Implement From<OwnedFd/Handle> for ChildStdin/out/err object

library/std/src/os/unix/process.rs

@@ -434,6 +434,20 @@ impl From<crate::process::ChildStdin> for OwnedFd {
     }
 }
 
+/// Create a `ChildStdin` from the provided `OwnedFd`.
+///
+/// The provided file descriptor must point to a pipe
+/// with the `CLOEXEC` flag set.
+#[stable(feature = "child_stream_from_fd", since = "CURRENT_RUSTC_VERSION")]
+impl From<OwnedFd> for process::ChildStdin {
+    #[inline]
+    fn from(fd: OwnedFd) -> process::ChildStdin {
+        let fd = sys::fd::FileDesc::from_inner(fd);
+        let pipe = sys::pipe::AnonPipe::from_inner(fd);
+        process::ChildStdin::from_inner(pipe)
+    }
+}
+
 #[stable(feature = "io_safety", since = "1.63.0")]
 impl AsFd for crate::process::ChildStdout {
     #[inline]
@@ -450,6 +464,20 @@ impl From<crate::process::ChildStdout> for OwnedFd {
     }
 }
 
+/// Create a `ChildStdout` from the provided `OwnedFd`.
+///
+/// The provided file descriptor must point to a pipe
+/// with the `CLOEXEC` flag set.
+#[stable(feature = "child_stream_from_fd", since = "CURRENT_RUSTC_VERSION")]
+impl From<OwnedFd> for process::ChildStdout {
+    #[inline]
+    fn from(fd: OwnedFd) -> process::ChildStdout {
+        let fd = sys::fd::FileDesc::from_inner(fd);
+        let pipe = sys::pipe::AnonPipe::from_inner(fd);
+        process::ChildStdout::from_inner(pipe)
+    }
+}
+
 #[stable(feature = "io_safety", since = "1.63.0")]
 impl AsFd for crate::process::ChildStderr {
     #[inline]
@@ -466,6 +494,20 @@ impl From<crate::process::ChildStderr> for OwnedFd {
     }
 }
 
+/// Create a `ChildStderr` from the provided `OwnedFd`.
+///
+/// The provided file descriptor must point to a pipe
+/// with the `CLOEXEC` flag set.
+#[stable(feature = "child_stream_from_fd", since = "CURRENT_RUSTC_VERSION")]
+impl From<OwnedFd> for process::ChildStderr {
+    #[inline]
+    fn from(fd: OwnedFd) -> process::ChildStderr {
+        let fd = sys::fd::FileDesc::from_inner(fd);
+        let pipe = sys::pipe::AnonPipe::from_inner(fd);
+        process::ChildStderr::from_inner(pipe)
+    }
+}
+
 /// Returns the OS-assigned process identifier associated with this process's parent.
 #[must_use]
 #[stable(feature = "unix_ppid", since = "1.27.0")]

library/std/src/os/windows/process.rs

@@ -106,6 +106,45 @@ impl IntoRawHandle for process::ChildStderr {
     }
 }
 
+/// Create a `ChildStdin` from the provided `OwnedHandle`.
+///
+/// The provided handle must be asynchronous, as reading and
+/// writing from and to it is implemented using asynchronous APIs.
+#[stable(feature = "child_stream_from_fd", since = "CURRENT_RUSTC_VERSION")]
+impl From<OwnedHandle> for process::ChildStdin {
+    fn from(handle: OwnedHandle) -> process::ChildStdin {
+        let handle = sys::handle::Handle::from_inner(handle);
+        let pipe = sys::pipe::AnonPipe::from_inner(handle);
+        process::ChildStdin::from_inner(pipe)
+    }
+}
+
+/// Create a `ChildStdout` from the provided `OwnedHandle`.
+///
+/// The provided handle must be asynchronous, as reading and
+/// writing from and to it is implemented using asynchronous APIs.
+#[stable(feature = "child_stream_from_fd", since = "CURRENT_RUSTC_VERSION")]
+impl From<OwnedHandle> for process::ChildStdout {
+    fn from(handle: OwnedHandle) -> process::ChildStdout {
+        let handle = sys::handle::Handle::from_inner(handle);
+        let pipe = sys::pipe::AnonPipe::from_inner(handle);
+        process::ChildStdout::from_inner(pipe)
+    }
+}
+
+/// Create a `ChildStderr` from the provided `OwnedHandle`.
+///
+/// The provided handle must be asynchronous, as reading and
+/// writing from and to it is implemented using asynchronous APIs.
+#[stable(feature = "child_stream_from_fd", since = "CURRENT_RUSTC_VERSION")]
+impl From<OwnedHandle> for process::ChildStderr {
+    fn from(handle: OwnedHandle) -> process::ChildStderr {
+        let handle = sys::handle::Handle::from_inner(handle);
+        let pipe = sys::pipe::AnonPipe::from_inner(handle);
+        process::ChildStderr::from_inner(pipe)
+    }
+}
+
 /// Windows-specific extensions to [`process::ExitStatus`].
 ///
 /// This trait is sealed: it cannot be implemented outside the standard library.

library/std/src/sys/unix/pipe.rs

@@ -3,7 +3,7 @@ use crate::mem;
 use crate::os::unix::io::{AsFd, AsRawFd, BorrowedFd, FromRawFd, IntoRawFd, RawFd};
 use crate::sys::fd::FileDesc;
 use crate::sys::{cvt, cvt_r};
-use crate::sys_common::IntoInner;
+use crate::sys_common::{FromInner, IntoInner};
 
 ////////////////////////////////////////////////////////////////////////////////
 // Anonymous pipes
@@ -158,3 +158,9 @@ impl FromRawFd for AnonPipe {
         Self(FromRawFd::from_raw_fd(raw_fd))
     }
 }
+
+impl FromInner<FileDesc> for AnonPipe {
+    fn from_inner(fd: FileDesc) -> Self {
+        Self(fd)
+    }
+}

library/std/src/sys/windows/pipe.rs

@@ -12,7 +12,7 @@ use crate::sys::c;
 use crate::sys::fs::{File, OpenOptions};
 use crate::sys::handle::Handle;
 use crate::sys::hashmap_random_keys;
-use crate::sys_common::IntoInner;
+use crate::sys_common::{FromInner, IntoInner};
 
 ////////////////////////////////////////////////////////////////////////////////
 // Anonymous pipes
@@ -28,6 +28,12 @@ impl IntoInner<Handle> for AnonPipe {
     }
 }
 
+impl FromInner<Handle> for AnonPipe {
+    fn from_inner(inner: Handle) -> AnonPipe {
+        Self { inner }
+    }
+}
+
 pub struct Pipes {
     pub ours: AnonPipe,
     pub theirs: AnonPipe,