Fall back from uv tty instances more aggressively

It appears that uv's support for interacting with a stdio stream as a tty when
it's actually a pipe is pretty problematic. To get around this, promote a check
to see if the stream is a tty to the top of the tty constructor, and bail out
quickly if it's not identified as a tty.

Closes #10237

1 files changed, 2 insertions, 4 deletions

diff --git a/src/libstd/rt/io/stdio.rs b/src/libstd/rt/io/stdio.rs
index d33821a34b1..674b34639bc 100644
--- a/src/libstd/rt/io/stdio.rs
+++ b/src/libstd/rt/io/stdio.rs
@@ -277,12 +277,10 @@ impl StdWriter {
         }
     }
 
-    /// Returns whether this tream is attached to a TTY instance or not.
-    ///
-    /// This is similar to libc's isatty() function
+    /// Returns whether this stream is attached to a TTY instance or not.
     pub fn isatty(&self) -> bool {
         match self.inner {
-            TTY(ref tty) => tty.isatty(),
+            TTY(*) => true,
             File(*) => false,
         }
     }