Array literal produces union type if the it is not contextually typed

tests/cases/conformance/types/union/unionTypeFromArrayLiteral.ts

@@ -0,0 +1,23 @@
+// The resulting type an array literal expression is determined as follows:
+// If the array literal is empty, the resulting type is an array type with the element type Undefined.
+// Otherwise, if the array literal is contextually typed by a type that has a property with the numeric name ‘0’, the resulting type is a tuple type constructed from the types of the element expressions.
+// Otherwise, the resulting type is an array type with an element type that is the union of the types of the element expressions.
+
+var arr1 = [1, 2]; // number[]
+var arr2 = ["hello", true]; // (string | number)[]
+var arr3Tuple: [number, string] = [3, "three"]; // [number, string]
+var arr4Tuple: [number, string] = [3, "three", "hello"]; // [number, string, string]
+var arrEmpty = [];
+var arr5Tuple: {
+    0: string;
+    5: number;
+} = ["hello", true, false, " hello", true, 10, "any"]; // Tuple
+class C { foo() { } }
+class D { foo2() { } }
+class E extends C { foo3() { } }
+class F extends C { foo4() { } }
+var c: C, d: D, e: E, f: F;
+var arr6 = [c, d];  // (C | D)[]
+var arr7 = [c, d, e]; // (C | D)[]
+var arr8 = [c, e]; // C[]
+var arr9 = [e, f]; // (E|F)[]