do not limit NiceRegionError to SubSupConflict or ConcreteFailure

Author: nikomatsakis

src/librustc/infer/error_reporting/nice_region_error/different_lifetimes.rs

@@ -45,7 +45,7 @@ impl<'a, 'tcx> NiceRegionError<'a, 'tcx> {
     ///
     /// It will later be extended to trait objects.
     pub(super) fn try_report_anon_anon_conflict(&self) -> Option<ErrorReported> {
-        let (span, sub, sup) = self.regions();
+        let (span, sub, sup) = self.regions()?;
 
         // Determine whether the sub and sup consist of both anonymous (elided) regions.
         let anon_reg_sup = self.tcx().is_suitable_region(sup)?;

src/librustc/infer/error_reporting/nice_region_error/mod.rs

@@ -17,11 +17,6 @@ mod util;
 
 impl<'cx, 'tcx> InferCtxt<'cx, 'tcx> {
     pub fn try_report_nice_region_error(&self, error: &RegionResolutionError<'tcx>) -> bool {
-        match *error {
-            ConcreteFailure(..) | SubSupConflict(..) => {}
-            _ => return false, // inapplicable
-        }
-
         if let Some(tables) = self.in_progress_tables {
             let tables = tables.borrow();
             NiceRegionError::new(self, error.clone(), Some(&tables)).try_report().is_some()
@@ -79,13 +74,14 @@ impl<'cx, 'tcx> NiceRegionError<'cx, 'tcx> {
             .or_else(|| self.try_report_impl_not_conforming_to_trait())
     }
 
-    pub fn regions(&self) -> (Span, ty::Region<'tcx>, ty::Region<'tcx>) {
+    pub fn regions(&self) -> Option<(Span, ty::Region<'tcx>, ty::Region<'tcx>)> {
         match (&self.error, self.regions) {
-            (Some(ConcreteFailure(origin, sub, sup)), None) => (origin.span(), sub, sup),
-            (Some(SubSupConflict(_, _, origin, sub, _, sup)), None) => (origin.span(), sub, sup),
-            (None, Some((span, sub, sup))) => (span, sub, sup),
-            (Some(_), Some(_)) => panic!("incorrectly built NiceRegionError"),
-            _ => panic!("trying to report on an incorrect lifetime failure"),
+            (Some(ConcreteFailure(origin, sub, sup)), None) => Some((origin.span(), sub, sup)),
+            (Some(SubSupConflict(_, _, origin, sub, _, sup)), None) => {
+                Some((origin.span(), sub, sup))
+            }
+            (None, Some((span, sub, sup))) => Some((span, sub, sup)),
+            _ => None,
         }
     }
 }

src/librustc/infer/error_reporting/nice_region_error/named_anon_conflict.rs

@@ -9,7 +9,7 @@ impl<'a, 'tcx> NiceRegionError<'a, 'tcx> {
     /// When given a `ConcreteFailure` for a function with parameters containing a named region and
     /// an anonymous region, emit an descriptive diagnostic error.
     pub(super) fn try_report_named_anon_conflict(&self) -> Option<DiagnosticBuilder<'a>> {
-        let (span, sub, sup) = self.regions();
+        let (span, sub, sup) = self.regions()?;
 
         debug!(
             "try_report_named_anon_conflict(sub={:?}, sup={:?}, error={:?})",