TypeScript Language Specification v1.5

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puts a statically unknown set of identifiers in scope in front of those that are statically known, it is not possible to meaningfully assign a static type to any identifier. 5.9 Switch Statements In a 'switch' statement, each 'case' expression must be of a type that is assignable to or from (section 3.10.4) the type of the 'switch' expression. 5.10 Throw Statements The expression specified in a 'throw' statement can be of any type. 5.11 Try Statements The variable introduced by a 'catch' clause of a 'try' statement is always of type Any. It is not possible to include a type annotation in a 'catch' clause. 94
6 Functions <strong>TypeScript</strong> extends JavaScript functions to include type parameters, parameter and return type annotations, overloads, default parameter values, and rest parameters. 6.1 Function Declarations Function declarations consist of an optional set of function overloads followed by an actual function implementation. FunctionDeclaration: ( Modified ) FunctionOverloads opt FunctionImplementation FunctionOverloads: FunctionOverload FunctionOverloads FunctionOverload FunctionOverload: function Identifier CallSignature ; FunctionImplementation: function Identifier CallSignature { FunctionBody } A function declaration introduces a function with the given name in the containing declaration space. Function overloads, if present, must specify the same name as the function implementation. If a function declaration includes overloads, the overloads determine the call signatures of the type given to the function object and the function implementation signature must be assignable to that type. Otherwise, the function implementation itself determines the call signature. Function overloads have no other effect on a function declaration. 6.2 Function Overloads Function overloads allow a more accurate specification of the patterns of invocation supported by a function than is possible with a single signature. The compile-time processing of a call to an overloaded function chooses the best candidate overload for the particular arguments and the return type of that overload becomes the result type the function call expression. Thus, using overloads it is possible to statically describe the manner in which a function's return type varies based on its arguments. Overload resolution in function calls is described further in section 4.12. Function overloads are purely a compile-time construct. They have no impact on the emitted JavaScript and thus no run-time cost. The parameter list of a function overload cannot specify default values for parameters. In other words, an overload may use only the ? form when specifying optional parameters. 95
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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.
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This TypeScript class declaration c
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Section 9 describes how programmers
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Interface definitions, like the one
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TypeScript modules provide a mechan
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2 Basic Concepts The remainder of t
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Each enum declaration has a declara
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When an identifier is resolved as a
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which infers the type of 'x' to be
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The only possible values for the Vo
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interface Array { length: number; [
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3.4 Union Types Union types represe
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3.5 Type Parameters A type paramete
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3.6 Named Types Classes, interfaces
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3.7.1 Predefined Types The any, num
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TypeMember: PropertySignature CallS
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3.7.8 Constructor Type Literals A c
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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 68 and 69: of the object literal includes a nu
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: 5.5 Continue Statements A 'continue
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
Page 119 and 120: The following constraints must be s
Page 121 and 122: Private and protected accessibility
Page 123 and 124: interface A { x: number; f: () => v
Page 125 and 126: ConstructorOverloads: ConstructorOv
Page 127 and 128: BaseClass.apply(this, arguments); a
Page 129 and 130: Initializer expressions for instanc
Page 131 and 132: var x = A.create(); // new A() var
Page 133 and 134: MemberVariableAssignments is a sequ
Page 135 and 136: In addition, the '__extends' functi
Page 137 and 138: 9 Enums An enum type is a distinct
Page 139 and 140: An identifier or property access th
Page 141: var Color; (function (Color) { Colo
Page 144 and 145: If the declaration of 'M' above had
Page 146 and 147: module A { export interface X { s:
Page 148 and 149: module outer { var local = 1; expor
Page 150 and 151: 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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