Auto merge of rust-lang#98265 - JohnTitor:rollup-wtfqc4g, r=JohnTitor

Rollup of 4 pull requests

Successful merges:

 - rust-lang#95534 (Add `core::mem::copy` to complement `core::mem::drop`.)
 - rust-lang#97912 (Stabilize `Path::try_exists()` and improve doc)
 - rust-lang#98225 (Make debug_triple depend on target json file content rather than file path)
 - rust-lang#98257 (Fix typos in `IntoFuture` docs)

Failed merges:

r? `@ghost`
`@rustbot` modify labels: rollup

compiler/rustc_error_messages/src/lib.rs

@@ -1,6 +1,5 @@
 #![feature(let_chains)]
 #![feature(once_cell)]
-#![feature(path_try_exists)]
 #![feature(rustc_attrs)]
 #![feature(type_alias_impl_trait)]
 

compiler/rustc_target/src/spec/mod.rs

@@ -39,11 +39,13 @@ use crate::json::{Json, ToJson};
 use crate::spec::abi::{lookup as lookup_abi, Abi};
 use crate::spec::crt_objects::{CrtObjects, CrtObjectsFallback};
 use rustc_data_structures::stable_hasher::{HashStable, StableHasher};
+use rustc_serialize::{Decodable, Decoder, Encodable, Encoder};
 use rustc_span::symbol::{sym, Symbol};
 use serde_json::Value;
 use std::borrow::Cow;
 use std::collections::BTreeMap;
 use std::convert::TryFrom;
+use std::hash::{Hash, Hasher};
 use std::iter::FromIterator;
 use std::ops::{Deref, DerefMut};
 use std::path::{Path, PathBuf};
@@ -2183,7 +2185,7 @@ impl Target {
             TargetTriple::TargetTriple(ref target_triple) => {
                 load_builtin(target_triple).expect("built-in target")
             }
-            TargetTriple::TargetPath(..) => {
+            TargetTriple::TargetJson { .. } => {
                 panic!("built-in targets doens't support target-paths")
             }
         }
@@ -2248,11 +2250,9 @@ impl Target {
 
                 Err(format!("Could not find specification for target {:?}", target_triple))
             }
-            TargetTriple::TargetPath(ref target_path) => {
-                if target_path.is_file() {
-                    return load_file(&target_path);
-                }
-                Err(format!("Target path {:?} is not a valid file", target_path))
+            TargetTriple::TargetJson { ref contents, .. } => {
+                let obj = serde_json::from_str(contents).map_err(|e| e.to_string())?;
+                Target::from_json(obj)
             }
         }
     }
@@ -2421,10 +2421,77 @@ impl ToJson for Target {
 }
 
 /// Either a target triple string or a path to a JSON file.
-#[derive(PartialEq, Clone, Debug, Hash, Encodable, Decodable)]
+#[derive(Clone, Debug)]
 pub enum TargetTriple {
     TargetTriple(String),
-    TargetPath(PathBuf),
+    TargetJson {
+        /// Warning: This field may only be used by rustdoc. Using it anywhere else will lead to
+        /// inconsistencies as it is discarded during serialization.
+        path_for_rustdoc: PathBuf,
+        triple: String,
+        contents: String,
+    },
+}
+
+// Use a manual implementation to ignore the path field
+impl PartialEq for TargetTriple {
+    fn eq(&self, other: &Self) -> bool {
+        match (self, other) {
+            (Self::TargetTriple(l0), Self::TargetTriple(r0)) => l0 == r0,
+            (
+                Self::TargetJson { path_for_rustdoc: _, triple: l_triple, contents: l_contents },
+                Self::TargetJson { path_for_rustdoc: _, triple: r_triple, contents: r_contents },
+            ) => l_triple == r_triple && l_contents == r_contents,
+            _ => false,
+        }
+    }
+}
+
+// Use a manual implementation to ignore the path field
+impl Hash for TargetTriple {
+    fn hash<H: Hasher>(&self, state: &mut H) -> () {
+        match self {
+            TargetTriple::TargetTriple(triple) => {
+                0u8.hash(state);
+                triple.hash(state)
+            }
+            TargetTriple::TargetJson { path_for_rustdoc: _, triple, contents } => {
+                1u8.hash(state);
+                triple.hash(state);
+                contents.hash(state)
+            }
+        }
+    }
+}
+
+// Use a manual implementation to prevent encoding the target json file path in the crate metadata
+impl<S: Encoder> Encodable<S> for TargetTriple {
+    fn encode(&self, s: &mut S) {
+        match self {
+            TargetTriple::TargetTriple(triple) => s.emit_enum_variant(0, |s| s.emit_str(triple)),
+            TargetTriple::TargetJson { path_for_rustdoc: _, triple, contents } => s
+                .emit_enum_variant(1, |s| {
+                    s.emit_str(triple);
+                    s.emit_str(contents)
+                }),
+        }
+    }
+}
+
+impl<D: Decoder> Decodable<D> for TargetTriple {
+    fn decode(d: &mut D) -> Self {
+        match d.read_usize() {
+            0 => TargetTriple::TargetTriple(d.read_str().to_owned()),
+            1 => TargetTriple::TargetJson {
+                path_for_rustdoc: PathBuf::new(),
+                triple: d.read_str().to_owned(),
+                contents: d.read_str().to_owned(),
+            },
+            _ => {
+                panic!("invalid enum variant tag while decoding `TargetTriple`, expected 0..2");
+            }
+        }
+    }
 }
 
 impl TargetTriple {
@@ -2436,20 +2503,28 @@ impl TargetTriple {
     /// Creates a target triple from the passed target path.
     pub fn from_path(path: &Path) -> Result<Self, io::Error> {
         let canonicalized_path = path.canonicalize()?;
-        Ok(TargetTriple::TargetPath(canonicalized_path))
+        let contents = std::fs::read_to_string(&canonicalized_path).map_err(|err| {
+            io::Error::new(
+                io::ErrorKind::InvalidInput,
+                format!("target path {:?} is not a valid file: {}", canonicalized_path, err),
+            )
+        })?;
+        let triple = canonicalized_path
+            .file_stem()
+            .expect("target path must not be empty")
+            .to_str()
+            .expect("target path must be valid unicode")
+            .to_owned();
+        Ok(TargetTriple::TargetJson { path_for_rustdoc: canonicalized_path, triple, contents })
     }
 
     /// Returns a string triple for this target.
     ///
     /// If this target is a path, the file name (without extension) is returned.
     pub fn triple(&self) -> &str {
         match *self {
-            TargetTriple::TargetTriple(ref triple) => triple,
-            TargetTriple::TargetPath(ref path) => path
-                .file_stem()
-                .expect("target path must not be empty")
-                .to_str()
-                .expect("target path must be valid unicode"),
+            TargetTriple::TargetTriple(ref triple)
+            | TargetTriple::TargetJson { ref triple, .. } => triple,
         }
     }
 
@@ -2459,16 +2534,15 @@ impl TargetTriple {
     /// by `triple()`.
     pub fn debug_triple(&self) -> String {
         use std::collections::hash_map::DefaultHasher;
-        use std::hash::{Hash, Hasher};
-
-        let triple = self.triple();
-        if let TargetTriple::TargetPath(ref path) = *self {
-            let mut hasher = DefaultHasher::new();
-            path.hash(&mut hasher);
-            let hash = hasher.finish();
-            format!("{}-{}", triple, hash)
-        } else {
-            triple.into()
+
+        match self {
+            TargetTriple::TargetTriple(triple) => triple.to_owned(),
+            TargetTriple::TargetJson { path_for_rustdoc: _, triple, contents: content } => {
+                let mut hasher = DefaultHasher::new();
+                content.hash(&mut hasher);
+                let hash = hasher.finish();
+                format!("{}-{}", triple, hash)
+            }
         }
     }
 }

library/core/src/future/into_future.rs

@@ -2,7 +2,7 @@ use crate::future::Future;
 
 /// Conversion into a `Future`.
 ///
-/// By implementing `Intofuture` for a type, you define how it will be
+/// By implementing `IntoFuture` for a type, you define how it will be
 /// converted to a future.
 ///
 /// # `.await` desugaring
@@ -29,7 +29,7 @@ use crate::future::Future;
 /// When implementing futures manually there will often be a choice between
 /// implementing `Future` or `IntoFuture` for a type. Implementing `Future` is a
 /// good choice in most cases. But implementing `IntoFuture` is most useful when
-/// implementing "async builder" types, which allows the type to be modified
+/// implementing "async builder" types, which allow their values to be modified
 /// multiple times before being `.await`ed.
 ///
 /// ```rust

library/core/src/mem/mod.rs

@@ -973,6 +973,28 @@ pub const fn replace<T>(dest: &mut T, src: T) -> T {
 #[cfg_attr(not(test), rustc_diagnostic_item = "mem_drop")]
 pub fn drop<T>(_x: T) {}
 
+/// Bitwise-copies a value.
+///
+/// This function is not magic; it is literally defined as
+/// ```
+/// pub fn copy<T: Copy>(x: &T) -> T { *x }
+/// ```
+///
+/// It is useful when you want to pass a function pointer to a combinator, rather than defining a new closure.
+///
+/// Example:
+/// ```
+/// #![feature(mem_copy_fn)]
+/// use core::mem::copy;
+/// let result_from_ffi_function: Result<(), &i32> = Err(&1);
+/// let result_copied: Result<(), i32> = result_from_ffi_function.map_err(copy);
+/// ```
+#[inline]
+#[unstable(feature = "mem_copy_fn", issue = "98262")]
+pub fn copy<T: Copy>(x: &T) -> T {
+    *x
+}
+
 /// Interprets `src` as having type `&U`, and then reads `src` without moving
 /// the contained value.
 ///

library/std/src/fs.rs

@@ -2317,10 +2317,14 @@ impl AsInnerMut<fs_imp::DirBuilder> for DirBuilder {
 /// unrelated to the path not existing. (E.g. it will return `Err(_)` in case of permission
 /// denied on some of the parent directories.)
 ///
+/// Note that while this avoids some pitfalls of the `exists()` method, it still can not
+/// prevent time-of-check to time-of-use (TOCTOU) bugs. You should only use it in scenarios
+/// where those bugs are not an issue.
+///
 /// # Examples
 ///
 /// ```no_run
-/// #![feature(path_try_exists)]
+/// #![feature(fs_try_exists)]
 /// use std::fs;
 ///
 /// assert!(!fs::try_exists("does_not_exist.txt").expect("Can't check existence of file does_not_exist.txt"));
@@ -2330,7 +2334,7 @@ impl AsInnerMut<fs_imp::DirBuilder> for DirBuilder {
 /// [`Path::exists`]: crate::path::Path::exists
 // FIXME: stabilization should modify documentation of `exists()` to recommend this method
 // instead.
-#[unstable(feature = "path_try_exists", issue = "83186")]
+#[unstable(feature = "fs_try_exists", issue = "83186")]
 #[inline]
 pub fn try_exists<P: AsRef<Path>>(path: P) -> io::Result<bool> {
     fs_imp::try_exists(path.as_ref())

library/std/src/path.rs

@@ -2705,6 +2705,9 @@ impl Path {
 
     /// Returns `true` if the path points at an existing entity.
     ///
+    /// Warning: this method may be error-prone, consider using [`try_exists()`] instead!
+    /// It also has a risk of introducing time-of-check to time-of-use (TOCTOU) bugs.
+    ///
     /// This function will traverse symbolic links to query information about the
     /// destination file.
     ///
@@ -2721,7 +2724,9 @@ impl Path {
     /// # See Also
     ///
     /// This is a convenience function that coerces errors to false. If you want to
-    /// check errors, call [`fs::metadata`].
+    /// check errors, call [`Path::try_exists`].
+    ///
+    /// [`try_exists()`]: Self::try_exists
     #[stable(feature = "path_ext", since = "1.5.0")]
     #[must_use]
     #[inline]
@@ -2738,20 +2743,20 @@ impl Path {
     /// unrelated to the path not existing. (E.g. it will return `Err(_)` in case of permission
     /// denied on some of the parent directories.)
     ///
+    /// Note that while this avoids some pitfalls of the `exists()` method, it still can not
+    /// prevent time-of-check to time-of-use (TOCTOU) bugs. You should only use it in scenarios
+    /// where those bugs are not an issue.
+    ///
     /// # Examples
     ///
     /// ```no_run
-    /// #![feature(path_try_exists)]
-    ///
     /// use std::path::Path;
     /// assert!(!Path::new("does_not_exist.txt").try_exists().expect("Can't check existence of file does_not_exist.txt"));
     /// assert!(Path::new("/root/secret_file.txt").try_exists().is_err());
     /// ```
     ///
     /// [`exists()`]: Self::exists
-    // FIXME: stabilization should modify documentation of `exists()` to recommend this method
-    // instead.
-    #[unstable(feature = "path_try_exists", issue = "83186")]
+    #[stable(feature = "path_try_exists", since = "1.63.0")]
     #[inline]
     pub fn try_exists(&self) -> io::Result<bool> {
         fs::try_exists(self)

src/librustdoc/doctest.rs

@@ -365,8 +365,8 @@ fn run_test(
     }
     compiler.arg("--target").arg(match target {
         TargetTriple::TargetTriple(s) => s,
-        TargetTriple::TargetPath(path) => {
-            path.to_str().expect("target path must be valid unicode").to_string()
+        TargetTriple::TargetJson { path_for_rustdoc, .. } => {
+            path_for_rustdoc.to_str().expect("target path must be valid unicode").to_string()
         }
     });
     if let ErrorOutputType::HumanReadable(kind) = rustdoc_options.error_format {