Add Array#concat and add a return type for Array#push (#214)

std/assembly/array.ts

@@ -181,6 +181,25 @@ export class Array<T> {
     return newLength;
   }
 
+  concat(items: Array<T>): Array<T> {
+    var thisLen: isize = this.length_;
+    var otherLen = (items == null) ? 0 : items.length_;
+    var outLen =  thisLen + otherLen;
+    var out: Array<T> = new Array<T>(outLen);
+
+    if (thisLen) {
+      memory.copy(changetype<usize>(out.buffer_) + HEADER_SIZE,
+      changetype<usize>(this.buffer_) + HEADER_SIZE,
+      <usize>(thisLen << alignof<T>()));
+    }
+    if (otherLen) {
+      memory.copy(changetype<usize>(out.buffer_) + HEADER_SIZE + <usize>(thisLen << alignof<T>()),
+      changetype<usize>(items.buffer_) + HEADER_SIZE,
+      <usize>(otherLen << alignof<T>()));
+    }
+    return out;
+  }
+
   pop(): T {
     var length = this.length_;
     if (length < 1) throw new RangeError("Array is empty");

std/assembly/index.d.ts

@@ -444,7 +444,8 @@ declare class Array<T> {
   includes(searchElement: T, fromIndex?: i32): bool;
   indexOf(searchElement: T, fromIndex?: i32): i32;
   lastIndexOf(searchElement: T, fromIndex?: i32): i32;
-  push(element: T): void;
+  push(element: T): i32;
+  concat(items: T[]): T[];
   pop(): T;
   forEach(callbackfn: (value: T, index: i32, array: Array<T>) => void): void;
   map<U>(callbackfn: (value: T, index: i32, array: Array<T>) => U): Array<U>;

std/portable/index.d.ts

@@ -253,7 +253,8 @@ declare class Array<T> {
   includes(searchElement: T, fromIndex?: i32): bool;
   indexOf(searchElement: T, fromIndex?: i32): i32;
   lastIndexOf(searchElement: T, fromIndex?: i32): i32;
-  push(element: T): void;
+  push(element: T): i32;
+  concat(items: T[]): T[];
   pop(): T;
   forEach(callbackfn: (value: T, index: i32, array: Array<T>) => void): void;
   map<U>(callbackfn: (value: T, index: i32, array: Array<T>) => U): Array<U>;

tests/compiler/std/array.ts

@@ -102,6 +102,49 @@ assert(arr[0] == 43);
 assert(arr[1] == 44);
 assert(arr[2] == 45);
 
+// Array#concat ///////////////////////////////////////////////////////////////////////////////////
+
+var other = new Array<i32>();
+
+var out = arr.concat(other);
+assert(internalCapacity<i32>(arr) == 3);
+assert(arr.length == 3);
+assert(out.length == 3);
+
+out.concat([]);
+assert(internalCapacity<i32>(arr) == 3);
+
+assert(out[0] == 43);
+assert(out[1] == 44);
+assert(out[2] == 45);
+
+other.push(46);
+other.push(47);
+
+out = arr.concat(other);
+
+assert(internalCapacity<i32>(arr) == 3);
+assert(other.length == 2);
+assert(out.length == 5);
+assert(out[0] == 43);
+assert(out[1] == 44);
+assert(out[2] == 45);
+assert(out[3] == 46);
+assert(out[4] == 47);
+
+out.pop();
+assert(out.length == 4);
+
+out = arr.concat(null);
+assert(out.length == 3);
+assert(out[2] == 45);
+
+var source: i32[] = [];
+assert(source.length == 0);
+out = source.concat(arr);
+assert(out.length == 3);
+assert(source.length == 0);
+
 // Array#unshift ///////////////////////////////////////////////////////////////////////////////////
 
 arr.unshift(42);