Implement reference counting (#592)

std/assembly/symbol.ts

@@ -1,10 +1,87 @@
 import { Map } from "./map";
 
-@lazy var stringToId: Map<string, usize>;
-@lazy var idToString: Map<usize, string>;
-@lazy var nextId: usize = 12; // Symbol.unscopables + 1
+// @ts-ignore: decorator
+@lazy
+var stringToId: Map<string, usize>;
+
+// @ts-ignore: decorator
+@lazy
+var idToString: Map<usize, string>;
+
+// @ts-ignore: decorator
+@lazy
+var nextId: usize = 12; // Symbol.unscopables + 1
+
+@unmanaged @sealed abstract class _Symbol {
+
+  // TODO: all of the following default symbols are unused currently yet add to
+  // binary size if #toString becomes compiled. Ultimately we'll most likely want
+  // to remove the unsupported ones and only keep what's actually supported.
+
+  // @ts-ignore: decorator
+  @lazy
+  static readonly hasInstance: symbol = changetype<symbol>(1);
+
+  // @ts-ignore: decorator
+  @lazy
+  static readonly isConcatSpreadable: symbol = changetype<symbol>(2);
+
+  // @ts-ignore: decorator
+  @lazy
+  static readonly isRegExp: symbol = changetype<symbol>(3);
+
+  // @ts-ignore: decorator
+  @lazy
+  static readonly iterator: symbol = changetype<symbol>(3);
+
+  // @ts-ignore: decorator
+  @lazy
+  static readonly match: symbol = changetype<symbol>(4);
+
+  // @ts-ignore: decorator
+  @lazy
+  static readonly replace: symbol = changetype<symbol>(5);
+
+  // @ts-ignore: decorator
+  @lazy
+  static readonly search: symbol = changetype<symbol>(6);
+
+  // @ts-ignore: decorator
+  @lazy
+  static readonly species: symbol = changetype<symbol>(7);
+
+  // @ts-ignore: decorator
+  @lazy
+  static readonly split: symbol = changetype<symbol>(8);
+
+  // @ts-ignore: decorator
+  @lazy
+  static readonly toPrimitive: symbol = changetype<symbol>(9);
+
+  // @ts-ignore: decorator
+  @lazy
+  static readonly toStringTag: symbol = changetype<symbol>(10);
+
+  // @ts-ignore: decorator
+  @lazy
+  static readonly unscopables: symbol = changetype<symbol>(11);
+
+  static for(key: string): symbol {
+    if (!stringToId) { stringToId = new Map(); idToString = new Map(); }
+    else if (stringToId.has(key)) return changetype<symbol>(stringToId.get(key));
+    var id = nextId++;
+    if (!id) unreachable(); // out of ids
+    stringToId.set(key, id);
+    idToString.set(id, key);
+    return changetype<symbol>(id);
+  }
+
+  static keyFor(sym: symbol): string | null {
+    return idToString !== null && idToString.has(changetype<usize>(sym))
+      ? idToString.get(changetype<usize>(sym))
+      : null;
+  }
 
-@unmanaged export class symbol {
   toString(): string {
     var id = changetype<usize>(this);
     var str = "";
@@ -35,37 +112,7 @@ export function Symbol(description: string | null = null): symbol {
   return changetype<symbol>(id);
 }
 
-export namespace Symbol {
+export type Symbol = _Symbol;
 
-  // well-known symbols
-  @lazy export const hasInstance        = changetype<symbol>(1);
-  @lazy export const isConcatSpreadable = changetype<symbol>(2);
-  @lazy export const isRegExp           = changetype<symbol>(3);
-  @lazy export const iterator           = changetype<symbol>(3);
-  @lazy export const match              = changetype<symbol>(4);
-  @lazy export const replace            = changetype<symbol>(5);
-  @lazy export const search             = changetype<symbol>(6);
-  @lazy export const species            = changetype<symbol>(7);
-  @lazy export const split              = changetype<symbol>(8);
-  @lazy export const toPrimitive        = changetype<symbol>(9);
-  @lazy export const toStringTag        = changetype<symbol>(10);
-  @lazy export const unscopables        = changetype<symbol>(11);
-
-  /* tslint:disable */// not valid TS
-  export function for(key: string): symbol {
-    if (!stringToId) { stringToId = new Map(); idToString = new Map(); }
-    else if (stringToId.has(key)) return changetype<symbol>(stringToId.get(key));
-    var id = nextId++;
-    if (!id) unreachable(); // out of ids
-    stringToId.set(key, id);
-    idToString.set(id, key);
-    return changetype<symbol>(id);
-  }
-  /* tslint:enable */
-
-  export function keyFor(sym: symbol): string | null {
-    return idToString !== null && idToString.has(changetype<usize>(sym))
-      ? idToString.get(changetype<usize>(sym))
-      : null;
-  }
-}
+// @ts-ignore: nolib
+export type symbol = _Symbol;