TypeScript Language Specification v1.5

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of the object literal includes a numeric index signature with the union type of the types of the numerically named properties (section 3.8.4) declared in the object literal, or the Undefined type if the object literal declares no numerically named properties. 4.6 Array Literals Array literals are extended to support the spread (...) operator. ElementList: ( Modified ) Elision opt AssignmentExpression Elision opt SpreadElement ElementList , Elision opt AssignmentExpression ElementList , Elision opt SpreadElement SpreadElement: ... AssignmentExpression An array literal [ expr1, expr2, ..., exprN ] denotes a value of an array type (section 3.3.2) or a tuple type (section 3.3.3) depending on context. Each element expression in a non-empty array literal is processed as follows: If the array literal contains no spread elements, and if the array literal is contextually typed (section 4.19) by a type T and T has a property with the numeric name N, where N is the index of the element expression in the array literal, the element expression is contextually typed by the type of that property. Otherwise, if the array literal is contextually typed by a type T with a numeric index signature, the element expression is contextually typed by the type of the numeric index signature. Otherwise, the element expression is not contextually typed. 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 contains no spread elements and is contextually typed by a tuple-like type (section 3.3.3), the resulting type is a tuple type constructed from the types of the element expressions. Otherwise, if the array literal contains no spread elements and is an array assignment pattern in a destructuring assignment (section 4.17.1), 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 non-spread element expressions and the numeric index signature types of the spread element expressions. 60
A spread element must specify an expression of an array-like type (section 3.3.2), or otherwise an error occurs. The rules above mean that an array literal is always of an array type, unless it is contextually typed by a tuple-like type. For example var a = [1, 2]; // number[] var b = ["hello", true]; // (string | boolean)[] var c: [number, string] = [3, "three"]; // [number, string] When the output target is ECMAScript 3 or 5, array literals containing spread elements are rewritten to invocations of the concat method. For example, the assignments var a = [2, 3, 4]; var b = [0, 1, ...a, 5, 6]; are rewritten to var a = [2, 3, 4]; var b = [0, 1].concat(a, [5, 6]); 4.7 Parentheses A parenthesized expression ( expr ) has the same type and classification as the contained expression itself. Specifically, if the contained expression is classified as a reference, so is the parenthesized expression. 4.8 The super Keyword The super keyword can be used in expressions to reference base class properties and the base class constructor. CallExpression: ( Modified ) … super ( ArgumentList opt ) super . IdentifierName 4.8.1 Super Calls Super calls consist of the keyword super followed by an argument list enclosed in parentheses. Super calls are only permitted in constructors of derived classes, as described in section 8.3.2. 61
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TypeScript Language Specification V
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Table of Contents 1 Introduction ..
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4.9.1 Standard Function Expressions
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9.1 Enum Declarations .............
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1 Introduction JavaScript applicati
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1.1 Ambient Declarations An ambient
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call '$' as a function. The behavio
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function getX(p: Point) { return p.
Page 17 and 18: This TypeScript class declaration c
Page 19 and 20: Section 9 describes how programmers
Page 21 and 22: Interface definitions, like the one
Page 23 and 24: TypeScript modules provide a mechan
Page 25 and 26: 2 Basic Concepts The remainder of t
Page 27 and 28: Each enum declaration has a declara
Page 29: When an identifier is resolved as a
Page 32 and 33: which infers the type of 'x' to be
Page 34 and 35: The only possible values for the Vo
Page 36 and 37: interface Array { length: number; [
Page 38 and 39: 3.4 Union Types Union types represe
Page 40 and 41: 3.5 Type Parameters A type paramete
Page 42 and 43: 3.6 Named Types Classes, interfaces
Page 44 and 45: 3.7.1 Predefined Types The any, num
Page 46 and 47: TypeMember: PropertySignature CallS
Page 48 and 49: 3.7.8 Constructor Type Literals A c
Page 50 and 51: 3.8.2 Call Signatures A call signat
Page 52 and 53: RestParameter: ... Identifier TypeA
Page 54 and 55: IndexSignature: [ Identifier : stri
Page 56 and 57: Type aliases are referenced using t
Page 58 and 59: o o If each type in U has an appare
Page 60 and 61: o o o M is a non-specialized call o
Page 62 and 63: 3.10.5 Contextual Signature Instant
Page 64 and 65: interface List { data: T; next: Lis
Page 66 and 67: 4.3 Identifiers When an expression
Page 70 and 71: A super call invokes the constructo
Page 72 and 73: ( id ) => { ... } ( id ) => expr Th
Page 74 and 75: A dot notation property access of t
Page 76 and 77: If func is of type Any, or of an ob
Page 78 and 79: An example: signature are fixed, an
Page 80 and 81: This rule means that the call to 'f
Page 82 and 83: 4.14.4 The delete Operator The 'del
Page 84 and 85: Any Boolean Number String Other Any
Page 86 and 87: where ??= is one of the compound as
Page 88 and 89: 4.18 The Comma Operator The comma o
Page 90 and 91: function foo(x: number | string) {
Page 92 and 93: function processValue(value: number
Page 95 and 96: 5 Statements This chapter describes
Page 97 and 98: BindingProperty: Identifier Initial
Page 99 and 100: Similarly, an array destructuring d
Page 101 and 102: 5.5 Continue Statements A 'continue
Page 103 and 104: 6 Functions TypeScript extends Java
Page 105 and 106: function f(x: number) { if (x
Page 107 and 108: When the output target is ECMAScrip
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Page 112 and 113: An interface has the members specif
Page 114 and 115: interface Document { createElement(
Page 117 and 118: 8 Classes TypeScript supports class
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The following constraints must be s
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Private and protected accessibility
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interface A { x: number; f: () => v
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ConstructorOverloads: ConstructorOv
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BaseClass.apply(this, arguments); a
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Initializer expressions for instanc
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var x = A.create(); // new A() var
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MemberVariableAssignments is a sequ
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In addition, the '__extends' functi
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9 Enums An enum type is a distinct
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An identifier or property access th
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var Color; (function (Color) { Colo
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If the declaration of 'M' above had
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module A { export interface X { s:
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module outer { var local = 1; expor
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where ModuleName is the name of the
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DeclarationElement: ExportAssignmen
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that source file is considered an e
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Unlike a non-instantiated internal
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import g = require("./geometry"); v
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12.1.3 Ambient Class Declarations A
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An ExternalImportDeclaration in an
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PrimaryType: ParenthesizedType Pred
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ParameterList: RequiredParameterLis
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UnaryExpression: ( Modified ) … <
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ClassExtendsClause: extends ClassTy
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ModuleBody: ModuleElements opt Modu
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AmbientClassBodyElements: AmbientCl
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TypeScript Language Specification v1.5

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