Deserialize Box<Path> through PathBuf::into_boxed_path

Including Rc<Path> et al.

Fixes https://github.com/serde-rs/serde/issues/1633

serde/build.rs

@@ -29,8 +29,9 @@ fn main() {
         println!("cargo:rustc-cfg=core_reverse");
     }
 
-    // CString::into_boxed_c_str stabilized in Rust 1.20:
+    // CString::into_boxed_c_str and PathBuf::into_boxed_path stabilized in Rust 1.20:
     // https://doc.rust-lang.org/std/ffi/struct.CString.html#method.into_boxed_c_str
+    // https://doc.rust-lang.org/std/path/struct.PathBuf.html#method.into_boxed_path
     if minor >= 20 {
         println!("cargo:rustc-cfg=de_boxed_c_str");
     }

serde/src/de/impls.rs

@@ -1610,6 +1610,9 @@ impl<'de> Deserialize<'de> for PathBuf {
     }
 }
 
+#[cfg(all(feature = "std", de_boxed_c_str))]
+forwarded_impl!((), Box<Path>, PathBuf::into_boxed_path);
+
 ////////////////////////////////////////////////////////////////////////////////
 
 // If this were outside of the serde crate, it would just use:

test_suite/tests/test_de.rs

@@ -907,6 +907,20 @@ declare_tests! {
             Token::ByteBuf(b"/usr/local/lib"),
         ],
     }
+    test_boxed_path {
+        PathBuf::from("/usr/local/lib").into_boxed_path() => &[
+            Token::Str("/usr/local/lib"),
+        ],
+        PathBuf::from("/usr/local/lib").into_boxed_path() => &[
+            Token::String("/usr/local/lib"),
+        ],
+        PathBuf::from("/usr/local/lib").into_boxed_path() => &[
+            Token::Bytes(b"/usr/local/lib"),
+        ],
+        PathBuf::from("/usr/local/lib").into_boxed_path() => &[
+            Token::ByteBuf(b"/usr/local/lib"),
+        ],
+    }
     test_cstring {
         CString::new("abc").unwrap() => &[
             Token::Bytes(b"abc"),