Simplify BoundUniversalRegionError

Author: matthewjasper

compiler/rustc_mir/src/borrow_check/diagnostics/region_errors.rs

@@ -75,8 +75,8 @@ crate enum RegionErrorKind<'tcx> {
         longer_fr: RegionVid,
         /// The region element that erroneously must be outlived by `longer_fr`.
         error_element: RegionElement,
-        /// The origin of the placeholder region.
-        fr_origin: NllRegionVariableOrigin,
+        /// The placeholder region.
+        placeholder: ty::PlaceholderRegion,
     },
 
     /// Any other lifetime error.
@@ -210,17 +210,17 @@ impl<'a, 'tcx> MirBorrowckCtxt<'a, 'tcx> {
 
                 RegionErrorKind::BoundUniversalRegionError {
                     longer_fr,
-                    fr_origin,
+                    placeholder,
                     error_element,
                 } => {
-                    let error_region = self.regioncx.region_from_element(longer_fr, error_element);
+                    let error_vid = self.regioncx.region_from_element(longer_fr, error_element);
 
                     // Find the code to blame for the fact that `longer_fr` outlives `error_fr`.
                     let (_, span) = self.regioncx.find_outlives_blame_span(
                         &self.body,
                         longer_fr,
-                        fr_origin,
-                        error_region,
+                        NllRegionVariableOrigin::Placeholder(placeholder),
+                        error_vid,
                     );
 
                     // FIXME: improve this error message

compiler/rustc_mir/src/borrow_check/region_infer/mod.rs

@@ -1632,7 +1632,7 @@ impl<'tcx> RegionInferenceContext<'tcx> {
         errors_buffer.push(RegionErrorKind::BoundUniversalRegionError {
             longer_fr,
             error_element,
-            fr_origin: NllRegionVariableOrigin::Placeholder(placeholder),
+            placeholder,
         });
     }
 

compiler/rustc_mir/src/borrow_check/region_infer/values.rs

@@ -114,7 +114,7 @@ rustc_index::newtype_index! {
 
 /// An individual element in a region value -- the value of a
 /// particular region variable consists of a set of these elements.
-#[derive(Debug, Clone)]
+#[derive(Debug, Copy, Clone)]
 crate enum RegionElement {
     /// A point in the control-flow graph.
     Location(Location),