Auto merge of #109971 - WaffleLapkin:yeet_ownership, r=Nilstrieb

Yeet `owning_ref`

Based on the discussions from https://github.com/rust-lang/rust/pull/109948

This replaces `owning_ref` with a far simpler & safer abstraction.

Fixes #109974

compiler/rustc_metadata/src/lib.rs

@@ -22,8 +22,6 @@ extern crate proc_macro;
 extern crate rustc_macros;
 #[macro_use]
 extern crate rustc_middle;
-#[macro_use]
-extern crate rustc_data_structures;
 
 #[macro_use]
 extern crate tracing;

compiler/rustc_metadata/src/locator.rs

@@ -218,7 +218,7 @@ use crate::rmeta::{rustc_version, MetadataBlob, METADATA_HEADER};
 
 use rustc_data_structures::fx::{FxHashMap, FxHashSet};
 use rustc_data_structures::memmap::Mmap;
-use rustc_data_structures::owning_ref::OwningRef;
+use rustc_data_structures::owned_slice::slice_owned;
 use rustc_data_structures::svh::Svh;
 use rustc_data_structures::sync::MetadataRef;
 use rustc_errors::{DiagnosticArgValue, FatalError, IntoDiagnosticArg};
@@ -236,6 +236,7 @@ use rustc_target::spec::{Target, TargetTriple};
 use snap::read::FrameDecoder;
 use std::borrow::Cow;
 use std::io::{Read, Result as IoResult, Write};
+use std::ops::Deref;
 use std::path::{Path, PathBuf};
 use std::{cmp, fmt};
 
@@ -814,15 +815,14 @@ fn get_metadata_section<'p>(
             // Assume the decompressed data will be at least the size of the compressed data, so we
             // don't have to grow the buffer as much.
             let mut inflated = Vec::with_capacity(compressed_bytes.len());
-            match FrameDecoder::new(compressed_bytes).read_to_end(&mut inflated) {
-                Ok(_) => rustc_erase_owner!(OwningRef::new(inflated).map_owner_box()),
-                Err(_) => {
-                    return Err(MetadataError::LoadFailure(format!(
-                        "failed to decompress metadata: {}",
-                        filename.display()
-                    )));
-                }
-            }
+            FrameDecoder::new(compressed_bytes).read_to_end(&mut inflated).map_err(|_| {
+                MetadataError::LoadFailure(format!(
+                    "failed to decompress metadata: {}",
+                    filename.display()
+                ))
+            })?;
+
+            slice_owned(inflated, Deref::deref)
         }
         CrateFlavor::Rmeta => {
             // mmap the file, because only a small fraction of it is read.
@@ -840,7 +840,7 @@ fn get_metadata_section<'p>(
                 ))
             })?;
 
-            rustc_erase_owner!(OwningRef::new(mmap).map_owner_box())
+            slice_owned(mmap, Deref::deref)
         }
     };
     let blob = MetadataBlob::new(raw_bytes);

compiler/rustc_metadata/src/rmeta/decoder.rs

@@ -51,12 +51,6 @@ mod cstore_impl;
 #[derive(Clone)]
 pub(crate) struct MetadataBlob(Lrc<MetadataRef>);
 
-// This is needed so we can create an OwningRef into the blob.
-// The data behind a `MetadataBlob` has a stable address because it is
-// contained within an Rc/Arc.
-unsafe impl rustc_data_structures::owning_ref::StableAddress for MetadataBlob {}
-
-// This is needed so we can create an OwningRef into the blob.
 impl std::ops::Deref for MetadataBlob {
     type Target = [u8];
 

compiler/rustc_metadata/src/rmeta/def_path_hash_map.rs

@@ -1,14 +1,14 @@
 use crate::rmeta::DecodeContext;
 use crate::rmeta::EncodeContext;
-use crate::rmeta::MetadataBlob;
-use rustc_data_structures::owning_ref::OwningRef;
+use rustc_data_structures::owned_slice::slice_owned;
+use rustc_data_structures::owned_slice::OwnedSlice;
 use rustc_hir::def_path_hash_map::{Config as HashMapConfig, DefPathHashMap};
 use rustc_middle::parameterized_over_tcx;
 use rustc_serialize::{Decodable, Decoder, Encodable, Encoder};
 use rustc_span::def_id::{DefIndex, DefPathHash};
 
 pub(crate) enum DefPathHashMapRef<'tcx> {
-    OwnedFromMetadata(odht::HashTable<HashMapConfig, OwningRef<MetadataBlob, [u8]>>),
+    OwnedFromMetadata(odht::HashTable<HashMapConfig, OwnedSlice>),
     BorrowedFromTcx(&'tcx DefPathHashMap),
 }
 
@@ -50,11 +50,11 @@ impl<'a, 'tcx> Decodable<DecodeContext<'a, 'tcx>> for DefPathHashMapRef<'static>
 
         let len = d.read_usize();
         let pos = d.position();
-        let o = OwningRef::new(d.blob().clone()).map(|x| &x[pos..pos + len]);
+        let o = slice_owned(d.blob().clone(), |blob| &blob[pos..pos + len]);
 
-        // Although we already have the data we need via the OwningRef, we still need
-        // to advance the DecodeContext's position so it's in a valid state after
-        // the method. We use read_raw_bytes() for that.
+        // Although we already have the data we need via the `OwnedSlice`, we still need
+        // to advance the `DecodeContext`'s position so it's in a valid state after
+        // the method. We use `read_raw_bytes()` for that.
         let _ = d.read_raw_bytes(len);
 
         let inner = odht::HashTable::from_raw_bytes(o).unwrap_or_else(|e| {