Auto merge of #50307 - petrochenkov:keyhyg2, r=nikomatsakis

Implement edition hygiene for keywords

Determine "keywordness" of an identifier in its hygienic context.
cc https://github.com/rust-lang/rust/pull/49611

I've resurrected `proc` as an Edition-2015-only keyword for testing purposes, but it should probably be buried again. EDIT: `proc` is removed again.

1 files changed, 8 insertions, 0 deletions

diff --git a/src/libsyntax_pos/lib.rs b/src/libsyntax_pos/lib.rs
index 73f0e6a6018..17163576901 100644
--- a/src/libsyntax_pos/lib.rs
+++ b/src/libsyntax_pos/lib.rs
@@ -20,6 +20,7 @@
 
 #![feature(const_fn)]
 #![feature(custom_attribute)]
+#![feature(non_exhaustive)]
 #![feature(optin_builtin_traits)]
 #![allow(unused_attributes)]
 #![feature(specialization)]
@@ -48,6 +49,7 @@ extern crate serialize as rustc_serialize; // used by deriving
 
 extern crate unicode_width;
 
+pub mod edition;
 pub mod hygiene;
 pub use hygiene::{Mark, SyntaxContext, ExpnInfo, ExpnFormat, NameAndSpan, CompilerDesugaringKind};
 
@@ -298,6 +300,12 @@ impl Span {
         self.ctxt().outer().expn_info().map(|i| i.call_site)
     }
 
+    /// Edition of the crate from which this span came.
+    pub fn edition(self) -> edition::Edition {
+        self.ctxt().outer().expn_info().map_or_else(|| hygiene::default_edition(),
+                                                    |einfo| einfo.callee.edition)
+    }
+
     /// Return the source callee.
     ///
     /// Returns None if the supplied span has no expansion trace,