diff options
Diffstat (limited to 'compiler/rustc_trait_selection/src/traits/error_reporting/on_unimplemented.rs')
| -rw-r--r-- | compiler/rustc_trait_selection/src/traits/error_reporting/on_unimplemented.rs | 272 |
1 files changed, 272 insertions, 0 deletions
diff --git a/compiler/rustc_trait_selection/src/traits/error_reporting/on_unimplemented.rs b/compiler/rustc_trait_selection/src/traits/error_reporting/on_unimplemented.rs new file mode 100644 index 000000000..e6907637c --- /dev/null +++ b/compiler/rustc_trait_selection/src/traits/error_reporting/on_unimplemented.rs @@ -0,0 +1,272 @@ +use super::{ + ObligationCauseCode, OnUnimplementedDirective, OnUnimplementedNote, PredicateObligation, +}; +use crate::infer::InferCtxt; +use rustc_hir as hir; +use rustc_hir::def_id::DefId; +use rustc_middle::ty::subst::{Subst, SubstsRef}; +use rustc_middle::ty::{self, GenericParamDefKind}; +use rustc_span::symbol::sym; +use std::iter; + +use super::InferCtxtPrivExt; + +pub trait InferCtxtExt<'tcx> { + /*private*/ + fn impl_similar_to( + &self, + trait_ref: ty::PolyTraitRef<'tcx>, + obligation: &PredicateObligation<'tcx>, + ) -> Option<(DefId, SubstsRef<'tcx>)>; + + /*private*/ + fn describe_enclosure(&self, hir_id: hir::HirId) -> Option<&'static str>; + + fn on_unimplemented_note( + &self, + trait_ref: ty::PolyTraitRef<'tcx>, + obligation: &PredicateObligation<'tcx>, + ) -> OnUnimplementedNote; +} + +impl<'a, 'tcx> InferCtxtExt<'tcx> for InferCtxt<'a, 'tcx> { + fn impl_similar_to( + &self, + trait_ref: ty::PolyTraitRef<'tcx>, + obligation: &PredicateObligation<'tcx>, + ) -> Option<(DefId, SubstsRef<'tcx>)> { + let tcx = self.tcx; + let param_env = obligation.param_env; + let trait_ref = tcx.erase_late_bound_regions(trait_ref); + let trait_self_ty = trait_ref.self_ty(); + + let mut self_match_impls = vec![]; + let mut fuzzy_match_impls = vec![]; + + self.tcx.for_each_relevant_impl(trait_ref.def_id, trait_self_ty, |def_id| { + let impl_substs = self.fresh_substs_for_item(obligation.cause.span, def_id); + let impl_trait_ref = tcx.bound_impl_trait_ref(def_id).unwrap().subst(tcx, impl_substs); + + let impl_self_ty = impl_trait_ref.self_ty(); + + if let Ok(..) = self.can_eq(param_env, trait_self_ty, impl_self_ty) { + self_match_impls.push((def_id, impl_substs)); + + if iter::zip( + trait_ref.substs.types().skip(1), + impl_trait_ref.substs.types().skip(1), + ) + .all(|(u, v)| self.fuzzy_match_tys(u, v, false).is_some()) + { + fuzzy_match_impls.push((def_id, impl_substs)); + } + } + }); + + let impl_def_id_and_substs = if self_match_impls.len() == 1 { + self_match_impls[0] + } else if fuzzy_match_impls.len() == 1 { + fuzzy_match_impls[0] + } else { + return None; + }; + + tcx.has_attr(impl_def_id_and_substs.0, sym::rustc_on_unimplemented) + .then_some(impl_def_id_and_substs) + } + + /// Used to set on_unimplemented's `ItemContext` + /// to be the enclosing (async) block/function/closure + fn describe_enclosure(&self, hir_id: hir::HirId) -> Option<&'static str> { + let hir = self.tcx.hir(); + let node = hir.find(hir_id)?; + match &node { + hir::Node::Item(hir::Item { kind: hir::ItemKind::Fn(sig, _, body_id), .. }) => { + self.describe_generator(*body_id).or_else(|| { + Some(match sig.header { + hir::FnHeader { asyncness: hir::IsAsync::Async, .. } => "an async function", + _ => "a function", + }) + }) + } + hir::Node::TraitItem(hir::TraitItem { + kind: hir::TraitItemKind::Fn(_, hir::TraitFn::Provided(body_id)), + .. + }) => self.describe_generator(*body_id).or_else(|| Some("a trait method")), + hir::Node::ImplItem(hir::ImplItem { + kind: hir::ImplItemKind::Fn(sig, body_id), + .. + }) => self.describe_generator(*body_id).or_else(|| { + Some(match sig.header { + hir::FnHeader { asyncness: hir::IsAsync::Async, .. } => "an async method", + _ => "a method", + }) + }), + hir::Node::Expr(hir::Expr { + kind: hir::ExprKind::Closure(hir::Closure { body, movability, .. }), + .. + }) => self.describe_generator(*body).or_else(|| { + Some(if movability.is_some() { "an async closure" } else { "a closure" }) + }), + hir::Node::Expr(hir::Expr { .. }) => { + let parent_hid = hir.get_parent_node(hir_id); + if parent_hid != hir_id { self.describe_enclosure(parent_hid) } else { None } + } + _ => None, + } + } + + fn on_unimplemented_note( + &self, + trait_ref: ty::PolyTraitRef<'tcx>, + obligation: &PredicateObligation<'tcx>, + ) -> OnUnimplementedNote { + let (def_id, substs) = self + .impl_similar_to(trait_ref, obligation) + .unwrap_or_else(|| (trait_ref.def_id(), trait_ref.skip_binder().substs)); + let trait_ref = trait_ref.skip_binder(); + + let mut flags = vec![( + sym::ItemContext, + self.describe_enclosure(obligation.cause.body_id).map(|s| s.to_owned()), + )]; + + match obligation.cause.code() { + ObligationCauseCode::BuiltinDerivedObligation(..) + | ObligationCauseCode::ImplDerivedObligation(..) + | ObligationCauseCode::DerivedObligation(..) => {} + _ => { + // this is a "direct", user-specified, rather than derived, + // obligation. + flags.push((sym::direct, None)); + } + } + + if let ObligationCauseCode::ItemObligation(item) + | ObligationCauseCode::BindingObligation(item, _) = *obligation.cause.code() + { + // FIXME: maybe also have some way of handling methods + // from other traits? That would require name resolution, + // which we might want to be some sort of hygienic. + // + // Currently I'm leaving it for what I need for `try`. + if self.tcx.trait_of_item(item) == Some(trait_ref.def_id) { + let method = self.tcx.item_name(item); + flags.push((sym::from_method, None)); + flags.push((sym::from_method, Some(method.to_string()))); + } + } + + if let Some(k) = obligation.cause.span.desugaring_kind() { + flags.push((sym::from_desugaring, None)); + flags.push((sym::from_desugaring, Some(format!("{:?}", k)))); + } + + // Add all types without trimmed paths. + ty::print::with_no_trimmed_paths!({ + let generics = self.tcx.generics_of(def_id); + let self_ty = trait_ref.self_ty(); + // This is also included through the generics list as `Self`, + // but the parser won't allow you to use it + flags.push((sym::_Self, Some(self_ty.to_string()))); + if let Some(def) = self_ty.ty_adt_def() { + // We also want to be able to select self's original + // signature with no type arguments resolved + flags.push((sym::_Self, Some(self.tcx.type_of(def.did()).to_string()))); + } + + for param in generics.params.iter() { + let value = match param.kind { + GenericParamDefKind::Type { .. } | GenericParamDefKind::Const { .. } => { + substs[param.index as usize].to_string() + } + GenericParamDefKind::Lifetime => continue, + }; + let name = param.name; + flags.push((name, Some(value))); + + if let GenericParamDefKind::Type { .. } = param.kind { + let param_ty = substs[param.index as usize].expect_ty(); + if let Some(def) = param_ty.ty_adt_def() { + // We also want to be able to select the parameter's + // original signature with no type arguments resolved + flags.push((name, Some(self.tcx.type_of(def.did()).to_string()))); + } + } + } + + if let Some(true) = self_ty.ty_adt_def().map(|def| def.did().is_local()) { + flags.push((sym::crate_local, None)); + } + + // Allow targeting all integers using `{integral}`, even if the exact type was resolved + if self_ty.is_integral() { + flags.push((sym::_Self, Some("{integral}".to_owned()))); + } + + if self_ty.is_array_slice() { + flags.push((sym::_Self, Some("&[]".to_owned()))); + } + + if self_ty.is_fn() { + let fn_sig = self_ty.fn_sig(self.tcx); + let shortname = match fn_sig.unsafety() { + hir::Unsafety::Normal => "fn", + hir::Unsafety::Unsafe => "unsafe fn", + }; + flags.push((sym::_Self, Some(shortname.to_owned()))); + } + + // Slices give us `[]`, `[{ty}]` + if let ty::Slice(aty) = self_ty.kind() { + flags.push((sym::_Self, Some("[]".to_string()))); + if let Some(def) = aty.ty_adt_def() { + // We also want to be able to select the slice's type's original + // signature with no type arguments resolved + flags.push((sym::_Self, Some(format!("[{}]", self.tcx.type_of(def.did()))))); + } + if aty.is_integral() { + flags.push((sym::_Self, Some("[{integral}]".to_string()))); + } + } + + // Arrays give us `[]`, `[{ty}; _]` and `[{ty}; N]` + if let ty::Array(aty, len) = self_ty.kind() { + flags.push((sym::_Self, Some("[]".to_string()))); + let len = len.kind().try_to_value().and_then(|v| v.try_to_machine_usize(self.tcx)); + flags.push((sym::_Self, Some(format!("[{}; _]", aty)))); + if let Some(n) = len { + flags.push((sym::_Self, Some(format!("[{}; {}]", aty, n)))); + } + if let Some(def) = aty.ty_adt_def() { + // We also want to be able to select the array's type's original + // signature with no type arguments resolved + let def_ty = self.tcx.type_of(def.did()); + flags.push((sym::_Self, Some(format!("[{def_ty}; _]")))); + if let Some(n) = len { + flags.push((sym::_Self, Some(format!("[{def_ty}; {n}]")))); + } + } + if aty.is_integral() { + flags.push((sym::_Self, Some("[{integral}; _]".to_string()))); + if let Some(n) = len { + flags.push((sym::_Self, Some(format!("[{{integral}}; {n}]")))); + } + } + } + if let ty::Dynamic(traits, _) = self_ty.kind() { + for t in traits.iter() { + if let ty::ExistentialPredicate::Trait(trait_ref) = t.skip_binder() { + flags.push((sym::_Self, Some(self.tcx.def_path_str(trait_ref.def_id)))) + } + } + } + }); + + if let Ok(Some(command)) = OnUnimplementedDirective::of_item(self.tcx, def_id) { + command.evaluate(self.tcx, trait_ref, &flags) + } else { + OnUnimplementedNote::default() + } + } +} |