use shutdown error values to throw exceptions in close stream

src/machine/streams.rs

@@ -160,20 +160,6 @@ impl StreamInstance {
     }
 }
 
-impl Drop for StreamInstance {
-    fn drop(&mut self) {
-        match self {
-            StreamInstance::TcpStream(_, ref mut tcp_stream) => {
-                tcp_stream.shutdown(Shutdown::Both).unwrap_or(())
-            }
-            StreamInstance::TlsStream(_, ref mut tls_stream) => {
-                tls_stream.shutdown().unwrap_or(());
-            }
-            _ => {}
-        }
-    }
-}
-
 impl fmt::Debug for StreamInstance {
     fn fmt(&self, fmt: &mut fmt::Formatter) -> fmt::Result {
         match self {
@@ -596,8 +582,18 @@ impl Stream {
     }
 
     #[inline]
-    pub(crate) fn close(&mut self) {
+    pub(crate) fn close(&mut self) -> Result<(), std::io::Error> {
+        let result = match self.stream_inst.0.borrow_mut().stream_inst {
+            StreamInstance::TcpStream(_, ref mut tcp_stream) => {
+                tcp_stream.shutdown(Shutdown::Both)
+            },
+            StreamInstance::TlsStream(_, ref mut tls_stream) => {
+                tls_stream.shutdown()
+            }
+            _ => Ok(())
+        };
         self.stream_inst.0.borrow_mut().stream_inst = StreamInstance::Null;
+        result
     }
 
     #[inline]
@@ -636,20 +632,6 @@ impl Stream {
         }
     }
 
-    pub(crate) fn is_closed(&self) -> bool {
-        match self.stream_inst.0.borrow_mut().stream_inst {
-            StreamInstance::Null => true,
-            StreamInstance::TcpStream(_, ref mut tcp_stream) => {
-                let mut buf = [0;8];
-                match tcp_stream.peek(&mut buf) {
-                    Ok(n_bytes) => n_bytes == 0,
-                    Err(_) => true
-                }
-            },
-            _ => false
-        }
-    }
-
     fn unpause_stream(&mut self) {
         let stream_inst = match self.stream_inst.0.borrow_mut().stream_inst {
             StreamInstance::PausedPrologStream(ref put_back, ref mut stream_inst)

src/machine/system_calls.rs

@@ -2704,7 +2704,12 @@ impl MachineState {
                 }
 
                 if !stream.is_stdin() && !stream.is_stdout() && !stream.is_stderr() {
-                    if stream.is_closed() {
+                    let close_result = stream.close();
+
+                    if let Some(ref alias) = stream.options().alias {
+                        indices.stream_aliases.remove(alias);
+                    }
+                    if let Err(_) = close_result {
                         let stub = MachineError::functor_stub(
                             clause_name!("close"),
                             1,
@@ -2721,12 +2726,6 @@ impl MachineState {
                             ),
                             stub,
                         ));
-                    } else {
-                        stream.close();
-
-                        if let Some(ref alias) = stream.options().alias {
-                            indices.stream_aliases.remove(alias);
-                        }
                     }
                 }
             }