slightly more verbose error msg

RalfJung · RalfJung · commit 694d2490f1f1 · 2018-11-21T16:02:38.000+01:00
diff --git a/src/stacked_borrows.rs b/src/stacked_borrows.rs
@@ -153,7 +153,7 @@ impl<'tcx> Stack {
     fn deref(&self, bor: Borrow, kind: RefKind) -> Result<Option<usize>, String> {
         // Exclude unique ref with frozen tag.
         if let (RefKind::Unique, Borrow::Shr(Some(_))) = (kind, bor) {
-            return Err(format!("Encountered mutable reference with frozen tag"));
+            return Err(format!("Encountered mutable reference with frozen tag ({:?})", bor));
         }
         // Checks related to freezing
         match bor {

Original file line number	Diff line number	Diff line change
`@@ -153,7 +153,7 @@ impl<'tcx> Stack {`
`153`	`153`	`fn deref(&self, bor: Borrow, kind: RefKind) -> Result<Option<usize>, String> {`
`154`	`154`	`// Exclude unique ref with frozen tag.`
`155`	`155`	`if let (RefKind::Unique, Borrow::Shr(Some(_))) = (kind, bor) {`
`156`		`- return Err(format!("Encountered mutable reference with frozen tag"));`
	`156`	`+ return Err(format!("Encountered mutable reference with frozen tag ({:?})", bor));`
`157`	`157`	`}`
`158`	`158`	`// Checks related to freezing`
`159`	`159`	`match bor {`