Implement reference counting (#592)

tests/compiler/constant-assign.ts

@@ -0,0 +1,30 @@
+// Expect error: TS2540
+// ^ TODO: Properly handle multiple
+
+function localConst(a: i32): void {
+  const b = a + 1;
+  b = 3;
+}
+localConst(1);
+
+function localConstInline(): void {
+  const a = 1;
+  a = 2;
+}
+localConstInline();
+
+function localConstArray(a: i32): void {
+  const b: i32[] = [ a ];
+  b = [ 2 ];
+}
+localConstArray(1);
+
+function localConstArrayInline(): void {
+  const a: i32[] = [ 1 ];
+  a = [ 2 ];
+}
+localConstArrayInline();
+
+// globalConst
+const a = 1;
+a = 2;