Remove stream_len functions entirely.

Most of the `seek_convenience` feature was stablized, but `stream_len`
was not [0]. To minimize version incompatibilities here, just remove
our `stream_len` functions for now and rely on the defaults.

[0]: rust-lang/rust#70904

Author: sunfishcode

Diff for: cap-async-std/src/fs/file.rs

@@ -298,8 +298,6 @@ impl Seek for File {
         Seek::poll_seek(Pin::new(&mut self.std), cx, pos)
     }
 
-    // async_std doesn't have `stream_len`.
-
     // async_std doesn't have `seek_convenience`.
 }
 
@@ -309,8 +307,6 @@ impl Seek for &File {
         Seek::poll_seek(Pin::new(&mut &self.std), cx, pos)
     }
 
-    // async_std doesn't have `stream_len`.
-
     // async_std doesn't have `seek_convenience`.
 }
 

Diff for: cap-async-std/src/fs_utf8/file.rs

@@ -268,8 +268,6 @@ impl Seek for File {
         Seek::poll_seek(Pin::new(&mut self.cap_std), cx, pos)
     }
 
-    // async_std doesn't have `stream_len`.
-
     // async_std doesn't have `stream_position`.
 }
 
@@ -279,8 +277,6 @@ impl Seek for &File {
         Seek::poll_seek(Pin::new(&mut &self.cap_std), cx, pos)
     }
 
-    // async_std doesn't have `stream_len`.
-
     // async_std doesn't have `stream_position`.
 }
 

Diff for: cap-std/src/fs/file.rs

@@ -323,12 +323,6 @@ impl Seek for File {
         self.std.seek(pos)
     }
 
-    #[cfg(seek_convenience)]
-    #[inline]
-    fn stream_len(&mut self) -> io::Result<u64> {
-        self.std.stream_len()
-    }
-
     #[cfg(seek_convenience)]
     #[inline]
     fn stream_position(&mut self) -> io::Result<u64> {
@@ -342,12 +336,6 @@ impl Seek for &File {
         (&mut &self.std).seek(pos)
     }
 
-    #[cfg(seek_convenience)]
-    #[inline]
-    fn stream_len(&mut self) -> io::Result<u64> {
-        (&mut &self.std).stream_len()
-    }
-
     #[cfg(seek_convenience)]
     #[inline]
     fn stream_position(&mut self) -> io::Result<u64> {

Diff for: cap-std/src/fs_utf8/file.rs

@@ -302,12 +302,6 @@ impl Seek for File {
         self.cap_std.seek(pos)
     }
 
-    #[cfg(seek_convenience)]
-    #[inline]
-    fn stream_len(&mut self) -> io::Result<u64> {
-        self.cap_std.stream_len()
-    }
-
     #[cfg(seek_convenience)]
     #[inline]
     fn stream_position(&mut self) -> io::Result<u64> {
@@ -321,12 +315,6 @@ impl Seek for &File {
         (&mut &self.cap_std).seek(pos)
     }
 
-    #[cfg(seek_convenience)]
-    #[inline]
-    fn stream_len(&mut self) -> io::Result<u64> {
-        (&mut &self.cap_std).stream_len()
-    }
-
     #[cfg(seek_convenience)]
     #[inline]
     fn stream_position(&mut self) -> io::Result<u64> {