Code change:
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If it's ok, I would like to give a shot. If you plan to work on it, please go ahead.
It's yours :)
claim
Hi, I would like to ask a question... I'm reading the code now and am thinking of extending the error messages by adding to . My plan is that start adding some fields (like ty::TraitRef) to and dbg! the output to get the value of trait information like for a new error message. Is my approach out of line or is there a better approach for that.
You don't have to hold information of in because we can get the info on-demand by the combination of and . Say you'd add a method of , the code will be something like this: For getting the name of the trait in question, or will be handy for you.
I appreciate your answer.
are you still working on this? :)

Related discussion:
text: } } <ins> /// Suggests moving redundant argument(s) of an associate function to the /// trait it belongs to. /// /// ```compile_fail /// Into::into::<Option<_>>(42) // suggests considering `Into::<Option<_>>::into(42)` /// ``` fn suggest_moving_args_from_assoc_fn_to_trait(&self, err: &mut Diagnostic) { let trait_ = match self.tcx.trait_of_item(self.def_id) { Some(def_id) => def_id, None => return, }; // Skip suggestion when the associated function is itself generic, it is unclear // how to split the provided parameters between those to suggest to the trait and // those to remain on the associated type. let num_assoc_fn_expected_args = self.num_expected_type_or_const_args() + self.num_expected_lifetime_args(); if num_assoc_fn_expected_args > 0 { return; } let num_assoc_fn_excess_args = self.num_excess_type_or_const_args() + self.num_excess_lifetime_args(); let trait_generics = self.tcx.generics_of(trait_); let num_trait_generics_except_self = trait_generics.count() - if trait_generics.has_self { 1 } else { 0 }; let msg = format!( "consider moving {these} generic argument{s} to the `{name}` trait, which takes up to {num} argument{s}", these = pluralize!("this", num_assoc_fn_excess_args), s = pluralize!(num_assoc_fn_excess_args), name = self.tcx.item_name(trait_), num = num_trait_generics_except_self, ); if let Some(hir_id) = self.path_segment.hir_id && let Some(parent_node) = self.tcx.hir().find_parent_node(hir_id) && let Some(parent_node) = self.tcx.hir().find(parent_node) && let hir::Node::Expr(expr) = parent_node { match expr.kind { hir::ExprKind::Path(ref qpath) => { self.suggest_moving_args_from_assoc_fn_to_trait_for_qualified_path( err, qpath, msg, num_assoc_fn_excess_args, num_trait_generics_except_self ) }, hir::ExprKind::MethodCall(..) => { self.suggest_moving_args_from_assoc_fn_to_trait_for_method_call( err, trait_, expr, msg, num_assoc_fn_excess_args, num_trait_generics_except_self ) }, _ => return, } } } fn suggest_moving_args_from_assoc_fn_to_trait_for_qualified_path( &self, err: &mut Diagnostic, qpath: &'tcx hir::QPath<'tcx>, msg: String, num_assoc_fn_excess_args: usize, num_trait_generics_except_self: usize, ) { if let hir::QPath::Resolved(_, path) = qpath && let Some(trait_path_segment) = path.segments.get(0) { let num_generic_args_supplied_to_trait = trait_path_segment.args().num_generic_params(); if num_assoc_fn_excess_args == num_trait_generics_except_self - num_generic_args_supplied_to_trait { if let Some(span) = self.gen_args.span_ext() && let Ok(snippet) = self.tcx.sess.source_map().span_to_snippet(span) { let sugg = vec![ (self.path_segment.ident.span, format!("{}::{}", snippet, self.path_segment.ident)), (span.with_lo(self.path_segment.ident.span.hi()), "".to_owned()) ]; err.multipart_suggestion( msg, sugg, Applicability::MaybeIncorrect ); } } } } fn suggest_moving_args_from_assoc_fn_to_trait_for_method_call( &self, err: &mut Diagnostic, trait_: DefId, expr: &'tcx hir::Expr<'tcx>, msg: String, num_assoc_fn_excess_args: usize, num_trait_generics_except_self: usize, ) { if let hir::ExprKind::MethodCall(_, args, _) = expr.kind { assert_eq!(args.len(), 1); if num_assoc_fn_excess_args == num_trait_generics_except_self { if let Some(gen_args) = self.gen_args.span_ext() && let Ok(gen_args) = self.tcx.sess.source_map().span_to_snippet(gen_args) && let Ok(args) = self.tcx.sess.source_map().span_to_snippet(args[0].span) { let sugg = format!("{}::{}::{}({})", self.tcx.item_name(trait_), gen_args, self.tcx.item_name(self.def_id), args); err.span_suggestion(expr.span, msg, sugg, Applicability::MaybeIncorrect); } } } } </ins> /// Suggests to remove redundant argument(s): /// /// ```text