Auto merge of #9183 - weihanglo:refactor/straighforward-deref, r=alexcrichton

refactor: make deref intentions more straightforward

Just some little tweaks to make intentions of deref more straightforward.

src/cargo/core/manifest.rs

@@ -285,7 +285,7 @@ impl ser::Serialize for Target {
             edition: &self.edition().to_string(),
             required_features: self
                 .required_features()
-                .map(|rf| rf.iter().map(|s| &**s).collect()),
+                .map(|rf| rf.iter().map(|s| s.as_str()).collect()),
             doc: self.documented(),
             doctest: self.doctested() && self.doctestable(),
             test: self.tested(),

src/cargo/core/source/mod.rs

@@ -271,20 +271,12 @@ impl<'src> SourceMap<'src> {
 
     /// Like `HashMap::get`.
     pub fn get(&self, id: SourceId) -> Option<&(dyn Source + 'src)> {
-        let source = self.map.get(&id);
-
-        source.map(|s| {
-            let s: &(dyn Source + 'src) = &**s;
-            s
-        })
+        self.map.get(&id).map(|s| s.as_ref())
     }
 
     /// Like `HashMap::get_mut`.
     pub fn get_mut(&mut self, id: SourceId) -> Option<&mut (dyn Source + 'src)> {
-        self.map.get_mut(&id).map(|s| {
-            let s: &mut (dyn Source + 'src) = &mut **s;
-            s
-        })
+        self.map.get_mut(&id).map(|s| s.as_mut())
     }
 
     /// Like `HashMap::get`, but first calculates the `SourceId` from a `PackageId`.

src/cargo/ops/lockfile.rs

@@ -96,7 +96,7 @@ fn resolve_to_string_orig(
         f.read_to_string(&mut s)?;
         Ok(s)
     });
-    let out = serialize_resolve(resolve, orig.as_ref().ok().map(|s| &**s));
+    let out = serialize_resolve(resolve, orig.as_deref().ok());
     (orig.ok(), out, ws_root)
 }
 

src/cargo/ops/vendor.rs

@@ -74,10 +74,7 @@ fn sync(
     opts: &VendorOptions<'_>,
 ) -> CargoResult<VendorConfig> {
     let canonical_destination = opts.destination.canonicalize();
-    let canonical_destination = canonical_destination
-        .as_ref()
-        .map(|p| &**p)
-        .unwrap_or(opts.destination);
+    let canonical_destination = canonical_destination.as_deref().unwrap_or(opts.destination);
 
     paths::create_dir_all(&canonical_destination)?;
     let mut to_remove = HashSet::new();