Implement optional type parameters (#360)

* Add a NATIVE<T> macro type to simplify use of a native WebAssembly type
* Add default type parameters for internal helpers for explicit loads and stores
* Unify loadUnsafe/loadUnsafeWithOffset etc. into one
* Renamed loadUnsafe etc. into just LOAD, like a macro
* Implement parsing of index signatures, but ignore them, for properly linting code
* Refactor TypedArray<T> to use macros

src/program.ts

@@ -965,6 +965,7 @@ export class Program extends DiagnosticEmitter {
           }
           break;
         }
+        case NodeKind.INDEXSIGNATUREDECLARATION: break; // ignored for now
         default: {
           assert(false); // should have been reported while parsing
           return;
@@ -2413,6 +2414,21 @@ export class FunctionPrototype extends Element {
     this.decoratorFlags = decoratorFlags;
   }
 
+  /** Applies class type arguments to the context of a partially resolved instance method. */
+  applyClassTypeArguments(contextualTypeArguments: Map<string,Type>): void {
+    var classTypeArguments = assert(this.classTypeArguments); // set only if partial
+    var classDeclaration = assert(this.classPrototype).declaration;
+    var classTypeParameters = classDeclaration.typeParameters;
+    var numClassTypeParameters = classTypeParameters.length;
+    assert(numClassTypeParameters == classTypeArguments.length);
+    for (let i = 0; i < numClassTypeParameters; ++i) {
+      contextualTypeArguments.set(
+        classTypeParameters[i].name.text,
+        classTypeArguments[i]
+      );
+    }
+  }
+
   toString(): string { return this.simpleName; }
 }