rustc: Accept 'const' as synonym for 'mutable?'

src/comp/syntax/parse/parser.rs

@@ -746,10 +746,13 @@ fn parse_path_and_ty_param_substs(p: parser) -> ast::path {
 
 fn parse_mutability(p: parser) -> ast::mutability {
     if eat_word(p, "mutable") {
-        if p.peek() == token::QUES { p.bump(); ret ast::maybe_mut; }
+        if p.peek() == token::QUES { p.bump(); ast::maybe_mut }
-        ret ast::mut;
+        else { ast::mut }
+    } else if eat_word(p, "const") {
+        ast::maybe_mut
+    } else {
+        ast::imm
     }
-    ret ast::imm;
 }
 
 fn parse_field(p: parser, sep: token::token) -> ast::field {

src/comp/syntax/print/pprust.rs

@@ -264,7 +264,7 @@ fn print_type(s: ps, &&ty: @ast::ty) {
         word(s.s, "[");
         alt mt.mut {
           ast::mut. { word_space(s, "mutable"); }
-          ast::maybe_mut. { word_space(s, "mutable?"); }
+          ast::maybe_mut. { word_space(s, "const"); }
           ast::imm. { }
         }
         print_type(s, mt.ty);

src/test/run-pass/maybe-mutable.rs

@@ -2,7 +2,7 @@
 
 
 // -*- rust -*-
-fn len(v: [mutable? int]) -> uint {
+fn len(v: [const int]) -> uint {
     let i = 0u;
     for x: int in v { i += 1u; }
     ret i;

src/test/run-pass/mutable-huh-variance-vec1.rs

@@ -6,7 +6,7 @@ fn main() {
     // This is ok because the outer vec is covariant with respect
     // to the inner vec. If the outer vec was mutable then we
     // couldn't do this.
-    fn f(&&v: [[mutable? int]]) {
+    fn f(&&v: [[const int]]) {
     }
 
     f(v);

src/test/run-pass/mutable-huh-variance-vec2.rs

@@ -6,7 +6,7 @@ fn main() {
     // This is ok because the outer vec is covariant with respect
     // to the inner vec. If the outer vec was mutable then we
     // couldn't do this.
-    fn f(&&v: [mutable? [mutable? int]]) {
+    fn f(&&v: [const [const int]]) {
     }
 
     f(v);