Auto merge of #3022 - RalfJung:upcast, r=compiler-errors

replace AsAny hack by trait upcasting :)

4 files changed, 22 insertions, 31 deletions

diff --git a/src/tools/miri/src/helpers.rs b/src/tools/miri/src/helpers.rs
index e0f74d03ff6..ea1931f7a18 100644
--- a/src/tools/miri/src/helpers.rs
+++ b/src/tools/miri/src/helpers.rs
@@ -1,6 +1,5 @@
 pub mod convert;
 
-use std::any::Any;
 use std::cmp;
 use std::iter;
 use std::num::NonZeroUsize;
@@ -25,24 +24,6 @@ use rand::RngCore;
 
 use crate::*;
 
-/// A trait to work around not having trait object upcasting:
-/// Add `AsAny` as supertrait and your trait objects can be turned into `&dyn Any` on which you can
-/// then call `downcast`.
-pub trait AsAny: Any {
-    fn as_any(&self) -> &dyn Any;
-    fn as_any_mut(&mut self) -> &mut dyn Any;
-}
-impl<T: Any> AsAny for T {
-    #[inline(always)]
-    fn as_any(&self) -> &dyn Any {
-        self
-    }
-    #[inline(always)]
-    fn as_any_mut(&mut self) -> &mut dyn Any {
-        self
-    }
-}
-
 // This mapping should match `decode_error_kind` in
 // <https://github.com/rust-lang/rust/blob/master/library/std/src/sys/unix/mod.rs>.
 const UNIX_IO_ERROR_TABLE: &[(&str, std::io::ErrorKind)] = {
diff --git a/src/tools/miri/src/lib.rs b/src/tools/miri/src/lib.rs
index 5327c2f24e0..3290e85532d 100644
--- a/src/tools/miri/src/lib.rs
+++ b/src/tools/miri/src/lib.rs
@@ -10,6 +10,7 @@
 #![feature(round_ties_even)]
 #![feature(os_str_bytes)]
 #![feature(lint_reasons)]
+#![feature(trait_upcasting)]
 // Configure clippy and other lints
 #![allow(
     clippy::collapsible_else_if,
diff --git a/src/tools/miri/src/shims/unix/fs.rs b/src/tools/miri/src/shims/unix/fs.rs
index 09349bfdead..beaef22075b 100644
--- a/src/tools/miri/src/shims/unix/fs.rs
+++ b/src/tools/miri/src/shims/unix/fs.rs
@@ -1,3 +1,4 @@
+use std::any::Any;
 use std::borrow::Cow;
 use std::collections::BTreeMap;
 use std::convert::TryInto;
@@ -24,7 +25,7 @@ pub struct FileHandle {
     writable: bool,
 }
 
-pub trait FileDescriptor: std::fmt::Debug + helpers::AsAny {
+pub trait FileDescriptor: std::fmt::Debug + Any {
     fn name(&self) -> &'static str;
 
     fn read<'tcx>(
@@ -72,6 +73,18 @@ pub trait FileDescriptor: std::fmt::Debug + helpers::AsAny {
     }
 }
 
+impl dyn FileDescriptor {
+    #[inline(always)]
+    pub fn downcast_ref<T: Any>(&self) -> Option<&T> {
+        (self as &dyn Any).downcast_ref()
+    }
+
+    #[inline(always)]
+    pub fn downcast_mut<T: Any>(&mut self) -> Option<&mut T> {
+        (self as &mut dyn Any).downcast_mut()
+    }
+}
+
 impl FileDescriptor for FileHandle {
     fn name(&self) -> &'static str {
         "FILE"
@@ -689,7 +702,7 @@ pub trait EvalContextExt<'mir, 'tcx: 'mir>: crate::MiriInterpCxExt<'mir, 'tcx> {
             if let Some(file_descriptor) = this.machine.file_handler.handles.get(&fd) {
                 // FIXME: Support fullfsync for all FDs
                 let FileHandle { file, writable } =
-                    file_descriptor.as_any().downcast_ref::<FileHandle>().ok_or_else(|| {
+                    file_descriptor.downcast_ref::<FileHandle>().ok_or_else(|| {
                         err_unsup_format!(
                             "`F_FULLFSYNC` is only supported on file-backed file descriptors"
                         )
@@ -1522,7 +1535,7 @@ pub trait EvalContextExt<'mir, 'tcx: 'mir>: crate::MiriInterpCxExt<'mir, 'tcx> {
             if let Some(file_descriptor) = this.machine.file_handler.handles.get_mut(&fd) {
                 // FIXME: Support ftruncate64 for all FDs
                 let FileHandle { file, writable } =
-                    file_descriptor.as_any().downcast_ref::<FileHandle>().ok_or_else(|| {
+                    file_descriptor.downcast_ref::<FileHandle>().ok_or_else(|| {
                         err_unsup_format!(
                             "`ftruncate64` is only supported on file-backed file descriptors"
                         )
@@ -1568,7 +1581,7 @@ pub trait EvalContextExt<'mir, 'tcx: 'mir>: crate::MiriInterpCxExt<'mir, 'tcx> {
         if let Some(file_descriptor) = this.machine.file_handler.handles.get(&fd) {
             // FIXME: Support fsync for all FDs
             let FileHandle { file, writable } =
-                file_descriptor.as_any().downcast_ref::<FileHandle>().ok_or_else(|| {
+                file_descriptor.downcast_ref::<FileHandle>().ok_or_else(|| {
                     err_unsup_format!("`fsync` is only supported on file-backed file descriptors")
                 })?;
             let io_result = maybe_sync_file(file, *writable, File::sync_all);
@@ -1593,7 +1606,7 @@ pub trait EvalContextExt<'mir, 'tcx: 'mir>: crate::MiriInterpCxExt<'mir, 'tcx> {
         if let Some(file_descriptor) = this.machine.file_handler.handles.get(&fd) {
             // FIXME: Support fdatasync for all FDs
             let FileHandle { file, writable } =
-                file_descriptor.as_any().downcast_ref::<FileHandle>().ok_or_else(|| {
+                file_descriptor.downcast_ref::<FileHandle>().ok_or_else(|| {
                     err_unsup_format!(
                         "`fdatasync` is only supported on file-backed file descriptors"
                     )
@@ -1643,7 +1656,7 @@ pub trait EvalContextExt<'mir, 'tcx: 'mir>: crate::MiriInterpCxExt<'mir, 'tcx> {
         if let Some(file_descriptor) = this.machine.file_handler.handles.get(&fd) {
             // FIXME: Support sync_data_range for all FDs
             let FileHandle { file, writable } =
-                file_descriptor.as_any().downcast_ref::<FileHandle>().ok_or_else(|| {
+                file_descriptor.downcast_ref::<FileHandle>().ok_or_else(|| {
                     err_unsup_format!(
                         "`sync_data_range` is only supported on file-backed file descriptors"
                     )
@@ -1953,7 +1966,6 @@ impl FileMetadata {
         let file = match option {
             Some(file_descriptor) =>
                 &file_descriptor
-                    .as_any()
                     .downcast_ref::<FileHandle>()
                     .ok_or_else(|| {
                         err_unsup_format!(
diff --git a/src/tools/miri/src/shims/unix/linux/fd.rs b/src/tools/miri/src/shims/unix/linux/fd.rs
index f2be89ce637..22fbb6da95a 100644
--- a/src/tools/miri/src/shims/unix/linux/fd.rs
+++ b/src/tools/miri/src/shims/unix/linux/fd.rs
@@ -1,3 +1,5 @@
+use std::cell::Cell;
+
 use rustc_middle::ty::ScalarInt;
 
 use crate::*;
@@ -7,8 +9,6 @@ use socketpair::SocketPair;
 
 use shims::unix::fs::EvalContextExt as _;
 
-use std::cell::Cell;
-
 pub mod epoll;
 pub mod event;
 pub mod socketpair;
@@ -81,7 +81,6 @@ pub trait EvalContextExt<'mir, 'tcx: 'mir>: crate::MiriInterpCxExt<'mir, 'tcx> {
 
             if let Some(epfd) = this.machine.file_handler.handles.get_mut(&epfd) {
                 let epfd = epfd
-                    .as_any_mut()
                     .downcast_mut::<Epoll>()
                     .ok_or_else(|| err_unsup_format!("non-epoll FD passed to `epoll_ctl`"))?;
 
@@ -93,7 +92,6 @@ pub trait EvalContextExt<'mir, 'tcx: 'mir>: crate::MiriInterpCxExt<'mir, 'tcx> {
         } else if op == epoll_ctl_del {
             if let Some(epfd) = this.machine.file_handler.handles.get_mut(&epfd) {
                 let epfd = epfd
-                    .as_any_mut()
                     .downcast_mut::<Epoll>()
                     .ok_or_else(|| err_unsup_format!("non-epoll FD passed to `epoll_ctl`"))?;
 
@@ -154,7 +152,6 @@ pub trait EvalContextExt<'mir, 'tcx: 'mir>: crate::MiriInterpCxExt<'mir, 'tcx> {
 
         if let Some(epfd) = this.machine.file_handler.handles.get_mut(&epfd) {
             let _epfd = epfd
-                .as_any_mut()
                 .downcast_mut::<Epoll>()
                 .ok_or_else(|| err_unsup_format!("non-epoll FD passed to `epoll_wait`"))?;