Don't crash when reporting nice region errors for generic const items

Author: fmease

compiler/rustc_infer/src/infer/error_reporting/nice_region_error/named_anon_conflict.rs

@@ -29,25 +29,15 @@ impl<'a, 'tcx> NiceRegionError<'a, 'tcx> {
         // version new_ty of its type where the anonymous region is replaced
         // with the named one.
         let (named, anon, anon_param_info, region_info) = if sub.has_name()
-            && self.tcx().is_suitable_region(sup).is_some()
-            && self.find_param_with_region(sup, sub).is_some()
+            && let Some(region_info) = self.tcx().is_suitable_region(sup)
+            && let Some(anon_param_info) = self.find_param_with_region(sup, sub)
         {
-            (
-                sub,
-                sup,
-                self.find_param_with_region(sup, sub).unwrap(),
-                self.tcx().is_suitable_region(sup).unwrap(),
-            )
+            (sub, sup, anon_param_info, region_info)
         } else if sup.has_name()
-            && self.tcx().is_suitable_region(sub).is_some()
-            && self.find_param_with_region(sub, sup).is_some()
+            && let Some(region_info) = self.tcx().is_suitable_region(sub)
+            && let Some(anon_param_info) = self.find_param_with_region(sub, sup)
         {
-            (
-                sup,
-                sub,
-                self.find_param_with_region(sub, sup).unwrap(),
-                self.tcx().is_suitable_region(sub).unwrap(),
-            )
+            (sup, sub, anon_param_info, region_info)
         } else {
             return None; // inapplicable
         };

compiler/rustc_infer/src/infer/error_reporting/nice_region_error/util.rs

@@ -64,7 +64,7 @@ pub fn find_param_with_region<'tcx>(
     let body_id = hir.maybe_body_owned_by(def_id)?;
 
     let owner_id = hir.body_owner(body_id);
-    let fn_decl = hir.fn_decl_by_hir_id(owner_id).unwrap();
+    let fn_decl = hir.fn_decl_by_hir_id(owner_id)?;
     let poly_fn_sig = tcx.fn_sig(id).instantiate_identity();
 
     let fn_sig = tcx.liberate_late_bound_regions(id, poly_fn_sig);

tests/ui/generic-const-items/reference-outlives-referent.rs

@@ -0,0 +1,9 @@
+// Test that we catch that the reference outlives the referent and we
+// successfully emit a diagnostic. Regression test for issue #114714.
+
+#![feature(generic_const_items)]
+#![allow(incomplete_features)]
+
+const Q<'a, 'b>: &'a &'b () = &&(); //~ ERROR reference has a longer lifetime than the data it references
+
+fn main() {}

tests/ui/generic-const-items/reference-outlives-referent.stderr

@@ -0,0 +1,20 @@
+error[E0491]: in type `&'a &'b ()`, reference has a longer lifetime than the data it references
+  --> $DIR/reference-outlives-referent.rs:7:18
+   |
+LL | const Q<'a, 'b>: &'a &'b () = &&();
+   |                  ^^^^^^^^^^
+   |
+note: the pointer is valid for the lifetime `'a` as defined here
+  --> $DIR/reference-outlives-referent.rs:7:9
+   |
+LL | const Q<'a, 'b>: &'a &'b () = &&();
+   |         ^^
+note: but the referenced data is only valid for the lifetime `'b` as defined here
+  --> $DIR/reference-outlives-referent.rs:7:13
+   |
+LL | const Q<'a, 'b>: &'a &'b () = &&();
+   |             ^^
+
+error: aborting due to previous error
+
+For more information about this error, try `rustc --explain E0491`.