Improve ArrayBuffer.isView (#930)

Author: MaxGraey

std/assembly/arraybuffer.ts

@@ -32,20 +32,21 @@ export abstract class ArrayBufferView {
 @sealed export class ArrayBuffer {
 
   static isView<T>(value: T): bool {
-    if (value) {
-      if (value instanceof Int8Array) return true;
-      if (value instanceof Uint8Array) return true;
-      if (value instanceof Uint8ClampedArray) return true;
-      if (value instanceof Int16Array) return true;
-      if (value instanceof Uint16Array) return true;
-      if (value instanceof Int32Array) return true;
-      if (value instanceof Uint32Array) return true;
-      if (value instanceof Int64Array) return true;
-      if (value instanceof Uint64Array) return true;
-      if (value instanceof Float32Array) return true;
-      if (value instanceof Float64Array) return true;
-      if (value instanceof DataView) return true;
+    if (isNullable<T>()) {
+      if (value === null) return false;
     }
+    if (value instanceof Int8Array) return true;
+    if (value instanceof Uint8Array) return true;
+    if (value instanceof Uint8ClampedArray) return true;
+    if (value instanceof Int16Array) return true;
+    if (value instanceof Uint16Array) return true;
+    if (value instanceof Int32Array) return true;
+    if (value instanceof Uint32Array) return true;
+    if (value instanceof Int64Array) return true;
+    if (value instanceof Uint64Array) return true;
+    if (value instanceof Float32Array) return true;
+    if (value instanceof Float64Array) return true;
+    if (value instanceof DataView) return true;
     return false;
   }