| use super::TypeErrCtxt; |
| use rustc_errors::Applicability::{MachineApplicable, MaybeIncorrect}; |
| use rustc_errors::{pluralize, Diagnostic, MultiSpan}; |
| use rustc_hir as hir; |
| use rustc_hir::def::DefKind; |
| use rustc_middle::traits::ObligationCauseCode; |
| use rustc_middle::ty::error::ExpectedFound; |
| use rustc_middle::ty::print::Printer; |
| use rustc_middle::{ |
| traits::ObligationCause, |
| ty::{self, error::TypeError, print::FmtPrinter, suggest_constraining_type_param, Ty}, |
| }; |
| use rustc_span::{def_id::DefId, sym, BytePos, Span, Symbol}; |
| |
| impl<'tcx> TypeErrCtxt<'_, 'tcx> { |
| pub fn note_and_explain_type_err( |
| &self, |
| diag: &mut Diagnostic, |
| err: TypeError<'tcx>, |
| cause: &ObligationCause<'tcx>, |
| sp: Span, |
| body_owner_def_id: DefId, |
| ) { |
| use ty::error::TypeError::*; |
| debug!("note_and_explain_type_err err={:?} cause={:?}", err, cause); |
| |
| let tcx = self.tcx; |
| |
| match err { |
| ArgumentSorts(values, _) | Sorts(values) => { |
| match (values.expected.kind(), values.found.kind()) { |
| (ty::Closure(..), ty::Closure(..)) => { |
| diag.note("no two closures, even if identical, have the same type"); |
| diag.help("consider boxing your closure and/or using it as a trait object"); |
| } |
| (ty::Alias(ty::Opaque, ..), ty::Alias(ty::Opaque, ..)) => { |
| // Issue #63167 |
| diag.note("distinct uses of `impl Trait` result in different opaque types"); |
| } |
| (ty::Float(_), ty::Infer(ty::IntVar(_))) |
| if let Ok( |
| // Issue #53280 |
| snippet, |
| ) = tcx.sess.source_map().span_to_snippet(sp) => |
| { |
| if snippet.chars().all(|c| c.is_digit(10) || c == '-' || c == '_') { |
| diag.span_suggestion( |
| sp, |
| "use a float literal", |
| format!("{snippet}.0"), |
| MachineApplicable, |
| ); |
| } |
| } |
| (ty::Param(expected), ty::Param(found)) => { |
| let generics = tcx.generics_of(body_owner_def_id); |
| let e_span = tcx.def_span(generics.type_param(expected, tcx).def_id); |
| if !sp.contains(e_span) { |
| diag.span_label(e_span, "expected type parameter"); |
| } |
| let f_span = tcx.def_span(generics.type_param(found, tcx).def_id); |
| if !sp.contains(f_span) { |
| diag.span_label(f_span, "found type parameter"); |
| } |
| diag.note( |
| "a type parameter was expected, but a different one was found; \ |
| you might be missing a type parameter or trait bound", |
| ); |
| diag.note( |
| "for more information, visit \ |
| https://doc.rust-lang.org/book/ch10-02-traits.html\ |
| #traits-as-parameters", |
| ); |
| } |
| (ty::Alias(ty::Projection | ty::Inherent, _), ty::Alias(ty::Projection | ty::Inherent, _)) => { |
| diag.note("an associated type was expected, but a different one was found"); |
| } |
| // FIXME(inherent_associated_types): Extend this to support `ty::Inherent`, too. |
| (ty::Param(p), ty::Alias(ty::Projection, proj)) | (ty::Alias(ty::Projection, proj), ty::Param(p)) |
| if !tcx.is_impl_trait_in_trait(proj.def_id) => |
| { |
| let p_def_id = tcx |
| .generics_of(body_owner_def_id) |
| .type_param(p, tcx) |
| .def_id; |
| let p_span = tcx.def_span(p_def_id); |
| if !sp.contains(p_span) { |
| diag.span_label(p_span, "this type parameter"); |
| } |
| let hir = tcx.hir(); |
| let mut note = true; |
| let parent = p_def_id |
| .as_local() |
| .and_then(|id| { |
| let local_id = hir.local_def_id_to_hir_id(id); |
| let generics = tcx.hir().find_parent(local_id)?.generics()?; |
| Some((id, generics)) |
| }); |
| if let Some((local_id, generics)) = parent |
| { |
| // Synthesize the associated type restriction `Add<Output = Expected>`. |
| // FIXME: extract this logic for use in other diagnostics. |
| let (trait_ref, assoc_args) = proj.trait_ref_and_own_args(tcx); |
| let item_name = tcx.item_name(proj.def_id); |
| let item_args = self.format_generic_args(assoc_args); |
| |
| // Here, we try to see if there's an existing |
| // trait implementation that matches the one that |
| // we're suggesting to restrict. If so, find the |
| // "end", whether it be at the end of the trait |
| // or the end of the generic arguments. |
| let mut matching_span = None; |
| let mut matched_end_of_args = false; |
| for bound in generics.bounds_for_param(local_id) { |
| let potential_spans = bound |
| .bounds |
| .iter() |
| .find_map(|bound| { |
| let bound_trait_path = bound.trait_ref()?.path; |
| let def_id = bound_trait_path.res.opt_def_id()?; |
| let generic_args = bound_trait_path.segments.iter().last().map(|path| path.args()); |
| (def_id == trait_ref.def_id).then_some((bound_trait_path.span, generic_args)) |
| }); |
| |
| if let Some((end_of_trait, end_of_args)) = potential_spans { |
| let args_span = end_of_args.and_then(|args| args.span()); |
| matched_end_of_args = args_span.is_some(); |
| matching_span = args_span |
| .or_else(|| Some(end_of_trait)) |
| .map(|span| span.shrink_to_hi()); |
| break; |
| } |
| } |
| |
| if matched_end_of_args { |
| // Append suggestion to the end of our args |
| let path = format!(", {item_name}{item_args} = {p}"); |
| note = !suggest_constraining_type_param( |
| tcx, |
| generics, |
| diag, |
| &proj.self_ty().to_string(), |
| &path, |
| None, |
| matching_span, |
| ); |
| } else { |
| // Suggest adding a bound to an existing trait |
| // or if the trait doesn't exist, add the trait |
| // and the suggested bounds. |
| let path = format!("<{item_name}{item_args} = {p}>"); |
| note = !suggest_constraining_type_param( |
| tcx, |
| generics, |
| diag, |
| &proj.self_ty().to_string(), |
| &path, |
| None, |
| matching_span, |
| ); |
| } |
| } |
| if note { |
| diag.note("you might be missing a type parameter or trait bound"); |
| } |
| } |
| (ty::Param(p), ty::Dynamic(..) | ty::Alias(ty::Opaque, ..)) |
| | (ty::Dynamic(..) | ty::Alias(ty::Opaque, ..), ty::Param(p)) => { |
| let generics = tcx.generics_of(body_owner_def_id); |
| let p_span = tcx.def_span(generics.type_param(p, tcx).def_id); |
| if !sp.contains(p_span) { |
| diag.span_label(p_span, "this type parameter"); |
| } |
| diag.help("type parameters must be constrained to match other types"); |
| if tcx.sess.teach(&diag.get_code().unwrap()) { |
| diag.help( |
| "given a type parameter `T` and a method `foo`: |
| ``` |
| trait Trait<T> { fn foo(&self) -> T; } |
| ``` |
| the only ways to implement method `foo` are: |
| - constrain `T` with an explicit type: |
| ``` |
| impl Trait<String> for X { |
| fn foo(&self) -> String { String::new() } |
| } |
| ``` |
| - add a trait bound to `T` and call a method on that trait that returns `Self`: |
| ``` |
| impl<T: std::default::Default> Trait<T> for X { |
| fn foo(&self) -> T { <T as std::default::Default>::default() } |
| } |
| ``` |
| - change `foo` to return an argument of type `T`: |
| ``` |
| impl<T> Trait<T> for X { |
| fn foo(&self, x: T) -> T { x } |
| } |
| ```", |
| ); |
| } |
| diag.note( |
| "for more information, visit \ |
| https://doc.rust-lang.org/book/ch10-02-traits.html\ |
| #traits-as-parameters", |
| ); |
| } |
| (ty::Param(p), ty::Closure(..) | ty::Generator(..)) => { |
| let generics = tcx.generics_of(body_owner_def_id); |
| let p_span = tcx.def_span(generics.type_param(p, tcx).def_id); |
| if !sp.contains(p_span) { |
| diag.span_label(p_span, "this type parameter"); |
| } |
| diag.help(format!( |
| "every closure has a distinct type and so could not always match the \ |
| caller-chosen type of parameter `{p}`" |
| )); |
| } |
| (ty::Param(p), _) | (_, ty::Param(p)) => { |
| let generics = tcx.generics_of(body_owner_def_id); |
| let p_span = tcx.def_span(generics.type_param(p, tcx).def_id); |
| if !sp.contains(p_span) { |
| diag.span_label(p_span, "this type parameter"); |
| } |
| } |
| (ty::Alias(ty::Projection | ty::Inherent, proj_ty), _) if !tcx.is_impl_trait_in_trait(proj_ty.def_id) => { |
| self.expected_projection( |
| diag, |
| proj_ty, |
| values, |
| body_owner_def_id, |
| cause.code(), |
| ); |
| } |
| (_, ty::Alias(ty::Projection | ty::Inherent, proj_ty)) if !tcx.is_impl_trait_in_trait(proj_ty.def_id) => { |
| let msg = || format!( |
| "consider constraining the associated type `{}` to `{}`", |
| values.found, values.expected, |
| ); |
| if !(self.suggest_constraining_opaque_associated_type( |
| diag, |
| msg, |
| proj_ty, |
| values.expected, |
| ) || self.suggest_constraint( |
| diag, |
| &msg, |
| body_owner_def_id, |
| proj_ty, |
| values.expected, |
| )) { |
| diag.help(msg()); |
| diag.note( |
| "for more information, visit \ |
| https://doc.rust-lang.org/book/ch19-03-advanced-traits.html", |
| ); |
| } |
| } |
| (ty::Alias(ty::Opaque, alias), _) | (_, ty::Alias(ty::Opaque, alias)) if alias.def_id.is_local() && matches!(tcx.def_kind(body_owner_def_id), DefKind::Fn | DefKind::Static(_) | DefKind::Const | DefKind::AssocFn | DefKind::AssocConst) => { |
| if tcx.is_type_alias_impl_trait(alias.def_id) { |
| if !tcx.opaque_types_defined_by(body_owner_def_id.expect_local()).contains(&alias.def_id.expect_local()) { |
| let sp = tcx.def_ident_span(body_owner_def_id).unwrap_or_else(|| tcx.def_span(body_owner_def_id)); |
| diag.span_note(sp, "\ |
| this item must have the opaque type in its signature \ |
| in order to be able to register hidden types"); |
| } |
| } |
| } |
| (ty::FnPtr(_), ty::FnDef(def, _)) |
| if let hir::def::DefKind::Fn = tcx.def_kind(def) => { |
| diag.note( |
| "when the arguments and return types match, functions can be coerced \ |
| to function pointers", |
| ); |
| } |
| _ => {} |
| } |
| debug!( |
| "note_and_explain_type_err expected={:?} ({:?}) found={:?} ({:?})", |
| values.expected, |
| values.expected.kind(), |
| values.found, |
| values.found.kind(), |
| ); |
| } |
| CyclicTy(ty) => { |
| // Watch out for various cases of cyclic types and try to explain. |
| if ty.is_closure() || ty.is_generator() { |
| diag.note( |
| "closures cannot capture themselves or take themselves as argument;\n\ |
| this error may be the result of a recent compiler bug-fix,\n\ |
| see issue #46062 <https://github.com/rust-lang/rust/issues/46062>\n\ |
| for more information", |
| ); |
| } |
| } |
| TargetFeatureCast(def_id) => { |
| let target_spans = tcx.get_attrs(def_id, sym::target_feature).map(|attr| attr.span); |
| diag.note( |
| "functions with `#[target_feature]` can only be coerced to `unsafe` function pointers" |
| ); |
| diag.span_labels(target_spans, "`#[target_feature]` added here"); |
| } |
| _ => {} |
| } |
| } |
| |
| fn suggest_constraint( |
| &self, |
| diag: &mut Diagnostic, |
| msg: impl Fn() -> String, |
| body_owner_def_id: DefId, |
| proj_ty: &ty::AliasTy<'tcx>, |
| ty: Ty<'tcx>, |
| ) -> bool { |
| let tcx = self.tcx; |
| let assoc = tcx.associated_item(proj_ty.def_id); |
| let (trait_ref, assoc_args) = proj_ty.trait_ref_and_own_args(tcx); |
| if let Some(item) = tcx.hir().get_if_local(body_owner_def_id) { |
| if let Some(hir_generics) = item.generics() { |
| // Get the `DefId` for the type parameter corresponding to `A` in `<A as T>::Foo`. |
| // This will also work for `impl Trait`. |
| let def_id = if let ty::Param(param_ty) = proj_ty.self_ty().kind() { |
| let generics = tcx.generics_of(body_owner_def_id); |
| generics.type_param(param_ty, tcx).def_id |
| } else { |
| return false; |
| }; |
| let Some(def_id) = def_id.as_local() else { |
| return false; |
| }; |
| |
| // First look in the `where` clause, as this might be |
| // `fn foo<T>(x: T) where T: Trait`. |
| for pred in hir_generics.bounds_for_param(def_id) { |
| if self.constrain_generic_bound_associated_type_structured_suggestion( |
| diag, |
| &trait_ref, |
| pred.bounds, |
| assoc, |
| assoc_args, |
| ty, |
| &msg, |
| false, |
| ) { |
| return true; |
| } |
| } |
| } |
| } |
| false |
| } |
| |
| /// An associated type was expected and a different type was found. |
| /// |
| /// We perform a few different checks to see what we can suggest: |
| /// |
| /// - In the current item, look for associated functions that return the expected type and |
| /// suggest calling them. (Not a structured suggestion.) |
| /// - If any of the item's generic bounds can be constrained, we suggest constraining the |
| /// associated type to the found type. |
| /// - If the associated type has a default type and was expected inside of a `trait`, we |
| /// mention that this is disallowed. |
| /// - If all other things fail, and the error is not because of a mismatch between the `trait` |
| /// and the `impl`, we provide a generic `help` to constrain the assoc type or call an assoc |
| /// fn that returns the type. |
| fn expected_projection( |
| &self, |
| diag: &mut Diagnostic, |
| proj_ty: &ty::AliasTy<'tcx>, |
| values: ExpectedFound<Ty<'tcx>>, |
| body_owner_def_id: DefId, |
| cause_code: &ObligationCauseCode<'_>, |
| ) { |
| let tcx = self.tcx; |
| |
| // Don't suggest constraining a projection to something containing itself |
| if self.tcx.erase_regions(values.found).contains(self.tcx.erase_regions(values.expected)) { |
| return; |
| } |
| |
| let msg = || { |
| format!( |
| "consider constraining the associated type `{}` to `{}`", |
| values.expected, values.found |
| ) |
| }; |
| |
| let body_owner = tcx.hir().get_if_local(body_owner_def_id); |
| let current_method_ident = body_owner.and_then(|n| n.ident()).map(|i| i.name); |
| |
| // We don't want to suggest calling an assoc fn in a scope where that isn't feasible. |
| let callable_scope = matches!( |
| body_owner, |
| Some( |
| hir::Node::Item(hir::Item { kind: hir::ItemKind::Fn(..), .. }) |
| | hir::Node::TraitItem(hir::TraitItem { kind: hir::TraitItemKind::Fn(..), .. }) |
| | hir::Node::ImplItem(hir::ImplItem { kind: hir::ImplItemKind::Fn(..), .. }), |
| ) |
| ); |
| let impl_comparison = |
| matches!(cause_code, ObligationCauseCode::CompareImplItemObligation { .. }); |
| let assoc = tcx.associated_item(proj_ty.def_id); |
| if !callable_scope || impl_comparison { |
| // We do not want to suggest calling functions when the reason of the |
| // type error is a comparison of an `impl` with its `trait` or when the |
| // scope is outside of a `Body`. |
| } else { |
| // If we find a suitable associated function that returns the expected type, we don't |
| // want the more general suggestion later in this method about "consider constraining |
| // the associated type or calling a method that returns the associated type". |
| let point_at_assoc_fn = self.point_at_methods_that_satisfy_associated_type( |
| diag, |
| assoc.container_id(tcx), |
| current_method_ident, |
| proj_ty.def_id, |
| values.expected, |
| ); |
| // Possibly suggest constraining the associated type to conform to the |
| // found type. |
| if self.suggest_constraint(diag, &msg, body_owner_def_id, proj_ty, values.found) |
| || point_at_assoc_fn |
| { |
| return; |
| } |
| } |
| |
| self.suggest_constraining_opaque_associated_type(diag, &msg, proj_ty, values.found); |
| |
| if self.point_at_associated_type(diag, body_owner_def_id, values.found) { |
| return; |
| } |
| |
| if !impl_comparison { |
| // Generic suggestion when we can't be more specific. |
| if callable_scope { |
| diag.help(format!( |
| "{} or calling a method that returns `{}`", |
| msg(), |
| values.expected |
| )); |
| } else { |
| diag.help(msg()); |
| } |
| diag.note( |
| "for more information, visit \ |
| https://doc.rust-lang.org/book/ch19-03-advanced-traits.html", |
| ); |
| } |
| if tcx.sess.teach(&diag.get_code().unwrap()) { |
| diag.help( |
| "given an associated type `T` and a method `foo`: |
| ``` |
| trait Trait { |
| type T; |
| fn foo(&self) -> Self::T; |
| } |
| ``` |
| the only way of implementing method `foo` is to constrain `T` with an explicit associated type: |
| ``` |
| impl Trait for X { |
| type T = String; |
| fn foo(&self) -> Self::T { String::new() } |
| } |
| ```", |
| ); |
| } |
| } |
| |
| /// When the expected `impl Trait` is not defined in the current item, it will come from |
| /// a return type. This can occur when dealing with `TryStream` (#71035). |
| fn suggest_constraining_opaque_associated_type( |
| &self, |
| diag: &mut Diagnostic, |
| msg: impl Fn() -> String, |
| proj_ty: &ty::AliasTy<'tcx>, |
| ty: Ty<'tcx>, |
| ) -> bool { |
| let tcx = self.tcx; |
| |
| let assoc = tcx.associated_item(proj_ty.def_id); |
| if let ty::Alias(ty::Opaque, ty::AliasTy { def_id, .. }) = *proj_ty.self_ty().kind() { |
| let opaque_local_def_id = def_id.as_local(); |
| let opaque_hir_ty = if let Some(opaque_local_def_id) = opaque_local_def_id { |
| tcx.hir().expect_item(opaque_local_def_id).expect_opaque_ty() |
| } else { |
| return false; |
| }; |
| |
| let (trait_ref, assoc_args) = proj_ty.trait_ref_and_own_args(tcx); |
| |
| self.constrain_generic_bound_associated_type_structured_suggestion( |
| diag, |
| &trait_ref, |
| opaque_hir_ty.bounds, |
| assoc, |
| assoc_args, |
| ty, |
| msg, |
| true, |
| ) |
| } else { |
| false |
| } |
| } |
| |
| fn point_at_methods_that_satisfy_associated_type( |
| &self, |
| diag: &mut Diagnostic, |
| assoc_container_id: DefId, |
| current_method_ident: Option<Symbol>, |
| proj_ty_item_def_id: DefId, |
| expected: Ty<'tcx>, |
| ) -> bool { |
| let tcx = self.tcx; |
| |
| let items = tcx.associated_items(assoc_container_id); |
| // Find all the methods in the trait that could be called to construct the |
| // expected associated type. |
| // FIXME: consider suggesting the use of associated `const`s. |
| let methods: Vec<(Span, String)> = items |
| .in_definition_order() |
| .filter(|item| { |
| ty::AssocKind::Fn == item.kind |
| && Some(item.name) != current_method_ident |
| && !tcx.is_doc_hidden(item.def_id) |
| }) |
| .filter_map(|item| { |
| let method = tcx.fn_sig(item.def_id).instantiate_identity(); |
| match *method.output().skip_binder().kind() { |
| ty::Alias(ty::Projection, ty::AliasTy { def_id: item_def_id, .. }) |
| if item_def_id == proj_ty_item_def_id => |
| { |
| Some(( |
| tcx.def_span(item.def_id), |
| format!("consider calling `{}`", tcx.def_path_str(item.def_id)), |
| )) |
| } |
| _ => None, |
| } |
| }) |
| .collect(); |
| if !methods.is_empty() { |
| // Use a single `help:` to show all the methods in the trait that can |
| // be used to construct the expected associated type. |
| let mut span: MultiSpan = |
| methods.iter().map(|(sp, _)| *sp).collect::<Vec<Span>>().into(); |
| let msg = format!( |
| "{some} method{s} {are} available that return{r} `{ty}`", |
| some = if methods.len() == 1 { "a" } else { "some" }, |
| s = pluralize!(methods.len()), |
| are = pluralize!("is", methods.len()), |
| r = if methods.len() == 1 { "s" } else { "" }, |
| ty = expected |
| ); |
| for (sp, label) in methods.into_iter() { |
| span.push_span_label(sp, label); |
| } |
| diag.span_help(span, msg); |
| return true; |
| } |
| false |
| } |
| |
| fn point_at_associated_type( |
| &self, |
| diag: &mut Diagnostic, |
| body_owner_def_id: DefId, |
| found: Ty<'tcx>, |
| ) -> bool { |
| let tcx = self.tcx; |
| |
| let Some(hir_id) = body_owner_def_id.as_local() else { |
| return false; |
| }; |
| let Some(hir_id) = tcx.opt_local_def_id_to_hir_id(hir_id) else { |
| return false; |
| }; |
| // When `body_owner` is an `impl` or `trait` item, look in its associated types for |
| // `expected` and point at it. |
| let parent_id = tcx.hir().get_parent_item(hir_id); |
| let item = tcx.hir().find_by_def_id(parent_id.def_id); |
| |
| debug!("expected_projection parent item {:?}", item); |
| |
| let param_env = tcx.param_env(body_owner_def_id); |
| |
| match item { |
| Some(hir::Node::Item(hir::Item { kind: hir::ItemKind::Trait(.., items), .. })) => { |
| // FIXME: account for `#![feature(specialization)]` |
| for item in &items[..] { |
| match item.kind { |
| hir::AssocItemKind::Type => { |
| // FIXME: account for returning some type in a trait fn impl that has |
| // an assoc type as a return type (#72076). |
| if let hir::Defaultness::Default { has_value: true } = |
| tcx.defaultness(item.id.owner_id) |
| { |
| let assoc_ty = tcx.type_of(item.id.owner_id).instantiate_identity(); |
| if self.infcx.can_eq(param_env, assoc_ty, found) { |
| diag.span_label( |
| item.span, |
| "associated type defaults can't be assumed inside the \ |
| trait defining them", |
| ); |
| return true; |
| } |
| } |
| } |
| _ => {} |
| } |
| } |
| } |
| Some(hir::Node::Item(hir::Item { |
| kind: hir::ItemKind::Impl(hir::Impl { items, .. }), |
| .. |
| })) => { |
| for item in &items[..] { |
| if let hir::AssocItemKind::Type = item.kind { |
| let assoc_ty = tcx.type_of(item.id.owner_id).instantiate_identity(); |
| |
| if self.infcx.can_eq(param_env, assoc_ty, found) { |
| diag.span_label(item.span, "expected this associated type"); |
| return true; |
| } |
| } |
| } |
| } |
| _ => {} |
| } |
| false |
| } |
| |
| /// Given a slice of `hir::GenericBound`s, if any of them corresponds to the `trait_ref` |
| /// requirement, provide a structured suggestion to constrain it to a given type `ty`. |
| /// |
| /// `is_bound_surely_present` indicates whether we know the bound we're looking for is |
| /// inside `bounds`. If that's the case then we can consider `bounds` containing only one |
| /// trait bound as the one we're looking for. This can help in cases where the associated |
| /// type is defined on a supertrait of the one present in the bounds. |
| fn constrain_generic_bound_associated_type_structured_suggestion( |
| &self, |
| diag: &mut Diagnostic, |
| trait_ref: &ty::TraitRef<'tcx>, |
| bounds: hir::GenericBounds<'_>, |
| assoc: ty::AssocItem, |
| assoc_args: &[ty::GenericArg<'tcx>], |
| ty: Ty<'tcx>, |
| msg: impl Fn() -> String, |
| is_bound_surely_present: bool, |
| ) -> bool { |
| // FIXME: we would want to call `resolve_vars_if_possible` on `ty` before suggesting. |
| |
| let trait_bounds = bounds.iter().filter_map(|bound| match bound { |
| hir::GenericBound::Trait(ptr, hir::TraitBoundModifier::None) => Some(ptr), |
| _ => None, |
| }); |
| |
| let matching_trait_bounds = trait_bounds |
| .clone() |
| .filter(|ptr| ptr.trait_ref.trait_def_id() == Some(trait_ref.def_id)) |
| .collect::<Vec<_>>(); |
| |
| let span = match &matching_trait_bounds[..] { |
| &[ptr] => ptr.span, |
| &[] if is_bound_surely_present => match &trait_bounds.collect::<Vec<_>>()[..] { |
| &[ptr] => ptr.span, |
| _ => return false, |
| }, |
| _ => return false, |
| }; |
| |
| self.constrain_associated_type_structured_suggestion(diag, span, assoc, assoc_args, ty, msg) |
| } |
| |
| /// Given a span corresponding to a bound, provide a structured suggestion to set an |
| /// associated type to a given type `ty`. |
| fn constrain_associated_type_structured_suggestion( |
| &self, |
| diag: &mut Diagnostic, |
| span: Span, |
| assoc: ty::AssocItem, |
| assoc_args: &[ty::GenericArg<'tcx>], |
| ty: Ty<'tcx>, |
| msg: impl Fn() -> String, |
| ) -> bool { |
| let tcx = self.tcx; |
| |
| if let Ok(has_params) = |
| tcx.sess.source_map().span_to_snippet(span).map(|snippet| snippet.ends_with('>')) |
| { |
| let (span, sugg) = if has_params { |
| let pos = span.hi() - BytePos(1); |
| let span = Span::new(pos, pos, span.ctxt(), span.parent()); |
| (span, format!(", {} = {}", assoc.ident(tcx), ty)) |
| } else { |
| let item_args = self.format_generic_args(assoc_args); |
| (span.shrink_to_hi(), format!("<{}{} = {}>", assoc.ident(tcx), item_args, ty)) |
| }; |
| diag.span_suggestion_verbose(span, msg(), sugg, MaybeIncorrect); |
| return true; |
| } |
| false |
| } |
| |
| pub fn format_generic_args(&self, args: &[ty::GenericArg<'tcx>]) -> String { |
| FmtPrinter::new(self.tcx, hir::def::Namespace::TypeNS) |
| .path_generic_args(Ok, args) |
| .expect("could not write to `String`.") |
| .into_buffer() |
| } |
| } |
