Rollup merge of #106714 - Ezrashaw:remove-e0490, r=davidtwco

remove unreachable error code `E0490`

AFAIK, the untested and undocumented error code `E0490` is now unreachable, it was from the days of the original borrow checker.

cc ``@GuillaumeGomez`` #61137

compiler/rustc_infer/src/infer/error_reporting/note.rs

@@ -29,15 +29,6 @@ impl<'tcx> TypeErrCtxt<'_, 'tcx> {
                 RegionOriginNote::Plain { span, msg: fluent::infer_relate_object_bound }
                     .add_to_diagnostic(err);
             }
-            infer::DataBorrowed(ty, span) => {
-                RegionOriginNote::WithName {
-                    span,
-                    msg: fluent::infer_data_borrowed,
-                    name: &self.ty_to_string(ty),
-                    continues: false,
-                }
-                .add_to_diagnostic(err);
-            }
             infer::ReferenceOutlivesReferent(ty, span) => {
                 RegionOriginNote::WithName {
                     span,
@@ -227,32 +218,6 @@ impl<'tcx> TypeErrCtxt<'_, 'tcx> {
                 );
                 err
             }
-            infer::DataBorrowed(ty, span) => {
-                let mut err = struct_span_err!(
-                    self.tcx.sess,
-                    span,
-                    E0490,
-                    "a value of type `{}` is borrowed for too long",
-                    self.ty_to_string(ty)
-                );
-                note_and_explain_region(
-                    self.tcx,
-                    &mut err,
-                    "the type is valid for ",
-                    sub,
-                    "",
-                    None,
-                );
-                note_and_explain_region(
-                    self.tcx,
-                    &mut err,
-                    "but the borrow lasts for ",
-                    sup,
-                    "",
-                    None,
-                );
-                err
-            }
             infer::ReferenceOutlivesReferent(ty, span) => {
                 let mut err = struct_span_err!(
                     self.tcx.sess,

compiler/rustc_infer/src/infer/lexical_region_resolve/mod.rs

@@ -702,26 +702,8 @@ impl<'cx, 'tcx> LexicalResolver<'cx, 'tcx> {
                     // Obtain the spans for all the places that can
                     // influence the constraints on this value for
                     // richer diagnostics in `static_impl_trait`.
-                    let influences: Vec<Span> = self
-                        .data
-                        .constraints
-                        .iter()
-                        .filter_map(|(constraint, origin)| match (constraint, origin) {
-                            (
-                                Constraint::VarSubVar(_, sup),
-                                SubregionOrigin::DataBorrowed(_, sp),
-                            ) if sup == &node_vid => Some(*sp),
-                            _ => None,
-                        })
-                        .collect();
 
-                    self.collect_error_for_expanding_node(
-                        graph,
-                        &mut dup_vec,
-                        node_vid,
-                        errors,
-                        influences,
-                    );
+                    self.collect_error_for_expanding_node(graph, &mut dup_vec, node_vid, errors);
                 }
             }
         }
@@ -775,7 +757,6 @@ impl<'cx, 'tcx> LexicalResolver<'cx, 'tcx> {
         dup_vec: &mut IndexVec<RegionVid, Option<RegionVid>>,
         node_idx: RegionVid,
         errors: &mut Vec<RegionResolutionError<'tcx>>,
-        influences: Vec<Span>,
     ) {
         // Errors in expanding nodes result from a lower-bound that is
         // not contained by an upper-bound.
@@ -830,7 +811,7 @@ impl<'cx, 'tcx> LexicalResolver<'cx, 'tcx> {
                         lower_bound.region,
                         upper_bound.origin.clone(),
                         upper_bound.region,
-                        influences,
+                        vec![],
                     ));
                     return;
                 }

compiler/rustc_infer/src/infer/mod.rs

@@ -410,9 +410,6 @@ pub enum SubregionOrigin<'tcx> {
     /// Creating a pointer `b` to contents of another reference
     Reborrow(Span),
 
-    /// Data with type `Ty<'tcx>` was borrowed
-    DataBorrowed(Ty<'tcx>, Span),
-
     /// (&'a &'b T) where a >= b
     ReferenceOutlivesReferent(Ty<'tcx>, Span),
 
@@ -1978,7 +1975,6 @@ impl<'tcx> SubregionOrigin<'tcx> {
             RelateParamBound(a, ..) => a,
             RelateRegionParamBound(a) => a,
             Reborrow(a) => a,
-            DataBorrowed(_, a) => a,
             ReferenceOutlivesReferent(_, a) => a,
             CompareImplItemObligation { span, .. } => span,
             AscribeUserTypeProvePredicate(span) => span,