Auto merge of #61541 - petrochenkov:tsp, r=oli-obk

syntax: Keep token span as a part of `Token`

In the world with proc macros and edition hygiene `Token` without a span is not self-contained.
In practice this means that tokens and spans are always stored and passed somewhere along with each other.
This PR combines them into a single struct by doing the next renaming/replacement:

- `Token` -> `TokenKind`
- `TokenAndSpan` -> `Token`
- `(Token, Span)` -> `Token`

Some later commits (https://github.com/rust-lang/rust/commit/fb6e2fe8fd6caed247857758c6c3549fe2b59527 and https://github.com/rust-lang/rust/commit/1cdee86940db892cd17239c26add5364335e895a) remove duplicate spans in `token::Ident` and `token::Lifetime`.
Those spans were supposed to be identical to token spans, but could easily go out of sync, as was noticed in https://github.com/rust-lang/rust/pull/60965#discussion_r285398523.
The `(Token, Span)` -> `Token` change is a soft pre-requisite for this de-duplication since it allows to avoid some larger churn (passing spans to most of functions classifying identifiers).

1 files changed, 5 insertions, 3 deletions

diff --git a/src/libsyntax/feature_gate.rs b/src/libsyntax/feature_gate.rs
index 4a95b6f69a1..64415204047 100644
--- a/src/libsyntax/feature_gate.rs
+++ b/src/libsyntax/feature_gate.rs
@@ -1958,9 +1958,11 @@ impl<'a> Visitor<'a> for PostExpansionVisitor<'a> {
                 name,
                 template
             ),
-            None => if let Some(TokenTree::Token(_, token::Eq)) = attr.tokens.trees().next() {
-                // All key-value attributes are restricted to meta-item syntax.
-                attr.parse_meta(self.context.parse_sess).map_err(|mut err| err.emit()).ok();
+            None => if let Some(TokenTree::Token(token)) = attr.tokens.trees().next() {
+                if token == token::Eq {
+                    // All key-value attributes are restricted to meta-item syntax.
+                    attr.parse_meta(self.context.parse_sess).map_err(|mut err| err.emit()).ok();
+                }
             }
         }
     }