librustc: Remove implicit self from the language, except for old-style drop blocks.

src/libsyntax/parse/obsolete.rs

@@ -56,6 +56,7 @@ pub enum ObsoleteSyntax {
     ObsoleteBareFnType,
     ObsoleteNewtypeEnum,
     ObsoleteMode,
+    ObsoleteImplicitSelf,
 }
 
 impl to_bytes::IterBytes for ObsoleteSyntax {
@@ -181,6 +182,11 @@ pub impl Parser {
                 "obsolete argument mode",
                 "replace `-` or `++` mode with `+`"
             ),
+            ObsoleteImplicitSelf => (
+                "implicit self",
+                "use an explicit `self` declaration or declare the method as \
+                 static"
+            ),
         };
 
         self.report(sp, kind, kind_str, desc);

src/libsyntax/parse/parser.rs

@@ -78,7 +78,7 @@ use parse::obsolete::{ObsoleteMutVector, ObsoleteTraitImplVisibility};
 use parse::obsolete::{ObsoleteRecordType, ObsoleteRecordPattern};
 use parse::obsolete::{ObsoleteAssertion, ObsoletePostFnTySigil};
 use parse::obsolete::{ObsoleteBareFnType, ObsoleteNewtypeEnum};
-use parse::obsolete::{ObsoleteMode};
+use parse::obsolete::{ObsoleteMode, ObsoleteImplicitSelf};
 use parse::prec::{as_prec, token_to_binop};
 use parse::token::{can_begin_expr, is_ident, is_ident_or_path};
 use parse::token::{is_plain_ident, INTERPOLATED, special_idents};
@@ -471,6 +471,10 @@ pub impl Parser {
             // XXX: Wrong. Shouldn't allow both static and self_ty
             let self_ty = if is_static { static_sty } else { self_ty };
 
+            if self_ty.node == sty_by_ref {
+                self.obsolete(self_ty.span, ObsoleteImplicitSelf);
+            }
+
             let hi = p.last_span.hi;
             debug!("parse_trait_methods(): trait method signature ends in \
                     `%s`",
@@ -2981,6 +2985,10 @@ pub impl Parser {
         // XXX: interaction between staticness, self_ty is broken now
         let self_ty = if is_static { static_sty} else { self_ty };
 
+        if self_ty.node == sty_by_ref {
+            self.obsolete(self_ty.span, ObsoleteImplicitSelf);
+        }
+
         let (inner_attrs, body) = self.parse_inner_attrs_and_block(true);
         let hi = body.span.hi;
         let attrs = vec::append(attrs, inner_attrs);