feat(wasm): add Supertype API

lib/binding_web/binding.js

@@ -5,6 +5,7 @@
 
 const C = Module;
 const INTERNAL = {};
+const SIZE_OF_SHORT = 2;
 const SIZE_OF_INT = 4;
 const SIZE_OF_CURSOR = 4 * SIZE_OF_INT;
 const SIZE_OF_NODE = 5 * SIZE_OF_INT;
@@ -858,6 +859,40 @@ class Language {
     return C._ts_language_type_is_visible_wasm(this[0], typeId) ? true : false;
   }
 
+  get supertypes() {
+    C._ts_language_supertypes_wasm(this[0]);
+    const count = getValue(TRANSFER_BUFFER, 'i32');
+    const buffer = getValue(TRANSFER_BUFFER + SIZE_OF_INT, 'i32');
+    const result = new Array(count);
+
+    if (count > 0) {
+      let address = buffer;
+      for (let i = 0; i < count; i++) {
+        result[i] = getValue(address, 'i16');
+        address += SIZE_OF_SHORT;
+      }
+    }
+
+    return result;
+  }
+
+  subtypes(supertype) {
+    C._ts_language_subtypes_wasm(this[0], supertype);
+    const count = getValue(TRANSFER_BUFFER, 'i32');
+    const buffer = getValue(TRANSFER_BUFFER + SIZE_OF_INT, 'i32');
+    const result = new Array(count);
+
+    if (count > 0) {
+      let address = buffer;
+      for (let i = 0; i < count; i++) {
+        result[i] = getValue(address, 'i16');
+        address += SIZE_OF_SHORT;
+      }
+    }
+
+    return result;
+  }
+
   nextState(stateId, typeId) {
     return C._ts_language_next_state(this[0], stateId, typeId);
   }