Filler implementation for std Set

tests/compiler/std/array.wast

@@ -4086,6 +4086,7 @@
   CLASS_PROTOTYPE: RegExp
   CLASS_PROTOTYPE: std:set/Set
   CLASS_PROTOTYPE: Set
+  PROPERTY: std:set/Set#size
   GLOBAL: std:string/EMPTY
   CLASS_PROTOTYPE: std:string/String
   CLASS_PROTOTYPE: String

tests/compiler/std/carray.wast

@@ -279,6 +279,7 @@
   CLASS_PROTOTYPE: RegExp
   CLASS_PROTOTYPE: std:set/Set
   CLASS_PROTOTYPE: Set
+  PROPERTY: std:set/Set#size
   GLOBAL: std:string/EMPTY
   CLASS_PROTOTYPE: std:string/String
   CLASS_PROTOTYPE: String

tests/compiler/std/heap.wast

@@ -2870,6 +2870,7 @@
   CLASS_PROTOTYPE: RegExp
   CLASS_PROTOTYPE: std:set/Set
   CLASS_PROTOTYPE: Set
+  PROPERTY: std:set/Set#size
   GLOBAL: std:string/EMPTY
   CLASS_PROTOTYPE: std:string/String
   CLASS_PROTOTYPE: String

tests/compiler/std/set.ts

@@ -0,0 +1,28 @@
+// note that this doesn't test a real set implementation yet, see std/assembly/set.ts
+
+var set = changetype<Set<i32>>(allocate_memory(sizeof<usize>() + 2 * sizeof<i32>()));
+
+assert(set.size == 0);
+
+set.add(1);
+set.add(0);
+set.add(2);
+
+assert(set.size == 3);
+
+assert(set.has(1));
+assert(set.has(0));
+assert(set.has(2));
+assert(!set.has(3));
+
+set.delete(0);
+
+assert(set.size == 2);
+assert(set.has(1));
+assert(!set.has(0));
+assert(set.has(2));
+
+set.clear();
+
+assert(set.size == 0);
+assert(!set.has(1));