make regionerrors a typedef

Author: mark-i-m

src/librustc_mir/borrow_check/diagnostics/region_errors.rs

@@ -63,10 +63,7 @@ enum Trace {
 
 /// A collection of errors encountered during region inference. This is needed to efficiently
 /// report errors after borrow checking.
-#[derive(Clone, Debug)]
-crate struct RegionErrors<'tcx> {
-    errors: smallvec::SmallVec<[RegionErrorKind<'tcx>; 4]>,
-}
+crate type RegionErrors<'tcx> = smallvec::SmallVec<[RegionErrorKind<'tcx>; 4]>;
 
 #[derive(Clone, Debug)]
 crate enum RegionErrorKind<'tcx> {
@@ -155,22 +152,6 @@ pub struct ErrorConstraintInfo {
     pub(super) span: Span,
 }
 
-impl<'tcx> RegionErrors<'tcx> {
-    pub fn new() -> Self {
-        RegionErrors {
-            errors: smallvec::SmallVec::new(),
-        }
-    }
-
-    pub fn push(&mut self, error: RegionErrorKind<'tcx>) {
-        self.errors.push(error)
-    }
-
-    pub fn into_iter(self) -> impl Iterator<Item=RegionErrorKind<'tcx>> {
-        self.errors.into_iter()
-    }
-}
-
 impl<'tcx> RegionInferenceContext<'tcx> {
     /// Converts a region inference variable into a `ty::Region` that
     /// we can use for error reporting. If `r` is universally bound,