Reset Formatter flags on exit from pad_integral

src/libcore/fmt/mod.rs

@@ -1244,12 +1244,15 @@ impl<'a> Formatter<'a> {
             // The sign and prefix goes before the padding if the fill character
             // is zero
             Some(min) if self.sign_aware_zero_pad() => {
-                self.fill = '0';
-                self.align = rt::v1::Alignment::Right;
+                let old_fill = crate::mem::replace(&mut self.fill, '0');
+                let old_align = crate::mem::replace(&mut self.align, rt::v1::Alignment::Right);
                 write_prefix(self, sign, prefix)?;
                 let post_padding = self.padding(min - width, rt::v1::Alignment::Right)?;
                 self.buf.write_str(buf)?;
-                post_padding.write(self.buf)
+                post_padding.write(self.buf)?;
+                self.fill = old_fill;
+                self.align = old_align;
+                Ok(())
             }
             // Otherwise, the sign and prefix goes after the padding
             Some(min) => {

src/libcore/tests/fmt/mod.rs

@@ -28,3 +28,18 @@ fn test_estimated_capacity() {
     assert_eq!(format_args!("{}, hello!", "World").estimated_capacity(), 0);
     assert_eq!(format_args!("{}. 16-bytes piece", "World").estimated_capacity(), 32);
 }
+
+#[test]
+fn pad_integral_resets() {
+    struct Bar;
+
+    impl core::fmt::Display for Bar {
+        fn fmt(&self, f: &mut core::fmt::Formatter<'_>) -> core::fmt::Result {
+            "1".fmt(f)?;
+            f.pad_integral(true, "", "5")?;
+            "1".fmt(f)
+        }
+    }
+
+    assert_eq!(format!("{:<03}", Bar), "1  0051  ");
+}