diff options
Diffstat (limited to 'compiler/rustc_infer/src/infer/error_reporting/mod.rs')
| -rw-r--r-- | compiler/rustc_infer/src/infer/error_reporting/mod.rs | 3121 |
1 files changed, 3121 insertions, 0 deletions
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<Span>, +) { + 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<Span>, +) -> (String, Option<Span>) { + 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<Span>, + 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<Span>, + 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<RegionResolutionError<'tcx>> { + debug!("process_errors()"); + + // We want to avoid reporting generic-bound failures if we can + // avoid it: these have a very high rate of being unhelpful in + // practice. This is because they are basically secondary + // checks that test the state of the region graph after the + // rest of inference is done, and the other kinds of errors + // indicate that the region constraint graph is internally + // inconsistent, so these test results are likely to be + // meaningless. + // + // Therefore, we filter them out of the list unless they are + // the only thing in the list. + + let is_bound_failure = |e: &RegionResolutionError<'tcx>| match *e { + RegionResolutionError::GenericBoundFailure(..) => true, + RegionResolutionError::ConcreteFailure(..) + | RegionResolutionError::SubSupConflict(..) + | 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<String>; + 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<Self::Region, Self::Error> { + Err(NonTrivialPath) + } + + fn print_type(self, _ty: Ty<'tcx>) -> Result<Self::Type, Self::Error> { + Err(NonTrivialPath) + } + + fn print_dyn_existential( + self, + _predicates: &'tcx ty::List<ty::Binder<'tcx, ty::ExistentialPredicate<'tcx>>>, + ) -> Result<Self::DynExistential, Self::Error> { + Err(NonTrivialPath) + } + + fn print_const(self, _ct: ty::Const<'tcx>) -> Result<Self::Const, Self::Error> { + Err(NonTrivialPath) + } + + fn path_crate(self, cnum: CrateNum) -> Result<Self::Path, Self::Error> { + Ok(vec![self.tcx.crate_name(cnum).to_string()]) + } + fn path_qualified( + self, + _self_ty: Ty<'tcx>, + _trait_ref: Option<ty::TraitRef<'tcx>>, + ) -> Result<Self::Path, Self::Error> { + Err(NonTrivialPath) + } + + fn path_append_impl( + self, + _print_prefix: impl FnOnce(Self) -> Result<Self::Path, Self::Error>, + _disambiguated_data: &DisambiguatedDefPathData, + _self_ty: Ty<'tcx>, + _trait_ref: Option<ty::TraitRef<'tcx>>, + ) -> Result<Self::Path, Self::Error> { + Err(NonTrivialPath) + } + fn path_append( + self, + print_prefix: impl FnOnce(Self) -> Result<Self::Path, Self::Error>, + disambiguated_data: &DisambiguatedDefPathData, + ) -> Result<Self::Path, Self::Error> { + 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<Self::Path, Self::Error>, + _args: &[GenericArg<'tcx>], + ) -> Result<Self::Path, Self::Error> { + 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<ty::error::ExpectedFound<Ty<'tcx>>>, + 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<hir::HirId>, + first_ty: Ty<'tcx>, + first_span: Span, + second_id: Option<hir::HirId>, + 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<Item = Span>, + ) { + 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<dyn".to_string()), + (return_sp.shrink_to_hi(), ">".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::<Vec<_>>(); + 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<Bar<Qux>> + /// ^^^^--------^ this is highlighted + /// | | + /// | this type argument is exactly the same as the other type, not highlighted + /// this is highlighted + /// Bar<Qux> + /// -------- this type is the same as a type argument in the other type, not highlighted + /// ``` + fn highlight_outer( + &self, + value: &mut DiagnosticStyledString, + other_value: &mut DiagnosticStyledString, + name: String, + sub: ty::subst::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::<Vec<_>>() + .join(", "); + if !lifetimes.is_empty() { + if sub.regions().count() < len { + value.push_normal(lifetimes + ", "); + } else { + value.push_normal(lifetimes); + } + } + + // Highlight all the type arguments that aren't at `pos` and compare the type argument at + // `pos` and `other_ty`. + for (i, type_arg) in sub.types().enumerate() { + if i == pos { + let values = self.cmp(type_arg, other_ty); + value.0.extend((values.0).0); + other_value.0.extend((values.1).0); + } else { + value.push_highlighted(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<Bar<Qux>> = foo::<Bar<Qux>>(); + /// ``` + /// + /// The type error output will behave in the following way: + /// + /// ```text + /// Foo<Bar<Qux>> + /// ^^^^--------^ this is highlighted + /// | | + /// | this type argument is exactly the same as the other type, not highlighted + /// this is highlighted + /// Bar<Qux> + /// -------- this type is the same as a type argument in the other type, not highlighted + /// ``` + fn cmp_type_arg( + &self, + mut t1_out: &mut DiagnosticStyledString, + mut t2_out: &mut DiagnosticStyledString, + path: String, + sub: &'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<String> = 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<Bar, Qux> = y::<Foo<Quz, Qux>>(); + // Foo<Bar, _> + // Foo<Quz, _> + // --- ^ type argument elided + // | + // highlighted in output + values.0.push_normal(path1); + values.1.push_normal(path2); + + // 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<Bar<Qux> = foo::<Bar<Qux>>(); + // Foo<Bar<Qux> + // ------- this type argument is exactly the same as the other type + // Bar<Qux> + if self + .cmp_type_arg( + &mut values.0, + &mut values.1, + path1.clone(), + sub_no_defaults_1, + path2.clone(), + t2, + ) + .is_some() + { + return values; + } + // Check for case: + // let x: Bar<Qux> = y:<Foo<Bar<Qux>>>(); + // Bar<Qux> + // Foo<Bar<Qux>> + // ------- this type argument is exactly the same as the other type + if self + .cmp_type_arg( + &mut values.1, + &mut values.0, + path2, + 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<Qux> = y:<foo::bar::Bar<Zar>>(); + // foo::bar::Baz<Qux> + // foo::bar::Bar<Zar> + // -------- 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<ValuePairs<'tcx>>, + 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<TyCategory, FxHashSet<Span>>, + expected: FxHashMap<TyCategory, FxHashSet<Span>>, + found: FxHashMap<TyCategory, FxHashSet<Span>>, + 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<TyCategory, FxHashSet<Span>>, + ) { + 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<Self::BreakTy> { + 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<Ty<'a>>), + 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<Ty<'tcx>>, + 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<Binder<'tcx, Ty<'tcx>>> { + 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<Output=U>` 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<Ty<'tcx>>, + 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<Ty<'tcx>>, + 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<Ty<'tcx>>, + 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<T>` to `Option<&T>` using \ + `.as_ref()`"; + let result_msg = "you can convert from `&Result<T, E>` 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<Ty<'tcx>>, + ) { + 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<ty::Term<'tcx>>, + ) -> 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<T: fmt::Display + TypeFoldable<'tcx>>( + &self, + exp_found: ty::error::ExpectedFound<T>, + ) -> 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<SubregionOrigin<'tcx>>, + 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<SubregionOrigin<'tcx>>, + 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::<Vec<_>>(); + 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, T>(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::<Vec<_>>(); + err.span_note(spans, "consider returning one of these bindings"); + true + } + _ => false, + } + } +} |