rollup merge of #23749: alexcrichton/remove-old-impl-check

Conflicts:
	src/libsyntax/feature_gate.rs

diff --cc src/libstd/lib.rs
Simple merge

diff --cc src/libstd/old_io/mod.rs
Simple merge

diff --cc src/libstd/old_io/net/pipe.rs
Simple merge

diff --cc src/libstd/old_io/net/tcp.rs
Simple merge

diff --cc src/libstd/old_io/result.rs
Simple merge

diff --cc src/libsyntax/feature_gate.rs
index ad0fa500c2875ddb15f879e2a29496cc3b708b07,0f281c6f8f9bd8551331fd98d1b3444e8f265e80..70f43776ff0c1ad6b3eed77777701e870ffa30b6
--- 1/src/libsyntax/feature_gate.rs
--- 2/src/libsyntax/feature_gate.rs
+++ b/src/libsyntax/feature_gate.rs
@@@ -276,12 -277,7 +273,11 @@@ pub const KNOWN_ATTRIBUTES: &'static [(
  
      // FIXME: #19470 this shouldn't be needed forever
      ("old_orphan_check", Whitelisted),
-     ("old_impl_check", Whitelisted),
 -    ("rustc_paren_sugar", Whitelisted), // FIXME: #18101 temporary unboxed closure hack
 +
 +    ("rustc_paren_sugar", Gated("unboxed_closures",
 +                                "unboxed_closures are still evolving")),
 +    ("rustc_reflect_like", Gated("reflect",
 +                                 "defining reflective traits is still evolving")),
  
      // Crate level attributes
      ("crate_name", CrateLevel),