Enforce mutability declarations in classes; correct shapes for classes

1. Enforce mutability declarations on class fields. Don't allow any
mutation of class fields not declared as mutable (except inside the
constructor).

2. Handle classes correctly in shape (treat classes like records).

src/rustc/metadata/common.rs

@@ -78,6 +78,7 @@ const tag_path_len: uint = 0x41u;
 const tag_path_elt_mod: uint = 0x42u;
 const tag_path_elt_name: uint = 0x43u;
 const tag_item_field: uint = 0x44u;
+const tag_class_mut: uint = 0x45u;
 
 // used to encode crate_ctxt side tables
 enum astencode_tag { // Reserves 0x50 -- 0x6f

src/rustc/metadata/decoder.rs

@@ -118,6 +118,18 @@ fn class_member_id(d: ebml::doc, cdata: cmd) -> ast::def_id {
     ret translate_def_id(cdata, parse_def_id(ebml::doc_data(tagdoc)));
 }
 
+fn field_mutability(d: ebml::doc) -> ast::class_mutability {
+    // Use maybe_get_doc in case it's a method
+    option::maybe(ebml::maybe_get_doc(d, tag_class_mut),
+                  ast::class_immutable,
+                  {|d|
+                  alt ebml::doc_as_u8(d) as char {
+                    'm' { ast::class_mutable }
+                    _   { ast::class_immutable }
+                  }
+                  })
+}
+
 fn variant_disr_val(d: ebml::doc) -> option<int> {
     option::chain(ebml::maybe_get_doc(d, tag_disr_val)) {|val_doc|
         int::parse_buf(ebml::doc_data(val_doc), 10u)
@@ -435,9 +447,9 @@ fn get_class_members(cdata: cmd, id: ast::node_id,
        if p(f) {
           let name = item_name(an_item);
           let did = class_member_id(an_item, cdata);
+          let mt = field_mutability(an_item);
           result += [{ident: name, id: did, privacy:
-                  // This won't work for methods, argh
-                  family_to_privacy(f)}];
+                  family_to_privacy(f), mutability: mt}];
        }
     }
     result

src/rustc/metadata/encoder.rs

@@ -47,6 +47,13 @@ fn encode_named_def_id(ebml_w: ebml::writer, name: str, id: def_id) {
     }
 }
 
+fn encode_mutability(ebml_w: ebml::writer, mt: class_mutability) {
+    ebml_w.wr_tag(tag_class_mut) {||
+        ebml_w.writer.write([alt mt { class_immutable { 'i' }
+                class_mutable { 'm' } } as u8]);
+        }
+}
+
 type entry<T> = {val: T, pos: uint};
 
 fn encode_enum_variant_paths(ebml_w: ebml::writer, variants: [variant],
@@ -370,7 +377,7 @@ fn encode_info_for_class(ecx: @encode_ctxt, ebml_w: ebml::writer,
      /* We encode both private and public fields -- need to include
         private fields to get the offsets right */
       alt ci.node.decl {
-        instance_var(nm, _, _, id) {
+        instance_var(nm, _, mt, id) {
           *index += [{val: id, pos: ebml_w.writer.tell()}];
           ebml_w.start_tag(tag_items_data_item);
           #debug("encode_info_for_class: doing %s %d", nm, id);
@@ -378,7 +385,7 @@ fn encode_info_for_class(ecx: @encode_ctxt, ebml_w: ebml::writer,
           encode_name(ebml_w, nm);
           encode_path(ebml_w, path, ast_map::path_name(nm));
           encode_type(ecx, ebml_w, node_id_to_type(tcx, id));
-          /* TODO: mutability */
+          encode_mutability(ebml_w, mt);
           encode_def_id(ebml_w, local_def(id));
           ebml_w.end_tag();
         }