libsyntax: Stop parsing ~mut

src/libsyntax/parse/obsolete.rs

@@ -48,6 +48,7 @@ pub enum ObsoleteSyntax {
     ObsoleteUnenforcedBound,
     ObsoleteImplSyntax,
     ObsoleteTraitBoundSeparator,
+    ObsoleteMutOwnedPointer,
 }
 
 pub impl to_bytes::IterBytes for ObsoleteSyntax {
@@ -126,6 +127,12 @@ pub impl Parser {
                 "space-separated trait bounds",
                 "write `+` between trait bounds"
             ),
+            ObsoleteMutOwnedPointer => (
+                "mutable owned pointer",
+                "mutability inherits through `~` pointers; place the `~` box
+                 in a mutable location, like a mutable local variable or an \
+                 `@mut` box"
+            ),
         };
 
         self.report(sp, kind, kind_str, desc);

src/libsyntax/parse/parser.rs

@@ -75,7 +75,7 @@ use parse::obsolete::{ObsoleteMoveInit, ObsoleteBinaryMove};
 use parse::obsolete::{ObsoleteStructCtor, ObsoleteWith};
 use parse::obsolete::{ObsoleteSyntax, ObsoleteLowerCaseKindBounds};
 use parse::obsolete::{ObsoleteUnsafeBlock, ObsoleteImplSyntax};
-use parse::obsolete::{ObsoleteTraitBoundSeparator};
+use parse::obsolete::{ObsoleteTraitBoundSeparator, ObsoleteMutOwnedPointer};
 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};
@@ -677,6 +677,11 @@ pub impl Parser {
         // rather than boxed ptrs.  But the special casing of str/vec is not
         // reflected in the AST type.
         let mt = self.parse_mt();
+
+        if mt.mutbl == m_mutbl && sigil == OwnedSigil {
+            self.obsolete(*self.last_span, ObsoleteMutOwnedPointer);
+        }
+
         ctor(mt)
     }