.found)) + { + if let ObligationCauseCode::Pattern { span: Some(span), .. } = *cause.code() { + if let Ok(snippet) = self.tcx.sess.source_map().span_to_snippet(span) { + let suggestion = if expected_def.is_struct() { + format!("{}.{}", snippet, name) + } else if expected_def.is_union() { + format!("unsafe {{ {}.{} }}", snippet, name) + } else { + return; + }; + diag.span_suggestion( + span, + &format!( + "you might have meant to use field `{}` whose type is `{}`", + name, ty + ), + suggestion, + Applicability::MaybeIncorrect, + ); + } + } + } + } + } + + /// When encountering a case where `.as_ref()` on a `Result` or `Option` would be appropriate, + /// suggests it. + fn suggest_as_ref_where_appropriate( + &self, + span: Span, + exp_found: &ty::error::ExpectedFound>, + diag: &mut Diagnostic, + ) { + if let (ty::Adt(exp_def, exp_substs), ty::Ref(_, found_ty, _)) = + (exp_found.expected.kind(), exp_found.found.kind()) + { + if let ty::Adt(found_def, found_substs) = *found_ty.kind() { + let path_str = format!("{:?}", exp_def); + if exp_def == &found_def { + let opt_msg = "you can convert from `&Option` to `Option<&T>` using \ + `.as_ref()`"; + let result_msg = "you can convert from `&Result` to \ + `Result<&T, &E>` using `.as_ref()`"; + let have_as_ref = &[ + ("std::option::Option", opt_msg), + ("core::option::Option", opt_msg), + ("std::result::Result", result_msg), + ("core::result::Result", result_msg), + ]; + if let Some(msg) = have_as_ref + .iter() + .find_map(|(path, msg)| (&path_str == path).then_some(msg)) + { + let mut show_suggestion = true; + for (exp_ty, found_ty) in + iter::zip(exp_substs.types(), found_substs.types()) + { + match *exp_ty.kind() { + ty::Ref(_, exp_ty, _) => { + match (exp_ty.kind(), found_ty.kind()) { + (_, ty::Param(_)) + | (_, ty::Infer(_)) + | (ty::Param(_), _) + | (ty::Infer(_), _) => {} + _ if self.same_type_modulo_infer(exp_ty, found_ty) => {} + _ => show_suggestion = false, + }; + } + ty::Param(_) | ty::Infer(_) => {} + _ => show_suggestion = false, + } + } + if let (Ok(snippet), true) = + (self.tcx.sess.source_map().span_to_snippet(span), show_suggestion) + { + diag.span_suggestion( + span, + *msg, + format!("{}.as_ref()", snippet), + Applicability::MachineApplicable, + ); + } + } + } + } + } + } + + pub fn report_and_explain_type_error( + &self, + trace: TypeTrace<'tcx>, + terr: &TypeError<'tcx>, + ) -> DiagnosticBuilder<'tcx, ErrorGuaranteed> { + use crate::traits::ObligationCauseCode::MatchExpressionArm; + + 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::Error0038(did) => { + let violations = self.tcx.object_safety_violations(did); + report_object_safety_error(self.tcx, span, did, violations) + } + 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) => { + let mut err = struct_span_err!(self.tcx.sess, span, E0308, "{}", failure_str); + if let Some((expected, found)) = trace.values.ty() { + match (expected.kind(), found.kind()) { + (ty::Tuple(_), ty::Tuple(_)) => {} + // If a tuple of length one was expected and the found expression has + // parentheses around it, perhaps the user meant to write `(expr,)` to + // build a tuple (issue #86100) + (ty::Tuple(fields), _) => { + self.emit_tuple_wrap_err(&mut err, span, found, fields) + } + // If a character was expected and the found expression is a string literal + // containing a single character, perhaps the user meant to write `'c'` to + // specify a character literal (issue #92479) + (ty::Char, ty::Ref(_, r, _)) if r.is_str() => { + if let Ok(code) = self.tcx.sess().source_map().span_to_snippet(span) + && let Some(code) = code.strip_prefix('"').and_then(|s| s.strip_suffix('"')) + && code.chars().count() == 1 + { + err.span_suggestion( + span, + "if you meant to write a `char` literal, use single quotes", + format!("'{}'", code), + Applicability::MachineApplicable, + ); + } + } + // If a string was expected and the found expression is a character literal, + // perhaps the user meant to write `"s"` to specify a string literal. + (ty::Ref(_, r, _), ty::Char) if r.is_str() => { + if let Ok(code) = self.tcx.sess().source_map().span_to_snippet(span) { + if let Some(code) = + code.strip_prefix('\'').and_then(|s| s.strip_suffix('\'')) + { + err.span_suggestion( + span, + "if you meant to write a `str` literal, use double quotes", + format!("\"{}\"", code), + Applicability::MachineApplicable, + ); + } + } + } + _ => {} + } + } + let code = trace.cause.code(); + if let &MatchExpressionArm(box MatchExpressionArmCause { source, .. }) = code + && let hir::MatchSource::TryDesugar = source + && let Some((expected_ty, found_ty)) = self.values_str(trace.values) + { + err.note(&format!( + "`?` operator cannot convert from `{}` to `{}`", + found_ty.content(), + expected_ty.content(), + )); + } + err + } + 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, false, false); + diag + } + + fn emit_tuple_wrap_err( + &self, + err: &mut Diagnostic, + span: Span, + found: Ty<'tcx>, + expected_fields: &List>, + ) { + let [expected_tup_elem] = expected_fields[..] else { return }; + + if !self.same_type_modulo_infer(expected_tup_elem, found) { + return; + } + + let Ok(code) = self.tcx.sess().source_map().span_to_snippet(span) + else { return }; + + let msg = "use a trailing comma to create a tuple with one element"; + if code.starts_with('(') && code.ends_with(')') { + let before_close = span.hi() - BytePos::from_u32(1); + err.span_suggestion( + span.with_hi(before_close).shrink_to_hi(), + msg, + ",", + Applicability::MachineApplicable, + ); + } else { + err.multipart_suggestion( + msg, + vec![(span.shrink_to_lo(), "(".into()), (span.shrink_to_hi(), ",)".into())], + Applicability::MachineApplicable, + ); + } + } + + fn values_str( + &self, + values: ValuePairs<'tcx>, + ) -> Option<(DiagnosticStyledString, DiagnosticStyledString)> { + match values { + infer::Regions(exp_found) => self.expected_found_str(exp_found), + infer::Terms(exp_found) => self.expected_found_str_term(exp_found), + infer::TraitRefs(exp_found) => { + let pretty_exp_found = ty::error::ExpectedFound { + expected: exp_found.expected.print_only_trait_path(), + found: exp_found.found.print_only_trait_path(), + }; + match self.expected_found_str(pretty_exp_found) { + Some((expected, found)) if expected == found => { + self.expected_found_str(exp_found) + } + ret => ret, + } + } + infer::PolyTraitRefs(exp_found) => { + let pretty_exp_found = ty::error::ExpectedFound { + expected: exp_found.expected.print_only_trait_path(), + found: exp_found.found.print_only_trait_path(), + }; + match self.expected_found_str(pretty_exp_found) { + Some((expected, found)) if expected == found => { + self.expected_found_str(exp_found) + } + ret => ret, + } + } + } + } + + fn expected_found_str_term( + &self, + exp_found: ty::error::ExpectedFound>, + ) -> Option<(DiagnosticStyledString, DiagnosticStyledString)> { + let exp_found = self.resolve_vars_if_possible(exp_found); + if exp_found.references_error() { + return None; + } + + Some(match (exp_found.expected, exp_found.found) { + (ty::Term::Ty(expected), ty::Term::Ty(found)) => self.cmp(expected, found), + (expected, found) => ( + DiagnosticStyledString::highlighted(expected.to_string()), + DiagnosticStyledString::highlighted(found.to_string()), + ), + }) + } + + /// Returns a string of the form "expected `{}`, found `{}`". + fn expected_found_str>( + &self, + exp_found: ty::error::ExpectedFound, + ) -> Option<(DiagnosticStyledString, DiagnosticStyledString)> { + let exp_found = self.resolve_vars_if_possible(exp_found); + if exp_found.references_error() { + return None; + } + + Some(( + DiagnosticStyledString::highlighted(exp_found.expected.to_string()), + DiagnosticStyledString::highlighted(exp_found.found.to_string()), + )) + } + + pub fn report_generic_bound_failure( + &self, + generic_param_scope: LocalDefId, + span: Span, + origin: Option>, + bound_kind: GenericKind<'tcx>, + sub: Region<'tcx>, + ) { + self.construct_generic_bound_failure(generic_param_scope, span, origin, bound_kind, sub) + .emit(); + } + + pub fn construct_generic_bound_failure( + &self, + generic_param_scope: LocalDefId, + span: Span, + origin: Option>, + bound_kind: GenericKind<'tcx>, + sub: Region<'tcx>, + ) -> DiagnosticBuilder<'a, ErrorGuaranteed> { + // Attempt to obtain the span of the parameter so we can + // suggest adding an explicit lifetime bound to it. + let generics = self.tcx.generics_of(generic_param_scope); + // type_param_span is (span, has_bounds) + let type_param_span = match bound_kind { + GenericKind::Param(ref param) => { + // Account for the case where `param` corresponds to `Self`, + // which doesn't have the expected type argument. + if !(generics.has_self && param.index == 0) { + let type_param = generics.type_param(param, self.tcx); + type_param.def_id.as_local().map(|def_id| { + // Get the `hir::Param` to verify whether 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 hir_id = self.tcx.hir().local_def_id_to_hir_id(def_id); + let ast_generics = self.tcx.hir().get_generics(hir_id.owner); + let bounds = + ast_generics.and_then(|g| g.bounds_span_for_suggestions(def_id)); + // `sp` only covers `T`, change it so that it covers + // `T:` when appropriate + if let Some(span) = bounds { + (span, true) + } else { + let sp = self.tcx.def_span(def_id); + (sp.shrink_to_hi(), false) + } + }) + } else { + None + } + } + _ => None, + }; + + let new_lt = { + let mut possible = (b'a'..=b'z').map(|c| format!("'{}", c as char)); + let lts_names = + iter::successors(Some(generics), |g| g.parent.map(|p| self.tcx.generics_of(p))) + .flat_map(|g| &g.params) + .filter(|p| matches!(p.kind, ty::GenericParamDefKind::Lifetime)) + .map(|p| p.name.as_str()) + .collect::>(); + possible + .find(|candidate| !lts_names.contains(&&candidate[..])) + .unwrap_or("'lt".to_string()) + }; + + let add_lt_sugg = generics + .params + .first() + .and_then(|param| param.def_id.as_local()) + .map(|def_id| (self.tcx.def_span(def_id).shrink_to_lo(), format!("{}, ", new_lt))); + + 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::CompareImplItemObligation { + span, + impl_item_def_id, + trait_item_def_id, + }) = origin + { + return self.report_extra_impl_obligation( + span, + impl_item_def_id, + trait_item_def_id, + &format!("`{}: {}`", bound_kind, sub), + ); + } + + fn binding_suggestion<'tcx, S: fmt::Display>( + err: &mut Diagnostic, + type_param_span: Option<(Span, bool)>, + bound_kind: GenericKind<'tcx>, + sub: S, + ) { + let msg = "consider adding an explicit lifetime bound"; + if let Some((sp, has_lifetimes)) = type_param_span { + let suggestion = + if has_lifetimes { format!(" + {}", sub) } else { format!(": {}", sub) }; + err.span_suggestion_verbose( + sp, + &format!("{}...", msg), + suggestion, + Applicability::MaybeIncorrect, // Issue #41966 + ); + } else { + let consider = format!("{} `{}: {}`...", msg, bound_kind, sub,); + err.help(&consider); + } + } + + let new_binding_suggestion = + |err: &mut Diagnostic, type_param_span: Option<(Span, bool)>| { + let msg = "consider introducing an explicit lifetime bound"; + if let Some((sp, has_lifetimes)) = type_param_span { + let suggestion = if has_lifetimes { + format!(" + {}", new_lt) + } else { + format!(": {}", new_lt) + }; + let mut sugg = + vec![(sp, suggestion), (span.shrink_to_hi(), format!(" + {}", new_lt))]; + if let Some(lt) = add_lt_sugg { + sugg.push(lt); + sugg.rotate_right(1); + } + // `MaybeIncorrect` due to issue #41966. + err.multipart_suggestion(msg, sugg, Applicability::MaybeIncorrect); + } + }; + + #[derive(Debug)] + enum SubOrigin<'hir> { + GAT(&'hir hir::Generics<'hir>), + Impl, + Trait, + Fn, + Unknown, + } + let sub_origin = 'origin: { + match *sub { + ty::ReEarlyBound(ty::EarlyBoundRegion { def_id, .. }) => { + let node = self.tcx.hir().get_if_local(def_id).unwrap(); + match node { + Node::GenericParam(param) => { + for h in self.tcx.hir().parent_iter(param.hir_id) { + break 'origin match h.1 { + Node::ImplItem(hir::ImplItem { + kind: hir::ImplItemKind::TyAlias(..), + generics, + .. + }) + | Node::TraitItem(hir::TraitItem { + kind: hir::TraitItemKind::Type(..), + generics, + .. + }) => SubOrigin::GAT(generics), + Node::ImplItem(hir::ImplItem { + kind: hir::ImplItemKind::Fn(..), + .. + }) + | Node::TraitItem(hir::TraitItem { + kind: hir::TraitItemKind::Fn(..), + .. + }) + | Node::Item(hir::Item { + kind: hir::ItemKind::Fn(..), .. + }) => SubOrigin::Fn, + Node::Item(hir::Item { + kind: hir::ItemKind::Trait(..), + .. + }) => SubOrigin::Trait, + Node::Item(hir::Item { + kind: hir::ItemKind::Impl(..), .. + }) => SubOrigin::Impl, + _ => continue, + }; + } + } + _ => {} + } + } + _ => {} + } + SubOrigin::Unknown + }; + debug!(?sub_origin); + + let mut err = match (*sub, sub_origin) { + // In the case of GATs, we have to be careful. If we a type parameter `T` on an impl, + // but a lifetime `'a` on an associated type, then we might need to suggest adding + // `where T: 'a`. Importantly, this is on the GAT span, not on the `T` declaration. + (ty::ReEarlyBound(ty::EarlyBoundRegion { name: _, .. }), SubOrigin::GAT(generics)) => { + // 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 + ); + let pred = format!("{}: {}", bound_kind, sub); + let suggestion = format!("{} {}", generics.add_where_or_trailing_comma(), pred,); + err.span_suggestion( + generics.tail_span_for_predicate_suggestion(), + "consider adding a where clause", + suggestion, + Applicability::MaybeIncorrect, + ); + err + } + ( + ty::ReEarlyBound(ty::EarlyBoundRegion { name, .. }) + | ty::ReFree(ty::FreeRegion { bound_region: ty::BrNamed(_, name), .. }), + _, + ) if name != kw::UnderscoreLifetime => { + // 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 + ); + // Explicitly use the name instead of `sub`'s `Display` impl. The `Display` impl + // for the bound is not suitable for suggestions when `-Zverbose` is set because it + // uses `Debug` output, so we handle it specially here so that suggestions are + // always correct. + binding_suggestion(&mut err, type_param_span, bound_kind, name); + 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 + ); + note_and_explain_region( + self.tcx, + &mut err, + &format!("{} must be valid for ", labeled_user_string), + sub, + "...", + None, + ); + if let Some(infer::RelateParamBound(_, t, _)) = origin { + let return_impl_trait = + self.tcx.return_type_impl_trait(generic_param_scope).is_some(); + let t = self.resolve_vars_if_possible(t); + match t.kind() { + // We've got: + // fn get_later(g: G, dest: &mut T) -> impl FnOnce() + '_ + // suggest: + // fn get_later<'a, G: 'a, T>(g: G, dest: &mut T) -> impl FnOnce() + '_ + 'a + ty::Closure(_, _substs) | ty::Opaque(_, _substs) if return_impl_trait => { + new_binding_suggestion(&mut err, type_param_span); + } + _ => { + binding_suggestion(&mut err, type_param_span, bound_kind, new_lt); + } + } + } + err + } + }; + + if let Some(origin) = origin { + self.note_region_origin(&mut err, &origin); + } + err + } + + fn report_sub_sup_conflict( + &self, + 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); + + note_and_explain_region( + self.tcx, + &mut err, + "first, the lifetime cannot outlive ", + sup_region, + "...", + None, + ); + + debug!("report_sub_sup_conflict: var_origin={:?}", var_origin); + debug!("report_sub_sup_conflict: sub_region={:?}", sub_region); + debug!("report_sub_sup_conflict: sub_origin={:?}", sub_origin); + debug!("report_sub_sup_conflict: sup_region={:?}", sup_region); + debug!("report_sub_sup_conflict: sup_origin={:?}", sup_origin); + + if let (&infer::Subtype(ref sup_trace), &infer::Subtype(ref sub_trace)) = + (&sup_origin, &sub_origin) + { + debug!("report_sub_sup_conflict: sup_trace={:?}", sup_trace); + debug!("report_sub_sup_conflict: sub_trace={:?}", sub_trace); + debug!("report_sub_sup_conflict: sup_trace.values={:?}", sup_trace.values); + debug!("report_sub_sup_conflict: sub_trace.values={:?}", sub_trace.values); + + if let (Some((sup_expected, sup_found)), Some((sub_expected, sub_found))) = + (self.values_str(sup_trace.values), self.values_str(sub_trace.values)) + { + if sub_expected == sup_expected && sub_found == sup_found { + note_and_explain_region( + self.tcx, + &mut err, + "...but the lifetime must also be valid for ", + sub_region, + "...", + None, + ); + err.span_note( + sup_trace.cause.span, + &format!("...so that the {}", sup_trace.cause.as_requirement_str()), + ); + + err.note_expected_found(&"", sup_expected, &"", sup_found); + err.emit(); + return; + } + } + } + + self.note_region_origin(&mut err, &sup_origin); + + note_and_explain_region( + self.tcx, + &mut err, + "but, the lifetime must be valid for ", + sub_region, + "...", + None, + ); + + self.note_region_origin(&mut err, &sub_origin); + err.emit(); + } + + /// Determine whether an error associated with the given span and definition + /// should be treated as being caused by the implicit `From` conversion + /// within `?` desugaring. + pub fn is_try_conversion(&self, span: Span, trait_def_id: DefId) -> bool { + span.is_desugaring(DesugaringKind::QuestionMark) + && self.tcx.is_diagnostic_item(sym::From, trait_def_id) + } + + /// Structurally compares two types, modulo any inference variables. + /// + /// Returns `true` if two types are equal, or if one type is an inference variable compatible + /// with the other type. A TyVar inference type is compatible with any type, and an IntVar or + /// FloatVar inference type are compatible with themselves or their concrete types (Int and + /// Float types, respectively). When comparing two ADTs, these rules apply recursively. + pub fn same_type_modulo_infer(&self, a: Ty<'tcx>, b: Ty<'tcx>) -> bool { + let (a, b) = self.resolve_vars_if_possible((a, b)); + match (a.kind(), b.kind()) { + (&ty::Adt(def_a, substs_a), &ty::Adt(def_b, substs_b)) => { + if def_a != def_b { + return false; + } + + substs_a + .types() + .zip(substs_b.types()) + .all(|(a, b)| self.same_type_modulo_infer(a, b)) + } + (&ty::FnDef(did_a, substs_a), &ty::FnDef(did_b, substs_b)) => { + if did_a != did_b { + return false; + } + + substs_a + .types() + .zip(substs_b.types()) + .all(|(a, b)| self.same_type_modulo_infer(a, b)) + } + (&ty::Int(_) | &ty::Uint(_), &ty::Infer(ty::InferTy::IntVar(_))) + | ( + &ty::Infer(ty::InferTy::IntVar(_)), + &ty::Int(_) | &ty::Uint(_) | &ty::Infer(ty::InferTy::IntVar(_)), + ) + | (&ty::Float(_), &ty::Infer(ty::InferTy::FloatVar(_))) + | ( + &ty::Infer(ty::InferTy::FloatVar(_)), + &ty::Float(_) | &ty::Infer(ty::InferTy::FloatVar(_)), + ) + | (&ty::Infer(ty::InferTy::TyVar(_)), _) + | (_, &ty::Infer(ty::InferTy::TyVar(_))) => true, + (&ty::Ref(_, ty_a, mut_a), &ty::Ref(_, ty_b, mut_b)) => { + mut_a == mut_b && self.same_type_modulo_infer(ty_a, ty_b) + } + (&ty::RawPtr(a), &ty::RawPtr(b)) => { + a.mutbl == b.mutbl && self.same_type_modulo_infer(a.ty, b.ty) + } + (&ty::Slice(a), &ty::Slice(b)) => self.same_type_modulo_infer(a, b), + (&ty::Array(a_ty, a_ct), &ty::Array(b_ty, b_ct)) => { + self.same_type_modulo_infer(a_ty, b_ty) && a_ct == b_ct + } + (&ty::Tuple(a), &ty::Tuple(b)) => { + if a.len() != b.len() { + return false; + } + std::iter::zip(a.iter(), b.iter()).all(|(a, b)| self.same_type_modulo_infer(a, b)) + } + (&ty::FnPtr(a), &ty::FnPtr(b)) => { + let a = a.skip_binder().inputs_and_output; + let b = b.skip_binder().inputs_and_output; + if a.len() != b.len() { + return false; + } + std::iter::zip(a.iter(), b.iter()).all(|(a, b)| self.same_type_modulo_infer(a, b)) + } + // FIXME(compiler-errors): This needs to be generalized more + _ => a == b, + } + } +} + +impl<'a, 'tcx> InferCtxt<'a, 'tcx> { + fn report_inference_failure( + &self, + var_origin: RegionVariableOrigin, + ) -> DiagnosticBuilder<'tcx, ErrorGuaranteed> { + let br_string = |br: ty::BoundRegionKind| { + let mut s = match br { + ty::BrNamed(_, name) => name.to_string(), + _ => String::new(), + }; + if !s.is_empty() { + s.push(' '); + } + s + }; + let var_description = match var_origin { + infer::MiscVariable(_) => String::new(), + 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::UpvarRegion(ref upvar_id, _) => { + let var_name = self.tcx.hir().name(upvar_id.var_path.hir_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 + ) + } +} + +pub enum FailureCode { + Error0038(DefId), + Error0317(&'static str), + Error0580(&'static str), + Error0308(&'static str), + Error0644(&'static str), +} + +pub trait ObligationCauseExt<'tcx> { + fn as_failure_code(&self, terr: &TypeError<'tcx>) -> FailureCode; + fn as_requirement_str(&self) -> &'static str; +} + +impl<'tcx> ObligationCauseExt<'tcx> for ObligationCause<'tcx> { + fn as_failure_code(&self, terr: &TypeError<'tcx>) -> FailureCode { + use self::FailureCode::*; + use crate::traits::ObligationCauseCode::*; + match self.code() { + CompareImplItemObligation { kind: ty::AssocKind::Fn, .. } => { + Error0308("method not compatible with trait") + } + CompareImplItemObligation { kind: ty::AssocKind::Type, .. } => { + Error0308("type not compatible with trait") + } + CompareImplItemObligation { kind: ty::AssocKind::Const, .. } => { + Error0308("const not compatible with trait") + } + MatchExpressionArm(box MatchExpressionArmCause { source, .. }) => { + Error0308(match source { + hir::MatchSource::TryDesugar => "`?` operator has incompatible types", + _ => "`match` arms have incompatible types", + }) + } + IfExpression { .. } => Error0308("`if` and `else` have incompatible types"), + IfExpressionWithNoElse => Error0317("`if` may be missing an `else` clause"), + LetElse => Error0308("`else` clause of `let...else` does not diverge"), + MainFunctionType => Error0580("`main` function has wrong type"), + StartFunctionType => Error0308("`#[start]` function has wrong type"), + IntrinsicType => Error0308("intrinsic has wrong type"), + MethodReceiver => Error0308("mismatched `self` parameter type"), + + // 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") + } + TypeError::IntrinsicCast => { + Error0308("cannot coerce intrinsics to function pointers") + } + TypeError::ObjectUnsafeCoercion(did) => Error0038(*did), + _ => Error0308("mismatched types"), + }, + } + } + + fn as_requirement_str(&self) -> &'static str { + use crate::traits::ObligationCauseCode::*; + match self.code() { + CompareImplItemObligation { kind: ty::AssocKind::Fn, .. } => { + "method type is compatible with trait" + } + CompareImplItemObligation { kind: ty::AssocKind::Type, .. } => { + "associated type is compatible with trait" + } + CompareImplItemObligation { kind: ty::AssocKind::Const, .. } => { + "const is compatible with trait" + } + ExprAssignable => "expression is assignable", + IfExpression { .. } => "`if` and `else` have incompatible types", + IfExpressionWithNoElse => "`if` missing an `else` returns `()`", + 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", + } + } +} + +/// This is a bare signal of what kind of type we're dealing with. `ty::TyKind` tracks +/// extra information about each type, but we only care about the category. +#[derive(Clone, Copy, PartialEq, Eq, Hash)] +pub enum TyCategory { + Closure, + Opaque, + Generator(hir::GeneratorKind), + Foreign, +} + +impl TyCategory { + fn descr(&self) -> &'static str { + match self { + Self::Closure => "closure", + Self::Opaque => "opaque type", + Self::Generator(gk) => gk.descr(), + Self::Foreign => "foreign type", + } + } + + pub fn from_ty(tcx: TyCtxt<'_>, ty: Ty<'_>) -> Option<(Self, DefId)> { + match *ty.kind() { + ty::Closure(def_id, _) => Some((Self::Closure, def_id)), + ty::Opaque(def_id, _) => Some((Self::Opaque, def_id)), + ty::Generator(def_id, ..) => { + Some((Self::Generator(tcx.generator_kind(def_id).unwrap()), def_id)) + } + ty::Foreign(def_id) => Some((Self::Foreign, def_id)), + _ => None, + } + } +} + +impl<'tcx> InferCtxt<'_, 'tcx> { + /// Given a [`hir::Block`], get the span of its last expression or + /// statement, peeling off any inner blocks. + pub fn find_block_span(&self, block: &'tcx hir::Block<'tcx>) -> Span { + let block = block.innermost_block(); + if let Some(expr) = &block.expr { + expr.span + } else if let Some(stmt) = block.stmts.last() { + // possibly incorrect trailing `;` in the else arm + stmt.span + } else { + // empty block; point at its entirety + block.span + } + } + + /// Given a [`hir::HirId`] for a block, get the span of its last expression + /// or statement, peeling off any inner blocks. + pub fn find_block_span_from_hir_id(&self, hir_id: hir::HirId) -> Span { + match self.tcx.hir().get(hir_id) { + hir::Node::Block(blk) => self.find_block_span(blk), + // The parser was in a weird state if either of these happen, but + // it's better not to panic. + hir::Node::Expr(e) => e.span, + _ => rustc_span::DUMMY_SP, + } + } + + /// Be helpful when the user wrote `{... expr; }` and taking the `;` off + /// is enough to fix the error. + pub fn could_remove_semicolon( + &self, + blk: &'tcx hir::Block<'tcx>, + expected_ty: Ty<'tcx>, + ) -> Option<(Span, StatementAsExpression)> { + let blk = blk.innermost_block(); + // Do not suggest if we have a tail expr. + if blk.expr.is_some() { + return None; + } + let last_stmt = blk.stmts.last()?; + let hir::StmtKind::Semi(ref last_expr) = last_stmt.kind else { + return None; + }; + let last_expr_ty = self.in_progress_typeck_results?.borrow().expr_ty_opt(*last_expr)?; + let needs_box = match (last_expr_ty.kind(), expected_ty.kind()) { + _ if last_expr_ty.references_error() => return None, + _ if self.same_type_modulo_infer(last_expr_ty, expected_ty) => { + StatementAsExpression::CorrectType + } + (ty::Opaque(last_def_id, _), ty::Opaque(exp_def_id, _)) + if last_def_id == exp_def_id => + { + StatementAsExpression::CorrectType + } + (ty::Opaque(last_def_id, last_bounds), ty::Opaque(exp_def_id, exp_bounds)) => { + debug!( + "both opaque, likely future {:?} {:?} {:?} {:?}", + last_def_id, last_bounds, exp_def_id, exp_bounds + ); + + let last_local_id = last_def_id.as_local()?; + let exp_local_id = exp_def_id.as_local()?; + + match ( + &self.tcx.hir().expect_item(last_local_id).kind, + &self.tcx.hir().expect_item(exp_local_id).kind, + ) { + ( + hir::ItemKind::OpaqueTy(hir::OpaqueTy { bounds: last_bounds, .. }), + hir::ItemKind::OpaqueTy(hir::OpaqueTy { bounds: exp_bounds, .. }), + ) if iter::zip(*last_bounds, *exp_bounds).all(|(left, right)| { + match (left, right) { + ( + hir::GenericBound::Trait(tl, ml), + hir::GenericBound::Trait(tr, mr), + ) if tl.trait_ref.trait_def_id() == tr.trait_ref.trait_def_id() + && ml == mr => + { + true + } + ( + hir::GenericBound::LangItemTrait(langl, _, _, argsl), + hir::GenericBound::LangItemTrait(langr, _, _, argsr), + ) if langl == langr => { + // FIXME: consider the bounds! + debug!("{:?} {:?}", argsl, argsr); + true + } + _ => false, + } + }) => + { + StatementAsExpression::NeedsBoxing + } + _ => StatementAsExpression::CorrectType, + } + } + _ => return None, + }; + let span = if last_stmt.span.from_expansion() { + let mac_call = rustc_span::source_map::original_sp(last_stmt.span, blk.span); + self.tcx.sess.source_map().mac_call_stmt_semi_span(mac_call)? + } else { + last_stmt.span.with_lo(last_stmt.span.hi() - BytePos(1)) + }; + Some((span, needs_box)) + } + + /// Suggest returning a local binding with a compatible type if the block + /// has no return expression. + pub fn consider_returning_binding( + &self, + blk: &'tcx hir::Block<'tcx>, + expected_ty: Ty<'tcx>, + err: &mut Diagnostic, + ) -> bool { + let blk = blk.innermost_block(); + // Do not suggest if we have a tail expr. + if blk.expr.is_some() { + return false; + } + let mut shadowed = FxHashSet::default(); + let mut candidate_idents = vec![]; + let mut find_compatible_candidates = |pat: &hir::Pat<'_>| { + if let hir::PatKind::Binding(_, hir_id, ident, _) = &pat.kind + && let Some(pat_ty) = self + .in_progress_typeck_results + .and_then(|typeck_results| typeck_results.borrow().node_type_opt(*hir_id)) + { + let pat_ty = self.resolve_vars_if_possible(pat_ty); + if self.same_type_modulo_infer(pat_ty, expected_ty) + && !(pat_ty, expected_ty).references_error() + && shadowed.insert(ident.name) + { + candidate_idents.push((*ident, pat_ty)); + } + } + true + }; + + let hir = self.tcx.hir(); + for stmt in blk.stmts.iter().rev() { + let hir::StmtKind::Local(local) = &stmt.kind else { continue; }; + local.pat.walk(&mut find_compatible_candidates); + } + match hir.find(hir.get_parent_node(blk.hir_id)) { + Some(hir::Node::Expr(hir::Expr { hir_id, .. })) => { + match hir.find(hir.get_parent_node(*hir_id)) { + Some(hir::Node::Arm(hir::Arm { pat, .. })) => { + pat.walk(&mut find_compatible_candidates); + } + Some( + hir::Node::Item(hir::Item { kind: hir::ItemKind::Fn(_, _, body), .. }) + | hir::Node::ImplItem(hir::ImplItem { + kind: hir::ImplItemKind::Fn(_, body), + .. + }) + | hir::Node::TraitItem(hir::TraitItem { + kind: hir::TraitItemKind::Fn(_, hir::TraitFn::Provided(body)), + .. + }) + | hir::Node::Expr(hir::Expr { + kind: hir::ExprKind::Closure(hir::Closure { body, .. }), + .. + }), + ) => { + for param in hir.body(*body).params { + param.pat.walk(&mut find_compatible_candidates); + } + } + Some(hir::Node::Expr(hir::Expr { + kind: + hir::ExprKind::If( + hir::Expr { kind: hir::ExprKind::Let(let_), .. }, + then_block, + _, + ), + .. + })) if then_block.hir_id == *hir_id => { + let_.pat.walk(&mut find_compatible_candidates); + } + _ => {} + } + } + _ => {} + } + + match &candidate_idents[..] { + [(ident, _ty)] => { + let sm = self.tcx.sess.source_map(); + if let Some(stmt) = blk.stmts.last() { + let stmt_span = sm.stmt_span(stmt.span, blk.span); + let sugg = if sm.is_multiline(blk.span) + && let Some(spacing) = sm.indentation_before(stmt_span) + { + format!("\n{spacing}{ident}") + } else { + format!(" {ident}") + }; + err.span_suggestion_verbose( + stmt_span.shrink_to_hi(), + format!("consider returning the local binding `{ident}`"), + sugg, + Applicability::MaybeIncorrect, + ); + } else { + let sugg = if sm.is_multiline(blk.span) + && let Some(spacing) = sm.indentation_before(blk.span.shrink_to_lo()) + { + format!("\n{spacing} {ident}\n{spacing}") + } else { + format!(" {ident} ") + }; + let left_span = sm.span_through_char(blk.span, '{').shrink_to_hi(); + err.span_suggestion_verbose( + sm.span_extend_while(left_span, |c| c.is_whitespace()).unwrap_or(left_span), + format!("consider returning the local binding `{ident}`"), + sugg, + Applicability::MaybeIncorrect, + ); + } + true + } + values if (1..3).contains(&values.len()) => { + let spans = values.iter().map(|(ident, _)| ident.span).collect::>(); + err.span_note(spans, "consider returning one of these bindings"); + true + } + _ => false, + } + } +} diff --git a/compiler/rustc_infer/src/infer/error_reporting/need_type_info.rs b/compiler/rustc_infer/src/infer/error_reporting/need_type_info.rs new file mode 100644 index 000000000..561d1354e --- /dev/null +++ b/compiler/rustc_infer/src/infer/error_reporting/need_type_info.rs @@ -0,0 +1,1134 @@ +use crate::infer::type_variable::{TypeVariableOrigin, TypeVariableOriginKind}; +use crate::infer::InferCtxt; +use rustc_errors::{pluralize, struct_span_err, Applicability, DiagnosticBuilder, ErrorGuaranteed}; +use rustc_hir as hir; +use rustc_hir::def::Res; +use rustc_hir::def::{CtorOf, DefKind, Namespace}; +use rustc_hir::def_id::DefId; +use rustc_hir::intravisit::{self, Visitor}; +use rustc_hir::{Body, Closure, Expr, ExprKind, FnRetTy, HirId, Local, LocalSource}; +use rustc_middle::hir::nested_filter; +use rustc_middle::infer::unify_key::{ConstVariableOrigin, ConstVariableOriginKind}; +use rustc_middle::ty::adjustment::{Adjust, Adjustment, AutoBorrow, AutoBorrowMutability}; +use rustc_middle::ty::print::{FmtPrinter, PrettyPrinter, Print, Printer}; +use rustc_middle::ty::subst::{GenericArg, GenericArgKind, Subst, SubstsRef}; +use rustc_middle::ty::{self, DefIdTree, InferConst}; +use rustc_middle::ty::{IsSuggestable, Ty, TyCtxt, TypeckResults}; +use rustc_span::symbol::{kw, Ident}; +use rustc_span::{BytePos, Span}; +use std::borrow::Cow; +use std::iter; + +pub enum TypeAnnotationNeeded { + /// ```compile_fail,E0282 + /// let x = "hello".chars().rev().collect(); + /// ``` + E0282, + /// An implementation cannot be chosen unambiguously because of lack of information. + /// ```compile_fail,E0283 + /// let _ = Default::default(); + /// ``` + E0283, + /// ```compile_fail,E0284 + /// let mut d: u64 = 2; + /// d = d % 1u32.into(); + /// ``` + E0284, +} + +impl Into for TypeAnnotationNeeded { + fn into(self) -> rustc_errors::DiagnosticId { + match self { + Self::E0282 => rustc_errors::error_code!(E0282), + Self::E0283 => rustc_errors::error_code!(E0283), + Self::E0284 => rustc_errors::error_code!(E0284), + } + } +} + +/// Information about a constant or a type containing inference variables. +pub struct InferenceDiagnosticsData { + pub name: String, + pub span: Option, + pub kind: UnderspecifiedArgKind, + pub parent: Option, +} + +/// Data on the parent definition where a generic argument was declared. +pub struct InferenceDiagnosticsParentData { + prefix: &'static str, + name: String, +} + +pub enum UnderspecifiedArgKind { + Type { prefix: Cow<'static, str> }, + Const { is_parameter: bool }, +} + +impl InferenceDiagnosticsData { + /// Generate a label for a generic argument which can't be inferred. When not + /// much is known about the argument, `use_diag` may be used to describe the + /// labeled value. + fn cannot_infer_msg(&self) -> String { + if self.name == "_" && matches!(self.kind, UnderspecifiedArgKind::Type { .. }) { + return "cannot infer type".to_string(); + } + + let suffix = match &self.parent { + Some(parent) => parent.suffix_string(), + None => String::new(), + }; + + // For example: "cannot infer type for type parameter `T`" + format!("cannot infer {} `{}`{}", self.kind.prefix_string(), self.name, suffix) + } + + fn where_x_is_specified(&self, in_type: Ty<'_>) -> String { + if in_type.is_ty_infer() { + String::new() + } else if self.name == "_" { + // FIXME: Consider specializing this message if there is a single `_` + // in the type. + ", where the placeholders `_` are specified".to_string() + } else { + format!(", where the {} `{}` is specified", self.kind.prefix_string(), self.name) + } + } +} + +impl InferenceDiagnosticsParentData { + fn for_parent_def_id( + tcx: TyCtxt<'_>, + parent_def_id: DefId, + ) -> Option { + let parent_name = + tcx.def_key(parent_def_id).disambiguated_data.data.get_opt_name()?.to_string(); + + Some(InferenceDiagnosticsParentData { + prefix: tcx.def_kind(parent_def_id).descr(parent_def_id), + name: parent_name, + }) + } + + fn for_def_id(tcx: TyCtxt<'_>, def_id: DefId) -> Option { + Self::for_parent_def_id(tcx, tcx.parent(def_id)) + } + + fn suffix_string(&self) -> String { + format!(" declared on the {} `{}`", self.prefix, self.name) + } +} + +impl UnderspecifiedArgKind { + fn prefix_string(&self) -> Cow<'static, str> { + match self { + Self::Type { prefix } => format!("type for {}", prefix).into(), + Self::Const { is_parameter: true } => "the value of const parameter".into(), + Self::Const { is_parameter: false } => "the value of the constant".into(), + } + } +} + +fn fmt_printer<'a, 'tcx>(infcx: &'a InferCtxt<'_, 'tcx>, ns: Namespace) -> FmtPrinter<'a, 'tcx> { + let mut printer = FmtPrinter::new(infcx.tcx, ns); + let ty_getter = move |ty_vid| { + if infcx.probe_ty_var(ty_vid).is_ok() { + warn!("resolved ty var in error message"); + } + if let TypeVariableOriginKind::TypeParameterDefinition(name, _) = + infcx.inner.borrow_mut().type_variables().var_origin(ty_vid).kind + { + Some(name) + } else { + None + } + }; + printer.ty_infer_name_resolver = Some(Box::new(ty_getter)); + let const_getter = move |ct_vid| { + if infcx.probe_const_var(ct_vid).is_ok() { + warn!("resolved const var in error message"); + } + if let ConstVariableOriginKind::ConstParameterDefinition(name, _) = + infcx.inner.borrow_mut().const_unification_table().probe_value(ct_vid).origin.kind + { + return Some(name); + } else { + None + } + }; + printer.const_infer_name_resolver = Some(Box::new(const_getter)); + printer +} + +fn ty_to_string<'tcx>(infcx: &InferCtxt<'_, 'tcx>, ty: Ty<'tcx>) -> String { + let printer = fmt_printer(infcx, Namespace::TypeNS); + let ty = infcx.resolve_vars_if_possible(ty); + match ty.kind() { + // We don't want the regular output for `fn`s because it includes its path in + // invalid pseudo-syntax, we want the `fn`-pointer output instead. + ty::FnDef(..) => ty.fn_sig(infcx.tcx).print(printer).unwrap().into_buffer(), + // FIXME: The same thing for closures, but this only works when the closure + // does not capture anything. + // + // We do have to hide the `extern "rust-call"` ABI in that case though, + // which is too much of a bother for now. + _ => ty.print(printer).unwrap().into_buffer(), + } +} + +/// We don't want to directly use `ty_to_string` for closures as their type isn't really +/// something users are familar with. Directly printing the `fn_sig` of closures also +/// doesn't work as they actually use the "rust-call" API. +fn closure_as_fn_str<'tcx>(infcx: &InferCtxt<'_, 'tcx>, ty: Ty<'tcx>) -> String { + let ty::Closure(_, substs) = ty.kind() else { unreachable!() }; + let fn_sig = substs.as_closure().sig(); + let args = fn_sig + .inputs() + .skip_binder() + .iter() + .next() + .map(|args| { + args.tuple_fields() + .iter() + .map(|arg| ty_to_string(infcx, arg)) + .collect::>() + .join(", ") + }) + .unwrap_or_default(); + let ret = if fn_sig.output().skip_binder().is_unit() { + String::new() + } else { + format!(" -> {}", ty_to_string(infcx, fn_sig.output().skip_binder())) + }; + format!("fn({}){}", args, ret) +} + +impl<'a, 'tcx> InferCtxt<'a, 'tcx> { + /// Extracts data used by diagnostic for either types or constants + /// which were stuck during inference. + pub fn extract_inference_diagnostics_data( + &self, + arg: GenericArg<'tcx>, + highlight: Option>, + ) -> InferenceDiagnosticsData { + match arg.unpack() { + GenericArgKind::Type(ty) => { + if let ty::Infer(ty::TyVar(ty_vid)) = *ty.kind() { + let mut inner = self.inner.borrow_mut(); + let ty_vars = &inner.type_variables(); + let var_origin = ty_vars.var_origin(ty_vid); + if let TypeVariableOriginKind::TypeParameterDefinition(name, def_id) = + var_origin.kind + { + if name != kw::SelfUpper { + return InferenceDiagnosticsData { + name: name.to_string(), + span: Some(var_origin.span), + kind: UnderspecifiedArgKind::Type { + prefix: "type parameter".into(), + }, + parent: def_id.and_then(|def_id| { + InferenceDiagnosticsParentData::for_def_id(self.tcx, def_id) + }), + }; + } + } + } + + let mut printer = ty::print::FmtPrinter::new(self.tcx, Namespace::TypeNS); + if let Some(highlight) = highlight { + printer.region_highlight_mode = highlight; + } + InferenceDiagnosticsData { + name: ty.print(printer).unwrap().into_buffer(), + span: None, + kind: UnderspecifiedArgKind::Type { prefix: ty.prefix_string(self.tcx) }, + parent: None, + } + } + GenericArgKind::Const(ct) => { + if let ty::ConstKind::Infer(InferConst::Var(vid)) = ct.kind() { + let origin = + self.inner.borrow_mut().const_unification_table().probe_value(vid).origin; + if let ConstVariableOriginKind::ConstParameterDefinition(name, def_id) = + origin.kind + { + return InferenceDiagnosticsData { + name: name.to_string(), + span: Some(origin.span), + kind: UnderspecifiedArgKind::Const { is_parameter: true }, + parent: InferenceDiagnosticsParentData::for_def_id(self.tcx, def_id), + }; + } + + debug_assert!(!origin.span.is_dummy()); + let mut printer = ty::print::FmtPrinter::new(self.tcx, Namespace::ValueNS); + if let Some(highlight) = highlight { + printer.region_highlight_mode = highlight; + } + InferenceDiagnosticsData { + name: ct.print(printer).unwrap().into_buffer(), + span: Some(origin.span), + kind: UnderspecifiedArgKind::Const { is_parameter: false }, + parent: None, + } + } else { + // If we end up here the `FindInferSourceVisitor` + // won't work, as its expected argument isn't an inference variable. + // + // FIXME: Ideally we should look into the generic constant + // to figure out which inference var is actually unresolved so that + // this path is unreachable. + let mut printer = ty::print::FmtPrinter::new(self.tcx, Namespace::ValueNS); + if let Some(highlight) = highlight { + printer.region_highlight_mode = highlight; + } + InferenceDiagnosticsData { + name: ct.print(printer).unwrap().into_buffer(), + span: None, + kind: UnderspecifiedArgKind::Const { is_parameter: false }, + parent: None, + } + } + } + GenericArgKind::Lifetime(_) => bug!("unexpected lifetime"), + } + } + + /// Used as a fallback in [InferCtxt::emit_inference_failure_err] + /// in case we weren't able to get a better error. + fn bad_inference_failure_err( + &self, + span: Span, + arg_data: InferenceDiagnosticsData, + error_code: TypeAnnotationNeeded, + ) -> DiagnosticBuilder<'tcx, ErrorGuaranteed> { + let error_code = error_code.into(); + let mut err = + self.tcx.sess.struct_span_err_with_code(span, "type annotations needed", error_code); + err.span_label(span, arg_data.cannot_infer_msg()); + err + } + + pub fn emit_inference_failure_err( + &self, + body_id: Option, + failure_span: Span, + arg: GenericArg<'tcx>, + error_code: TypeAnnotationNeeded, + should_label_span: bool, + ) -> DiagnosticBuilder<'tcx, ErrorGuaranteed> { + let arg = self.resolve_vars_if_possible(arg); + let arg_data = self.extract_inference_diagnostics_data(arg, None); + + let Some(typeck_results) = self.in_progress_typeck_results else { + // If we don't have any typeck results we're outside + // of a body, so we won't be able to get better info + // here. + return self.bad_inference_failure_err(failure_span, arg_data, error_code); + }; + let typeck_results = typeck_results.borrow(); + let typeck_results = &typeck_results; + + let mut local_visitor = FindInferSourceVisitor::new(&self, typeck_results, arg); + if let Some(body_id) = body_id { + let expr = self.tcx.hir().expect_expr(body_id.hir_id); + local_visitor.visit_expr(expr); + } + + let Some(InferSource { span, kind }) = local_visitor.infer_source else { + return self.bad_inference_failure_err(failure_span, arg_data, error_code) + }; + + let error_code = error_code.into(); + let mut err = self.tcx.sess.struct_span_err_with_code( + span, + &format!("type annotations needed{}", kind.ty_msg(self)), + error_code, + ); + + if should_label_span && !failure_span.overlaps(span) { + err.span_label(failure_span, "type must be known at this point"); + } + + match kind { + InferSourceKind::LetBinding { insert_span, pattern_name, ty } => { + let suggestion_msg = if let Some(name) = pattern_name { + format!( + "consider giving `{}` an explicit type{}", + name, + arg_data.where_x_is_specified(ty) + ) + } else { + format!( + "consider giving this pattern a type{}", + arg_data.where_x_is_specified(ty) + ) + }; + err.span_suggestion_verbose( + insert_span, + &suggestion_msg, + format!(": {}", ty_to_string(self, ty)), + Applicability::HasPlaceholders, + ); + } + InferSourceKind::ClosureArg { insert_span, ty } => { + err.span_suggestion_verbose( + insert_span, + &format!( + "consider giving this closure parameter an explicit type{}", + arg_data.where_x_is_specified(ty) + ), + format!(": {}", ty_to_string(self, ty)), + Applicability::HasPlaceholders, + ); + } + InferSourceKind::GenericArg { + insert_span, + argument_index, + generics_def_id, + def_id: _, + generic_args, + } => { + let generics = self.tcx.generics_of(generics_def_id); + let is_type = matches!(arg.unpack(), GenericArgKind::Type(_)); + + let cannot_infer_msg = format!( + "cannot infer {} of the {} parameter `{}`{}", + if is_type { "type" } else { "the value" }, + if is_type { "type" } else { "const" }, + generics.params[argument_index].name, + // We use the `generics_def_id` here, as even when suggesting `None::`, + // the type parameter `T` was still declared on the enum, not on the + // variant. + InferenceDiagnosticsParentData::for_parent_def_id(self.tcx, generics_def_id) + .map_or(String::new(), |parent| parent.suffix_string()), + ); + + err.span_label(span, cannot_infer_msg); + + let args = fmt_printer(self, Namespace::TypeNS) + .comma_sep(generic_args.iter().copied().map(|arg| { + if arg.is_suggestable(self.tcx, true) { + return arg; + } + + match arg.unpack() { + GenericArgKind::Lifetime(_) => bug!("unexpected lifetime"), + GenericArgKind::Type(_) => self + .next_ty_var(TypeVariableOrigin { + span: rustc_span::DUMMY_SP, + kind: TypeVariableOriginKind::MiscVariable, + }) + .into(), + GenericArgKind::Const(arg) => self + .next_const_var( + arg.ty(), + ConstVariableOrigin { + span: rustc_span::DUMMY_SP, + kind: ConstVariableOriginKind::MiscVariable, + }, + ) + .into(), + } + })) + .unwrap() + .into_buffer(); + + err.span_suggestion_verbose( + insert_span, + &format!( + "consider specifying the generic argument{}", + pluralize!(generic_args.len()), + ), + format!("::<{}>", args), + Applicability::HasPlaceholders, + ); + } + InferSourceKind::FullyQualifiedMethodCall { receiver, successor, substs, def_id } => { + let printer = fmt_printer(self, Namespace::ValueNS); + let def_path = printer.print_def_path(def_id, substs).unwrap().into_buffer(); + + // We only care about whether we have to add `&` or `&mut ` for now. + // This is the case if the last adjustment is a borrow and the + // first adjustment was not a builtin deref. + let adjustment = match typeck_results.expr_adjustments(receiver) { + [ + Adjustment { kind: Adjust::Deref(None), target: _ }, + .., + Adjustment { kind: Adjust::Borrow(AutoBorrow::Ref(..)), target: _ }, + ] => "", + [ + .., + Adjustment { kind: Adjust::Borrow(AutoBorrow::Ref(_, mut_)), target: _ }, + ] => match mut_ { + AutoBorrowMutability::Mut { .. } => "&mut ", + AutoBorrowMutability::Not => "&", + }, + _ => "", + }; + + let suggestion = vec![ + (receiver.span.shrink_to_lo(), format!("{def_path}({adjustment}")), + (receiver.span.shrink_to_hi().with_hi(successor.1), successor.0.to_string()), + ]; + err.multipart_suggestion_verbose( + "try using a fully qualified path to specify the expected types", + suggestion, + Applicability::HasPlaceholders, + ); + } + InferSourceKind::ClosureReturn { ty, data, should_wrap_expr } => { + let ret = ty_to_string(self, ty); + let (arrow, post) = match data { + FnRetTy::DefaultReturn(_) => ("-> ", " "), + _ => ("", ""), + }; + let suggestion = match should_wrap_expr { + Some(end_span) => vec![ + (data.span(), format!("{}{}{}{{ ", arrow, ret, post)), + (end_span, " }".to_string()), + ], + None => vec![(data.span(), format!("{}{}{}", arrow, ret, post))], + }; + err.multipart_suggestion_verbose( + "try giving this closure an explicit return type", + suggestion, + Applicability::HasPlaceholders, + ); + } + } + err + } + + pub fn need_type_info_err_in_generator( + &self, + kind: hir::GeneratorKind, + span: Span, + ty: Ty<'tcx>, + ) -> DiagnosticBuilder<'tcx, ErrorGuaranteed> { + let ty = self.resolve_vars_if_possible(ty); + let data = self.extract_inference_diagnostics_data(ty.into(), None); + + let mut err = struct_span_err!( + self.tcx.sess, + span, + E0698, + "type inside {} must be known in this context", + kind, + ); + err.span_label(span, data.cannot_infer_msg()); + err + } +} + +#[derive(Debug)] +struct InferSource<'tcx> { + span: Span, + kind: InferSourceKind<'tcx>, +} + +#[derive(Debug)] +enum InferSourceKind<'tcx> { + LetBinding { + insert_span: Span, + pattern_name: Option, + ty: Ty<'tcx>, + }, + ClosureArg { + insert_span: Span, + ty: Ty<'tcx>, + }, + GenericArg { + insert_span: Span, + argument_index: usize, + generics_def_id: DefId, + def_id: DefId, + generic_args: &'tcx [GenericArg<'tcx>], + }, + FullyQualifiedMethodCall { + receiver: &'tcx Expr<'tcx>, + /// If the method has other arguments, this is ", " and the start of the first argument, + /// while for methods without arguments this is ")" and the end of the method call. + successor: (&'static str, BytePos), + substs: SubstsRef<'tcx>, + def_id: DefId, + }, + ClosureReturn { + ty: Ty<'tcx>, + data: &'tcx FnRetTy<'tcx>, + should_wrap_expr: Option, + }, +} + +impl<'tcx> InferSource<'tcx> { + fn from_expansion(&self) -> bool { + let source_from_expansion = match self.kind { + InferSourceKind::LetBinding { insert_span, .. } + | InferSourceKind::ClosureArg { insert_span, .. } + | InferSourceKind::GenericArg { insert_span, .. } => insert_span.from_expansion(), + InferSourceKind::FullyQualifiedMethodCall { receiver, .. } => { + receiver.span.from_expansion() + } + InferSourceKind::ClosureReturn { data, should_wrap_expr, .. } => { + data.span().from_expansion() || should_wrap_expr.map_or(false, Span::from_expansion) + } + }; + source_from_expansion || self.span.from_expansion() + } +} + +impl<'tcx> InferSourceKind<'tcx> { + fn ty_msg(&self, infcx: &InferCtxt<'_, 'tcx>) -> String { + match *self { + InferSourceKind::LetBinding { ty, .. } + | InferSourceKind::ClosureArg { ty, .. } + | InferSourceKind::ClosureReturn { ty, .. } => { + if ty.is_closure() { + format!(" for the closure `{}`", closure_as_fn_str(infcx, ty)) + } else if !ty.is_ty_infer() { + format!(" for `{}`", ty_to_string(infcx, ty)) + } else { + String::new() + } + } + // FIXME: We should be able to add some additional info here. + InferSourceKind::GenericArg { .. } + | InferSourceKind::FullyQualifiedMethodCall { .. } => String::new(), + } + } +} + +#[derive(Debug)] +struct InsertableGenericArgs<'tcx> { + insert_span: Span, + substs: SubstsRef<'tcx>, + generics_def_id: DefId, + def_id: DefId, +} + +/// A visitor which searches for the "best" spot to use in the inference error. +/// +/// For this it walks over the hir body and tries to check all places where +/// inference variables could be bound. +/// +/// While doing so, the currently best spot is stored in `infer_source`. +/// For details on how we rank spots, see [Self::source_cost] +struct FindInferSourceVisitor<'a, 'tcx> { + infcx: &'a InferCtxt<'a, 'tcx>, + typeck_results: &'a TypeckResults<'tcx>, + + target: GenericArg<'tcx>, + + attempt: usize, + infer_source_cost: usize, + infer_source: Option>, +} + +impl<'a, 'tcx> FindInferSourceVisitor<'a, 'tcx> { + fn new( + infcx: &'a InferCtxt<'a, 'tcx>, + typeck_results: &'a TypeckResults<'tcx>, + target: GenericArg<'tcx>, + ) -> Self { + FindInferSourceVisitor { + infcx, + typeck_results, + + target, + + attempt: 0, + infer_source_cost: usize::MAX, + infer_source: None, + } + } + + /// Computes cost for the given source. + /// + /// Sources with a small cost are prefer and should result + /// in a clearer and idiomatic suggestion. + fn source_cost(&self, source: &InferSource<'tcx>) -> usize { + #[derive(Clone, Copy)] + struct CostCtxt<'tcx> { + tcx: TyCtxt<'tcx>, + } + impl<'tcx> CostCtxt<'tcx> { + fn arg_cost(self, arg: GenericArg<'tcx>) -> usize { + match arg.unpack() { + GenericArgKind::Lifetime(_) => 0, // erased + GenericArgKind::Type(ty) => self.ty_cost(ty), + GenericArgKind::Const(_) => 3, // some non-zero value + } + } + fn ty_cost(self, ty: Ty<'tcx>) -> usize { + match *ty.kind() { + ty::Closure(..) => 1000, + ty::FnDef(..) => 150, + ty::FnPtr(..) => 30, + ty::Adt(def, substs) => { + 5 + self + .tcx + .generics_of(def.did()) + .own_substs_no_defaults(self.tcx, substs) + .iter() + .map(|&arg| self.arg_cost(arg)) + .sum::() + } + ty::Tuple(args) => 5 + args.iter().map(|arg| self.ty_cost(arg)).sum::(), + ty::Ref(_, ty, _) => 2 + self.ty_cost(ty), + ty::Infer(..) => 0, + _ => 1, + } + } + } + + // The sources are listed in order of preference here. + let tcx = self.infcx.tcx; + let ctx = CostCtxt { tcx }; + let base_cost = match source.kind { + InferSourceKind::LetBinding { ty, .. } => ctx.ty_cost(ty), + InferSourceKind::ClosureArg { ty, .. } => ctx.ty_cost(ty), + InferSourceKind::GenericArg { def_id, generic_args, .. } => { + let variant_cost = match tcx.def_kind(def_id) { + // `None::` and friends are ugly. + DefKind::Variant | DefKind::Ctor(CtorOf::Variant, _) => 15, + _ => 10, + }; + variant_cost + generic_args.iter().map(|&arg| ctx.arg_cost(arg)).sum::() + } + InferSourceKind::FullyQualifiedMethodCall { substs, .. } => { + 20 + substs.iter().map(|arg| ctx.arg_cost(arg)).sum::() + } + InferSourceKind::ClosureReturn { ty, should_wrap_expr, .. } => { + 30 + ctx.ty_cost(ty) + if should_wrap_expr.is_some() { 10 } else { 0 } + } + }; + + let suggestion_may_apply = if source.from_expansion() { 10000 } else { 0 }; + + base_cost + suggestion_may_apply + } + + /// Uses `fn source_cost` to determine whether this inference source is preferable to + /// previous sources. We generally prefer earlier sources. + #[instrument(level = "debug", skip(self))] + fn update_infer_source(&mut self, new_source: InferSource<'tcx>) { + let cost = self.source_cost(&new_source) + self.attempt; + debug!(?cost); + self.attempt += 1; + if cost < self.infer_source_cost { + self.infer_source_cost = cost; + self.infer_source = Some(new_source); + } + } + + fn node_substs_opt(&self, hir_id: HirId) -> Option> { + let substs = self.typeck_results.node_substs_opt(hir_id); + self.infcx.resolve_vars_if_possible(substs) + } + + fn opt_node_type(&self, hir_id: HirId) -> Option> { + let ty = self.typeck_results.node_type_opt(hir_id); + self.infcx.resolve_vars_if_possible(ty) + } + + // Check whether this generic argument is the inference variable we + // are looking for. + fn generic_arg_is_target(&self, arg: GenericArg<'tcx>) -> bool { + if arg == self.target { + return true; + } + + match (arg.unpack(), self.target.unpack()) { + (GenericArgKind::Type(inner_ty), GenericArgKind::Type(target_ty)) => { + use ty::{Infer, TyVar}; + match (inner_ty.kind(), target_ty.kind()) { + (&Infer(TyVar(a_vid)), &Infer(TyVar(b_vid))) => { + self.infcx.inner.borrow_mut().type_variables().sub_unified(a_vid, b_vid) + } + _ => false, + } + } + (GenericArgKind::Const(inner_ct), GenericArgKind::Const(target_ct)) => { + use ty::InferConst::*; + match (inner_ct.kind(), target_ct.kind()) { + (ty::ConstKind::Infer(Var(a_vid)), ty::ConstKind::Infer(Var(b_vid))) => self + .infcx + .inner + .borrow_mut() + .const_unification_table() + .unioned(a_vid, b_vid), + _ => false, + } + } + _ => false, + } + } + + /// Does this generic argument contain our target inference variable + /// in a way which can be written by the user. + fn generic_arg_contains_target(&self, arg: GenericArg<'tcx>) -> bool { + let mut walker = arg.walk(); + while let Some(inner) = walker.next() { + if self.generic_arg_is_target(inner) { + return true; + } + match inner.unpack() { + GenericArgKind::Lifetime(_) => {} + GenericArgKind::Type(ty) => { + if matches!(ty.kind(), ty::Opaque(..) | ty::Closure(..) | ty::Generator(..)) { + // Opaque types can't be named by the user right now. + // + // Both the generic arguments of closures and generators can + // also not be named. We may want to only look into the closure + // signature in case it has no captures, as that can be represented + // using `fn(T) -> R`. + + // FIXME(type_alias_impl_trait): These opaque types + // can actually be named, so it would make sense to + // adjust this case and add a test for it. + walker.skip_current_subtree(); + } + } + GenericArgKind::Const(ct) => { + if matches!(ct.kind(), ty::ConstKind::Unevaluated(..)) { + // You can't write the generic arguments for + // unevaluated constants. + walker.skip_current_subtree(); + } + } + } + } + false + } + + fn expr_inferred_subst_iter( + &self, + expr: &'tcx hir::Expr<'tcx>, + ) -> Box> + 'a> { + let tcx = self.infcx.tcx; + match expr.kind { + hir::ExprKind::Path(ref path) => { + if let Some(substs) = self.node_substs_opt(expr.hir_id) { + return self.path_inferred_subst_iter(expr.hir_id, substs, path); + } + } + // FIXME(#98711): Ideally we would also deal with type relative + // paths here, even if that is quite rare. + // + // See the `need_type_info/expr-struct-type-relative-gat.rs` test + // for an example where that would be needed. + // + // However, the `type_dependent_def_id` for `Self::Output` in an + // impl is currently the `DefId` of `Output` in the trait definition + // which makes this somewhat difficult and prevents us from just + // using `self.path_inferred_subst_iter` here. + hir::ExprKind::Struct(&hir::QPath::Resolved(_self_ty, path), _, _) => { + if let Some(ty) = self.opt_node_type(expr.hir_id) { + if let ty::Adt(_, substs) = ty.kind() { + return Box::new(self.resolved_path_inferred_subst_iter(path, substs)); + } + } + } + hir::ExprKind::MethodCall(segment, _, _) => { + if let Some(def_id) = self.typeck_results.type_dependent_def_id(expr.hir_id) { + let generics = tcx.generics_of(def_id); + let insertable: Option<_> = try { + if generics.has_impl_trait() { + None? + } + let substs = self.node_substs_opt(expr.hir_id)?; + let span = tcx.hir().span(segment.hir_id?); + let insert_span = segment.ident.span.shrink_to_hi().with_hi(span.hi()); + InsertableGenericArgs { + insert_span, + substs, + generics_def_id: def_id, + def_id, + } + }; + return Box::new(insertable.into_iter()); + } + } + _ => {} + } + + Box::new(iter::empty()) + } + + fn resolved_path_inferred_subst_iter( + &self, + path: &'tcx hir::Path<'tcx>, + substs: SubstsRef<'tcx>, + ) -> impl Iterator> + 'a { + let tcx = self.infcx.tcx; + // The last segment of a path often has `Res::Err` and the + // correct `Res` is the one of the whole path. + // + // FIXME: We deal with that one separately for now, + // would be good to remove this special case. + let last_segment_using_path_data: Option<_> = try { + let generics_def_id = tcx.res_generics_def_id(path.res)?; + let generics = tcx.generics_of(generics_def_id); + if generics.has_impl_trait() { + None? + } + let insert_span = + path.segments.last().unwrap().ident.span.shrink_to_hi().with_hi(path.span.hi()); + InsertableGenericArgs { + insert_span, + substs, + generics_def_id, + def_id: path.res.def_id(), + } + }; + + path.segments + .iter() + .filter_map(move |segment| { + let res = segment.res?; + let generics_def_id = tcx.res_generics_def_id(res)?; + let generics = tcx.generics_of(generics_def_id); + if generics.has_impl_trait() { + return None; + } + let span = tcx.hir().span(segment.hir_id?); + let insert_span = segment.ident.span.shrink_to_hi().with_hi(span.hi()); + Some(InsertableGenericArgs { + insert_span, + substs, + generics_def_id, + def_id: res.def_id(), + }) + }) + .chain(last_segment_using_path_data) + } + + fn path_inferred_subst_iter( + &self, + hir_id: HirId, + substs: SubstsRef<'tcx>, + qpath: &'tcx hir::QPath<'tcx>, + ) -> Box> + 'a> { + let tcx = self.infcx.tcx; + match qpath { + hir::QPath::Resolved(_self_ty, path) => { + Box::new(self.resolved_path_inferred_subst_iter(path, substs)) + } + hir::QPath::TypeRelative(ty, segment) => { + let Some(def_id) = self.typeck_results.type_dependent_def_id(hir_id) else { + return Box::new(iter::empty()); + }; + + let generics = tcx.generics_of(def_id); + let segment: Option<_> = try { + if !segment.infer_args || generics.has_impl_trait() { + None?; + } + let span = tcx.hir().span(segment.hir_id?); + let insert_span = segment.ident.span.shrink_to_hi().with_hi(span.hi()); + InsertableGenericArgs { insert_span, substs, generics_def_id: def_id, def_id } + }; + + let parent_def_id = generics.parent.unwrap(); + if tcx.def_kind(parent_def_id) == DefKind::Impl { + let parent_ty = tcx.bound_type_of(parent_def_id).subst(tcx, substs); + match (parent_ty.kind(), &ty.kind) { + ( + ty::Adt(def, substs), + hir::TyKind::Path(hir::QPath::Resolved(_self_ty, path)), + ) => { + if tcx.res_generics_def_id(path.res) != Some(def.did()) { + match path.res { + Res::Def(DefKind::TyAlias, _) => { + // FIXME: Ideally we should support this. For that + // we have to map back from the self type to the + // type alias though. That's difficult. + // + // See the `need_type_info/type-alias.rs` test for + // some examples. + } + // There cannot be inference variables in the self type, + // so there's nothing for us to do here. + Res::SelfTy { .. } => {} + _ => warn!( + "unexpected path: def={:?} substs={:?} path={:?}", + def, substs, path, + ), + } + } else { + return Box::new( + self.resolved_path_inferred_subst_iter(path, substs) + .chain(segment), + ); + } + } + _ => (), + } + } + + Box::new(segment.into_iter()) + } + hir::QPath::LangItem(_, _, _) => Box::new(iter::empty()), + } + } +} + +impl<'a, 'tcx> Visitor<'tcx> for FindInferSourceVisitor<'a, 'tcx> { + type NestedFilter = nested_filter::OnlyBodies; + + fn nested_visit_map(&mut self) -> Self::Map { + self.infcx.tcx.hir() + } + + fn visit_local(&mut self, local: &'tcx Local<'tcx>) { + intravisit::walk_local(self, local); + + if let Some(ty) = self.opt_node_type(local.hir_id) { + if self.generic_arg_contains_target(ty.into()) { + match local.source { + LocalSource::Normal if local.ty.is_none() => { + self.update_infer_source(InferSource { + span: local.pat.span, + kind: InferSourceKind::LetBinding { + insert_span: local.pat.span.shrink_to_hi(), + pattern_name: local.pat.simple_ident(), + ty, + }, + }) + } + _ => {} + } + } + } + } + + /// For closures, we first visit the parameters and then the content, + /// as we prefer those. + fn visit_body(&mut self, body: &'tcx Body<'tcx>) { + for param in body.params { + debug!( + "param: span {:?}, ty_span {:?}, pat.span {:?}", + param.span, param.ty_span, param.pat.span + ); + if param.ty_span != param.pat.span { + debug!("skipping param: has explicit type"); + continue; + } + + let Some(param_ty) = self.opt_node_type(param.hir_id) else { + continue + }; + + if self.generic_arg_contains_target(param_ty.into()) { + self.update_infer_source(InferSource { + span: param.pat.span, + kind: InferSourceKind::ClosureArg { + insert_span: param.pat.span.shrink_to_hi(), + ty: param_ty, + }, + }) + } + } + intravisit::walk_body(self, body); + } + + #[instrument(level = "debug", skip(self))] + fn visit_expr(&mut self, expr: &'tcx Expr<'tcx>) { + let tcx = self.infcx.tcx; + match expr.kind { + // When encountering `func(arg)` first look into `arg` and then `func`, + // as `arg` is "more specific". + ExprKind::Call(func, args) => { + for arg in args { + self.visit_expr(arg); + } + self.visit_expr(func); + } + _ => intravisit::walk_expr(self, expr), + } + + for args in self.expr_inferred_subst_iter(expr) { + debug!(?args); + let InsertableGenericArgs { insert_span, substs, generics_def_id, def_id } = args; + let generics = tcx.generics_of(generics_def_id); + if let Some(argument_index) = generics + .own_substs(substs) + .iter() + .position(|&arg| self.generic_arg_contains_target(arg)) + { + let substs = self.infcx.resolve_vars_if_possible(substs); + let generic_args = &generics.own_substs_no_defaults(tcx, substs) + [generics.own_counts().lifetimes..]; + let span = match expr.kind { + ExprKind::MethodCall(path, _, _) => path.ident.span, + _ => expr.span, + }; + + self.update_infer_source(InferSource { + span, + kind: InferSourceKind::GenericArg { + insert_span, + argument_index, + generics_def_id, + def_id, + generic_args, + }, + }); + } + } + + if let Some(node_ty) = self.opt_node_type(expr.hir_id) { + if let ( + &ExprKind::Closure(&Closure { fn_decl, body, fn_decl_span, .. }), + ty::Closure(_, substs), + ) = (&expr.kind, node_ty.kind()) + { + let output = substs.as_closure().sig().output().skip_binder(); + if self.generic_arg_contains_target(output.into()) { + let body = self.infcx.tcx.hir().body(body); + let should_wrap_expr = if matches!(body.value.kind, ExprKind::Block(..)) { + None + } else { + Some(body.value.span.shrink_to_hi()) + }; + self.update_infer_source(InferSource { + span: fn_decl_span, + kind: InferSourceKind::ClosureReturn { + ty: output, + data: &fn_decl.output, + should_wrap_expr, + }, + }) + } + } + } + + let has_impl_trait = |def_id| { + iter::successors(Some(tcx.generics_of(def_id)), |generics| { + generics.parent.map(|def_id| tcx.generics_of(def_id)) + }) + .any(|generics| generics.has_impl_trait()) + }; + if let ExprKind::MethodCall(path, args, span) = expr.kind + && let Some(substs) = self.node_substs_opt(expr.hir_id) + && substs.iter().any(|arg| self.generic_arg_contains_target(arg)) + && let Some(def_id) = self.typeck_results.type_dependent_def_id(expr.hir_id) + && self.infcx.tcx.trait_of_item(def_id).is_some() + && !has_impl_trait(def_id) + { + let successor = + args.get(1).map_or_else(|| (")", span.hi()), |arg| (", ", arg.span.lo())); + let substs = self.infcx.resolve_vars_if_possible(substs); + self.update_infer_source(InferSource { + span: path.ident.span, + kind: InferSourceKind::FullyQualifiedMethodCall { + receiver: args.first().unwrap(), + successor, + substs, + def_id, + } + }) + } + } +} diff --git a/compiler/rustc_infer/src/infer/error_reporting/nice_region_error/different_lifetimes.rs b/compiler/rustc_infer/src/infer/error_reporting/nice_region_error/different_lifetimes.rs new file mode 100644 index 000000000..9a2ab3e32 --- /dev/null +++ b/compiler/rustc_infer/src/infer/error_reporting/nice_region_error/different_lifetimes.rs @@ -0,0 +1,234 @@ +//! Error Reporting for Anonymous Region Lifetime Errors +//! where both the regions are anonymous. + +use crate::infer::error_reporting::nice_region_error::find_anon_type::find_anon_type; +use crate::infer::error_reporting::nice_region_error::util::AnonymousParamInfo; +use crate::infer::error_reporting::nice_region_error::NiceRegionError; +use crate::infer::lexical_region_resolve::RegionResolutionError; +use crate::infer::SubregionOrigin; +use crate::infer::TyCtxt; + +use rustc_errors::{struct_span_err, Applicability, Diagnostic, ErrorGuaranteed}; +use rustc_hir as hir; +use rustc_hir::{GenericParamKind, Ty}; +use rustc_middle::ty::Region; +use rustc_span::symbol::kw; + +impl<'a, 'tcx> NiceRegionError<'a, 'tcx> { + /// Print the error message for lifetime errors when both the concerned regions are anonymous. + /// + /// Consider a case where we have + /// + /// ```compile_fail,E0623 + /// fn foo(x: &mut Vec<&u8>, y: &u8) { + /// x.push(y); + /// } + /// ``` + /// + /// The example gives + /// + /// ```text + /// fn foo(x: &mut Vec<&u8>, y: &u8) { + /// --- --- these references are declared with different lifetimes... + /// x.push(y); + /// ^ ...but data from `y` flows into `x` here + /// ``` + /// + /// It has been extended for the case of structs too. + /// + /// Consider the example + /// + /// ```no_run + /// struct Ref<'a> { x: &'a u32 } + /// ``` + /// + /// ```text + /// fn foo(mut x: Vec, y: Ref) { + /// --- --- these structs are declared with different lifetimes... + /// x.push(y); + /// ^ ...but data from `y` flows into `x` here + /// } + /// ``` + /// + /// It will later be extended to trait objects. + pub(super) fn try_report_anon_anon_conflict(&self) -> Option { + let (span, sub, sup) = self.regions()?; + + if let Some(RegionResolutionError::ConcreteFailure( + SubregionOrigin::ReferenceOutlivesReferent(..), + .., + )) = self.error + { + // This error doesn't make much sense in this case. + return None; + } + + // Determine whether the sub and sup consist of both anonymous (elided) regions. + let anon_reg_sup = self.tcx().is_suitable_region(sup)?; + + let anon_reg_sub = self.tcx().is_suitable_region(sub)?; + let scope_def_id_sup = anon_reg_sup.def_id; + let bregion_sup = anon_reg_sup.boundregion; + let scope_def_id_sub = anon_reg_sub.def_id; + let bregion_sub = anon_reg_sub.boundregion; + + let ty_sup = find_anon_type(self.tcx(), sup, &bregion_sup)?; + + let ty_sub = find_anon_type(self.tcx(), sub, &bregion_sub)?; + + debug!( + "try_report_anon_anon_conflict: found_param1={:?} sup={:?} br1={:?}", + ty_sub, sup, bregion_sup + ); + debug!( + "try_report_anon_anon_conflict: found_param2={:?} sub={:?} br2={:?}", + ty_sup, sub, bregion_sub + ); + + let (ty_sup, ty_fndecl_sup) = ty_sup; + let (ty_sub, ty_fndecl_sub) = ty_sub; + + let AnonymousParamInfo { param: anon_param_sup, .. } = + self.find_param_with_region(sup, sup)?; + let AnonymousParamInfo { param: anon_param_sub, .. } = + self.find_param_with_region(sub, sub)?; + + let sup_is_ret_type = + self.is_return_type_anon(scope_def_id_sup, bregion_sup, ty_fndecl_sup); + let sub_is_ret_type = + self.is_return_type_anon(scope_def_id_sub, bregion_sub, ty_fndecl_sub); + + let span_label_var1 = match anon_param_sup.pat.simple_ident() { + Some(simple_ident) => format!(" from `{}`", simple_ident), + None => String::new(), + }; + + let span_label_var2 = match anon_param_sub.pat.simple_ident() { + Some(simple_ident) => format!(" into `{}`", simple_ident), + None => String::new(), + }; + + debug!( + "try_report_anon_anon_conflict: sub_is_ret_type={:?} sup_is_ret_type={:?}", + sub_is_ret_type, sup_is_ret_type + ); + + let mut err = struct_span_err!(self.tcx().sess, span, E0623, "lifetime mismatch"); + + match (sup_is_ret_type, sub_is_ret_type) { + (ret_capture @ Some(ret_span), _) | (_, ret_capture @ Some(ret_span)) => { + let param_span = + if sup_is_ret_type == ret_capture { ty_sub.span } else { ty_sup.span }; + + err.span_label( + param_span, + "this parameter and the return type are declared with different lifetimes...", + ); + err.span_label(ret_span, ""); + err.span_label(span, format!("...but data{} is returned here", span_label_var1)); + } + + (None, None) => { + if ty_sup.hir_id == ty_sub.hir_id { + err.span_label(ty_sup.span, "this type is declared with multiple lifetimes..."); + err.span_label(ty_sub.span, ""); + err.span_label(span, "...but data with one lifetime flows into the other here"); + } else { + err.span_label( + ty_sup.span, + "these two types are declared with different lifetimes...", + ); + err.span_label(ty_sub.span, ""); + err.span_label( + span, + format!("...but data{} flows{} here", span_label_var1, span_label_var2), + ); + } + } + } + + if suggest_adding_lifetime_params(self.tcx(), sub, ty_sup, ty_sub, &mut err) { + err.note("each elided lifetime in input position becomes a distinct lifetime"); + } + + let reported = err.emit(); + Some(reported) + } +} + +pub fn suggest_adding_lifetime_params<'tcx>( + tcx: TyCtxt<'tcx>, + sub: Region<'tcx>, + ty_sup: &Ty<'_>, + ty_sub: &Ty<'_>, + err: &mut Diagnostic, +) -> bool { + let ( + hir::Ty { kind: hir::TyKind::Rptr(lifetime_sub, _), .. }, + hir::Ty { kind: hir::TyKind::Rptr(lifetime_sup, _), .. }, + ) = (ty_sub, ty_sup) else { + return false; + }; + + if !lifetime_sub.name.is_anonymous() || !lifetime_sup.name.is_anonymous() { + return false; + }; + + let Some(anon_reg) = tcx.is_suitable_region(sub) else { + return false; + }; + + let hir_id = tcx.hir().local_def_id_to_hir_id(anon_reg.def_id); + + let node = tcx.hir().get(hir_id); + let is_impl = matches!(&node, hir::Node::ImplItem(_)); + let generics = match node { + hir::Node::Item(&hir::Item { kind: hir::ItemKind::Fn(_, ref generics, ..), .. }) + | hir::Node::TraitItem(&hir::TraitItem { ref generics, .. }) + | hir::Node::ImplItem(&hir::ImplItem { ref generics, .. }) => generics, + _ => return false, + }; + + let suggestion_param_name = generics + .params + .iter() + .filter(|p| matches!(p.kind, GenericParamKind::Lifetime { .. })) + .map(|p| p.name.ident().name) + .find(|i| *i != kw::UnderscoreLifetime); + let introduce_new = suggestion_param_name.is_none(); + let suggestion_param_name = + suggestion_param_name.map(|n| n.to_string()).unwrap_or_else(|| "'a".to_owned()); + + debug!(?lifetime_sup.span); + debug!(?lifetime_sub.span); + let make_suggestion = |span: rustc_span::Span| { + if span.is_empty() { + (span, format!("{}, ", suggestion_param_name)) + } else if let Ok("&") = tcx.sess.source_map().span_to_snippet(span).as_deref() { + (span.shrink_to_hi(), format!("{} ", suggestion_param_name)) + } else { + (span, suggestion_param_name.clone()) + } + }; + let mut suggestions = + vec![make_suggestion(lifetime_sub.span), make_suggestion(lifetime_sup.span)]; + + if introduce_new { + let new_param_suggestion = + if let Some(first) = generics.params.iter().find(|p| !p.name.ident().span.is_empty()) { + (first.span.shrink_to_lo(), format!("{}, ", suggestion_param_name)) + } else { + (generics.span, format!("<{}>", suggestion_param_name)) + }; + + suggestions.push(new_param_suggestion); + } + + let mut sugg = String::from("consider introducing a named lifetime parameter"); + if is_impl { + sugg.push_str(" and update trait if needed"); + } + err.multipart_suggestion(sugg, suggestions, Applicability::MaybeIncorrect); + + true +} diff --git a/compiler/rustc_infer/src/infer/error_reporting/nice_region_error/find_anon_type.rs b/compiler/rustc_infer/src/infer/error_reporting/nice_region_error/find_anon_type.rs new file mode 100644 index 000000000..c1b201da6 --- /dev/null +++ b/compiler/rustc_infer/src/infer/error_reporting/nice_region_error/find_anon_type.rs @@ -0,0 +1,234 @@ +use rustc_hir as hir; +use rustc_hir::intravisit::{self, Visitor}; +use rustc_middle::hir::map::Map; +use rustc_middle::hir::nested_filter; +use rustc_middle::middle::resolve_lifetime as rl; +use rustc_middle::ty::{self, Region, TyCtxt}; + +/// This function calls the `visit_ty` method for the parameters +/// corresponding to the anonymous regions. The `nested_visitor.found_type` +/// contains the anonymous type. +/// +/// # Arguments +/// region - the anonymous region corresponding to the anon_anon conflict +/// br - the bound region corresponding to the above region which is of type `BrAnon(_)` +/// +/// # Example +/// ```compile_fail,E0623 +/// fn foo(x: &mut Vec<&u8>, y: &u8) +/// { x.push(y); } +/// ``` +/// The function returns the nested type corresponding to the anonymous region +/// for e.g., `&u8` and `Vec<&u8>`. +pub fn find_anon_type<'tcx>( + tcx: TyCtxt<'tcx>, + region: Region<'tcx>, + br: &ty::BoundRegionKind, +) -> Option<(&'tcx hir::Ty<'tcx>, &'tcx hir::FnSig<'tcx>)> { + let anon_reg = tcx.is_suitable_region(region)?; + let hir_id = tcx.hir().local_def_id_to_hir_id(anon_reg.def_id); + let fn_sig = tcx.hir().get(hir_id).fn_sig()?; + + fn_sig + .decl + .inputs + .iter() + .find_map(|arg| find_component_for_bound_region(tcx, arg, br)) + .map(|ty| (ty, fn_sig)) +} + +// This method creates a FindNestedTypeVisitor which returns the type corresponding +// to the anonymous region. +fn find_component_for_bound_region<'tcx>( + tcx: TyCtxt<'tcx>, + arg: &'tcx hir::Ty<'tcx>, + br: &ty::BoundRegionKind, +) -> Option<&'tcx hir::Ty<'tcx>> { + let mut nested_visitor = FindNestedTypeVisitor { + tcx, + bound_region: *br, + found_type: None, + current_index: ty::INNERMOST, + }; + nested_visitor.visit_ty(arg); + nested_visitor.found_type +} + +// The FindNestedTypeVisitor captures the corresponding `hir::Ty` of the +// anonymous region. The example above would lead to a conflict between +// the two anonymous lifetimes for &u8 in x and y respectively. This visitor +// would be invoked twice, once for each lifetime, and would +// walk the types like &mut Vec<&u8> and &u8 looking for the HIR +// where that lifetime appears. This allows us to highlight the +// specific part of the type in the error message. +struct FindNestedTypeVisitor<'tcx> { + tcx: TyCtxt<'tcx>, + // The bound_region corresponding to the Refree(freeregion) + // associated with the anonymous region we are looking for. + bound_region: ty::BoundRegionKind, + // The type where the anonymous lifetime appears + // for e.g., Vec<`&u8`> and <`&u8`> + found_type: Option<&'tcx hir::Ty<'tcx>>, + current_index: ty::DebruijnIndex, +} + +impl<'tcx> Visitor<'tcx> for FindNestedTypeVisitor<'tcx> { + type NestedFilter = nested_filter::OnlyBodies; + + fn nested_visit_map(&mut self) -> Self::Map { + self.tcx.hir() + } + + fn visit_ty(&mut self, arg: &'tcx hir::Ty<'tcx>) { + match arg.kind { + hir::TyKind::BareFn(_) => { + self.current_index.shift_in(1); + intravisit::walk_ty(self, arg); + self.current_index.shift_out(1); + return; + } + + hir::TyKind::TraitObject(bounds, ..) => { + for bound in bounds { + self.current_index.shift_in(1); + self.visit_poly_trait_ref(bound, hir::TraitBoundModifier::None); + self.current_index.shift_out(1); + } + } + + hir::TyKind::Rptr(ref lifetime, _) => { + // the lifetime of the TyRptr + let hir_id = lifetime.hir_id; + match (self.tcx.named_region(hir_id), self.bound_region) { + // Find the index of the named region that was part of the + // error. We will then search the function parameters for a bound + // region at the right depth with the same index + (Some(rl::Region::EarlyBound(_, id)), ty::BrNamed(def_id, _)) => { + debug!("EarlyBound id={:?} def_id={:?}", id, def_id); + if id == def_id { + self.found_type = Some(arg); + return; // we can stop visiting now + } + } + + // Find the index of the named region that was part of the + // error. We will then search the function parameters for a bound + // region at the right depth with the same index + ( + Some(rl::Region::LateBound(debruijn_index, _, id)), + ty::BrNamed(def_id, _), + ) => { + debug!( + "FindNestedTypeVisitor::visit_ty: LateBound depth = {:?}", + debruijn_index + ); + debug!("LateBound id={:?} def_id={:?}", id, def_id); + if debruijn_index == self.current_index && id == def_id { + self.found_type = Some(arg); + return; // we can stop visiting now + } + } + + ( + Some( + rl::Region::Static + | rl::Region::Free(_, _) + | rl::Region::EarlyBound(_, _) + | rl::Region::LateBound(_, _, _), + ) + | None, + _, + ) => { + debug!("no arg found"); + } + } + } + // Checks if it is of type `hir::TyKind::Path` which corresponds to a struct. + hir::TyKind::Path(_) => { + let subvisitor = &mut TyPathVisitor { + tcx: self.tcx, + found_it: false, + bound_region: self.bound_region, + current_index: self.current_index, + }; + intravisit::walk_ty(subvisitor, arg); // call walk_ty; as visit_ty is empty, + // this will visit only outermost type + if subvisitor.found_it { + self.found_type = Some(arg); + } + } + _ => {} + } + // walk the embedded contents: e.g., if we are visiting `Vec<&Foo>`, + // go on to visit `&Foo` + intravisit::walk_ty(self, arg); + } +} + +// The visitor captures the corresponding `hir::Ty` of the anonymous region +// in the case of structs ie. `hir::TyKind::Path`. +// This visitor would be invoked for each lifetime corresponding to a struct, +// and would walk the types like Vec in the above example and Ref looking for the HIR +// where that lifetime appears. This allows us to highlight the +// specific part of the type in the error message. +struct TyPathVisitor<'tcx> { + tcx: TyCtxt<'tcx>, + found_it: bool, + bound_region: ty::BoundRegionKind, + current_index: ty::DebruijnIndex, +} + +impl<'tcx> Visitor<'tcx> for TyPathVisitor<'tcx> { + type NestedFilter = nested_filter::OnlyBodies; + + fn nested_visit_map(&mut self) -> Map<'tcx> { + self.tcx.hir() + } + + fn visit_lifetime(&mut self, lifetime: &hir::Lifetime) { + match (self.tcx.named_region(lifetime.hir_id), self.bound_region) { + // the lifetime of the TyPath! + (Some(rl::Region::EarlyBound(_, id)), ty::BrNamed(def_id, _)) => { + debug!("EarlyBound id={:?} def_id={:?}", id, def_id); + if id == def_id { + self.found_it = true; + return; // we can stop visiting now + } + } + + (Some(rl::Region::LateBound(debruijn_index, _, id)), ty::BrNamed(def_id, _)) => { + debug!("FindNestedTypeVisitor::visit_ty: LateBound depth = {:?}", debruijn_index,); + debug!("id={:?}", id); + debug!("def_id={:?}", def_id); + if debruijn_index == self.current_index && id == def_id { + self.found_it = true; + return; // we can stop visiting now + } + } + + ( + Some( + rl::Region::Static + | rl::Region::EarlyBound(_, _) + | rl::Region::LateBound(_, _, _) + | rl::Region::Free(_, _), + ) + | None, + _, + ) => { + debug!("no arg found"); + } + } + } + + fn visit_ty(&mut self, arg: &'tcx hir::Ty<'tcx>) { + // ignore nested types + // + // If you have a type like `Foo<'a, &Ty>` we + // are only interested in the immediate lifetimes ('a). + // + // Making `visit_ty` empty will ignore the `&Ty` embedded + // inside, it will get reached by the outer visitor. + debug!("`Ty` corresponding to a struct is {:?}", arg); + } +} diff --git a/compiler/rustc_infer/src/infer/error_reporting/nice_region_error/mismatched_static_lifetime.rs b/compiler/rustc_infer/src/infer/error_reporting/nice_region_error/mismatched_static_lifetime.rs new file mode 100644 index 000000000..893ca3cf7 --- /dev/null +++ b/compiler/rustc_infer/src/infer/error_reporting/nice_region_error/mismatched_static_lifetime.rs @@ -0,0 +1,102 @@ +//! Error Reporting for when the lifetime for a type doesn't match the `impl` selected for a predicate +//! to hold. + +use crate::infer::error_reporting::nice_region_error::NiceRegionError; +use crate::infer::error_reporting::note_and_explain_region; +use crate::infer::lexical_region_resolve::RegionResolutionError; +use crate::infer::{SubregionOrigin, TypeTrace}; +use crate::traits::ObligationCauseCode; +use rustc_data_structures::fx::FxHashSet; +use rustc_errors::{Applicability, ErrorGuaranteed, MultiSpan}; +use rustc_hir as hir; +use rustc_hir::intravisit::Visitor; +use rustc_middle::ty::TypeVisitor; + +impl<'a, 'tcx> NiceRegionError<'a, 'tcx> { + pub(super) fn try_report_mismatched_static_lifetime(&self) -> Option { + let error = self.error.as_ref()?; + debug!("try_report_mismatched_static_lifetime {:?}", error); + + let RegionResolutionError::ConcreteFailure(origin, sub, sup) = error.clone() else { + return None; + }; + if !sub.is_static() { + return None; + } + let SubregionOrigin::Subtype(box TypeTrace { ref cause, .. }) = origin else { + return None; + }; + // If we added a "points at argument expression" obligation, we remove it here, we care + // about the original obligation only. + let code = match cause.code() { + ObligationCauseCode::FunctionArgumentObligation { parent_code, .. } => &*parent_code, + code => code, + }; + let ObligationCauseCode::MatchImpl(parent, impl_def_id) = code else { + return None; + }; + let ObligationCauseCode::BindingObligation(_def_id, binding_span) = *parent.code() else { + return None; + }; + let mut err = self.tcx().sess.struct_span_err(cause.span, "incompatible lifetime on type"); + // FIXME: we should point at the lifetime + let mut multi_span: MultiSpan = vec![binding_span].into(); + multi_span.push_span_label(binding_span, "introduces a `'static` lifetime requirement"); + err.span_note(multi_span, "because this has an unmet lifetime requirement"); + note_and_explain_region(self.tcx(), &mut err, "", sup, "...", Some(binding_span)); + if let Some(impl_node) = self.tcx().hir().get_if_local(*impl_def_id) { + // If an impl is local, then maybe this isn't what they want. Try to + // be as helpful as possible with implicit lifetimes. + + // First, let's get the hir self type of the impl + let hir::Node::Item(hir::Item { + kind: hir::ItemKind::Impl(hir::Impl { self_ty: impl_self_ty, .. }), + .. + }) = impl_node else { + bug!("Node not an impl."); + }; + + // Next, let's figure out the set of trait objects with implicit static bounds + let ty = self.tcx().type_of(*impl_def_id); + let mut v = super::static_impl_trait::TraitObjectVisitor(FxHashSet::default()); + v.visit_ty(ty); + let mut traits = vec![]; + for matching_def_id in v.0 { + let mut hir_v = + super::static_impl_trait::HirTraitObjectVisitor(&mut traits, matching_def_id); + hir_v.visit_ty(&impl_self_ty); + } + + if traits.is_empty() { + // If there are no trait object traits to point at, either because + // there aren't trait objects or because none are implicit, then just + // write a single note on the impl itself. + + let impl_span = self.tcx().def_span(*impl_def_id); + err.span_note(impl_span, "...does not necessarily outlive the static lifetime introduced by the compatible `impl`"); + } else { + // Otherwise, point at all implicit static lifetimes + + err.note("...does not necessarily outlive the static lifetime introduced by the compatible `impl`"); + for span in &traits { + err.span_note(*span, "this has an implicit `'static` lifetime requirement"); + // It would be nice to put this immediately under the above note, but they get + // pushed to the end. + err.span_suggestion_verbose( + span.shrink_to_hi(), + "consider relaxing the implicit `'static` requirement", + " + '_", + Applicability::MaybeIncorrect, + ); + } + } + } else { + // Otherwise just point out the impl. + + let impl_span = self.tcx().def_span(*impl_def_id); + err.span_note(impl_span, "...does not necessarily outlive the static lifetime introduced by the compatible `impl`"); + } + let reported = err.emit(); + Some(reported) + } +} diff --git a/compiler/rustc_infer/src/infer/error_reporting/nice_region_error/mod.rs b/compiler/rustc_infer/src/infer/error_reporting/nice_region_error/mod.rs new file mode 100644 index 000000000..53d9acf7d --- /dev/null +++ b/compiler/rustc_infer/src/infer/error_reporting/nice_region_error/mod.rs @@ -0,0 +1,77 @@ +use crate::infer::lexical_region_resolve::RegionResolutionError; +use crate::infer::lexical_region_resolve::RegionResolutionError::*; +use crate::infer::InferCtxt; +use rustc_errors::{DiagnosticBuilder, ErrorGuaranteed}; +use rustc_middle::ty::{self, TyCtxt}; +use rustc_span::source_map::Span; + +mod different_lifetimes; +pub mod find_anon_type; +mod mismatched_static_lifetime; +mod named_anon_conflict; +mod placeholder_error; +mod static_impl_trait; +mod trait_impl_difference; +mod util; + +pub use different_lifetimes::suggest_adding_lifetime_params; +pub use find_anon_type::find_anon_type; +pub use static_impl_trait::{suggest_new_region_bound, HirTraitObjectVisitor, TraitObjectVisitor}; +pub use util::find_param_with_region; + +impl<'cx, 'tcx> InferCtxt<'cx, 'tcx> { + pub fn try_report_nice_region_error(&self, error: &RegionResolutionError<'tcx>) -> bool { + NiceRegionError::new(self, error.clone()).try_report().is_some() + } +} + +pub struct NiceRegionError<'cx, 'tcx> { + infcx: &'cx InferCtxt<'cx, 'tcx>, + error: Option>, + regions: Option<(Span, ty::Region<'tcx>, ty::Region<'tcx>)>, +} + +impl<'cx, 'tcx> NiceRegionError<'cx, 'tcx> { + pub fn new(infcx: &'cx InferCtxt<'cx, 'tcx>, error: RegionResolutionError<'tcx>) -> Self { + Self { infcx, error: Some(error), regions: None } + } + + pub fn new_from_span( + infcx: &'cx InferCtxt<'cx, 'tcx>, + span: Span, + sub: ty::Region<'tcx>, + sup: ty::Region<'tcx>, + ) -> Self { + Self { infcx, error: None, regions: Some((span, sub, sup)) } + } + + fn tcx(&self) -> TyCtxt<'tcx> { + self.infcx.tcx + } + + pub fn try_report_from_nll(&self) -> Option> { + // Due to the improved diagnostics returned by the MIR borrow checker, only a subset of + // the nice region errors are required when running under the MIR borrow checker. + self.try_report_named_anon_conflict().or_else(|| self.try_report_placeholder_conflict()) + } + + pub fn try_report(&self) -> Option { + self.try_report_from_nll() + .map(|mut diag| diag.emit()) + .or_else(|| self.try_report_impl_not_conforming_to_trait()) + .or_else(|| self.try_report_anon_anon_conflict()) + .or_else(|| self.try_report_static_impl_trait()) + .or_else(|| self.try_report_mismatched_static_lifetime()) + } + + pub(super) fn regions(&self) -> Option<(Span, ty::Region<'tcx>, ty::Region<'tcx>)> { + match (&self.error, self.regions) { + (Some(ConcreteFailure(origin, sub, sup)), None) => Some((origin.span(), *sub, *sup)), + (Some(SubSupConflict(_, _, origin, sub, _, sup, _)), None) => { + Some((origin.span(), *sub, *sup)) + } + (None, Some((span, sub, sup))) => Some((span, sub, sup)), + _ => None, + } + } +} diff --git a/compiler/rustc_infer/src/infer/error_reporting/nice_region_error/named_anon_conflict.rs b/compiler/rustc_infer/src/infer/error_reporting/nice_region_error/named_anon_conflict.rs new file mode 100644 index 000000000..76cb76d9f --- /dev/null +++ b/compiler/rustc_infer/src/infer/error_reporting/nice_region_error/named_anon_conflict.rs @@ -0,0 +1,116 @@ +//! Error Reporting for Anonymous Region Lifetime Errors +//! where one region is named and the other is anonymous. +use crate::infer::error_reporting::nice_region_error::find_anon_type::find_anon_type; +use crate::infer::error_reporting::nice_region_error::NiceRegionError; +use rustc_errors::{struct_span_err, Applicability, DiagnosticBuilder, ErrorGuaranteed}; +use rustc_middle::ty; +use rustc_span::symbol::kw; + +impl<'a, 'tcx> NiceRegionError<'a, 'tcx> { + /// When given a `ConcreteFailure` for a function with parameters containing a named region and + /// an anonymous region, emit an descriptive diagnostic error. + pub(super) fn try_report_named_anon_conflict( + &self, + ) -> Option> { + let (span, sub, sup) = self.regions()?; + + debug!( + "try_report_named_anon_conflict(sub={:?}, sup={:?}, error={:?})", + sub, sup, self.error, + ); + + // Determine whether the sub and sup consist of one named region ('a) + // and one anonymous (elided) region. If so, find the parameter arg + // where the anonymous region appears (there must always be one; we + // only introduced anonymous regions in parameters) as well as a + // version new_ty of its type where the anonymous region is replaced + // with the named one. + let (named, anon, anon_param_info, region_info) = if sub.has_name() + && self.tcx().is_suitable_region(sup).is_some() + && self.find_param_with_region(sup, sub).is_some() + { + ( + sub, + sup, + self.find_param_with_region(sup, sub).unwrap(), + self.tcx().is_suitable_region(sup).unwrap(), + ) + } else if sup.has_name() + && self.tcx().is_suitable_region(sub).is_some() + && self.find_param_with_region(sub, sup).is_some() + { + ( + sup, + sub, + self.find_param_with_region(sub, sup).unwrap(), + self.tcx().is_suitable_region(sub).unwrap(), + ) + } else { + return None; // inapplicable + }; + + // Suggesting to add a `'static` lifetime to a parameter is nearly always incorrect, + // and can steer users down the wrong path. + if named.is_static() { + return None; + } + + debug!("try_report_named_anon_conflict: named = {:?}", named); + debug!("try_report_named_anon_conflict: anon_param_info = {:?}", anon_param_info); + debug!("try_report_named_anon_conflict: region_info = {:?}", region_info); + + let param = anon_param_info.param; + let new_ty = anon_param_info.param_ty; + let new_ty_span = anon_param_info.param_ty_span; + let br = anon_param_info.bound_region; + let is_first = anon_param_info.is_first; + let scope_def_id = region_info.def_id; + let is_impl_item = region_info.is_impl_item; + + match br { + ty::BrNamed(_, kw::UnderscoreLifetime) | ty::BrAnon(_) => {} + _ => { + /* not an anonymous region */ + debug!("try_report_named_anon_conflict: not an anonymous region"); + return None; + } + } + + if is_impl_item { + debug!("try_report_named_anon_conflict: impl item, bail out"); + return None; + } + + if find_anon_type(self.tcx(), anon, &br).is_some() + && self.is_self_anon(is_first, scope_def_id) + { + return None; + } + + let (error_var, span_label_var) = match param.pat.simple_ident() { + Some(simple_ident) => ( + format!("the type of `{}`", simple_ident), + format!("the type of `{}`", simple_ident), + ), + None => ("parameter type".to_owned(), "type".to_owned()), + }; + + let mut diag = struct_span_err!( + self.tcx().sess, + span, + E0621, + "explicit lifetime required in {}", + error_var + ); + + diag.span_label(span, format!("lifetime `{}` required", named)); + diag.span_suggestion( + new_ty_span, + &format!("add explicit lifetime `{}` to {}", named, span_label_var), + new_ty, + Applicability::Unspecified, + ); + + Some(diag) + } +} diff --git a/compiler/rustc_infer/src/infer/error_reporting/nice_region_error/placeholder_error.rs b/compiler/rustc_infer/src/infer/error_reporting/nice_region_error/placeholder_error.rs new file mode 100644 index 000000000..998699158 --- /dev/null +++ b/compiler/rustc_infer/src/infer/error_reporting/nice_region_error/placeholder_error.rs @@ -0,0 +1,501 @@ +use crate::infer::error_reporting::nice_region_error::NiceRegionError; +use crate::infer::lexical_region_resolve::RegionResolutionError; +use crate::infer::ValuePairs; +use crate::infer::{SubregionOrigin, TypeTrace}; +use crate::traits::{ObligationCause, ObligationCauseCode}; +use rustc_data_structures::intern::Interned; +use rustc_errors::{Diagnostic, DiagnosticBuilder, ErrorGuaranteed}; +use rustc_hir::def::Namespace; +use rustc_hir::def_id::DefId; +use rustc_middle::ty::error::ExpectedFound; +use rustc_middle::ty::print::{FmtPrinter, Print, RegionHighlightMode}; +use rustc_middle::ty::subst::SubstsRef; +use rustc_middle::ty::{self, RePlaceholder, ReVar, Region, TyCtxt}; + +use std::fmt::{self, Write}; + +impl<'tcx> NiceRegionError<'_, 'tcx> { + /// When given a `ConcreteFailure` for a function with arguments containing a named region and + /// an anonymous region, emit a descriptive diagnostic error. + pub(super) fn try_report_placeholder_conflict( + &self, + ) -> Option> { + match &self.error { + /////////////////////////////////////////////////////////////////////////// + // NB. The ordering of cases in this match is very + // sensitive, because we are often matching against + // specific cases and then using an `_` to match all + // others. + + /////////////////////////////////////////////////////////////////////////// + // Check for errors from comparing trait failures -- first + // with two placeholders, then with one. + Some(RegionResolutionError::SubSupConflict( + vid, + _, + SubregionOrigin::Subtype(box TypeTrace { cause, values }), + sub_placeholder @ Region(Interned(RePlaceholder(_), _)), + _, + sup_placeholder @ Region(Interned(RePlaceholder(_), _)), + _, + )) => self.try_report_trait_placeholder_mismatch( + Some(self.tcx().mk_region(ReVar(*vid))), + cause, + Some(*sub_placeholder), + Some(*sup_placeholder), + values, + ), + + Some(RegionResolutionError::SubSupConflict( + vid, + _, + SubregionOrigin::Subtype(box TypeTrace { cause, values }), + sub_placeholder @ Region(Interned(RePlaceholder(_), _)), + _, + _, + _, + )) => self.try_report_trait_placeholder_mismatch( + Some(self.tcx().mk_region(ReVar(*vid))), + cause, + Some(*sub_placeholder), + None, + values, + ), + + Some(RegionResolutionError::SubSupConflict( + vid, + _, + SubregionOrigin::Subtype(box TypeTrace { cause, values }), + _, + _, + sup_placeholder @ Region(Interned(RePlaceholder(_), _)), + _, + )) => self.try_report_trait_placeholder_mismatch( + Some(self.tcx().mk_region(ReVar(*vid))), + cause, + None, + Some(*sup_placeholder), + values, + ), + + Some(RegionResolutionError::SubSupConflict( + vid, + _, + _, + _, + SubregionOrigin::Subtype(box TypeTrace { cause, values }), + sup_placeholder @ Region(Interned(RePlaceholder(_), _)), + _, + )) => self.try_report_trait_placeholder_mismatch( + Some(self.tcx().mk_region(ReVar(*vid))), + cause, + None, + Some(*sup_placeholder), + values, + ), + + Some(RegionResolutionError::UpperBoundUniverseConflict( + vid, + _, + _, + SubregionOrigin::Subtype(box TypeTrace { cause, values }), + sup_placeholder @ Region(Interned(RePlaceholder(_), _)), + )) => self.try_report_trait_placeholder_mismatch( + Some(self.tcx().mk_region(ReVar(*vid))), + cause, + None, + Some(*sup_placeholder), + values, + ), + + Some(RegionResolutionError::ConcreteFailure( + SubregionOrigin::Subtype(box TypeTrace { cause, values }), + sub_region @ Region(Interned(RePlaceholder(_), _)), + sup_region @ Region(Interned(RePlaceholder(_), _)), + )) => self.try_report_trait_placeholder_mismatch( + None, + cause, + Some(*sub_region), + Some(*sup_region), + values, + ), + + Some(RegionResolutionError::ConcreteFailure( + SubregionOrigin::Subtype(box TypeTrace { cause, values }), + sub_region @ Region(Interned(RePlaceholder(_), _)), + sup_region, + )) => self.try_report_trait_placeholder_mismatch( + (!sup_region.has_name()).then_some(*sup_region), + cause, + Some(*sub_region), + None, + values, + ), + + Some(RegionResolutionError::ConcreteFailure( + SubregionOrigin::Subtype(box TypeTrace { cause, values }), + sub_region, + sup_region @ Region(Interned(RePlaceholder(_), _)), + )) => self.try_report_trait_placeholder_mismatch( + (!sub_region.has_name()).then_some(*sub_region), + cause, + None, + Some(*sup_region), + values, + ), + + _ => None, + } + } + + fn try_report_trait_placeholder_mismatch( + &self, + vid: Option>, + cause: &ObligationCause<'tcx>, + sub_placeholder: Option>, + sup_placeholder: Option>, + value_pairs: &ValuePairs<'tcx>, + ) -> Option> { + let (expected_substs, found_substs, trait_def_id) = match value_pairs { + ValuePairs::TraitRefs(ExpectedFound { expected, found }) + if expected.def_id == found.def_id => + { + (expected.substs, found.substs, expected.def_id) + } + ValuePairs::PolyTraitRefs(ExpectedFound { expected, found }) + if expected.def_id() == found.def_id() => + { + // It's possible that the placeholders come from a binder + // outside of this value pair. Use `no_bound_vars` as a + // simple heuristic for that. + (expected.no_bound_vars()?.substs, found.no_bound_vars()?.substs, expected.def_id()) + } + _ => return None, + }; + + Some(self.report_trait_placeholder_mismatch( + vid, + cause, + sub_placeholder, + sup_placeholder, + trait_def_id, + expected_substs, + found_substs, + )) + } + + // error[E0308]: implementation of `Foo` does not apply to enough lifetimes + // --> /home/nmatsakis/tmp/foo.rs:12:5 + // | + // 12 | all::<&'static u32>(); + // | ^^^^^^^^^^^^^^^^^^^ lifetime mismatch + // | + // = note: Due to a where-clause on the function `all`, + // = note: `T` must implement `...` for any two lifetimes `'1` and `'2`. + // = note: However, the type `T` only implements `...` for some specific lifetime `'2`. + #[instrument(level = "debug", skip(self))] + fn report_trait_placeholder_mismatch( + &self, + vid: Option>, + cause: &ObligationCause<'tcx>, + sub_placeholder: Option>, + sup_placeholder: Option>, + trait_def_id: DefId, + expected_substs: SubstsRef<'tcx>, + actual_substs: SubstsRef<'tcx>, + ) -> DiagnosticBuilder<'tcx, ErrorGuaranteed> { + let span = cause.span(); + let msg = format!( + "implementation of `{}` is not general enough", + self.tcx().def_path_str(trait_def_id), + ); + let mut err = self.tcx().sess.struct_span_err(span, &msg); + + let leading_ellipsis = if let ObligationCauseCode::ItemObligation(def_id) = *cause.code() { + err.span_label(span, "doesn't satisfy where-clause"); + err.span_label( + self.tcx().def_span(def_id), + &format!("due to a where-clause on `{}`...", self.tcx().def_path_str(def_id)), + ); + true + } else { + err.span_label(span, &msg); + false + }; + + let expected_trait_ref = self.infcx.resolve_vars_if_possible(ty::TraitRef { + def_id: trait_def_id, + substs: expected_substs, + }); + let actual_trait_ref = self + .infcx + .resolve_vars_if_possible(ty::TraitRef { def_id: trait_def_id, substs: actual_substs }); + + // Search the expected and actual trait references to see (a) + // whether the sub/sup placeholders appear in them (sometimes + // you have a trait ref like `T: Foo`, where the + // placeholder was created as part of an inner type) and (b) + // whether the inference variable appears. In each case, + // assign a counter value in each case if so. + let mut counter = 0; + let mut has_sub = None; + let mut has_sup = None; + + let mut actual_has_vid = None; + let mut expected_has_vid = None; + + self.tcx().for_each_free_region(&expected_trait_ref, |r| { + if Some(r) == sub_placeholder && has_sub.is_none() { + has_sub = Some(counter); + counter += 1; + } else if Some(r) == sup_placeholder && has_sup.is_none() { + has_sup = Some(counter); + counter += 1; + } + + if Some(r) == vid && expected_has_vid.is_none() { + expected_has_vid = Some(counter); + counter += 1; + } + }); + + self.tcx().for_each_free_region(&actual_trait_ref, |r| { + if Some(r) == vid && actual_has_vid.is_none() { + actual_has_vid = Some(counter); + counter += 1; + } + }); + + let actual_self_ty_has_vid = + self.tcx().any_free_region_meets(&actual_trait_ref.self_ty(), |r| Some(r) == vid); + + let expected_self_ty_has_vid = + self.tcx().any_free_region_meets(&expected_trait_ref.self_ty(), |r| Some(r) == vid); + + let any_self_ty_has_vid = actual_self_ty_has_vid || expected_self_ty_has_vid; + + debug!( + ?actual_has_vid, + ?expected_has_vid, + ?has_sub, + ?has_sup, + ?actual_self_ty_has_vid, + ?expected_self_ty_has_vid, + ); + + self.explain_actual_impl_that_was_found( + &mut err, + sub_placeholder, + sup_placeholder, + has_sub, + has_sup, + expected_trait_ref, + actual_trait_ref, + vid, + expected_has_vid, + actual_has_vid, + any_self_ty_has_vid, + leading_ellipsis, + ); + + err + } + + /// Add notes with details about the expected and actual trait refs, with attention to cases + /// when placeholder regions are involved: either the trait or the self type containing + /// them needs to be mentioned the closest to the placeholders. + /// This makes the error messages read better, however at the cost of some complexity + /// due to the number of combinations we have to deal with. + fn explain_actual_impl_that_was_found( + &self, + err: &mut Diagnostic, + sub_placeholder: Option>, + sup_placeholder: Option>, + has_sub: Option, + has_sup: Option, + expected_trait_ref: ty::TraitRef<'tcx>, + actual_trait_ref: ty::TraitRef<'tcx>, + vid: Option>, + expected_has_vid: Option, + actual_has_vid: Option, + any_self_ty_has_vid: bool, + leading_ellipsis: bool, + ) { + // HACK(eddyb) maybe move this in a more central location. + #[derive(Copy, Clone)] + struct Highlighted<'tcx, T> { + tcx: TyCtxt<'tcx>, + highlight: RegionHighlightMode<'tcx>, + value: T, + } + + impl<'tcx, T> Highlighted<'tcx, T> { + fn map(self, f: impl FnOnce(T) -> U) -> Highlighted<'tcx, U> { + Highlighted { tcx: self.tcx, highlight: self.highlight, value: f(self.value) } + } + } + + impl<'tcx, T> fmt::Display for Highlighted<'tcx, T> + where + T: for<'a> Print< + 'tcx, + FmtPrinter<'a, 'tcx>, + Error = fmt::Error, + Output = FmtPrinter<'a, 'tcx>, + >, + { + fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result { + let mut printer = ty::print::FmtPrinter::new(self.tcx, Namespace::TypeNS); + printer.region_highlight_mode = self.highlight; + + let s = self.value.print(printer)?.into_buffer(); + f.write_str(&s) + } + } + + // The weird thing here with the `maybe_highlighting_region` calls and the + // the match inside is meant to be like this: + // + // - The match checks whether the given things (placeholders, etc) appear + // in the types are about to print + // - Meanwhile, the `maybe_highlighting_region` calls set up + // highlights so that, if they do appear, we will replace + // them `'0` and whatever. (This replacement takes place + // inside the closure given to `maybe_highlighting_region`.) + // + // There is some duplication between the calls -- i.e., the + // `maybe_highlighting_region` checks if (e.g.) `has_sub` is + // None, an then we check again inside the closure, but this + // setup sort of minimized the number of calls and so form. + + let highlight_trait_ref = |trait_ref| Highlighted { + tcx: self.tcx(), + highlight: RegionHighlightMode::new(self.tcx()), + value: trait_ref, + }; + + let same_self_type = actual_trait_ref.self_ty() == expected_trait_ref.self_ty(); + + let mut expected_trait_ref = highlight_trait_ref(expected_trait_ref); + expected_trait_ref.highlight.maybe_highlighting_region(sub_placeholder, has_sub); + expected_trait_ref.highlight.maybe_highlighting_region(sup_placeholder, has_sup); + err.note(&{ + let passive_voice = match (has_sub, has_sup) { + (Some(_), _) | (_, Some(_)) => any_self_ty_has_vid, + (None, None) => { + expected_trait_ref.highlight.maybe_highlighting_region(vid, expected_has_vid); + match expected_has_vid { + Some(_) => true, + None => any_self_ty_has_vid, + } + } + }; + + let mut note = if same_self_type { + let mut self_ty = expected_trait_ref.map(|tr| tr.self_ty()); + self_ty.highlight.maybe_highlighting_region(vid, actual_has_vid); + + if self_ty.value.is_closure() + && self + .tcx() + .fn_trait_kind_from_lang_item(expected_trait_ref.value.def_id) + .is_some() + { + let closure_sig = self_ty.map(|closure| { + if let ty::Closure(_, substs) = closure.kind() { + self.tcx().signature_unclosure( + substs.as_closure().sig(), + rustc_hir::Unsafety::Normal, + ) + } else { + bug!("type is not longer closure"); + } + }); + + format!( + "{}closure with signature `{}` must implement `{}`", + if leading_ellipsis { "..." } else { "" }, + closure_sig, + expected_trait_ref.map(|tr| tr.print_only_trait_path()), + ) + } else { + format!( + "{}`{}` must implement `{}`", + if leading_ellipsis { "..." } else { "" }, + self_ty, + expected_trait_ref.map(|tr| tr.print_only_trait_path()), + ) + } + } else if passive_voice { + format!( + "{}`{}` would have to be implemented for the type `{}`", + if leading_ellipsis { "..." } else { "" }, + expected_trait_ref.map(|tr| tr.print_only_trait_path()), + expected_trait_ref.map(|tr| tr.self_ty()), + ) + } else { + format!( + "{}`{}` must implement `{}`", + if leading_ellipsis { "..." } else { "" }, + expected_trait_ref.map(|tr| tr.self_ty()), + expected_trait_ref.map(|tr| tr.print_only_trait_path()), + ) + }; + + match (has_sub, has_sup) { + (Some(n1), Some(n2)) => { + let _ = write!( + note, + ", for any two lifetimes `'{}` and `'{}`...", + std::cmp::min(n1, n2), + std::cmp::max(n1, n2), + ); + } + (Some(n), _) | (_, Some(n)) => { + let _ = write!(note, ", for any lifetime `'{}`...", n,); + } + (None, None) => { + if let Some(n) = expected_has_vid { + let _ = write!(note, ", for some specific lifetime `'{}`...", n,); + } + } + } + + note + }); + + let mut actual_trait_ref = highlight_trait_ref(actual_trait_ref); + actual_trait_ref.highlight.maybe_highlighting_region(vid, actual_has_vid); + err.note(&{ + let passive_voice = match actual_has_vid { + Some(_) => any_self_ty_has_vid, + None => true, + }; + + let mut note = if same_self_type { + format!( + "...but it actually implements `{}`", + actual_trait_ref.map(|tr| tr.print_only_trait_path()), + ) + } else if passive_voice { + format!( + "...but `{}` is actually implemented for the type `{}`", + actual_trait_ref.map(|tr| tr.print_only_trait_path()), + actual_trait_ref.map(|tr| tr.self_ty()), + ) + } else { + format!( + "...but `{}` actually implements `{}`", + actual_trait_ref.map(|tr| tr.self_ty()), + actual_trait_ref.map(|tr| tr.print_only_trait_path()), + ) + }; + + if let Some(n) = actual_has_vid { + let _ = write!(note, ", for some specific lifetime `'{}`", n); + } + + note + }); + } +} diff --git a/compiler/rustc_infer/src/infer/error_reporting/nice_region_error/static_impl_trait.rs b/compiler/rustc_infer/src/infer/error_reporting/nice_region_error/static_impl_trait.rs new file mode 100644 index 000000000..9886c572a --- /dev/null +++ b/compiler/rustc_infer/src/infer/error_reporting/nice_region_error/static_impl_trait.rs @@ -0,0 +1,577 @@ +//! Error Reporting for static impl Traits. + +use crate::infer::error_reporting::nice_region_error::NiceRegionError; +use crate::infer::lexical_region_resolve::RegionResolutionError; +use crate::infer::{SubregionOrigin, TypeTrace}; +use crate::traits::{ObligationCauseCode, UnifyReceiverContext}; +use rustc_data_structures::fx::FxHashSet; +use rustc_errors::{struct_span_err, Applicability, Diagnostic, ErrorGuaranteed, MultiSpan}; +use rustc_hir::def_id::DefId; +use rustc_hir::intravisit::{walk_ty, Visitor}; +use rustc_hir::{self as hir, GenericBound, Item, ItemKind, Lifetime, LifetimeName, Node, TyKind}; +use rustc_middle::ty::{ + self, AssocItemContainer, StaticLifetimeVisitor, Ty, TyCtxt, TypeSuperVisitable, TypeVisitor, +}; +use rustc_span::symbol::Ident; +use rustc_span::Span; + +use std::ops::ControlFlow; + +impl<'a, 'tcx> NiceRegionError<'a, 'tcx> { + /// Print the error message for lifetime errors when the return type is a static `impl Trait`, + /// `dyn Trait` or if a method call on a trait object introduces a static requirement. + pub(super) fn try_report_static_impl_trait(&self) -> Option { + debug!("try_report_static_impl_trait(error={:?})", self.error); + let tcx = self.tcx(); + let (var_origin, sub_origin, sub_r, sup_origin, sup_r, spans) = match self.error.as_ref()? { + RegionResolutionError::SubSupConflict( + _, + var_origin, + sub_origin, + sub_r, + sup_origin, + sup_r, + spans, + ) if sub_r.is_static() => (var_origin, sub_origin, sub_r, sup_origin, sup_r, spans), + RegionResolutionError::ConcreteFailure( + SubregionOrigin::Subtype(box TypeTrace { cause, .. }), + sub_r, + sup_r, + ) if sub_r.is_static() => { + // This is for an implicit `'static` requirement coming from `impl dyn Trait {}`. + if let ObligationCauseCode::UnifyReceiver(ctxt) = cause.code() { + // This may have a closure and it would cause ICE + // through `find_param_with_region` (#78262). + let anon_reg_sup = tcx.is_suitable_region(*sup_r)?; + let fn_returns = tcx.return_type_impl_or_dyn_traits(anon_reg_sup.def_id); + if fn_returns.is_empty() { + return None; + } + + let param = self.find_param_with_region(*sup_r, *sub_r)?; + let lifetime = if sup_r.has_name() { + format!("lifetime `{}`", sup_r) + } else { + "an anonymous lifetime `'_`".to_string() + }; + let mut err = struct_span_err!( + tcx.sess, + cause.span, + E0772, + "{} has {} but calling `{}` introduces an implicit `'static` lifetime \ + requirement", + param + .param + .pat + .simple_ident() + .map(|s| format!("`{}`", s)) + .unwrap_or_else(|| "`fn` parameter".to_string()), + lifetime, + ctxt.assoc_item.name, + ); + err.span_label(param.param_ty_span, &format!("this data with {}...", lifetime)); + err.span_label( + cause.span, + &format!( + "...is used and required to live as long as `'static` here \ + because of an implicit lifetime bound on the {}", + match ctxt.assoc_item.container { + AssocItemContainer::TraitContainer => { + let id = ctxt.assoc_item.container_id(tcx); + format!("`impl` of `{}`", tcx.def_path_str(id)) + } + AssocItemContainer::ImplContainer => "inherent `impl`".to_string(), + }, + ), + ); + if self.find_impl_on_dyn_trait(&mut err, param.param_ty, &ctxt) { + let reported = err.emit(); + return Some(reported); + } else { + err.cancel(); + } + } + return None; + } + _ => return None, + }; + debug!( + "try_report_static_impl_trait(var={:?}, sub={:?} {:?} sup={:?} {:?})", + var_origin, sub_origin, sub_r, sup_origin, sup_r + ); + let anon_reg_sup = tcx.is_suitable_region(*sup_r)?; + debug!("try_report_static_impl_trait: anon_reg_sup={:?}", anon_reg_sup); + let sp = var_origin.span(); + let return_sp = sub_origin.span(); + let param = self.find_param_with_region(*sup_r, *sub_r)?; + let (lifetime_name, lifetime) = if sup_r.has_name() { + (sup_r.to_string(), format!("lifetime `{}`", sup_r)) + } else { + ("'_".to_owned(), "an anonymous lifetime `'_`".to_string()) + }; + let param_name = param + .param + .pat + .simple_ident() + .map(|s| format!("`{}`", s)) + .unwrap_or_else(|| "`fn` parameter".to_string()); + let mut err = struct_span_err!( + tcx.sess, + sp, + E0759, + "{} has {} but it needs to satisfy a `'static` lifetime requirement", + param_name, + lifetime, + ); + + let (mention_influencer, influencer_point) = + if sup_origin.span().overlaps(param.param_ty_span) { + // Account for `async fn` like in `async-await/issues/issue-62097.rs`. + // The desugaring of `async `fn`s causes `sup_origin` and `param` to point at the same + // place (but with different `ctxt`, hence `overlaps` instead of `==` above). + // + // This avoids the following: + // + // LL | pub async fn run_dummy_fn(&self) { + // | ^^^^^ + // | | + // | this data with an anonymous lifetime `'_`... + // | ...is captured here... + (false, sup_origin.span()) + } else { + (!sup_origin.span().overlaps(return_sp), param.param_ty_span) + }; + err.span_label(influencer_point, &format!("this data with {}...", lifetime)); + + debug!("try_report_static_impl_trait: param_info={:?}", param); + + let mut spans = spans.clone(); + + if mention_influencer { + spans.push(sup_origin.span()); + } + // We dedup the spans *ignoring* expansion context. + spans.sort(); + spans.dedup_by_key(|span| (span.lo(), span.hi())); + + // We try to make the output have fewer overlapping spans if possible. + let require_msg = if spans.is_empty() { + "...is used and required to live as long as `'static` here" + } else { + "...and is required to live as long as `'static` here" + }; + let require_span = + if sup_origin.span().overlaps(return_sp) { sup_origin.span() } else { return_sp }; + + for span in &spans { + err.span_label(*span, "...is used here..."); + } + + if spans.iter().any(|sp| sp.overlaps(return_sp) || *sp > return_sp) { + // If any of the "captured here" labels appears on the same line or after + // `require_span`, we put it on a note to ensure the text flows by appearing + // always at the end. + err.span_note(require_span, require_msg); + } else { + // We don't need a note, it's already at the end, it can be shown as a `span_label`. + err.span_label(require_span, require_msg); + } + + if let SubregionOrigin::RelateParamBound(_, _, Some(bound)) = sub_origin { + err.span_note(*bound, "`'static` lifetime requirement introduced by this bound"); + } + if let SubregionOrigin::Subtype(box TypeTrace { cause, .. }) = sub_origin { + if let ObligationCauseCode::ReturnValue(hir_id) + | ObligationCauseCode::BlockTailExpression(hir_id) = cause.code() + { + let parent_id = tcx.hir().get_parent_item(*hir_id); + let parent_id = tcx.hir().local_def_id_to_hir_id(parent_id); + if let Some(fn_decl) = tcx.hir().fn_decl_by_hir_id(parent_id) { + let mut span: MultiSpan = fn_decl.output.span().into(); + let mut add_label = true; + if let hir::FnRetTy::Return(ty) = fn_decl.output { + let mut v = StaticLifetimeVisitor(vec![], tcx.hir()); + v.visit_ty(ty); + if !v.0.is_empty() { + span = v.0.clone().into(); + for sp in v.0 { + span.push_span_label(sp, "`'static` requirement introduced here"); + } + add_label = false; + } + } + if add_label { + span.push_span_label( + fn_decl.output.span(), + "requirement introduced by this return type", + ); + } + span.push_span_label(cause.span, "because of this returned expression"); + err.span_note( + span, + "`'static` lifetime requirement introduced by the return type", + ); + } + } + } + + let fn_returns = tcx.return_type_impl_or_dyn_traits(anon_reg_sup.def_id); + + let mut override_error_code = None; + if let SubregionOrigin::Subtype(box TypeTrace { cause, .. }) = &sup_origin + && let ObligationCauseCode::UnifyReceiver(ctxt) = cause.code() + // Handle case of `impl Foo for dyn Bar { fn qux(&self) {} }` introducing a + // `'static` lifetime when called as a method on a binding: `bar.qux()`. + && self.find_impl_on_dyn_trait(&mut err, param.param_ty, &ctxt) + { + override_error_code = Some(ctxt.assoc_item.name); + } + + if let SubregionOrigin::Subtype(box TypeTrace { cause, .. }) = &sub_origin + && let code = match cause.code() { + ObligationCauseCode::MatchImpl(parent, ..) => parent.code(), + _ => cause.code(), + } + && let (&ObligationCauseCode::ItemObligation(item_def_id), None) = (code, override_error_code) + { + // Same case of `impl Foo for dyn Bar { fn qux(&self) {} }` introducing a `'static` + // lifetime as above, but called using a fully-qualified path to the method: + // `Foo::qux(bar)`. + let mut v = TraitObjectVisitor(FxHashSet::default()); + v.visit_ty(param.param_ty); + if let Some((ident, self_ty)) = + self.get_impl_ident_and_self_ty_from_trait(item_def_id, &v.0) + && self.suggest_constrain_dyn_trait_in_impl(&mut err, &v.0, ident, self_ty) + { + override_error_code = Some(ident.name); + } + } + if let (Some(ident), true) = (override_error_code, fn_returns.is_empty()) { + // Provide a more targeted error code and description. + err.code(rustc_errors::error_code!(E0772)); + err.set_primary_message(&format!( + "{} has {} but calling `{}` introduces an implicit `'static` lifetime \ + requirement", + param_name, lifetime, ident, + )); + } + + let arg = match param.param.pat.simple_ident() { + Some(simple_ident) => format!("argument `{}`", simple_ident), + None => "the argument".to_string(), + }; + let captures = format!("captures data from {}", arg); + suggest_new_region_bound( + tcx, + &mut err, + fn_returns, + lifetime_name, + Some(arg), + captures, + Some((param.param_ty_span, param.param_ty.to_string())), + ); + + let reported = err.emit(); + Some(reported) + } +} + +pub fn suggest_new_region_bound( + tcx: TyCtxt<'_>, + err: &mut Diagnostic, + fn_returns: Vec<&rustc_hir::Ty<'_>>, + lifetime_name: String, + arg: Option, + captures: String, + param: Option<(Span, String)>, +) { + debug!("try_report_static_impl_trait: fn_return={:?}", fn_returns); + // FIXME: account for the need of parens in `&(dyn Trait + '_)` + let consider = "consider changing the"; + let declare = "to declare that the"; + let explicit = format!("you can add an explicit `{}` lifetime bound", lifetime_name); + let explicit_static = + arg.map(|arg| format!("explicit `'static` bound to the lifetime of {}", arg)); + let add_static_bound = "alternatively, add an explicit `'static` bound to this reference"; + let plus_lt = format!(" + {}", lifetime_name); + for fn_return in fn_returns { + if fn_return.span.desugaring_kind().is_some() { + // Skip `async` desugaring `impl Future`. + continue; + } + match fn_return.kind { + TyKind::OpaqueDef(item_id, _) => { + let item = tcx.hir().item(item_id); + let ItemKind::OpaqueTy(opaque) = &item.kind else { + return; + }; + + if let Some(span) = opaque + .bounds + .iter() + .filter_map(|arg| match arg { + GenericBound::Outlives(Lifetime { + name: LifetimeName::Static, + span, + .. + }) => Some(*span), + _ => None, + }) + .next() + { + if let Some(explicit_static) = &explicit_static { + err.span_suggestion_verbose( + span, + &format!("{} `impl Trait`'s {}", consider, explicit_static), + &lifetime_name, + Applicability::MaybeIncorrect, + ); + } + if let Some((param_span, param_ty)) = param.clone() { + err.span_suggestion_verbose( + param_span, + add_static_bound, + param_ty, + Applicability::MaybeIncorrect, + ); + } + } else if opaque + .bounds + .iter() + .filter_map(|arg| match arg { + GenericBound::Outlives(Lifetime { name, span, .. }) + if name.ident().to_string() == lifetime_name => + { + Some(*span) + } + _ => None, + }) + .next() + .is_some() + { + } else { + err.span_suggestion_verbose( + fn_return.span.shrink_to_hi(), + &format!( + "{declare} `impl Trait` {captures}, {explicit}", + declare = declare, + captures = captures, + explicit = explicit, + ), + &plus_lt, + Applicability::MaybeIncorrect, + ); + } + } + TyKind::TraitObject(_, lt, _) => match lt.name { + LifetimeName::ImplicitObjectLifetimeDefault => { + err.span_suggestion_verbose( + fn_return.span.shrink_to_hi(), + &format!( + "{declare} trait object {captures}, {explicit}", + declare = declare, + captures = captures, + explicit = explicit, + ), + &plus_lt, + Applicability::MaybeIncorrect, + ); + } + name if name.ident().to_string() != lifetime_name => { + // With this check we avoid suggesting redundant bounds. This + // would happen if there are nested impl/dyn traits and only + // one of them has the bound we'd suggest already there, like + // in `impl Foo + '_`. + if let Some(explicit_static) = &explicit_static { + err.span_suggestion_verbose( + lt.span, + &format!("{} trait object's {}", consider, explicit_static), + &lifetime_name, + Applicability::MaybeIncorrect, + ); + } + if let Some((param_span, param_ty)) = param.clone() { + err.span_suggestion_verbose( + param_span, + add_static_bound, + param_ty, + Applicability::MaybeIncorrect, + ); + } + } + _ => {} + }, + _ => {} + } + } +} + +impl<'a, 'tcx> NiceRegionError<'a, 'tcx> { + fn get_impl_ident_and_self_ty_from_trait( + &self, + def_id: DefId, + trait_objects: &FxHashSet, + ) -> Option<(Ident, &'tcx hir::Ty<'tcx>)> { + let tcx = self.tcx(); + match tcx.hir().get_if_local(def_id) { + Some(Node::ImplItem(impl_item)) => { + match tcx.hir().find_by_def_id(tcx.hir().get_parent_item(impl_item.hir_id())) { + Some(Node::Item(Item { + kind: ItemKind::Impl(hir::Impl { self_ty, .. }), + .. + })) => Some((impl_item.ident, self_ty)), + _ => None, + } + } + Some(Node::TraitItem(trait_item)) => { + let trait_did = tcx.hir().get_parent_item(trait_item.hir_id()); + match tcx.hir().find_by_def_id(trait_did) { + Some(Node::Item(Item { kind: ItemKind::Trait(..), .. })) => { + // The method being called is defined in the `trait`, but the `'static` + // obligation comes from the `impl`. Find that `impl` so that we can point + // at it in the suggestion. + let trait_did = trait_did.to_def_id(); + match tcx + .hir() + .trait_impls(trait_did) + .iter() + .filter_map(|&impl_did| { + match tcx.hir().get_if_local(impl_did.to_def_id()) { + Some(Node::Item(Item { + kind: ItemKind::Impl(hir::Impl { self_ty, .. }), + .. + })) if trait_objects.iter().all(|did| { + // FIXME: we should check `self_ty` against the receiver + // type in the `UnifyReceiver` context, but for now, use + // this imperfect proxy. This will fail if there are + // multiple `impl`s for the same trait like + // `impl Foo for Box` and `impl Foo for dyn Bar`. + // In that case, only the first one will get suggestions. + let mut traits = vec![]; + let mut hir_v = HirTraitObjectVisitor(&mut traits, *did); + hir_v.visit_ty(self_ty); + !traits.is_empty() + }) => + { + Some(self_ty) + } + _ => None, + } + }) + .next() + { + Some(self_ty) => Some((trait_item.ident, self_ty)), + _ => None, + } + } + _ => None, + } + } + _ => None, + } + } + + /// When we call a method coming from an `impl Foo for dyn Bar`, `dyn Bar` introduces a default + /// `'static` obligation. Suggest relaxing that implicit bound. + fn find_impl_on_dyn_trait( + &self, + err: &mut Diagnostic, + ty: Ty<'_>, + ctxt: &UnifyReceiverContext<'tcx>, + ) -> bool { + let tcx = self.tcx(); + + // Find the method being called. + let Ok(Some(instance)) = ty::Instance::resolve( + tcx, + ctxt.param_env, + ctxt.assoc_item.def_id, + self.infcx.resolve_vars_if_possible(ctxt.substs), + ) else { + return false; + }; + + let mut v = TraitObjectVisitor(FxHashSet::default()); + v.visit_ty(ty); + + // Get the `Ident` of the method being called and the corresponding `impl` (to point at + // `Bar` in `impl Foo for dyn Bar {}` and the definition of the method being called). + let Some((ident, self_ty)) = self.get_impl_ident_and_self_ty_from_trait(instance.def_id(), &v.0) else { + return false; + }; + + // Find the trait object types in the argument, so we point at *only* the trait object. + self.suggest_constrain_dyn_trait_in_impl(err, &v.0, ident, self_ty) + } + + fn suggest_constrain_dyn_trait_in_impl( + &self, + err: &mut Diagnostic, + found_dids: &FxHashSet, + ident: Ident, + self_ty: &hir::Ty<'_>, + ) -> bool { + let mut suggested = false; + for found_did in found_dids { + let mut traits = vec![]; + let mut hir_v = HirTraitObjectVisitor(&mut traits, *found_did); + hir_v.visit_ty(&self_ty); + for span in &traits { + let mut multi_span: MultiSpan = vec![*span].into(); + multi_span + .push_span_label(*span, "this has an implicit `'static` lifetime requirement"); + multi_span.push_span_label( + ident.span, + "calling this method introduces the `impl`'s 'static` requirement", + ); + err.span_note(multi_span, "the used `impl` has a `'static` requirement"); + err.span_suggestion_verbose( + span.shrink_to_hi(), + "consider relaxing the implicit `'static` requirement", + " + '_", + Applicability::MaybeIncorrect, + ); + suggested = true; + } + } + suggested + } +} + +/// Collect all the trait objects in a type that could have received an implicit `'static` lifetime. +pub struct TraitObjectVisitor(pub FxHashSet); + +impl<'tcx> TypeVisitor<'tcx> for TraitObjectVisitor { + fn visit_ty(&mut self, t: Ty<'tcx>) -> ControlFlow { + match t.kind() { + ty::Dynamic(preds, re) if re.is_static() => { + if let Some(def_id) = preds.principal_def_id() { + self.0.insert(def_id); + } + ControlFlow::CONTINUE + } + _ => t.super_visit_with(self), + } + } +} + +/// Collect all `hir::Ty<'_>` `Span`s for trait objects with an implicit lifetime. +pub struct HirTraitObjectVisitor<'a>(pub &'a mut Vec, pub DefId); + +impl<'a, 'tcx> Visitor<'tcx> for HirTraitObjectVisitor<'a> { + fn visit_ty(&mut self, t: &'tcx hir::Ty<'tcx>) { + if let TyKind::TraitObject( + poly_trait_refs, + Lifetime { name: LifetimeName::ImplicitObjectLifetimeDefault, .. }, + _, + ) = t.kind + { + for ptr in poly_trait_refs { + if Some(self.1) == ptr.trait_ref.trait_def_id() { + self.0.push(ptr.span); + } + } + } + walk_ty(self, t); + } +} diff --git a/compiler/rustc_infer/src/infer/error_reporting/nice_region_error/trait_impl_difference.rs b/compiler/rustc_infer/src/infer/error_reporting/nice_region_error/trait_impl_difference.rs new file mode 100644 index 000000000..da465a764 --- /dev/null +++ b/compiler/rustc_infer/src/infer/error_reporting/nice_region_error/trait_impl_difference.rs @@ -0,0 +1,176 @@ +//! Error Reporting for `impl` items that do not match the obligations from their `trait`. + +use crate::infer::error_reporting::nice_region_error::NiceRegionError; +use crate::infer::lexical_region_resolve::RegionResolutionError; +use crate::infer::Subtype; +use crate::traits::ObligationCauseCode::CompareImplItemObligation; +use rustc_errors::{ErrorGuaranteed, MultiSpan}; +use rustc_hir as hir; +use rustc_hir::def::Res; +use rustc_hir::def_id::DefId; +use rustc_hir::intravisit::Visitor; +use rustc_middle::hir::nested_filter; +use rustc_middle::ty::print::RegionHighlightMode; +use rustc_middle::ty::{self, Ty, TyCtxt, TypeSuperVisitable, TypeVisitor}; +use rustc_span::Span; + +use std::ops::ControlFlow; + +impl<'a, 'tcx> NiceRegionError<'a, 'tcx> { + /// Print the error message for lifetime errors when the `impl` doesn't conform to the `trait`. + pub(super) fn try_report_impl_not_conforming_to_trait(&self) -> Option { + let error = self.error.as_ref()?; + debug!("try_report_impl_not_conforming_to_trait {:?}", error); + if let RegionResolutionError::SubSupConflict( + _, + var_origin, + sub_origin, + _sub, + sup_origin, + _sup, + _, + ) = error.clone() + && let (Subtype(sup_trace), Subtype(sub_trace)) = (&sup_origin, &sub_origin) + && let sub_expected_found @ Some((sub_expected, sub_found)) = sub_trace.values.ty() + && let sup_expected_found @ Some(_) = sup_trace.values.ty() + && let CompareImplItemObligation { trait_item_def_id, .. } = sub_trace.cause.code() + && sup_expected_found == sub_expected_found + { + let guar = + self.emit_err(var_origin.span(), sub_expected, sub_found, *trait_item_def_id); + return Some(guar); + } + None + } + + fn emit_err( + &self, + sp: Span, + expected: Ty<'tcx>, + found: Ty<'tcx>, + trait_def_id: DefId, + ) -> ErrorGuaranteed { + let trait_sp = self.tcx().def_span(trait_def_id); + let mut err = self + .tcx() + .sess + .struct_span_err(sp, "`impl` item signature doesn't match `trait` item signature"); + + // Mark all unnamed regions in the type with a number. + // This diagnostic is called in response to lifetime errors, so be informative. + struct HighlightBuilder<'tcx> { + highlight: RegionHighlightMode<'tcx>, + counter: usize, + } + + impl<'tcx> HighlightBuilder<'tcx> { + fn build(tcx: TyCtxt<'tcx>, ty: Ty<'tcx>) -> RegionHighlightMode<'tcx> { + let mut builder = + HighlightBuilder { highlight: RegionHighlightMode::new(tcx), counter: 1 }; + builder.visit_ty(ty); + builder.highlight + } + } + + impl<'tcx> ty::visit::TypeVisitor<'tcx> for HighlightBuilder<'tcx> { + fn visit_region(&mut self, r: ty::Region<'tcx>) -> ControlFlow { + if !r.has_name() && self.counter <= 3 { + self.highlight.highlighting_region(r, self.counter); + self.counter += 1; + } + r.super_visit_with(self) + } + } + + let expected_highlight = HighlightBuilder::build(self.tcx(), expected); + let expected = self + .infcx + .extract_inference_diagnostics_data(expected.into(), Some(expected_highlight)) + .name; + let found_highlight = HighlightBuilder::build(self.tcx(), found); + let found = + self.infcx.extract_inference_diagnostics_data(found.into(), Some(found_highlight)).name; + + err.span_label(sp, &format!("found `{}`", found)); + err.span_label(trait_sp, &format!("expected `{}`", expected)); + + // Get the span of all the used type parameters in the method. + let assoc_item = self.tcx().associated_item(trait_def_id); + let mut visitor = TypeParamSpanVisitor { tcx: self.tcx(), types: vec![] }; + match assoc_item.kind { + ty::AssocKind::Fn => { + let hir = self.tcx().hir(); + if let Some(hir_id) = + assoc_item.def_id.as_local().map(|id| hir.local_def_id_to_hir_id(id)) + { + if let Some(decl) = hir.fn_decl_by_hir_id(hir_id) { + visitor.visit_fn_decl(decl); + } + } + } + _ => {} + } + let mut type_param_span: MultiSpan = visitor.types.to_vec().into(); + for &span in &visitor.types { + type_param_span + .push_span_label(span, "consider borrowing this type parameter in the trait"); + } + + err.note(&format!("expected `{}`\n found `{}`", expected, found)); + + err.span_help( + type_param_span, + "the lifetime requirements from the `impl` do not correspond to the requirements in \ + the `trait`", + ); + if visitor.types.is_empty() { + err.help( + "verify the lifetime relationships in the `trait` and `impl` between the `self` \ + argument, the other inputs and its output", + ); + } + err.emit() + } +} + +struct TypeParamSpanVisitor<'tcx> { + tcx: TyCtxt<'tcx>, + types: Vec, +} + +impl<'tcx> Visitor<'tcx> for TypeParamSpanVisitor<'tcx> { + type NestedFilter = nested_filter::OnlyBodies; + + fn nested_visit_map(&mut self) -> Self::Map { + self.tcx.hir() + } + + fn visit_ty(&mut self, arg: &'tcx hir::Ty<'tcx>) { + match arg.kind { + hir::TyKind::Rptr(_, ref mut_ty) => { + // We don't want to suggest looking into borrowing `&T` or `&Self`. + hir::intravisit::walk_ty(self, mut_ty.ty); + return; + } + hir::TyKind::Path(hir::QPath::Resolved(None, path)) => match &path.segments { + [segment] + if segment + .res + .map(|res| { + matches!( + res, + Res::SelfTy { trait_: _, alias_to: _ } + | Res::Def(hir::def::DefKind::TyParam, _) + ) + }) + .unwrap_or(false) => + { + self.types.push(path.span); + } + _ => {} + }, + _ => {} + } + hir::intravisit::walk_ty(self, arg); + } +} diff --git a/compiler/rustc_infer/src/infer/error_reporting/nice_region_error/util.rs b/compiler/rustc_infer/src/infer/error_reporting/nice_region_error/util.rs new file mode 100644 index 000000000..3e9d491af --- /dev/null +++ b/compiler/rustc_infer/src/infer/error_reporting/nice_region_error/util.rs @@ -0,0 +1,167 @@ +//! Helper functions corresponding to lifetime errors due to +//! anonymous regions. + +use crate::infer::error_reporting::nice_region_error::NiceRegionError; +use crate::infer::TyCtxt; +use rustc_hir as hir; +use rustc_hir::def_id::LocalDefId; +use rustc_middle::ty::{self, Binder, DefIdTree, Region, Ty, TypeVisitable}; +use rustc_span::Span; + +/// Information about the anonymous region we are searching for. +#[derive(Debug)] +pub struct AnonymousParamInfo<'tcx> { + /// The parameter corresponding to the anonymous region. + pub param: &'tcx hir::Param<'tcx>, + /// The type corresponding to the anonymous region parameter. + pub param_ty: Ty<'tcx>, + /// The ty::BoundRegionKind corresponding to the anonymous region. + pub bound_region: ty::BoundRegionKind, + /// The `Span` of the parameter type. + pub param_ty_span: Span, + /// Signals that the argument is the first parameter in the declaration. + pub is_first: bool, +} + +// This method walks the Type of the function body parameters using +// `fold_regions()` function and returns the +// &hir::Param of the function parameter corresponding to the anonymous +// region and the Ty corresponding to the named region. +// Currently only the case where the function declaration consists of +// one named region and one anonymous region is handled. +// Consider the example `fn foo<'a>(x: &'a i32, y: &i32) -> &'a i32` +// Here, we would return the hir::Param for y, we return the type &'a +// i32, which is the type of y but with the anonymous region replaced +// with 'a, the corresponding bound region and is_first which is true if +// the hir::Param is the first parameter in the function declaration. +#[instrument(skip(tcx), level = "debug")] +pub fn find_param_with_region<'tcx>( + tcx: TyCtxt<'tcx>, + anon_region: Region<'tcx>, + replace_region: Region<'tcx>, +) -> Option> { + let (id, bound_region) = match *anon_region { + ty::ReFree(ref free_region) => (free_region.scope, free_region.bound_region), + ty::ReEarlyBound(ebr) => { + (tcx.parent(ebr.def_id), ty::BoundRegionKind::BrNamed(ebr.def_id, ebr.name)) + } + _ => return None, // not a free region + }; + + let hir = &tcx.hir(); + let def_id = id.as_local()?; + let hir_id = hir.local_def_id_to_hir_id(def_id); + + // FIXME: use def_kind + // Don't perform this on closures + match hir.get(hir_id) { + hir::Node::Expr(&hir::Expr { kind: hir::ExprKind::Closure { .. }, .. }) => { + return None; + } + _ => {} + } + + let body_id = hir.maybe_body_owned_by(def_id)?; + + let owner_id = hir.body_owner(body_id); + let fn_decl = hir.fn_decl_by_hir_id(owner_id).unwrap(); + let poly_fn_sig = tcx.fn_sig(id); + + let fn_sig = tcx.liberate_late_bound_regions(id, poly_fn_sig); + let body = hir.body(body_id); + body.params + .iter() + .take(if fn_sig.c_variadic { + fn_sig.inputs().len() + } else { + assert_eq!(fn_sig.inputs().len(), body.params.len()); + body.params.len() + }) + .enumerate() + .find_map(|(index, param)| { + // May return None; sometimes the tables are not yet populated. + let ty = fn_sig.inputs()[index]; + let mut found_anon_region = false; + let new_param_ty = tcx.fold_regions(ty, |r, _| { + if r == anon_region { + found_anon_region = true; + replace_region + } else { + r + } + }); + if found_anon_region { + let ty_hir_id = fn_decl.inputs[index].hir_id; + let param_ty_span = hir.span(ty_hir_id); + let is_first = index == 0; + Some(AnonymousParamInfo { + param, + param_ty: new_param_ty, + param_ty_span, + bound_region, + is_first, + }) + } else { + None + } + }) +} + +impl<'a, 'tcx> NiceRegionError<'a, 'tcx> { + pub(super) fn find_param_with_region( + &self, + anon_region: Region<'tcx>, + replace_region: Region<'tcx>, + ) -> Option> { + find_param_with_region(self.tcx(), anon_region, replace_region) + } + + // Here, we check for the case where the anonymous region + // is in the return type as written by the user. + // FIXME(#42703) - Need to handle certain cases here. + pub(super) fn is_return_type_anon( + &self, + scope_def_id: LocalDefId, + br: ty::BoundRegionKind, + hir_sig: &hir::FnSig<'_>, + ) -> Option { + let fn_ty = self.tcx().type_of(scope_def_id); + if let ty::FnDef(_, _) = fn_ty.kind() { + let ret_ty = fn_ty.fn_sig(self.tcx()).output(); + let span = hir_sig.decl.output.span(); + let future_output = if hir_sig.header.is_async() { + ret_ty.map_bound(|ty| self.infcx.get_impl_future_output_ty(ty)).transpose() + } else { + None + }; + return match future_output { + Some(output) if self.includes_region(output, br) => Some(span), + None if self.includes_region(ret_ty, br) => Some(span), + _ => None, + }; + } + None + } + + fn includes_region( + &self, + ty: Binder<'tcx, impl TypeVisitable<'tcx>>, + region: ty::BoundRegionKind, + ) -> bool { + let late_bound_regions = self.tcx().collect_referenced_late_bound_regions(&ty); + late_bound_regions.iter().any(|r| *r == region) + } + + // Here we check for the case where anonymous region + // corresponds to self and if yes, we display E0312. + // FIXME(#42700) - Need to format self properly to + // enable E0621 for it. + pub(super) fn is_self_anon(&self, is_first: bool, scope_def_id: LocalDefId) -> bool { + is_first + && self + .tcx() + .opt_associated_item(scope_def_id.to_def_id()) + .map(|i| i.fn_has_self_parameter) + == Some(true) + } +} diff --git a/compiler/rustc_infer/src/infer/error_reporting/note.rs b/compiler/rustc_infer/src/infer/error_reporting/note.rs new file mode 100644 index 000000000..c1940c5c0 --- /dev/null +++ b/compiler/rustc_infer/src/infer/error_reporting/note.rs @@ -0,0 +1,414 @@ +use crate::infer::error_reporting::{note_and_explain_region, ObligationCauseExt}; +use crate::infer::{self, InferCtxt, SubregionOrigin}; +use rustc_errors::{struct_span_err, Diagnostic, DiagnosticBuilder, ErrorGuaranteed}; +use rustc_middle::traits::ObligationCauseCode; +use rustc_middle::ty::error::TypeError; +use rustc_middle::ty::{self, Region}; + +impl<'a, 'tcx> InferCtxt<'a, 'tcx> { + pub(super) fn note_region_origin(&self, err: &mut Diagnostic, origin: &SubregionOrigin<'tcx>) { + let mut label_or_note = |span, msg: &str| { + let sub_count = err.children.iter().filter(|d| d.span.is_dummy()).count(); + let expanded_sub_count = err.children.iter().filter(|d| !d.span.is_dummy()).count(); + let span_is_primary = err.span.primary_spans().iter().all(|&sp| sp == span); + if span_is_primary && sub_count == 0 && expanded_sub_count == 0 { + err.span_label(span, msg); + } else if span_is_primary && expanded_sub_count == 0 { + err.note(msg); + } else { + err.span_note(span, msg); + } + }; + match *origin { + infer::Subtype(ref trace) => { + if let Some((expected, found)) = self.values_str(trace.values) { + label_or_note( + trace.cause.span, + &format!("...so that the {}", trace.cause.as_requirement_str()), + ); + + err.note_expected_found(&"", expected, &"", found); + } else { + // FIXME: this really should be handled at some earlier stage. Our + // handling of region checking when type errors are present is + // *terrible*. + + label_or_note( + trace.cause.span, + &format!("...so that {}", trace.cause.as_requirement_str()), + ); + } + } + infer::Reborrow(span) => { + label_or_note(span, "...so that reference does not outlive borrowed content"); + } + infer::ReborrowUpvar(span, ref upvar_id) => { + let var_name = self.tcx.hir().name(upvar_id.var_path.hir_id); + label_or_note(span, &format!("...so that closure can access `{}`", var_name)); + } + infer::RelateObjectBound(span) => { + label_or_note(span, "...so that it can be closed over into an object"); + } + infer::DataBorrowed(ty, span) => { + label_or_note( + span, + &format!( + "...so that the type `{}` is not borrowed for too long", + self.ty_to_string(ty) + ), + ); + } + infer::ReferenceOutlivesReferent(ty, span) => { + label_or_note( + span, + &format!( + "...so that the reference type `{}` does not outlive the data it points at", + self.ty_to_string(ty) + ), + ); + } + infer::RelateParamBound(span, t, opt_span) => { + label_or_note( + span, + &format!( + "...so that the type `{}` will meet its required lifetime bounds{}", + self.ty_to_string(t), + if opt_span.is_some() { "..." } else { "" }, + ), + ); + if let Some(span) = opt_span { + err.span_note(span, "...that is required by this bound"); + } + } + infer::RelateRegionParamBound(span) => { + label_or_note( + span, + "...so that the declared lifetime parameter bounds are satisfied", + ); + } + infer::CompareImplItemObligation { span, .. } => { + label_or_note( + span, + "...so that the definition in impl matches the definition from the trait", + ); + } + infer::CheckAssociatedTypeBounds { ref parent, .. } => { + self.note_region_origin(err, &parent); + } + } + } + + pub(super) fn report_concrete_failure( + &self, + origin: SubregionOrigin<'tcx>, + sub: Region<'tcx>, + sup: Region<'tcx>, + ) -> DiagnosticBuilder<'tcx, ErrorGuaranteed> { + match origin { + infer::Subtype(box trace) => { + let terr = TypeError::RegionsDoesNotOutlive(sup, sub); + let mut err = self.report_and_explain_type_error(trace, &terr); + match (*sub, *sup) { + (ty::RePlaceholder(_), ty::RePlaceholder(_)) => {} + (ty::RePlaceholder(_), _) => { + note_and_explain_region( + self.tcx, + &mut err, + "", + sup, + " doesn't meet the lifetime requirements", + None, + ); + } + (_, ty::RePlaceholder(_)) => { + note_and_explain_region( + self.tcx, + &mut err, + "the required lifetime does not necessarily outlive ", + sub, + "", + None, + ); + } + _ => { + note_and_explain_region(self.tcx, &mut err, "", sup, "...", None); + note_and_explain_region( + self.tcx, + &mut err, + "...does not necessarily outlive ", + sub, + "", + None, + ); + } + } + err + } + infer::Reborrow(span) => { + let mut err = struct_span_err!( + self.tcx.sess, + span, + E0312, + "lifetime of reference outlives lifetime of borrowed content..." + ); + note_and_explain_region( + self.tcx, + &mut err, + "...the reference is valid for ", + sub, + "...", + None, + ); + note_and_explain_region( + self.tcx, + &mut err, + "...but the borrowed content is only valid for ", + sup, + "", + None, + ); + err + } + infer::ReborrowUpvar(span, ref upvar_id) => { + let var_name = self.tcx.hir().name(upvar_id.var_path.hir_id); + let mut err = struct_span_err!( + self.tcx.sess, + span, + E0313, + "lifetime of borrowed pointer outlives lifetime of captured variable `{}`...", + var_name + ); + note_and_explain_region( + self.tcx, + &mut err, + "...the borrowed pointer is valid for ", + sub, + "...", + None, + ); + note_and_explain_region( + self.tcx, + &mut err, + &format!("...but `{}` is only valid for ", var_name), + sup, + "", + None, + ); + err + } + infer::RelateObjectBound(span) => { + let mut err = struct_span_err!( + self.tcx.sess, + span, + E0476, + "lifetime of the source pointer does not outlive lifetime bound of the \ + object type" + ); + note_and_explain_region( + self.tcx, + &mut err, + "object type is valid for ", + sub, + "", + None, + ); + note_and_explain_region( + self.tcx, + &mut err, + "source pointer is only valid for ", + sup, + "", + None, + ); + err + } + infer::RelateParamBound(span, ty, opt_span) => { + let mut err = struct_span_err!( + self.tcx.sess, + span, + E0477, + "the type `{}` does not fulfill the required lifetime", + self.ty_to_string(ty) + ); + match *sub { + ty::ReStatic => note_and_explain_region( + self.tcx, + &mut err, + "type must satisfy ", + sub, + if opt_span.is_some() { " as required by this binding" } else { "" }, + opt_span, + ), + _ => note_and_explain_region( + self.tcx, + &mut err, + "type must outlive ", + sub, + if opt_span.is_some() { " as required by this binding" } else { "" }, + opt_span, + ), + } + err + } + infer::RelateRegionParamBound(span) => { + let mut err = + struct_span_err!(self.tcx.sess, span, E0478, "lifetime bound not satisfied"); + note_and_explain_region( + self.tcx, + &mut err, + "lifetime parameter instantiated with ", + sup, + "", + None, + ); + note_and_explain_region( + self.tcx, + &mut err, + "but lifetime parameter must outlive ", + sub, + "", + None, + ); + err + } + infer::DataBorrowed(ty, span) => { + let mut err = struct_span_err!( + self.tcx.sess, + span, + E0490, + "a value of type `{}` is borrowed for too long", + self.ty_to_string(ty) + ); + note_and_explain_region( + self.tcx, + &mut err, + "the type is valid for ", + sub, + "", + None, + ); + note_and_explain_region( + self.tcx, + &mut err, + "but the borrow lasts for ", + sup, + "", + None, + ); + err + } + infer::ReferenceOutlivesReferent(ty, span) => { + let mut err = struct_span_err!( + self.tcx.sess, + span, + E0491, + "in type `{}`, reference has a longer lifetime than the data it references", + self.ty_to_string(ty) + ); + note_and_explain_region( + self.tcx, + &mut err, + "the pointer is valid for ", + sub, + "", + None, + ); + note_and_explain_region( + self.tcx, + &mut err, + "but the referenced data is only valid for ", + sup, + "", + None, + ); + err + } + infer::CompareImplItemObligation { span, impl_item_def_id, trait_item_def_id } => self + .report_extra_impl_obligation( + span, + impl_item_def_id, + trait_item_def_id, + &format!("`{}: {}`", sup, sub), + ), + infer::CheckAssociatedTypeBounds { impl_item_def_id, trait_item_def_id, parent } => { + let mut err = self.report_concrete_failure(*parent, sub, sup); + + let trait_item_span = self.tcx.def_span(trait_item_def_id); + let item_name = self.tcx.item_name(impl_item_def_id.to_def_id()); + err.span_label( + trait_item_span, + format!("definition of `{}` from trait", item_name), + ); + + let trait_predicates = self.tcx.explicit_predicates_of(trait_item_def_id); + let impl_predicates = self.tcx.explicit_predicates_of(impl_item_def_id); + + let impl_predicates: rustc_data_structures::fx::FxHashSet<_> = + impl_predicates.predicates.into_iter().map(|(pred, _)| pred).collect(); + let clauses: Vec<_> = trait_predicates + .predicates + .into_iter() + .filter(|&(pred, _)| !impl_predicates.contains(pred)) + .map(|(pred, _)| format!("{}", pred)) + .collect(); + + if !clauses.is_empty() { + let generics = self.tcx.hir().get_generics(impl_item_def_id).unwrap(); + let where_clause_span = generics.tail_span_for_predicate_suggestion(); + + let suggestion = format!( + "{} {}", + generics.add_where_or_trailing_comma(), + clauses.join(", "), + ); + err.span_suggestion( + where_clause_span, + &format!( + "try copying {} from the trait", + if clauses.len() > 1 { "these clauses" } else { "this clause" } + ), + suggestion, + rustc_errors::Applicability::MaybeIncorrect, + ); + } + + err + } + } + } + + pub(super) fn report_placeholder_failure( + &self, + placeholder_origin: SubregionOrigin<'tcx>, + sub: Region<'tcx>, + sup: Region<'tcx>, + ) -> DiagnosticBuilder<'tcx, ErrorGuaranteed> { + // I can't think how to do better than this right now. -nikomatsakis + debug!(?placeholder_origin, ?sub, ?sup, "report_placeholder_failure"); + match placeholder_origin { + infer::Subtype(box ref trace) + if matches!( + &trace.cause.code().peel_derives(), + ObligationCauseCode::BindingObligation(..) + ) => + { + // Hack to get around the borrow checker because trace.cause has an `Rc`. + if let ObligationCauseCode::BindingObligation(_, span) = + &trace.cause.code().peel_derives() + { + let span = *span; + let mut err = self.report_concrete_failure(placeholder_origin, sub, sup); + err.span_note(span, "the lifetime requirement is introduced here"); + err + } else { + unreachable!() + } + } + infer::Subtype(box trace) => { + let terr = TypeError::RegionsPlaceholderMismatch; + return self.report_and_explain_type_error(trace, &terr); + } + _ => return self.report_concrete_failure(placeholder_origin, sub, sup), + } + } +} -- cgit v1.2.3