1 files changed, 48 insertions, 0 deletions
diff --git a/tests/ui/write-fmt-errors.rs b/tests/ui/write-fmt-errors.rs
new file mode 100644
index 00000000000..3fcaefaa63e
--- /dev/null
+++ b/tests/ui/write-fmt-errors.rs
@@ -0,0 +1,48 @@
+// run-pass
+
+#![feature(io_error_uncategorized)]
+
+use std::fmt;
+use std::io::{self, Error, Write, sink};
+
+struct ErrorDisplay;
+
+impl fmt::Display for ErrorDisplay {
+    fn fmt(&self, _: &mut fmt::Formatter) -> fmt::Result {
+        Err(fmt::Error)
+    }
+}
+
+struct ErrorWriter;
+
+const FORMAT_ERROR: io::ErrorKind = io::ErrorKind::Uncategorized;
+const WRITER_ERROR: io::ErrorKind = io::ErrorKind::NotConnected;
+
+impl Write for ErrorWriter {
+    fn write(&mut self, _buf: &[u8]) -> io::Result<usize> {
+        Err(Error::new(WRITER_ERROR, "not connected"))
+    }
+
+    fn flush(&mut self) -> io::Result<()> { Ok(()) }
+}
+
+fn main() {
+    // Test that the error from the formatter is propagated.
+    let res = write!(sink(), "{} {} {}", 1, ErrorDisplay, "bar");
+    assert!(res.is_err(), "formatter error did not propagate");
+    assert_eq!(res.unwrap_err().kind(), FORMAT_ERROR);
+
+    // Test that an underlying error is propagated
+    let res = write!(ErrorWriter, "abc");
+    assert!(res.is_err(), "writer error did not propagate");
+
+    // Writer error
+    let res = write!(ErrorWriter, "abc {}", ErrorDisplay);
+    assert!(res.is_err(), "writer error did not propagate");
+    assert_eq!(res.unwrap_err().kind(), WRITER_ERROR);
+
+    // Formatter error
+    let res = write!(ErrorWriter, "{} abc", ErrorDisplay);
+    assert!(res.is_err(), "formatter error did not propagate");
+    assert_eq!(res.unwrap_err().kind(), FORMAT_ERROR);
+}