Tidy no longer fails when there are no files or subdirectories in a test directory.

src/test/ui/borrowck/borrowck-feature-nll-overrides-migrate.edition.stderr

@@ -0,0 +1,9 @@
+error[E0507]: cannot move out of borrowed content
+  --> $DIR/borrowck-feature-nll-overrides-migrate.rs:32:17
+   |
+LL |                 (|| { let bar = foo; bar.take() })();
+   |                 ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ cannot move out of borrowed content
+
+error: aborting due to previous error
+
+For more information about this error, try `rustc --explain E0507`.

src/test/ui/borrowck/borrowck-feature-nll-overrides-migrate.zflag.stderr

@@ -0,0 +1,9 @@
+error[E0507]: cannot move out of borrowed content
+  --> $DIR/borrowck-feature-nll-overrides-migrate.rs:32:17
+   |
+LL |                 (|| { let bar = foo; bar.take() })();
+   |                 ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ cannot move out of borrowed content
+
+error: aborting due to previous error
+
+For more information about this error, try `rustc --explain E0507`.

src/test/ui/borrowck/borrowck-migrate-to-nll.edition.stderr

@@ -0,0 +1,24 @@
+warning[E0507]: cannot move out of borrowed content
+  --> $DIR/borrowck-migrate-to-nll.rs:35:17
+   |
+LL |                 (|| { let bar = foo; bar.take() })();
+   |                 ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ cannot move out of borrowed content
+   |
+   = warning: This error has been downgraded to a warning for backwards compatibility with previous releases.
+           It represents potential unsoundness in your code.
+           This warning will become a hard error in the future.
+
+warning[E0507]: cannot move out of `foo`, as it is immutable for the pattern guard
+  --> $DIR/borrowck-migrate-to-nll.rs:35:17
+   |
+LL |                 (|| { let bar = foo; bar.take() })();
+   |                 ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+   |                 |
+   |                 cannot move out of `foo`, as it is immutable for the pattern guard
+   |                 cannot move
+   |
+   = note: variables bound in patterns are immutable until the end of the pattern guard
+   = warning: This error has been downgraded to a warning for backwards compatibility with previous releases.
+           It represents potential unsoundness in your code.
+           This warning will become a hard error in the future.
+

src/test/ui/borrowck/borrowck-migrate-to-nll.zflag.stderr

@@ -0,0 +1,24 @@
+warning[E0507]: cannot move out of borrowed content
+  --> $DIR/borrowck-migrate-to-nll.rs:35:17
+   |
+LL |                 (|| { let bar = foo; bar.take() })();
+   |                 ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ cannot move out of borrowed content
+   |
+   = warning: This error has been downgraded to a warning for backwards compatibility with previous releases.
+           It represents potential unsoundness in your code.
+           This warning will become a hard error in the future.
+
+warning[E0507]: cannot move out of `foo`, as it is immutable for the pattern guard
+  --> $DIR/borrowck-migrate-to-nll.rs:35:17
+   |
+LL |                 (|| { let bar = foo; bar.take() })();
+   |                 ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+   |                 |
+   |                 cannot move out of `foo`, as it is immutable for the pattern guard
+   |                 cannot move
+   |
+   = note: variables bound in patterns are immutable until the end of the pattern guard
+   = warning: This error has been downgraded to a warning for backwards compatibility with previous releases.
+           It represents potential unsoundness in your code.
+           This warning will become a hard error in the future.
+

src/test/ui/borrowck/issue-45983.migrate.stderr

@@ -0,0 +1,12 @@
+error: borrowed data cannot be stored outside of its closure
+  --> $DIR/issue-45983.rs:36:27
+   |
+LL |     let x = None;
+   |         - borrowed data cannot be stored into here...
+LL |     give_any(|y| x = Some(y));
+   |              ---          ^ cannot be stored outside of its closure
+   |              |
+   |              ...because it cannot outlive this closure
+
+error: aborting due to previous error
+

src/test/ui/obsolete-in-place/bad.bad.stderr

@@ -0,0 +1,18 @@
+error: emplacement syntax is obsolete (for now, anyway)
+  --> $DIR/bad.rs:19:5
+   |
+LL |     x <- y; //[bad]~ ERROR emplacement syntax is obsolete
+   |     ^^^^^^
+   |
+   = note: for more information, see <https://github.com/rust-lang/rust/issues/27779#issuecomment-378416911>
+
+error: emplacement syntax is obsolete (for now, anyway)
+  --> $DIR/bad.rs:20:5
+   |
+LL |     in(foo) { bar }; //[bad]~ ERROR emplacement syntax is obsolete
+   |     ^^^^^^^^^^^^^^^
+   |
+   = note: for more information, see <https://github.com/rust-lang/rust/issues/27779#issuecomment-378416911>
+
+error: aborting due to 2 previous errors
+

src/tools/tidy/src/lib.rs

@@ -89,16 +89,18 @@ fn walk_many(paths: &[&Path], skip: &mut dyn FnMut(&Path) -> bool, f: &mut dyn F
 }
 
 fn walk(path: &Path, skip: &mut dyn FnMut(&Path) -> bool, f: &mut dyn FnMut(&Path)) {
-    for entry in t!(fs::read_dir(path), path) {
-        let entry = t!(entry);
-        let kind = t!(entry.file_type());
-        let path = entry.path();
-        if kind.is_dir() {
-            if !skip(&path) {
-                walk(&path, skip, f);
+    if let Ok(dir) = fs::read_dir(path) {
+        for entry in dir {
+            let entry = t!(entry);
+            let kind = t!(entry.file_type());
+            let path = entry.path();
+            if kind.is_dir() {
+                if !skip(&path) {
+                    walk(&path, skip, f);
+                }
+            } else {
+                f(&path);
             }
-        } else {
-            f(&path);
         }
     }
 }