From 4c053668d6b170232fadb37082f7c590ce84aa4f Mon Sep 17 00:00:00 2001 From: Nathan Fenner Date: Mon, 6 Feb 2023 17:21:16 -0800 Subject: [PATCH] Split fn_ctxt/adjust_fulfillment_errors from fn_ctxt/checks --- .../src/fn_ctxt/adjust_fulfillment_errors.rs | 374 +++++++++++++++++- .../rustc_hir_typeck/src/fn_ctxt/checks.rs | 370 +---------------- 2 files changed, 374 insertions(+), 370 deletions(-) diff --git a/compiler/rustc_hir_typeck/src/fn_ctxt/adjust_fulfillment_errors.rs b/compiler/rustc_hir_typeck/src/fn_ctxt/adjust_fulfillment_errors.rs index 2eab68050d4..db1acb59927 100644 --- a/compiler/rustc_hir_typeck/src/fn_ctxt/adjust_fulfillment_errors.rs +++ b/compiler/rustc_hir_typeck/src/fn_ctxt/adjust_fulfillment_errors.rs @@ -1,10 +1,382 @@ use crate::FnCtxt; use rustc_hir as hir; use rustc_hir::def::Res; -use rustc_middle::ty::{self, DefIdTree, Ty}; +use rustc_hir::def_id::DefId; +use rustc_infer::traits::ObligationCauseCode; +use rustc_middle::ty::{self, DefIdTree, Ty, TypeSuperVisitable, TypeVisitable, TypeVisitor}; +use rustc_span::{self, Span}; use rustc_trait_selection::traits; +use std::ops::ControlFlow; + impl<'a, 'tcx> FnCtxt<'a, 'tcx> { + pub fn adjust_fulfillment_error_for_expr_obligation( + &self, + error: &mut traits::FulfillmentError<'tcx>, + ) -> bool { + let (traits::ExprItemObligation(def_id, hir_id, idx) | traits::ExprBindingObligation(def_id, _, hir_id, idx)) + = *error.obligation.cause.code().peel_derives() else { return false; }; + let hir = self.tcx.hir(); + let hir::Node::Expr(expr) = hir.get(hir_id) else { return false; }; + + let Some(unsubstituted_pred) = + self.tcx.predicates_of(def_id).instantiate_identity(self.tcx).predicates.into_iter().nth(idx) + else { return false; }; + + let generics = self.tcx.generics_of(def_id); + let predicate_substs = match unsubstituted_pred.kind().skip_binder() { + ty::PredicateKind::Clause(ty::Clause::Trait(pred)) => pred.trait_ref.substs, + ty::PredicateKind::Clause(ty::Clause::Projection(pred)) => pred.projection_ty.substs, + _ => ty::List::empty(), + }; + + let find_param_matching = |matches: &dyn Fn(&ty::ParamTy) -> bool| { + predicate_substs.types().find_map(|ty| { + ty.walk().find_map(|arg| { + if let ty::GenericArgKind::Type(ty) = arg.unpack() + && let ty::Param(param_ty) = ty.kind() + && matches(param_ty) + { + Some(arg) + } else { + None + } + }) + }) + }; + + // Prefer generics that are local to the fn item, since these are likely + // to be the cause of the unsatisfied predicate. + let mut param_to_point_at = find_param_matching(&|param_ty| { + self.tcx.parent(generics.type_param(param_ty, self.tcx).def_id) == def_id + }); + // Fall back to generic that isn't local to the fn item. This will come + // from a trait or impl, for example. + let mut fallback_param_to_point_at = find_param_matching(&|param_ty| { + self.tcx.parent(generics.type_param(param_ty, self.tcx).def_id) != def_id + && param_ty.name != rustc_span::symbol::kw::SelfUpper + }); + // Finally, the `Self` parameter is possibly the reason that the predicate + // is unsatisfied. This is less likely to be true for methods, because + // method probe means that we already kinda check that the predicates due + // to the `Self` type are true. + let mut self_param_to_point_at = + find_param_matching(&|param_ty| param_ty.name == rustc_span::symbol::kw::SelfUpper); + + // Finally, for ambiguity-related errors, we actually want to look + // for a parameter that is the source of the inference type left + // over in this predicate. + if let traits::FulfillmentErrorCode::CodeAmbiguity = error.code { + fallback_param_to_point_at = None; + self_param_to_point_at = None; + param_to_point_at = + self.find_ambiguous_parameter_in(def_id, error.root_obligation.predicate); + } + + if self.closure_span_overlaps_error(error, expr.span) { + return false; + } + + match &expr.kind { + hir::ExprKind::Path(qpath) => { + if let hir::Node::Expr(hir::Expr { + kind: hir::ExprKind::Call(callee, args), + hir_id: call_hir_id, + span: call_span, + .. + }) = hir.get_parent(expr.hir_id) + && callee.hir_id == expr.hir_id + { + if self.closure_span_overlaps_error(error, *call_span) { + return false; + } + + for param in + [param_to_point_at, fallback_param_to_point_at, self_param_to_point_at] + .into_iter() + .flatten() + { + if self.blame_specific_arg_if_possible( + error, + def_id, + param, + *call_hir_id, + callee.span, + None, + args, + ) + { + return true; + } + } + } + // Notably, we only point to params that are local to the + // item we're checking, since those are the ones we are able + // to look in the final `hir::PathSegment` for. Everything else + // would require a deeper search into the `qpath` than I think + // is worthwhile. + if let Some(param_to_point_at) = param_to_point_at + && self.point_at_path_if_possible(error, def_id, param_to_point_at, qpath) + { + return true; + } + } + hir::ExprKind::MethodCall(segment, receiver, args, ..) => { + for param in [param_to_point_at, fallback_param_to_point_at, self_param_to_point_at] + .into_iter() + .flatten() + { + if self.blame_specific_arg_if_possible( + error, + def_id, + param, + hir_id, + segment.ident.span, + Some(receiver), + args, + ) { + return true; + } + } + if let Some(param_to_point_at) = param_to_point_at + && self.point_at_generic_if_possible(error, def_id, param_to_point_at, segment) + { + return true; + } + } + hir::ExprKind::Struct(qpath, fields, ..) => { + if let Res::Def( + hir::def::DefKind::Struct | hir::def::DefKind::Variant, + variant_def_id, + ) = self.typeck_results.borrow().qpath_res(qpath, hir_id) + { + for param in + [param_to_point_at, fallback_param_to_point_at, self_param_to_point_at] + { + if let Some(param) = param { + let refined_expr = self.point_at_field_if_possible( + def_id, + param, + variant_def_id, + fields, + ); + + match refined_expr { + None => {} + Some((refined_expr, _)) => { + error.obligation.cause.span = refined_expr + .span + .find_ancestor_in_same_ctxt(error.obligation.cause.span) + .unwrap_or(refined_expr.span); + return true; + } + } + } + } + } + if let Some(param_to_point_at) = param_to_point_at + && self.point_at_path_if_possible(error, def_id, param_to_point_at, qpath) + { + return true; + } + } + _ => {} + } + + false + } + + fn point_at_path_if_possible( + &self, + error: &mut traits::FulfillmentError<'tcx>, + def_id: DefId, + param: ty::GenericArg<'tcx>, + qpath: &hir::QPath<'tcx>, + ) -> bool { + match qpath { + hir::QPath::Resolved(_, path) => { + if let Some(segment) = path.segments.last() + && self.point_at_generic_if_possible(error, def_id, param, segment) + { + return true; + } + } + hir::QPath::TypeRelative(_, segment) => { + if self.point_at_generic_if_possible(error, def_id, param, segment) { + return true; + } + } + _ => {} + } + + false + } + + fn point_at_generic_if_possible( + &self, + error: &mut traits::FulfillmentError<'tcx>, + def_id: DefId, + param_to_point_at: ty::GenericArg<'tcx>, + segment: &hir::PathSegment<'tcx>, + ) -> bool { + let own_substs = self + .tcx + .generics_of(def_id) + .own_substs(ty::InternalSubsts::identity_for_item(self.tcx, def_id)); + let Some((index, _)) = own_substs + .iter() + .filter(|arg| matches!(arg.unpack(), ty::GenericArgKind::Type(_))) + .enumerate() + .find(|(_, arg)| **arg == param_to_point_at) else { return false }; + let Some(arg) = segment + .args() + .args + .iter() + .filter(|arg| matches!(arg, hir::GenericArg::Type(_))) + .nth(index) else { return false; }; + error.obligation.cause.span = arg + .span() + .find_ancestor_in_same_ctxt(error.obligation.cause.span) + .unwrap_or(arg.span()); + true + } + + fn find_ambiguous_parameter_in>( + &self, + item_def_id: DefId, + t: T, + ) -> Option> { + struct FindAmbiguousParameter<'a, 'tcx>(&'a FnCtxt<'a, 'tcx>, DefId); + impl<'tcx> TypeVisitor<'tcx> for FindAmbiguousParameter<'_, 'tcx> { + type BreakTy = ty::GenericArg<'tcx>; + fn visit_ty(&mut self, ty: Ty<'tcx>) -> std::ops::ControlFlow { + if let Some(origin) = self.0.type_var_origin(ty) + && let rustc_infer::infer::type_variable::TypeVariableOriginKind::TypeParameterDefinition(_, Some(def_id)) = + origin.kind + && let generics = self.0.tcx.generics_of(self.1) + && let Some(index) = generics.param_def_id_to_index(self.0.tcx, def_id) + && let Some(subst) = ty::InternalSubsts::identity_for_item(self.0.tcx, self.1) + .get(index as usize) + { + ControlFlow::Break(*subst) + } else { + ty.super_visit_with(self) + } + } + } + t.visit_with(&mut FindAmbiguousParameter(self, item_def_id)).break_value() + } + + fn closure_span_overlaps_error( + &self, + error: &traits::FulfillmentError<'tcx>, + span: Span, + ) -> bool { + if let traits::FulfillmentErrorCode::CodeSelectionError( + traits::SelectionError::OutputTypeParameterMismatch(_, expected, _), + ) = error.code + && let ty::Closure(def_id, _) | ty::Generator(def_id, ..) = expected.skip_binder().self_ty().kind() + && span.overlaps(self.tcx.def_span(*def_id)) + { + true + } else { + false + } + } + + fn point_at_field_if_possible( + &self, + def_id: DefId, + param_to_point_at: ty::GenericArg<'tcx>, + variant_def_id: DefId, + expr_fields: &[hir::ExprField<'tcx>], + ) -> Option<(&'tcx hir::Expr<'tcx>, Ty<'tcx>)> { + let def = self.tcx.adt_def(def_id); + + let identity_substs = ty::InternalSubsts::identity_for_item(self.tcx, def_id); + let fields_referencing_param: Vec<_> = def + .variant_with_id(variant_def_id) + .fields + .iter() + .filter(|field| { + let field_ty = field.ty(self.tcx, identity_substs); + Self::find_param_in_ty(field_ty.into(), param_to_point_at) + }) + .collect(); + + if let [field] = fields_referencing_param.as_slice() { + for expr_field in expr_fields { + // Look for the ExprField that matches the field, using the + // same rules that check_expr_struct uses for macro hygiene. + if self.tcx.adjust_ident(expr_field.ident, variant_def_id) == field.ident(self.tcx) + { + return Some((expr_field.expr, self.tcx.type_of(field.did))); + } + } + } + + None + } + + /// - `blame_specific_*` means that the function will recursively traverse the expression, + /// looking for the most-specific-possible span to blame. + /// + /// - `point_at_*` means that the function will only go "one level", pointing at the specific + /// expression mentioned. + /// + /// `blame_specific_arg_if_possible` will find the most-specific expression anywhere inside + /// the provided function call expression, and mark it as responsible for the fullfillment + /// error. + fn blame_specific_arg_if_possible( + &self, + error: &mut traits::FulfillmentError<'tcx>, + def_id: DefId, + param_to_point_at: ty::GenericArg<'tcx>, + call_hir_id: hir::HirId, + callee_span: Span, + receiver: Option<&'tcx hir::Expr<'tcx>>, + args: &'tcx [hir::Expr<'tcx>], + ) -> bool { + let ty = self.tcx.type_of(def_id); + if !ty.is_fn() { + return false; + } + let sig = ty.fn_sig(self.tcx).skip_binder(); + let args_referencing_param: Vec<_> = sig + .inputs() + .iter() + .enumerate() + .filter(|(_, ty)| Self::find_param_in_ty((**ty).into(), param_to_point_at)) + .collect(); + // If there's one field that references the given generic, great! + if let [(idx, _)] = args_referencing_param.as_slice() + && let Some(arg) = receiver + .map_or(args.get(*idx), |rcvr| if *idx == 0 { Some(rcvr) } else { args.get(*idx - 1) }) { + + error.obligation.cause.span = arg.span.find_ancestor_in_same_ctxt(error.obligation.cause.span).unwrap_or(arg.span); + + if let hir::Node::Expr(arg_expr) = self.tcx.hir().get(arg.hir_id) { + // This is more specific than pointing at the entire argument. + self.blame_specific_expr_if_possible(error, arg_expr) + } + + error.obligation.cause.map_code(|parent_code| { + ObligationCauseCode::FunctionArgumentObligation { + arg_hir_id: arg.hir_id, + call_hir_id, + parent_code, + } + }); + return true; + } else if args_referencing_param.len() > 0 { + // If more than one argument applies, then point to the callee span at least... + // We have chance to fix this up further in `point_at_generics_if_possible` + error.obligation.cause.span = callee_span; + } + + false + } + /** * Recursively searches for the most-specific blamable expression. * For example, if you have a chain of constraints like: diff --git a/compiler/rustc_hir_typeck/src/fn_ctxt/checks.rs b/compiler/rustc_hir_typeck/src/fn_ctxt/checks.rs index 1055ee953ea..2a1265600de 100644 --- a/compiler/rustc_hir_typeck/src/fn_ctxt/checks.rs +++ b/compiler/rustc_hir_typeck/src/fn_ctxt/checks.rs @@ -26,7 +26,7 @@ use rustc_infer::infer::TypeTrace; use rustc_middle::ty::adjustment::AllowTwoPhase; use rustc_middle::ty::visit::TypeVisitable; -use rustc_middle::ty::{self, DefIdTree, IsSuggestable, Ty, TypeSuperVisitable, TypeVisitor}; +use rustc_middle::ty::{self, DefIdTree, IsSuggestable, Ty}; use rustc_session::Session; use rustc_span::symbol::{kw, Ident}; use rustc_span::{self, sym, Span}; @@ -36,8 +36,6 @@ use std::mem; use std::slice; -use std::ops::ControlFlow; - impl<'a, 'tcx> FnCtxt<'a, 'tcx> { pub(in super::super) fn check_casts(&mut self) { // don't hold the borrow to deferred_cast_checks while checking to avoid borrow checker errors @@ -1758,372 +1756,6 @@ pub(super) fn adjust_fulfillment_errors_for_expr_obligation( } } - fn adjust_fulfillment_error_for_expr_obligation( - &self, - error: &mut traits::FulfillmentError<'tcx>, - ) -> bool { - let (traits::ExprItemObligation(def_id, hir_id, idx) | traits::ExprBindingObligation(def_id, _, hir_id, idx)) - = *error.obligation.cause.code().peel_derives() else { return false; }; - let hir = self.tcx.hir(); - let hir::Node::Expr(expr) = hir.get(hir_id) else { return false; }; - - let Some(unsubstituted_pred) = - self.tcx.predicates_of(def_id).instantiate_identity(self.tcx).predicates.into_iter().nth(idx) - else { return false; }; - - let generics = self.tcx.generics_of(def_id); - let predicate_substs = match unsubstituted_pred.kind().skip_binder() { - ty::PredicateKind::Clause(ty::Clause::Trait(pred)) => pred.trait_ref.substs, - ty::PredicateKind::Clause(ty::Clause::Projection(pred)) => pred.projection_ty.substs, - _ => ty::List::empty(), - }; - - let find_param_matching = |matches: &dyn Fn(&ty::ParamTy) -> bool| { - predicate_substs.types().find_map(|ty| { - ty.walk().find_map(|arg| { - if let ty::GenericArgKind::Type(ty) = arg.unpack() - && let ty::Param(param_ty) = ty.kind() - && matches(param_ty) - { - Some(arg) - } else { - None - } - }) - }) - }; - - // Prefer generics that are local to the fn item, since these are likely - // to be the cause of the unsatisfied predicate. - let mut param_to_point_at = find_param_matching(&|param_ty| { - self.tcx.parent(generics.type_param(param_ty, self.tcx).def_id) == def_id - }); - // Fall back to generic that isn't local to the fn item. This will come - // from a trait or impl, for example. - let mut fallback_param_to_point_at = find_param_matching(&|param_ty| { - self.tcx.parent(generics.type_param(param_ty, self.tcx).def_id) != def_id - && param_ty.name != rustc_span::symbol::kw::SelfUpper - }); - // Finally, the `Self` parameter is possibly the reason that the predicate - // is unsatisfied. This is less likely to be true for methods, because - // method probe means that we already kinda check that the predicates due - // to the `Self` type are true. - let mut self_param_to_point_at = - find_param_matching(&|param_ty| param_ty.name == rustc_span::symbol::kw::SelfUpper); - - // Finally, for ambiguity-related errors, we actually want to look - // for a parameter that is the source of the inference type left - // over in this predicate. - if let traits::FulfillmentErrorCode::CodeAmbiguity = error.code { - fallback_param_to_point_at = None; - self_param_to_point_at = None; - param_to_point_at = - self.find_ambiguous_parameter_in(def_id, error.root_obligation.predicate); - } - - if self.closure_span_overlaps_error(error, expr.span) { - return false; - } - - match &expr.kind { - hir::ExprKind::Path(qpath) => { - if let hir::Node::Expr(hir::Expr { - kind: hir::ExprKind::Call(callee, args), - hir_id: call_hir_id, - span: call_span, - .. - }) = hir.get_parent(expr.hir_id) - && callee.hir_id == expr.hir_id - { - if self.closure_span_overlaps_error(error, *call_span) { - return false; - } - - for param in - [param_to_point_at, fallback_param_to_point_at, self_param_to_point_at] - .into_iter() - .flatten() - { - if self.blame_specific_arg_if_possible( - error, - def_id, - param, - *call_hir_id, - callee.span, - None, - args, - ) - { - return true; - } - } - } - // Notably, we only point to params that are local to the - // item we're checking, since those are the ones we are able - // to look in the final `hir::PathSegment` for. Everything else - // would require a deeper search into the `qpath` than I think - // is worthwhile. - if let Some(param_to_point_at) = param_to_point_at - && self.point_at_path_if_possible(error, def_id, param_to_point_at, qpath) - { - return true; - } - } - hir::ExprKind::MethodCall(segment, receiver, args, ..) => { - for param in [param_to_point_at, fallback_param_to_point_at, self_param_to_point_at] - .into_iter() - .flatten() - { - if self.blame_specific_arg_if_possible( - error, - def_id, - param, - hir_id, - segment.ident.span, - Some(receiver), - args, - ) { - return true; - } - } - if let Some(param_to_point_at) = param_to_point_at - && self.point_at_generic_if_possible(error, def_id, param_to_point_at, segment) - { - return true; - } - } - hir::ExprKind::Struct(qpath, fields, ..) => { - if let Res::Def(DefKind::Struct | DefKind::Variant, variant_def_id) = - self.typeck_results.borrow().qpath_res(qpath, hir_id) - { - for param in - [param_to_point_at, fallback_param_to_point_at, self_param_to_point_at] - { - if let Some(param) = param { - let refined_expr = self.point_at_field_if_possible( - def_id, - param, - variant_def_id, - fields, - ); - - match refined_expr { - None => {} - Some((refined_expr, _)) => { - error.obligation.cause.span = refined_expr - .span - .find_ancestor_in_same_ctxt(error.obligation.cause.span) - .unwrap_or(refined_expr.span); - return true; - } - } - } - } - } - if let Some(param_to_point_at) = param_to_point_at - && self.point_at_path_if_possible(error, def_id, param_to_point_at, qpath) - { - return true; - } - } - _ => {} - } - - false - } - - fn closure_span_overlaps_error( - &self, - error: &traits::FulfillmentError<'tcx>, - span: Span, - ) -> bool { - if let traits::FulfillmentErrorCode::CodeSelectionError( - traits::SelectionError::OutputTypeParameterMismatch(_, expected, _), - ) = error.code - && let ty::Closure(def_id, _) | ty::Generator(def_id, ..) = expected.skip_binder().self_ty().kind() - && span.overlaps(self.tcx.def_span(*def_id)) - { - true - } else { - false - } - } - - /// - `blame_specific_*` means that the function will recursively traverse the expression, - /// looking for the most-specific-possible span to blame. - /// - /// - `point_at_*` means that the function will only go "one level", pointing at the specific - /// expression mentioned. - /// - /// `blame_specific_arg_if_possible` will find the most-specific expression anywhere inside - /// the provided function call expression, and mark it as responsible for the fullfillment - /// error. - fn blame_specific_arg_if_possible( - &self, - error: &mut traits::FulfillmentError<'tcx>, - def_id: DefId, - param_to_point_at: ty::GenericArg<'tcx>, - call_hir_id: hir::HirId, - callee_span: Span, - receiver: Option<&'tcx hir::Expr<'tcx>>, - args: &'tcx [hir::Expr<'tcx>], - ) -> bool { - let ty = self.tcx.type_of(def_id); - if !ty.is_fn() { - return false; - } - let sig = ty.fn_sig(self.tcx).skip_binder(); - let args_referencing_param: Vec<_> = sig - .inputs() - .iter() - .enumerate() - .filter(|(_, ty)| Self::find_param_in_ty((**ty).into(), param_to_point_at)) - .collect(); - // If there's one field that references the given generic, great! - if let [(idx, _)] = args_referencing_param.as_slice() - && let Some(arg) = receiver - .map_or(args.get(*idx), |rcvr| if *idx == 0 { Some(rcvr) } else { args.get(*idx - 1) }) { - - error.obligation.cause.span = arg.span.find_ancestor_in_same_ctxt(error.obligation.cause.span).unwrap_or(arg.span); - - if let hir::Node::Expr(arg_expr) = self.tcx.hir().get(arg.hir_id) { - // This is more specific than pointing at the entire argument. - self.blame_specific_expr_if_possible(error, arg_expr) - } - - error.obligation.cause.map_code(|parent_code| { - ObligationCauseCode::FunctionArgumentObligation { - arg_hir_id: arg.hir_id, - call_hir_id, - parent_code, - } - }); - return true; - } else if args_referencing_param.len() > 0 { - // If more than one argument applies, then point to the callee span at least... - // We have chance to fix this up further in `point_at_generics_if_possible` - error.obligation.cause.span = callee_span; - } - - false - } - - // FIXME: Make this private and move to mod adjust_fulfillment_errors - pub fn point_at_field_if_possible( - &self, - def_id: DefId, - param_to_point_at: ty::GenericArg<'tcx>, - variant_def_id: DefId, - expr_fields: &[hir::ExprField<'tcx>], - ) -> Option<(&'tcx hir::Expr<'tcx>, Ty<'tcx>)> { - let def = self.tcx.adt_def(def_id); - - let identity_substs = ty::InternalSubsts::identity_for_item(self.tcx, def_id); - let fields_referencing_param: Vec<_> = def - .variant_with_id(variant_def_id) - .fields - .iter() - .filter(|field| { - let field_ty = field.ty(self.tcx, identity_substs); - Self::find_param_in_ty(field_ty.into(), param_to_point_at) - }) - .collect(); - - if let [field] = fields_referencing_param.as_slice() { - for expr_field in expr_fields { - // Look for the ExprField that matches the field, using the - // same rules that check_expr_struct uses for macro hygiene. - if self.tcx.adjust_ident(expr_field.ident, variant_def_id) == field.ident(self.tcx) - { - return Some((expr_field.expr, self.tcx.type_of(field.did))); - } - } - } - - None - } - - fn point_at_path_if_possible( - &self, - error: &mut traits::FulfillmentError<'tcx>, - def_id: DefId, - param: ty::GenericArg<'tcx>, - qpath: &QPath<'tcx>, - ) -> bool { - match qpath { - hir::QPath::Resolved(_, path) => { - if let Some(segment) = path.segments.last() - && self.point_at_generic_if_possible(error, def_id, param, segment) - { - return true; - } - } - hir::QPath::TypeRelative(_, segment) => { - if self.point_at_generic_if_possible(error, def_id, param, segment) { - return true; - } - } - _ => {} - } - - false - } - - fn point_at_generic_if_possible( - &self, - error: &mut traits::FulfillmentError<'tcx>, - def_id: DefId, - param_to_point_at: ty::GenericArg<'tcx>, - segment: &hir::PathSegment<'tcx>, - ) -> bool { - let own_substs = self - .tcx - .generics_of(def_id) - .own_substs(ty::InternalSubsts::identity_for_item(self.tcx, def_id)); - let Some((index, _)) = own_substs - .iter() - .filter(|arg| matches!(arg.unpack(), ty::GenericArgKind::Type(_))) - .enumerate() - .find(|(_, arg)| **arg == param_to_point_at) else { return false }; - let Some(arg) = segment - .args() - .args - .iter() - .filter(|arg| matches!(arg, hir::GenericArg::Type(_))) - .nth(index) else { return false; }; - error.obligation.cause.span = arg - .span() - .find_ancestor_in_same_ctxt(error.obligation.cause.span) - .unwrap_or(arg.span()); - true - } - - fn find_ambiguous_parameter_in>( - &self, - item_def_id: DefId, - t: T, - ) -> Option> { - struct FindAmbiguousParameter<'a, 'tcx>(&'a FnCtxt<'a, 'tcx>, DefId); - impl<'tcx> TypeVisitor<'tcx> for FindAmbiguousParameter<'_, 'tcx> { - type BreakTy = ty::GenericArg<'tcx>; - fn visit_ty(&mut self, ty: Ty<'tcx>) -> std::ops::ControlFlow { - if let Some(origin) = self.0.type_var_origin(ty) - && let TypeVariableOriginKind::TypeParameterDefinition(_, Some(def_id)) = - origin.kind - && let generics = self.0.tcx.generics_of(self.1) - && let Some(index) = generics.param_def_id_to_index(self.0.tcx, def_id) - && let Some(subst) = ty::InternalSubsts::identity_for_item(self.0.tcx, self.1) - .get(index as usize) - { - ControlFlow::Break(*subst) - } else { - ty.super_visit_with(self) - } - } - } - t.visit_with(&mut FindAmbiguousParameter(self, item_def_id)).break_value() - } - fn label_fn_like( &self, err: &mut Diagnostic, -- 2.44.0