types.ts

namespace ts {
    export interface Map<T> {
        [index: string]: T;
    }

    // branded string type used to store absolute, normalized and canonicalized paths
    // arbitrary file name can be converted to Path via toPath function
    export type Path = string & { __pathBrand: any };

    export interface FileMap<T> {
        get(fileName: Path): T;
        set(fileName: Path, value: T): void;
        contains(fileName: Path): boolean;
        remove(fileName: Path): void;

        forEachValue(f: (key: Path, v: T) => void): void;
        clear(): void;
    }

    export interface TextRange {
        pos: number;
        end: number;
    }

    // token > SyntaxKind.Identifer => token is a keyword
    // Also, If you add a new SyntaxKind be sure to keep the `Markers` section at the bottom in sync
    export const enum SyntaxKind {
        Unknown,
        EndOfFileToken,
        SingleLineCommentTrivia,
        MultiLineCommentTrivia,
        NewLineTrivia,
        WhitespaceTrivia,
        // We detect and preserve #! on the first line
        ShebangTrivia,
        // We detect and provide better error recovery when we encounter a git merge marker.  This
        // allows us to edit files with git-conflict markers in them in a much more pleasant manner.
        ConflictMarkerTrivia,
        // Literals
        NumericLiteral,
        StringLiteral,
        RegularExpressionLiteral,
        NoSubstitutionTemplateLiteral,
        // Pseudo-literals
        TemplateHead,
        TemplateMiddle,
        TemplateTail,
        // Punctuation
        OpenBraceToken,
        CloseBraceToken,
        OpenParenToken,
        CloseParenToken,
        OpenBracketToken,
        CloseBracketToken,
        DotToken,
        DotDotDotToken,
        SemicolonToken,
        CommaToken,
        LessThanToken,
        LessThanSlashToken,
        GreaterThanToken,
        LessThanEqualsToken,
        GreaterThanEqualsToken,
        EqualsEqualsToken,
        ExclamationEqualsToken,
        EqualsEqualsEqualsToken,
        ExclamationEqualsEqualsToken,
        EqualsGreaterThanToken,
        PlusToken,
        MinusToken,
        AsteriskToken,
        AsteriskAsteriskToken,
        SlashToken,
        PercentToken,
        PlusPlusToken,
        MinusMinusToken,
        LessThanLessThanToken,
        GreaterThanGreaterThanToken,
        GreaterThanGreaterThanGreaterThanToken,
        AmpersandToken,
        BarToken,
        CaretToken,
        ExclamationToken,
        TildeToken,
        AmpersandAmpersandToken,
        BarBarToken,
        QuestionToken,
        ColonToken,
        AtToken,
        // Assignments
        EqualsToken,
        PlusEqualsToken,
        MinusEqualsToken,
        AsteriskEqualsToken,
        AsteriskAsteriskEqualsToken,
        SlashEqualsToken,
        PercentEqualsToken,
        LessThanLessThanEqualsToken,
        GreaterThanGreaterThanEqualsToken,
        GreaterThanGreaterThanGreaterThanEqualsToken,
        AmpersandEqualsToken,
        BarEqualsToken,
        CaretEqualsToken,
        // Identifiers
        Identifier,
        // Reserved words
        BreakKeyword,
        CaseKeyword,
        CatchKeyword,
        ClassKeyword,
        ConstKeyword,
        ContinueKeyword,
        DebuggerKeyword,
        DefaultKeyword,
        DeleteKeyword,
        DoKeyword,
        ElseKeyword,
        EnumKeyword,
        ExportKeyword,
        ExtendsKeyword,
        FalseKeyword,
        FinallyKeyword,
        ForKeyword,
        FunctionKeyword,
        IfKeyword,
        ImportKeyword,
        InKeyword,
        InstanceOfKeyword,
        NewKeyword,
        NullKeyword,
        ReturnKeyword,
        SuperKeyword,
        SwitchKeyword,
        ThisKeyword,
        ThrowKeyword,
        TrueKeyword,
        TryKeyword,
        TypeOfKeyword,
        VarKeyword,
        VoidKeyword,
        WhileKeyword,
        WithKeyword,
        // Strict mode reserved words
        ImplementsKeyword,
        InterfaceKeyword,
        LetKeyword,
        PackageKeyword,
        PrivateKeyword,
        ProtectedKeyword,
        PublicKeyword,
        StaticKeyword,
        YieldKeyword,
        // Contextual keywords
        AbstractKeyword,
        AsKeyword,
        AnyKeyword,
        AsyncKeyword,
        AwaitKeyword,
        BooleanKeyword,
        ConstructorKeyword,
        DeclareKeyword,
        GetKeyword,
        IsKeyword,
        ModuleKeyword,
        NamespaceKeyword,
        RequireKeyword,
        NumberKeyword,
        SetKeyword,
        StringKeyword,
        SymbolKeyword,
        TypeKeyword,
        FromKeyword,
        OfKeyword, // LastKeyword and LastToken

        // Parse tree nodes

        // Names
        QualifiedName,
        ComputedPropertyName,
        // Signature elements
        TypeParameter,
        Parameter,
        Decorator,
        // TypeMember
        PropertySignature,
        PropertyDeclaration,
        MethodSignature,
        MethodDeclaration,
        Constructor,
        GetAccessor,
        SetAccessor,
        CallSignature,
        ConstructSignature,
        IndexSignature,
        // Type
        TypePredicate,
        TypeReference,
        FunctionType,
        ConstructorType,
        TypeQuery,
        TypeLiteral,
        ArrayType,
        TupleType,
        UnionType,
        IntersectionType,
        ParenthesizedType,
        // Binding patterns
        ObjectBindingPattern,
        ArrayBindingPattern,
        BindingElement,
        // Expression
        ArrayLiteralExpression,
        ObjectLiteralExpression,
        PropertyAccessExpression,
        ElementAccessExpression,
        CallExpression,
        NewExpression,
        TaggedTemplateExpression,
        TypeAssertionExpression,
        ParenthesizedExpression,
        FunctionExpression,
        ArrowFunction,
        DeleteExpression,
        TypeOfExpression,
        VoidExpression,
        AwaitExpression,
        PrefixUnaryExpression,
        PostfixUnaryExpression,
        BinaryExpression,
        ConditionalExpression,
        TemplateExpression,
        YieldExpression,
        SpreadElementExpression,
        ClassExpression,
        OmittedExpression,
        ExpressionWithTypeArguments,
        AsExpression,

        // Misc
        TemplateSpan,
        SemicolonClassElement,
        // Element
        Block,
        VariableStatement,
        EmptyStatement,
        ExpressionStatement,
        IfStatement,
        DoStatement,
        WhileStatement,
        ForStatement,
        ForInStatement,
        ForOfStatement,
        ContinueStatement,
        BreakStatement,
        ReturnStatement,
        WithStatement,
        SwitchStatement,
        LabeledStatement,
        ThrowStatement,
        TryStatement,
        DebuggerStatement,
        VariableDeclaration,
        VariableDeclarationList,
        FunctionDeclaration,
        ClassDeclaration,
        InterfaceDeclaration,
        TypeAliasDeclaration,
        EnumDeclaration,
        ModuleDeclaration,
        ModuleBlock,
        CaseBlock,
        ImportEqualsDeclaration,
        ImportDeclaration,
        ImportClause,
        NamespaceImport,
        NamedImports,
        ImportSpecifier,
        ExportAssignment,
        ExportDeclaration,
        NamedExports,
        ExportSpecifier,
        MissingDeclaration,

        // Module references
        ExternalModuleReference,

        // JSX
        JsxElement,
        JsxSelfClosingElement,
        JsxOpeningElement,
        JsxText,
        JsxClosingElement,
        JsxAttribute,
        JsxSpreadAttribute,
        JsxExpression,

        // Clauses
        CaseClause,
        DefaultClause,
        HeritageClause,
        CatchClause,

        // Property assignments
        PropertyAssignment,
        ShorthandPropertyAssignment,

        // Enum
        EnumMember,
        // Top-level nodes
        SourceFile,

        // JSDoc nodes.
        JSDocTypeExpression,
        // The * type.
        JSDocAllType,
        // The ? type.
        JSDocUnknownType,
        JSDocArrayType,
        JSDocUnionType,
        JSDocTupleType,
        JSDocNullableType,
        JSDocNonNullableType,
        JSDocRecordType,
        JSDocRecordMember,
        JSDocTypeReference,
        JSDocOptionalType,
        JSDocFunctionType,
        JSDocVariadicType,
        JSDocConstructorType,
        JSDocThisType,
        JSDocComment,
        JSDocTag,
        JSDocParameterTag,
        JSDocReturnTag,
        JSDocTypeTag,
        JSDocTemplateTag,

        // Synthesized list
        SyntaxList,
        // Enum value count
        Count,
        // Markers
        FirstAssignment = EqualsToken,
        LastAssignment = CaretEqualsToken,
        FirstReservedWord = BreakKeyword,
        LastReservedWord = WithKeyword,
        FirstKeyword = BreakKeyword,
        LastKeyword = OfKeyword,
        FirstFutureReservedWord = ImplementsKeyword,
        LastFutureReservedWord = YieldKeyword,
        FirstTypeNode = TypeReference,
        LastTypeNode = ParenthesizedType,
        FirstPunctuation = OpenBraceToken,
        LastPunctuation = CaretEqualsToken,
        FirstToken = Unknown,
        LastToken = LastKeyword,
        FirstTriviaToken = SingleLineCommentTrivia,
        LastTriviaToken = ConflictMarkerTrivia,
        FirstLiteralToken = NumericLiteral,
        LastLiteralToken = NoSubstitutionTemplateLiteral,
        FirstTemplateToken = NoSubstitutionTemplateLiteral,
        LastTemplateToken = TemplateTail,
        FirstBinaryOperator = LessThanToken,
        LastBinaryOperator = CaretEqualsToken,
        FirstNode = QualifiedName,
    }

    export const enum NodeFlags {
        None =              0,
        Export =            1 << 1,  // Declarations
        Ambient =           1 << 2,  // Declarations
        Public =            1 << 3,  // Property/Method
        Private =           1 << 4,  // Property/Method
        Protected =         1 << 5,  // Property/Method
        Static =            1 << 6,  // Property/Method
        Abstract =          1 << 7,  // Class/Method/ConstructSignature
        Async =             1 << 8,  // Property/Method/Function
        Default =           1 << 9,  // Function/Class (export default declaration)
        MultiLine =         1 << 10,  // Multi-line array or object literal
        Synthetic =         1 << 11,  // Synthetic node (for full fidelity)
        DeclarationFile =   1 << 12,  // Node is a .d.ts file
        Let =               1 << 13,  // Variable declaration
        Const =             1 << 14,  // Variable declaration
        OctalLiteral =      1 << 15,  // Octal numeric literal
        Namespace =         1 << 16,  // Namespace declaration
        ExportContext =     1 << 17,  // Export context (initialized by binding)
        ContainsThis =      1 << 18,  // Interface contains references to "this"
        HasImplicitReturn =     1 << 19,  // If function implicitly returns on one of codepaths (initialized by binding)
        HasExplicitReturn =     1 << 20,  // If function has explicit reachable return on one of codepaths (initialized by binding)
        Modifier = Export | Ambient | Public | Private | Protected | Static | Abstract | Default | Async,
        AccessibilityModifier = Public | Private | Protected,
        BlockScoped = Let | Const,

        ReachabilityCheckFlags = HasImplicitReturn | HasExplicitReturn
    }

    /* @internal */
    export const enum ParserContextFlags {
        None = 0,

        // If this node was parsed in a context where 'in-expressions' are not allowed.
        DisallowIn = 1 << 0,

        // If this node was parsed in the 'yield' context created when parsing a generator.
        Yield = 1 << 1,

        // If this node was parsed as part of a decorator
        Decorator = 1 << 2,

        // If this node was parsed in the 'await' context created when parsing an async function.
        Await = 1 << 3,

        // If the parser encountered an error when parsing the code that created this node.  Note
        // the parser only sets this directly on the node it creates right after encountering the
        // error.
        ThisNodeHasError = 1 << 4,

        // This node was parsed in a JavaScript file and can be processed differently.  For example
        // its type can be specified usign a JSDoc comment.
        JavaScriptFile = 1 << 5,

        // Context flags set directly by the parser.
        ParserGeneratedFlags = DisallowIn | Yield | Decorator | ThisNodeHasError | Await,

        // Exclude these flags when parsing a Type
        TypeExcludesFlags = Yield | Await,

        // Context flags computed by aggregating child flags upwards.

        // Used during incremental parsing to determine if this node or any of its children had an
        // error.  Computed only once and then cached.
        ThisNodeOrAnySubNodesHasError = 1 << 6,

        // Used to know if we've computed data from children and cached it in this node.
        HasAggregatedChildData = 1 << 7
    }

    export const enum JsxFlags {
        None = 0,
        IntrinsicNamedElement = 1 << 0,
        IntrinsicIndexedElement = 1 << 1,
        ClassElement = 1 << 2,
        UnknownElement = 1 << 3,

        IntrinsicElement = IntrinsicNamedElement | IntrinsicIndexedElement
    }


    /* @internal */
    export const enum RelationComparisonResult {
        Succeeded = 1, // Should be truthy
        Failed = 2,
        FailedAndReported = 3
    }

    export interface Node extends TextRange {
        kind: SyntaxKind;
        flags: NodeFlags;
        // Specific context the parser was in when this node was created.  Normally undefined.
        // Only set when the parser was in some interesting context (like async/yield).
        /* @internal */ parserContextFlags?: ParserContextFlags;
        decorators?: NodeArray<Decorator>;              // Array of decorators (in document order)
        modifiers?: ModifiersArray;                     // Array of modifiers
        /* @internal */ id?: number;                    // Unique id (used to look up NodeLinks)
        parent?: Node;                                  // Parent node (initialized by binding
        /* @internal */ jsDocComment?: JSDocComment;    // JSDoc for the node, if it has any.  Only for .js files.
        /* @internal */ symbol?: Symbol;                // Symbol declared by node (initialized by binding)
        /* @internal */ locals?: SymbolTable;           // Locals associated with node (initialized by binding)
        /* @internal */ nextContainer?: Node;           // Next container in declaration order (initialized by binding)
        /* @internal */ localSymbol?: Symbol;           // Local symbol declared by node (initialized by binding only for exported nodes)
    }

    export interface NodeArray<T> extends Array<T>, TextRange {
        hasTrailingComma?: boolean;
    }

    export interface ModifiersArray extends NodeArray<Node> {
        flags: number;
    }

    export interface Identifier extends PrimaryExpression {
        text: string;                                  // Text of identifier (with escapes converted to characters)
        originalKeywordKind?: SyntaxKind;              // Original syntaxKind which get set so that we can report an error later
    }

    export interface QualifiedName extends Node {
        // Must have same layout as PropertyAccess
        left: EntityName;
        right: Identifier;
    }

    export type EntityName = Identifier | QualifiedName;

    export type DeclarationName = Identifier | LiteralExpression | ComputedPropertyName | BindingPattern;

    export interface Declaration extends Node {
        _declarationBrand: any;
        name?: DeclarationName;
    }

    export interface ComputedPropertyName extends Node {
        expression: Expression;
    }

    export interface Decorator extends Node {
        expression: LeftHandSideExpression;
    }

    export interface TypeParameterDeclaration extends Declaration {
        name: Identifier;
        constraint?: TypeNode;

        // For error recovery purposes.
        expression?: Expression;
    }

    export interface SignatureDeclaration extends Declaration {
        typeParameters?: NodeArray<TypeParameterDeclaration>;
        parameters: NodeArray<ParameterDeclaration>;
        type?: TypeNode;
    }

    // SyntaxKind.VariableDeclaration
    export interface VariableDeclaration extends Declaration {
        parent?: VariableDeclarationList;
        name: Identifier | BindingPattern;  // Declared variable name
        type?: TypeNode;                    // Optional type annotation
        initializer?: Expression;           // Optional initializer
    }

    export interface VariableDeclarationList extends Node {
        declarations: NodeArray<VariableDeclaration>;
    }

    // SyntaxKind.Parameter
    export interface ParameterDeclaration extends Declaration {
        dotDotDotToken?: Node;              // Present on rest parameter
        name: Identifier | BindingPattern;  // Declared parameter name
        questionToken?: Node;               // Present on optional parameter
        type?: TypeNode;                    // Optional type annotation
        initializer?: Expression;           // Optional initializer
    }

    // SyntaxKind.BindingElement
    export interface BindingElement extends Declaration {
        propertyName?: Identifier;          // Binding property name (in object binding pattern)
        dotDotDotToken?: Node;              // Present on rest binding element
        name: Identifier | BindingPattern;  // Declared binding element name
        initializer?: Expression;           // Optional initializer
    }

    // SyntaxKind.Property
    export interface PropertyDeclaration extends Declaration, ClassElement {
        name: DeclarationName;              // Declared property name
        questionToken?: Node;               // Present on optional property
        type?: TypeNode;                    // Optional type annotation
        initializer?: Expression;           // Optional initializer
    }

    export interface ObjectLiteralElement extends Declaration {
        _objectLiteralBrandBrand: any;
    }

    // SyntaxKind.PropertyAssignment
    export interface PropertyAssignment extends ObjectLiteralElement {
        _propertyAssignmentBrand: any;
        name: DeclarationName;
        questionToken?: Node;
        initializer: Expression;
    }

    // SyntaxKind.ShorthandPropertyAssignment
    export interface ShorthandPropertyAssignment extends ObjectLiteralElement {
        name: Identifier;
        questionToken?: Node;
        // used when ObjectLiteralExpression is used in ObjectAssignmentPattern
        // it is grammar error to appear in actual object initializer
        equalsToken?: Node;
        objectAssignmentInitializer?: Expression;
    }

    // SyntaxKind.VariableDeclaration
    // SyntaxKind.Parameter
    // SyntaxKind.BindingElement
    // SyntaxKind.Property
    // SyntaxKind.PropertyAssignment
    // SyntaxKind.ShorthandPropertyAssignment
    // SyntaxKind.EnumMember
    export interface VariableLikeDeclaration extends Declaration {
        propertyName?: Identifier;
        dotDotDotToken?: Node;
        name: DeclarationName;
        questionToken?: Node;
        type?: TypeNode;
        initializer?: Expression;
    }

    export interface BindingPattern extends Node {
        elements: NodeArray<BindingElement>;
    }

    /**
     * Several node kinds share function-like features such as a signature,
     * a name, and a body. These nodes should extend FunctionLikeDeclaration.
     * Examples:
     * - FunctionDeclaration
     * - MethodDeclaration
     * - AccessorDeclaration
     */
    export interface FunctionLikeDeclaration extends SignatureDeclaration {
        _functionLikeDeclarationBrand: any;

        asteriskToken?: Node;
        questionToken?: Node;
        body?: Block | Expression;
    }

    export interface FunctionDeclaration extends FunctionLikeDeclaration, Statement {
        name?: Identifier;
        body?: Block;
    }

    // Note that a MethodDeclaration is considered both a ClassElement and an ObjectLiteralElement.
    // Both the grammars for ClassDeclaration and ObjectLiteralExpression allow for MethodDeclarations
    // as child elements, and so a MethodDeclaration satisfies both interfaces.  This avoids the
    // alternative where we would need separate kinds/types for ClassMethodDeclaration and
    // ObjectLiteralMethodDeclaration, which would look identical.
    //
    // Because of this, it may be necessary to determine what sort of MethodDeclaration you have
    // at later stages of the compiler pipeline.  In that case, you can either check the parent kind
    // of the method, or use helpers like isObjectLiteralMethodDeclaration
    export interface MethodDeclaration extends FunctionLikeDeclaration, ClassElement, ObjectLiteralElement {
        body?: Block;
    }

    export interface ConstructorDeclaration extends FunctionLikeDeclaration, ClassElement {
        body?: Block;
    }

    // For when we encounter a semicolon in a class declaration.  ES6 allows these as class elements.
    export interface SemicolonClassElement extends ClassElement {
        _semicolonClassElementBrand: any;
    }

    // See the comment on MethodDeclaration for the intuition behind AccessorDeclaration being a
    // ClassElement and an ObjectLiteralElement.
    export interface AccessorDeclaration extends FunctionLikeDeclaration, ClassElement, ObjectLiteralElement {
        _accessorDeclarationBrand: any;
        body: Block;
    }

    export interface IndexSignatureDeclaration extends SignatureDeclaration, ClassElement {
        _indexSignatureDeclarationBrand: any;
    }

    export interface TypeNode extends Node {
        _typeNodeBrand: any;
    }

    export interface FunctionOrConstructorTypeNode extends TypeNode, SignatureDeclaration {
        _functionOrConstructorTypeNodeBrand: any;
    }

    export interface TypeReferenceNode extends TypeNode {
        typeName: EntityName;
        typeArguments?: NodeArray<TypeNode>;
    }

    export interface TypePredicateNode extends TypeNode {
        parameterName: Identifier;
        type: TypeNode;
    }

    export interface TypeQueryNode extends TypeNode {
        exprName: EntityName;
    }

    // A TypeLiteral is the declaration node for an anonymous symbol.
    export interface TypeLiteralNode extends TypeNode, Declaration {
        members: NodeArray<Node>;
    }

    export interface ArrayTypeNode extends TypeNode {
        elementType: TypeNode;
    }

    export interface TupleTypeNode extends TypeNode {
        elementTypes: NodeArray<TypeNode>;
    }

    export interface UnionOrIntersectionTypeNode extends TypeNode {
        types: NodeArray<TypeNode>;
    }

    export interface UnionTypeNode extends UnionOrIntersectionTypeNode { }

    export interface IntersectionTypeNode extends UnionOrIntersectionTypeNode { }

    export interface ParenthesizedTypeNode extends TypeNode {
        type: TypeNode;
    }

    // Note that a StringLiteral AST node is both an Expression and a TypeNode.  The latter is
    // because string literals can appear in type annotations as well.
    export interface StringLiteral extends LiteralExpression, TypeNode {
        _stringLiteralBrand: any;
    }

    // Note: 'brands' in our syntax nodes serve to give us a small amount of nominal typing.
    // Consider 'Expression'.  Without the brand, 'Expression' is actually no different
    // (structurally) than 'Node'.  Because of this you can pass any Node to a function that
    // takes an Expression without any error.  By using the 'brands' we ensure that the type
    // checker actually thinks you have something of the right type.  Note: the brands are
    // never actually given values.  At runtime they have zero cost.

    export interface Expression extends Node {
        _expressionBrand: any;
        contextualType?: Type;  // Used to temporarily assign a contextual type during overload resolution
    }

    export interface UnaryExpression extends Expression {
        _unaryExpressionBrand: any;
    }

    export interface IncrementExpression extends UnaryExpression {
        _incrementExpressionBrand: any;
    }

    export interface PrefixUnaryExpression extends IncrementExpression {
        operator: SyntaxKind;
        operand: UnaryExpression;
    }

    export interface PostfixUnaryExpression extends IncrementExpression {
        operand: LeftHandSideExpression;
        operator: SyntaxKind;
    }

    export interface PostfixExpression extends UnaryExpression {
        _postfixExpressionBrand: any;
    }

    export interface LeftHandSideExpression extends IncrementExpression {
        _leftHandSideExpressionBrand: any;
    }

    export interface MemberExpression extends LeftHandSideExpression {
        _memberExpressionBrand: any;
    }

    export interface PrimaryExpression extends MemberExpression {
        _primaryExpressionBrand: any;
    }

    export interface DeleteExpression extends UnaryExpression {
        expression: UnaryExpression;
    }

    export interface TypeOfExpression extends UnaryExpression {
        expression: UnaryExpression;
    }

    export interface VoidExpression extends UnaryExpression {
        expression: UnaryExpression;
    }

    export interface AwaitExpression extends UnaryExpression {
        expression: UnaryExpression;
    }

    export interface YieldExpression extends Expression {
        asteriskToken?: Node;
        expression?: Expression;
    }

    export interface BinaryExpression extends Expression {
        left: Expression;
        operatorToken: Node;
        right: Expression;
    }

    export interface ConditionalExpression extends Expression {
        condition: Expression;
        questionToken: Node;
        whenTrue: Expression;
        colonToken: Node;
        whenFalse: Expression;
    }

    export interface FunctionExpression extends PrimaryExpression, FunctionLikeDeclaration {
        name?: Identifier;
        body: Block | Expression;  // Required, whereas the member inherited from FunctionDeclaration is optional
    }

    export interface ArrowFunction extends Expression, FunctionLikeDeclaration {
        equalsGreaterThanToken: Node;
    }

    // The text property of a LiteralExpression stores the interpreted value of the literal in text form. For a StringLiteral,
    // or any literal of a template, this means quotes have been removed and escapes have been converted to actual characters.
    // For a NumericLiteral, the stored value is the toString() representation of the number. For example 1, 1.00, and 1e0 are all stored as just "1".
    export interface LiteralExpression extends PrimaryExpression {
        text: string;
        isUnterminated?: boolean;
        hasExtendedUnicodeEscape?: boolean;
    }

    export interface TemplateExpression extends PrimaryExpression {
        head: LiteralExpression;
        templateSpans: NodeArray<TemplateSpan>;
    }

    // Each of these corresponds to a substitution expression and a template literal, in that order.
    // The template literal must have kind TemplateMiddleLiteral or TemplateTailLiteral.
    export interface TemplateSpan extends Node {
        expression: Expression;
        literal: LiteralExpression;
    }

    export interface ParenthesizedExpression extends PrimaryExpression {
        expression: Expression;
    }

    export interface ArrayLiteralExpression extends PrimaryExpression {
        elements: NodeArray<Expression>;
    }

    export interface SpreadElementExpression extends Expression {
        expression: Expression;
    }

    // An ObjectLiteralExpression is the declaration node for an anonymous symbol.
    export interface ObjectLiteralExpression extends PrimaryExpression, Declaration {
        properties: NodeArray<ObjectLiteralElement>;
    }

    export interface PropertyAccessExpression extends MemberExpression {
        expression: LeftHandSideExpression;
        dotToken: Node;
        name: Identifier;
    }

    export interface ElementAccessExpression extends MemberExpression {
        expression: LeftHandSideExpression;
        argumentExpression?: Expression;
    }

    export interface CallExpression extends LeftHandSideExpression {
        expression: LeftHandSideExpression;
        typeArguments?: NodeArray<TypeNode>;
        arguments: NodeArray<Expression>;
    }

    export interface ExpressionWithTypeArguments extends TypeNode {
        expression: LeftHandSideExpression;
        typeArguments?: NodeArray<TypeNode>;
    }

    export interface NewExpression extends CallExpression, PrimaryExpression { }

    export interface TaggedTemplateExpression extends MemberExpression {
        tag: LeftHandSideExpression;
        template: LiteralExpression | TemplateExpression;
    }

    export type CallLikeExpression = CallExpression | NewExpression | TaggedTemplateExpression | Decorator;

    export interface AsExpression extends Expression {
        expression: Expression;
        type: TypeNode;
    }

    export interface TypeAssertion extends UnaryExpression {
        type: TypeNode;
        expression: UnaryExpression;
    }

    export type AssertionExpression = TypeAssertion | AsExpression;

    /// A JSX expression of the form <TagName attrs>...</TagName>
    export interface JsxElement extends PrimaryExpression {
        openingElement: JsxOpeningElement;
        children: NodeArray<JsxChild>;
        closingElement: JsxClosingElement;
    }

    /// The opening element of a <Tag>...</Tag> JsxElement
    export interface JsxOpeningElement extends Expression {
        _openingElementBrand?: any;
        tagName: EntityName;
        attributes: NodeArray<JsxAttribute | JsxSpreadAttribute>;
    }

    /// A JSX expression of the form <TagName attrs />
    export interface JsxSelfClosingElement extends PrimaryExpression, JsxOpeningElement {
        _selfClosingElementBrand?: any;
    }

    /// Either the opening tag in a <Tag>...</Tag> pair, or the lone <Tag /> in a self-closing form
    export type JsxOpeningLikeElement = JsxSelfClosingElement | JsxOpeningElement;

    export interface JsxAttribute extends Node {
        name: Identifier;
        /// JSX attribute initializers are optional; <X y /> is sugar for <X y={true} />
        initializer?: Expression;
    }

    export interface JsxSpreadAttribute extends Node {
        expression: Expression;
    }

    export interface JsxClosingElement extends Node {
        tagName: EntityName;
    }

    export interface JsxExpression extends Expression {
        expression?: Expression;
    }

    export interface JsxText extends Node {
        _jsxTextExpressionBrand: any;
    }

    export type JsxChild = JsxText | JsxExpression | JsxElement | JsxSelfClosingElement;

    export interface Statement extends Node {
        _statementBrand: any;
    }

    export interface Block extends Statement {
        statements: NodeArray<Statement>;
    }

    export interface VariableStatement extends Statement {
        declarationList: VariableDeclarationList;
    }

    export interface ExpressionStatement extends Statement {
        expression: Expression;
    }

    export interface IfStatement extends Statement {
        expression: Expression;
        thenStatement: Statement;
        elseStatement?: Statement;
    }

    export interface IterationStatement extends Statement {
        statement: Statement;
    }

    export interface DoStatement extends IterationStatement {
        expression: Expression;
    }

    export interface WhileStatement extends IterationStatement {
        expression: Expression;
    }

    export interface ForStatement extends IterationStatement {
        initializer?: VariableDeclarationList | Expression;
        condition?: Expression;
        incrementor?: Expression;
    }

    export interface ForInStatement extends IterationStatement {
        initializer: VariableDeclarationList | Expression;
        expression: Expression;
    }

    export interface ForOfStatement extends IterationStatement {
        initializer: VariableDeclarationList | Expression;
        expression: Expression;
    }

    export interface BreakOrContinueStatement extends Statement {
        label?: Identifier;
    }

    export interface ReturnStatement extends Statement {
        expression?: Expression;
    }

    export interface WithStatement extends Statement {
        expression: Expression;
        statement: Statement;
    }

    export interface SwitchStatement extends Statement {
        expression: Expression;
        caseBlock: CaseBlock;
    }

    export interface CaseBlock extends Node {
        clauses: NodeArray<CaseOrDefaultClause>;
    }

    export interface CaseClause extends Node {
        expression?: Expression;
        statements: NodeArray<Statement>;
    }

    export interface DefaultClause extends Node {
        statements: NodeArray<Statement>;
    }

    export type CaseOrDefaultClause = CaseClause | DefaultClause;

    export interface LabeledStatement extends Statement {
        label: Identifier;
        statement: Statement;
    }

    export interface ThrowStatement extends Statement {
        expression: Expression;
    }

    export interface TryStatement extends Statement {
        tryBlock: Block;
        catchClause?: CatchClause;
        finallyBlock?: Block;
    }

    export interface CatchClause extends Node {
        variableDeclaration: VariableDeclaration;
        block: Block;
    }

    export interface ClassLikeDeclaration extends Declaration {
        name?: Identifier;
        typeParameters?: NodeArray<TypeParameterDeclaration>;
        heritageClauses?: NodeArray<HeritageClause>;
        members: NodeArray<ClassElement>;
    }

    export interface ClassDeclaration extends ClassLikeDeclaration, Statement {
    }

    export interface ClassExpression extends ClassLikeDeclaration, PrimaryExpression {
    }

    export interface ClassElement extends Declaration {
        _classElementBrand: any;
    }

    export interface InterfaceDeclaration extends Declaration, Statement {
        name: Identifier;
        typeParameters?: NodeArray<TypeParameterDeclaration>;
        heritageClauses?: NodeArray<HeritageClause>;
        members: NodeArray<Declaration>;
    }

    export interface HeritageClause extends Node {
        token: SyntaxKind;
        types?: NodeArray<ExpressionWithTypeArguments>;
    }

    export interface TypeAliasDeclaration extends Declaration, Statement {
        name: Identifier;
        typeParameters?: NodeArray<TypeParameterDeclaration>;
        type: TypeNode;
    }

    export interface EnumMember extends Declaration {
        // This does include ComputedPropertyName, but the parser will give an error
        // if it parses a ComputedPropertyName in an EnumMember
        name: DeclarationName;
        initializer?: Expression;
    }

    export interface EnumDeclaration extends Declaration, Statement {
        name: Identifier;
        members: NodeArray<EnumMember>;
    }

    export interface ModuleDeclaration extends Declaration, Statement {
        name: Identifier | LiteralExpression;
        body: ModuleBlock | ModuleDeclaration;
    }

    export interface ModuleBlock extends Node, Statement {
        statements: NodeArray<Statement>;
    }

    export interface ImportEqualsDeclaration extends Declaration, Statement {
        name: Identifier;

        // 'EntityName' for an internal module reference, 'ExternalModuleReference' for an external
        // module reference.
        moduleReference: EntityName | ExternalModuleReference;
    }

    export interface ExternalModuleReference extends Node {
        expression?: Expression;
    }

    // In case of:
    // import "mod"  => importClause = undefined, moduleSpecifier = "mod"
    // In rest of the cases, module specifier is string literal corresponding to module
    // ImportClause information is shown at its declaration below.
    export interface ImportDeclaration extends Statement {
        importClause?: ImportClause;
        moduleSpecifier: Expression;
    }

    // In case of:
    // import d from "mod" => name = d, namedBinding = undefined
    // import * as ns from "mod" => name = undefined, namedBinding: NamespaceImport = { name: ns }
    // import d, * as ns from "mod" => name = d, namedBinding: NamespaceImport = { name: ns }
    // import { a, b as x } from "mod" => name = undefined, namedBinding: NamedImports = { elements: [{ name: a }, { name: x, propertyName: b}]}
    // import d, { a, b as x } from "mod" => name = d, namedBinding: NamedImports = { elements: [{ name: a }, { name: x, propertyName: b}]}
    export interface ImportClause extends Declaration {
        name?: Identifier; // Default binding
        namedBindings?: NamespaceImport | NamedImports;
    }

    export interface NamespaceImport extends Declaration {
        name: Identifier;
    }

    export interface ExportDeclaration extends Declaration, Statement {
        exportClause?: NamedExports;
        moduleSpecifier?: Expression;
    }

    export interface NamedImportsOrExports extends Node {
        elements: NodeArray<ImportOrExportSpecifier>;
    }

    export type NamedImports = NamedImportsOrExports;
    export type NamedExports = NamedImportsOrExports;

    export interface ImportOrExportSpecifier extends Declaration {
        propertyName?: Identifier;  // Name preceding "as" keyword (or undefined when "as" is absent)
        name: Identifier;           // Declared name
    }

    export type ImportSpecifier = ImportOrExportSpecifier;
    export type ExportSpecifier = ImportOrExportSpecifier;

    export interface ExportAssignment extends Declaration, Statement {
        isExportEquals?: boolean;
        expression: Expression;
    }

    export interface FileReference extends TextRange {
        fileName: string;
    }

    export interface CommentRange extends TextRange {
        hasTrailingNewLine?: boolean;
        kind: SyntaxKind;
    }

    // represents a top level: { type } expression in a JSDoc comment.
    export interface JSDocTypeExpression extends Node {
        type: JSDocType;
    }

    export interface JSDocType extends TypeNode {
        _jsDocTypeBrand: any;
    }

    export interface JSDocAllType extends JSDocType {
        _JSDocAllTypeBrand: any;
    }

    export interface JSDocUnknownType extends JSDocType {
        _JSDocUnknownTypeBrand: any;
    }

    export interface JSDocArrayType extends JSDocType {
        elementType: JSDocType;
    }

    export interface JSDocUnionType extends JSDocType {
        types: NodeArray<JSDocType>;
    }

    export interface JSDocTupleType extends JSDocType {
        types: NodeArray<JSDocType>;
    }

    export interface JSDocNonNullableType extends JSDocType {
        type: JSDocType;
    }

    export interface JSDocNullableType extends JSDocType {
        type: JSDocType;
    }

    export interface JSDocRecordType extends JSDocType, TypeLiteralNode {
        members: NodeArray<JSDocRecordMember>;
    }

    export interface JSDocTypeReference extends JSDocType {
        name: EntityName;
        typeArguments: NodeArray<JSDocType>;
    }

    export interface JSDocOptionalType extends JSDocType {
        type: JSDocType;
    }

    export interface JSDocFunctionType extends JSDocType, SignatureDeclaration {
        parameters: NodeArray<ParameterDeclaration>;
        type: JSDocType;
    }

    export interface JSDocVariadicType extends JSDocType {
        type: JSDocType;
    }

    export interface JSDocConstructorType extends JSDocType {
        type: JSDocType;
    }

    export interface JSDocThisType extends JSDocType {
        type: JSDocType;
    }

    export interface JSDocRecordMember extends PropertyDeclaration {
        name: Identifier | LiteralExpression;
        type?: JSDocType;
    }

    export interface JSDocComment extends Node {
        tags: NodeArray<JSDocTag>;
    }

    export interface JSDocTag extends Node {
        atToken: Node;
        tagName: Identifier;
    }

    export interface JSDocTemplateTag extends JSDocTag {
        typeParameters: NodeArray<TypeParameterDeclaration>;
    }

    export interface JSDocReturnTag extends JSDocTag {
        typeExpression: JSDocTypeExpression;
    }

    export interface JSDocTypeTag extends JSDocTag {
        typeExpression: JSDocTypeExpression;
    }

    export interface JSDocParameterTag extends JSDocTag {
        preParameterName?: Identifier;
        typeExpression?: JSDocTypeExpression;
        postParameterName?: Identifier;
        isBracketed: boolean;
    }

    // Source files are declarations when they are external modules.
    export interface SourceFile extends Declaration {
        statements: NodeArray<Statement>;
        endOfFileToken: Node;

        fileName: string;
        /* internal */ path: Path;
        text: string;

        amdDependencies: {path: string; name: string}[];
        moduleName: string;
        referencedFiles: FileReference[];
        languageVariant: LanguageVariant;

        // this map is used by transpiler to supply alternative names for dependencies (i.e. in case of bundling)
        /* @internal */
        renamedDependencies?: Map<string>;

        /**
         * lib.d.ts should have a reference comment like
         *
         *  /// <reference no-default-lib="true"/>
         *
         * If any other file has this comment, it signals not to include lib.d.ts
         * because this containing file is intended to act as a default library.
         */
        hasNoDefaultLib: boolean;

        languageVersion: ScriptTarget;

        // The first node that causes this file to be an external module
        /* @internal */ externalModuleIndicator: Node;

        /* @internal */ isDefaultLib: boolean;
        /* @internal */ identifiers: Map<string>;
        /* @internal */ nodeCount: number;
        /* @internal */ identifierCount: number;
        /* @internal */ symbolCount: number;

        // File level diagnostics reported by the parser (includes diagnostics about /// references
        // as well as code diagnostics).
        /* @internal */ parseDiagnostics: Diagnostic[];

        // File level diagnostics reported by the binder.
        /* @internal */ bindDiagnostics: Diagnostic[];

        // Stores a line map for the file.
        // This field should never be used directly to obtain line map, use getLineMap function instead.
        /* @internal */ lineMap: number[];
        /* @internal */ classifiableNames?: Map<string>;
        // Stores a mapping 'external module reference text' -> 'resolved file name' | undefined
        // It is used to resolve module names in the checker.
        // Content of this fiels should never be used directly - use getResolvedModuleFileName/setResolvedModuleFileName functions instead
        /* @internal */ resolvedModules: Map<ResolvedModule>;
        /* @internal */ imports: LiteralExpression[];
    }

    export interface ScriptReferenceHost {
        getCompilerOptions(): CompilerOptions;
        getSourceFile(fileName: string): SourceFile;
        getCurrentDirectory(): string;
    }

    export interface ParseConfigHost {
        readDirectory(rootDir: string, extension: string, exclude: string[]): string[];
    }

    export interface WriteFileCallback {
        (fileName: string, data: string, writeByteOrderMark: boolean, onError?: (message: string) => void): void;
    }

    export class OperationCanceledException { }

    export interface CancellationToken {
        isCancellationRequested(): boolean;

        /** @throws OperationCanceledException if isCancellationRequested is true */
        throwIfCancellationRequested(): void;
    }

    export interface Program extends ScriptReferenceHost {

        /**
         * Get a list of root file names that were passed to a 'createProgram'
         */
        getRootFileNames(): string[];

        /**
         * Get a list of files in the program
         */
        getSourceFiles(): SourceFile[];

        /**
         * Emits the JavaScript and declaration files.  If targetSourceFile is not specified, then
         * the JavaScript and declaration files will be produced for all the files in this program.
         * If targetSourceFile is specified, then only the JavaScript and declaration for that
         * specific file will be generated.
         *
         * If writeFile is not specified then the writeFile callback from the compiler host will be
         * used for writing the JavaScript and declaration files.  Otherwise, the writeFile parameter
         * will be invoked when writing the JavaScript and declaration files.
         */
        emit(targetSourceFile?: SourceFile, writeFile?: WriteFileCallback, cancellationToken?: CancellationToken): EmitResult;

        getOptionsDiagnostics(cancellationToken?: CancellationToken): Diagnostic[];
        getGlobalDiagnostics(cancellationToken?: CancellationToken): Diagnostic[];
        getSyntacticDiagnostics(sourceFile?: SourceFile, cancellationToken?: CancellationToken): Diagnostic[];
        getSemanticDiagnostics(sourceFile?: SourceFile, cancellationToken?: CancellationToken): Diagnostic[];
        getDeclarationDiagnostics(sourceFile?: SourceFile, cancellationToken?: CancellationToken): Diagnostic[];

        /**
         * Gets a type checker that can be used to semantically analyze source fils in the program.
         */
        getTypeChecker(): TypeChecker;

        /* @internal */ getCommonSourceDirectory(): string;

        // For testing purposes only.  Should not be used by any other consumers (including the
        // language service).
        /* @internal */ getDiagnosticsProducingTypeChecker(): TypeChecker;

        /* @internal */ getClassifiableNames(): Map<string>;

        /* @internal */ getNodeCount(): number;
        /* @internal */ getIdentifierCount(): number;
        /* @internal */ getSymbolCount(): number;
        /* @internal */ getTypeCount(): number;

        /* @internal */ getFileProcessingDiagnostics(): DiagnosticCollection;
        // For testing purposes only.
        /* @internal */ structureIsReused?: boolean;
    }

    export interface SourceMapSpan {
        /** Line number in the .js file. */
        emittedLine: number;
        /** Column number in the .js file. */
        emittedColumn: number;
        /** Line number in the .ts file. */
        sourceLine: number;
        /** Column number in the .ts file. */
        sourceColumn: number;
        /** Optional name (index into names array) associated with this span. */
        nameIndex?: number;
        /** .ts file (index into sources array) associated with this span */
        sourceIndex: number;
    }

    export interface SourceMapData {
        sourceMapFilePath: string;           // Where the sourcemap file is written
        jsSourceMappingURL: string;          // source map URL written in the .js file
        sourceMapFile: string;               // Source map's file field - .js file name
        sourceMapSourceRoot: string;         // Source map's sourceRoot field - location where the sources will be present if not ""
        sourceMapSources: string[];          // Source map's sources field - list of sources that can be indexed in this source map
        sourceMapSourcesContent?: string[];  // Source map's sourcesContent field - list of the sources' text to be embedded in the source map
        inputSourceFileNames: string[];      // Input source file (which one can use on program to get the file), 1:1 mapping with the sourceMapSources list
        sourceMapNames?: string[];           // Source map's names field - list of names that can be indexed in this source map
        sourceMapMappings: string;           // Source map's mapping field - encoded source map spans
        sourceMapDecodedMappings: SourceMapSpan[];  // Raw source map spans that were encoded into the sourceMapMappings
    }

    /** Return code used by getEmitOutput function to indicate status of the function */
    export enum ExitStatus {
        // Compiler ran successfully.  Either this was a simple do-nothing compilation (for example,
        // when -version or -help was provided, or this was a normal compilation, no diagnostics
        // were produced, and all outputs were generated successfully.
        Success = 0,

        // Diagnostics were produced and because of them no code was generated.
        DiagnosticsPresent_OutputsSkipped = 1,

        // Diagnostics were produced and outputs were generated in spite of them.
        DiagnosticsPresent_OutputsGenerated = 2,
    }

    export interface EmitResult {
        emitSkipped: boolean;
        diagnostics: Diagnostic[];
        /* @internal */ sourceMaps: SourceMapData[];  // Array of sourceMapData if compiler emitted sourcemaps
    }

    /* @internal */
    export interface TypeCheckerHost {
        getCompilerOptions(): CompilerOptions;

        getSourceFiles(): SourceFile[];
        getSourceFile(fileName: string): SourceFile;
    }

    export interface TypeChecker {
        getTypeOfSymbolAtLocation(symbol: Symbol, node: Node): Type;
        getDeclaredTypeOfSymbol(symbol: Symbol): Type;
        getPropertiesOfType(type: Type): Symbol[];
        getPropertyOfType(type: Type, propertyName: string): Symbol;
        getSignaturesOfType(type: Type, kind: SignatureKind): Signature[];
        getIndexTypeOfType(type: Type, kind: IndexKind): Type;
        getBaseTypes(type: InterfaceType): ObjectType[];
        getReturnTypeOfSignature(signature: Signature): Type;

        getSymbolsInScope(location: Node, meaning: SymbolFlags): Symbol[];
        getSymbolAtLocation(node: Node): Symbol;
        getShorthandAssignmentValueSymbol(location: Node): Symbol;
        getTypeAtLocation(node: Node): Type;
        typeToString(type: Type, enclosingDeclaration?: Node, flags?: TypeFormatFlags): string;
        symbolToString(symbol: Symbol, enclosingDeclaration?: Node, meaning?: SymbolFlags): string;
        getSymbolDisplayBuilder(): SymbolDisplayBuilder;
        getFullyQualifiedName(symbol: Symbol): string;
        getAugmentedPropertiesOfType(type: Type): Symbol[];
        getRootSymbols(symbol: Symbol): Symbol[];
        getContextualType(node: Expression): Type;
        getResolvedSignature(node: CallLikeExpression, candidatesOutArray?: Signature[]): Signature;
        getSignatureFromDeclaration(declaration: SignatureDeclaration): Signature;
        isImplementationOfOverload(node: FunctionLikeDeclaration): boolean;
        isUndefinedSymbol(symbol: Symbol): boolean;
        isArgumentsSymbol(symbol: Symbol): boolean;

        getConstantValue(node: EnumMember | PropertyAccessExpression | ElementAccessExpression): number;
        isValidPropertyAccess(node: PropertyAccessExpression | QualifiedName, propertyName: string): boolean;
        getAliasedSymbol(symbol: Symbol): Symbol;
        getExportsOfModule(moduleSymbol: Symbol): Symbol[];

        getJsxElementAttributesType(elementNode: JsxOpeningLikeElement): Type;
        getJsxIntrinsicTagNames(): Symbol[];
        isOptionalParameter(node: ParameterDeclaration): boolean;

        // Should not be called directly.  Should only be accessed through the Program instance.
        /* @internal */ getDiagnostics(sourceFile?: SourceFile, cancellationToken?: CancellationToken): Diagnostic[];
        /* @internal */ getGlobalDiagnostics(): Diagnostic[];
        /* @internal */ getEmitResolver(sourceFile?: SourceFile, cancellationToken?: CancellationToken): EmitResolver;

        /* @internal */ getNodeCount(): number;
        /* @internal */ getIdentifierCount(): number;
        /* @internal */ getSymbolCount(): number;
        /* @internal */ getTypeCount(): number;
    }

    export interface SymbolDisplayBuilder {
        buildTypeDisplay(type: Type, writer: SymbolWriter, enclosingDeclaration?: Node, flags?: TypeFormatFlags): void;
        buildSymbolDisplay(symbol: Symbol, writer: SymbolWriter, enclosingDeclaration?: Node, meaning?: SymbolFlags, flags?: SymbolFormatFlags): void;
        buildSignatureDisplay(signatures: Signature, writer: SymbolWriter, enclosingDeclaration?: Node, flags?: TypeFormatFlags): void;
        buildParameterDisplay(parameter: Symbol, writer: SymbolWriter, enclosingDeclaration?: Node, flags?: TypeFormatFlags): void;
        buildTypeParameterDisplay(tp: TypeParameter, writer: SymbolWriter, enclosingDeclaration?: Node, flags?: TypeFormatFlags): void;
        buildTypeParameterDisplayFromSymbol(symbol: Symbol, writer: SymbolWriter, enclosingDeclaraiton?: Node, flags?: TypeFormatFlags): void;
        buildDisplayForParametersAndDelimiters(parameters: Symbol[], writer: SymbolWriter, enclosingDeclaration?: Node, flags?: TypeFormatFlags): void;
        buildDisplayForTypeParametersAndDelimiters(typeParameters: TypeParameter[], writer: SymbolWriter, enclosingDeclaration?: Node, flags?: TypeFormatFlags): void;
        buildReturnTypeDisplay(signature: Signature, writer: SymbolWriter, enclosingDeclaration?: Node, flags?: TypeFormatFlags): void;
    }

    export interface SymbolWriter {
        writeKeyword(text: string): void;
        writeOperator(text: string): void;
        writePunctuation(text: string): void;
        writeSpace(text: string): void;
        writeStringLiteral(text: string): void;
        writeParameter(text: string): void;
        writeSymbol(text: string, symbol: Symbol): void;
        writeLine(): void;
        increaseIndent(): void;
        decreaseIndent(): void;
        clear(): void;

        // Called when the symbol writer encounters a symbol to write.  Currently only used by the
        // declaration emitter to help determine if it should patch up the final declaration file
        // with import statements it previously saw (but chose not to emit).
        trackSymbol(symbol: Symbol, enclosingDeclaration?: Node, meaning?: SymbolFlags): void;
        reportInaccessibleThisError(): void;
    }

    export const enum TypeFormatFlags {
        None                            = 0x00000000,
        WriteArrayAsGenericType         = 0x00000001,  // Write Array<T> instead T[]
        UseTypeOfFunction               = 0x00000002,  // Write typeof instead of function type literal
        NoTruncation                    = 0x00000004,  // Don't truncate typeToString result
        WriteArrowStyleSignature        = 0x00000008,  // Write arrow style signature
        WriteOwnNameForAnyLike          = 0x00000010,  // Write symbol's own name instead of 'any' for any like types (eg. unknown, __resolving__ etc)
        WriteTypeArgumentsOfSignature   = 0x00000020,  // Write the type arguments instead of type parameters of the signature
        InElementType                   = 0x00000040,  // Writing an array or union element type
        UseFullyQualifiedType           = 0x00000080,  // Write out the fully qualified type name (eg. Module.Type, instead of Type)
    }

    export const enum SymbolFormatFlags {
        None = 0x00000000,

        // Write symbols's type argument if it is instantiated symbol
        // eg. class C<T> { p: T }   <-- Show p as C<T>.p here
        //     var a: C<number>;
        //     var p = a.p;  <--- Here p is property of C<number> so show it as C<number>.p instead of just C.p
        WriteTypeParametersOrArguments = 0x00000001,

        // Use only external alias information to get the symbol name in the given context
        // eg.  module m { export class c { } } import x = m.c;
        // When this flag is specified m.c will be used to refer to the class instead of alias symbol x
        UseOnlyExternalAliasing = 0x00000002,
    }

    /* @internal */
    export const enum SymbolAccessibility {
        Accessible,
        NotAccessible,
        CannotBeNamed
    }

    export interface TypePredicate {
        parameterName: string;
        parameterIndex: number;
        type: Type;
    }

    /* @internal */
    export type AnyImportSyntax = ImportDeclaration | ImportEqualsDeclaration;

    /* @internal */
    export interface SymbolVisibilityResult {
        accessibility: SymbolAccessibility;
        aliasesToMakeVisible?: AnyImportSyntax[]; // aliases that need to have this symbol visible
        errorSymbolName?: string; // Optional symbol name that results in error
        errorNode?: Node; // optional node that results in error
    }

    /* @internal */
    export interface SymbolAccessiblityResult extends SymbolVisibilityResult {
        errorModuleName?: string; // If the symbol is not visible from module, module's name
    }

    /** Indicates how to serialize the name for a TypeReferenceNode when emitting decorator
      * metadata */
    /* @internal */
    export enum TypeReferenceSerializationKind {
        Unknown,                            // The TypeReferenceNode could not be resolved. The type name
                                            // should be emitted using a safe fallback.
        TypeWithConstructSignatureAndValue, // The TypeReferenceNode resolves to a type with a constructor
                                            // function that can be reached at runtime (e.g. a `class`
                                            // declaration or a `var` declaration for the static side
                                            // of a type, such as the global `Promise` type in lib.d.ts).
        VoidType,                           // The TypeReferenceNode resolves to a Void-like type.
        NumberLikeType,                     // The TypeReferenceNode resolves to a Number-like type.
        StringLikeType,                     // The TypeReferenceNode resolves to a String-like type.
        BooleanType,                        // The TypeReferenceNode resolves to a Boolean-like type.
        ArrayLikeType,                      // The TypeReferenceNode resolves to an Array-like type.
        ESSymbolType,                       // The TypeReferenceNode resolves to the ESSymbol type.
        TypeWithCallSignature,              // The TypeReferenceNode resolves to a Function type or a type
                                            // with call signatures.
        ObjectType,                         // The TypeReferenceNode resolves to any other type.
    }

    /* @internal */
    export interface EmitResolver {
        hasGlobalName(name: string): boolean;
        getReferencedExportContainer(node: Identifier): SourceFile | ModuleDeclaration | EnumDeclaration;
        getReferencedImportDeclaration(node: Identifier): Declaration;
        getReferencedNestedRedeclaration(node: Identifier): Declaration;
        isNestedRedeclaration(node: Declaration): boolean;
        isValueAliasDeclaration(node: Node): boolean;
        isReferencedAliasDeclaration(node: Node, checkChildren?: boolean): boolean;
        isTopLevelValueImportEqualsWithEntityName(node: ImportEqualsDeclaration): boolean;
        getNodeCheckFlags(node: Node): NodeCheckFlags;
        isDeclarationVisible(node: Declaration): boolean;
        collectLinkedAliases(node: Identifier): Node[];
        isImplementationOfOverload(node: FunctionLikeDeclaration): boolean;
        writeTypeOfDeclaration(declaration: AccessorDeclaration | VariableLikeDeclaration, enclosingDeclaration: Node, flags: TypeFormatFlags, writer: SymbolWriter): void;
        writeReturnTypeOfSignatureDeclaration(signatureDeclaration: SignatureDeclaration, enclosingDeclaration: Node, flags: TypeFormatFlags, writer: SymbolWriter): void;
        writeTypeOfExpression(expr: Expression, enclosingDeclaration: Node, flags: TypeFormatFlags, writer: SymbolWriter): void;
        isSymbolAccessible(symbol: Symbol, enclosingDeclaration: Node, meaning: SymbolFlags): SymbolAccessiblityResult;
        isEntityNameVisible(entityName: EntityName | Expression, enclosingDeclaration: Node): SymbolVisibilityResult;
        // Returns the constant value this property access resolves to, or 'undefined' for a non-constant
        getConstantValue(node: EnumMember | PropertyAccessExpression | ElementAccessExpression): number;
        getReferencedValueDeclaration(reference: Identifier): Declaration;
        getTypeReferenceSerializationKind(typeName: EntityName): TypeReferenceSerializationKind;
        isOptionalParameter(node: ParameterDeclaration): boolean;
        isArgumentsLocalBinding(node: Identifier): boolean;
    }

    export const enum SymbolFlags {
        None                    = 0,
        FunctionScopedVariable  = 0x00000001,  // Variable (var) or parameter
        BlockScopedVariable     = 0x00000002,  // A block-scoped variable (let or const)
        Property                = 0x00000004,  // Property or enum member
        EnumMember              = 0x00000008,  // Enum member
        Function                = 0x00000010,  // Function
        Class                   = 0x00000020,  // Class
        Interface               = 0x00000040,  // Interface
        ConstEnum               = 0x00000080,  // Const enum
        RegularEnum             = 0x00000100,  // Enum
        ValueModule             = 0x00000200,  // Instantiated module
        NamespaceModule         = 0x00000400,  // Uninstantiated module
        TypeLiteral             = 0x00000800,  // Type Literal
        ObjectLiteral           = 0x00001000,  // Object Literal
        Method                  = 0x00002000,  // Method
        Constructor             = 0x00004000,  // Constructor
        GetAccessor             = 0x00008000,  // Get accessor
        SetAccessor             = 0x00010000,  // Set accessor
        Signature               = 0x00020000,  // Call, construct, or index signature
        TypeParameter           = 0x00040000,  // Type parameter
        TypeAlias               = 0x00080000,  // Type alias
        ExportValue             = 0x00100000,  // Exported value marker (see comment in declareModuleMember in binder)
        ExportType              = 0x00200000,  // Exported type marker (see comment in declareModuleMember in binder)
        ExportNamespace         = 0x00400000,  // Exported namespace marker (see comment in declareModuleMember in binder)
        Alias                   = 0x00800000,  // An alias for another symbol (see comment in isAliasSymbolDeclaration in checker)
        Instantiated            = 0x01000000,  // Instantiated symbol
        Merged                  = 0x02000000,  // Merged symbol (created during program binding)
        Transient               = 0x04000000,  // Transient symbol (created during type check)
        Prototype               = 0x08000000,  // Prototype property (no source representation)
        SyntheticProperty       = 0x10000000,  // Property in union or intersection type
        Optional                = 0x20000000,  // Optional property
        ExportStar              = 0x40000000,  // Export * declaration

        Enum = RegularEnum | ConstEnum,
        Variable = FunctionScopedVariable | BlockScopedVariable,
        Value = Variable | Property | EnumMember | Function | Class | Enum | ValueModule | Method | GetAccessor | SetAccessor,
        Type = Class | Interface | Enum | TypeLiteral | ObjectLiteral | TypeParameter | TypeAlias,
        Namespace = ValueModule | NamespaceModule,
        Module = ValueModule | NamespaceModule,
        Accessor = GetAccessor | SetAccessor,

        // Variables can be redeclared, but can not redeclare a block-scoped declaration with the
        // same name, or any other value that is not a variable, e.g. ValueModule or Class
        FunctionScopedVariableExcludes = Value & ~FunctionScopedVariable,

        // Block-scoped declarations are not allowed to be re-declared
        // they can not merge with anything in the value space
        BlockScopedVariableExcludes = Value,

        ParameterExcludes = Value,
        PropertyExcludes = Value,
        EnumMemberExcludes = Value,
        FunctionExcludes = Value & ~(Function | ValueModule),
        ClassExcludes = (Value | Type) & ~(ValueModule | Interface), // class-interface mergability done in checker.ts
        InterfaceExcludes = Type & ~(Interface | Class),
        RegularEnumExcludes = (Value | Type) & ~(RegularEnum | ValueModule), // regular enums merge only with regular enums and modules
        ConstEnumExcludes = (Value | Type) & ~ConstEnum, // const enums merge only with const enums
        ValueModuleExcludes = Value & ~(Function | Class | RegularEnum | ValueModule),
        NamespaceModuleExcludes = 0,
        MethodExcludes = Value & ~Method,
        GetAccessorExcludes = Value & ~SetAccessor,
        SetAccessorExcludes = Value & ~GetAccessor,
        TypeParameterExcludes = Type & ~TypeParameter,
        TypeAliasExcludes = Type,
        AliasExcludes = Alias,

        ModuleMember = Variable | Function | Class | Interface | Enum | Module | TypeAlias | Alias,

        ExportHasLocal = Function | Class | Enum | ValueModule,

        HasExports = Class | Enum | Module,
        HasMembers = Class | Interface | TypeLiteral | ObjectLiteral,

        BlockScoped = BlockScopedVariable | Class | Enum,

        PropertyOrAccessor = Property | Accessor,
        Export = ExportNamespace | ExportType | ExportValue,

        /* @internal */
        // The set of things we consider semantically classifiable.  Used to speed up the LS during
        // classification.
        Classifiable = Class | Enum | TypeAlias | Interface | TypeParameter | Module,
    }

    export interface Symbol {
        flags: SymbolFlags;                     // Symbol flags
        name: string;                           // Name of symbol
        declarations?: Declaration[];           // Declarations associated with this symbol
        valueDeclaration?: Declaration;         // First value declaration of the symbol

        members?: SymbolTable;                  // Class, interface or literal instance members
        exports?: SymbolTable;                  // Module exports
        /* @internal */ id?: number;            // Unique id (used to look up SymbolLinks)
        /* @internal */ mergeId?: number;       // Merge id (used to look up merged symbol)
        /* @internal */ parent?: Symbol;        // Parent symbol
        /* @internal */ exportSymbol?: Symbol;  // Exported symbol associated with this symbol
        /* @internal */ constEnumOnlyModule?: boolean; // True if module contains only const enums or other modules with only const enums
    }

    /* @internal */
    export interface SymbolLinks {
        target?: Symbol;                    // Resolved (non-alias) target of an alias
        type?: Type;                        // Type of value symbol
        declaredType?: Type;                // Type of class, interface, enum, type alias, or type parameter
        typeParameters?: TypeParameter[];   // Type parameters of type alias (undefined if non-generic)
        instantiations?: Map<Type>;         // Instantiations of generic type alias (undefined if non-generic)
        mapper?: TypeMapper;                // Type mapper for instantiation alias
        referenced?: boolean;               // True if alias symbol has been referenced as a value
        containingType?: UnionOrIntersectionType; // Containing union or intersection type for synthetic property
        resolvedExports?: SymbolTable;      // Resolved exports of module
        exportsChecked?: boolean;           // True if exports of external module have been checked
        isNestedRedeclaration?: boolean;    // True if symbol is block scoped redeclaration
        bindingElement?: BindingElement;    // Binding element associated with property symbol
    }

    /* @internal */
    export interface TransientSymbol extends Symbol, SymbolLinks { }

    export interface SymbolTable {
        [index: string]: Symbol;
    }

    /* @internal */
    export const enum NodeCheckFlags {
        TypeChecked                 = 0x00000001,  // Node has been type checked
        LexicalThis                 = 0x00000002,  // Lexical 'this' reference
        CaptureThis                 = 0x00000004,  // Lexical 'this' used in body
        EmitExtends                 = 0x00000008,  // Emit __extends
        EmitDecorate                = 0x00000010,  // Emit __decorate
        EmitParam                   = 0x00000020,  // Emit __param helper for decorators
        EmitAwaiter                 = 0x00000040,  // Emit __awaiter
        EmitGenerator               = 0x00000080,  // Emit __generator
        SuperInstance               = 0x00000100,  // Instance 'super' reference
        SuperStatic                 = 0x00000200,  // Static 'super' reference
        ContextChecked              = 0x00000400,  // Contextual types have been assigned
        LexicalArguments            = 0x00000800,
        CaptureArguments            = 0x00001000,  // Lexical 'arguments' used in body (for async functions)

        // Values for enum members have been computed, and any errors have been reported for them.
        EnumValuesComputed          = 0x00002000,
        BlockScopedBindingInLoop    = 0x00004000,
        LexicalModuleMergesWithClass = 0x00008000,  // Instantiated lexical module declaration is merged with a previous class declaration.
        LoopWithBlockScopedBindingCapturedInFunction = 0x00010000, // Loop that contains block scoped variable captured in closure
    }

    /* @internal */
    export interface NodeLinks {
        resolvedType?: Type;              // Cached type of type node
        resolvedAwaitedType?: Type;       // Cached awaited type of type node
        resolvedSignature?: Signature;    // Cached signature of signature node or call expression
        resolvedSymbol?: Symbol;          // Cached name resolution result
        flags?: NodeCheckFlags;           // Set of flags specific to Node
        enumMemberValue?: number;         // Constant value of enum member
        isIllegalTypeReferenceInConstraint?: boolean; // Is type reference in constraint refers to the type parameter from the same list
        isVisible?: boolean;              // Is this node visible
        generatedName?: string;           // Generated name for module, enum, or import declaration
        generatedNames?: Map<string>;     // Generated names table for source file
        assignmentChecks?: Map<boolean>;  // Cache of assignment checks
        hasReportedStatementInAmbientContext?: boolean;  // Cache boolean if we report statements in ambient context
        importOnRightSide?: Symbol;       // for import declarations - import that appear on the right side
        jsxFlags?: JsxFlags;              // flags for knowning what kind of element/attributes we're dealing with
        resolvedJsxType?: Type;           // resolved element attributes type of a JSX openinglike element
    }

    export const enum TypeFlags {
        Any                     = 0x00000001,
        String                  = 0x00000002,
        Number                  = 0x00000004,
        Boolean                 = 0x00000008,
        Void                    = 0x00000010,
        Undefined               = 0x00000020,
        Null                    = 0x00000040,
        Enum                    = 0x00000080,  // Enum type
        StringLiteral           = 0x00000100,  // String literal type
        TypeParameter           = 0x00000200,  // Type parameter
        Class                   = 0x00000400,  // Class
        Interface               = 0x00000800,  // Interface
        Reference               = 0x00001000,  // Generic type reference
        Tuple                   = 0x00002000,  // Tuple
        Union                   = 0x00004000,  // Union (T | U)
        Intersection            = 0x00008000,  // Intersection (T & U)
        Anonymous               = 0x00010000,  // Anonymous
        Instantiated            = 0x00020000,  // Instantiated anonymous type
        /* @internal */
        FromSignature           = 0x00040000,  // Created for signature assignment check
        ObjectLiteral           = 0x00080000,  // Originates in an object literal
        /* @internal */
        FreshObjectLiteral      = 0x00100000,  // Fresh object literal type
        /* @internal */
        ContainsUndefinedOrNull = 0x00200000,  // Type is or contains Undefined or Null type
        /* @internal */
        ContainsObjectLiteral   = 0x00400000,  // Type is or contains object literal type
        /* @internal */
        ContainsAnyFunctionType = 0x00800000,  // Type is or contains object literal type
        ESSymbol                = 0x01000000,  // Type of symbol primitive introduced in ES6
        ThisType                = 0x02000000,  // This type

        /* @internal */
        Intrinsic = Any | String | Number | Boolean | ESSymbol | Void | Undefined | Null,
        /* @internal */
        Primitive = String | Number | Boolean | ESSymbol | Void | Undefined | Null | StringLiteral | Enum,
        StringLike = String | StringLiteral,
        NumberLike = Number | Enum,
        ObjectType = Class | Interface | Reference | Tuple | Anonymous,
        UnionOrIntersection = Union | Intersection,
        StructuredType = ObjectType | Union | Intersection,
        /* @internal */
        RequiresWidening = ContainsUndefinedOrNull | ContainsObjectLiteral,
        /* @internal */
        PropagatingFlags = ContainsUndefinedOrNull | ContainsObjectLiteral | ContainsAnyFunctionType
    }

    export type DestructuringPattern = BindingPattern | ObjectLiteralExpression | ArrayLiteralExpression;

    // Properties common to all types
    export interface Type {
        flags: TypeFlags;                // Flags
        /* @internal */ id: number;      // Unique ID
        symbol?: Symbol;                 // Symbol associated with type (if any)
        pattern?: DestructuringPattern;  // Destructuring pattern represented by type (if any)
    }

    /* @internal */
    // Intrinsic types (TypeFlags.Intrinsic)
    export interface IntrinsicType extends Type {
        intrinsicName: string;  // Name of intrinsic type
    }

    // String literal types (TypeFlags.StringLiteral)
    export interface StringLiteralType extends Type {
        text: string;  // Text of string literal
    }

    // Object types (TypeFlags.ObjectType)
    export interface ObjectType extends Type { }

    // Class and interface types (TypeFlags.Class and TypeFlags.Interface)
    export interface InterfaceType extends ObjectType {
        typeParameters: TypeParameter[];           // Type parameters (undefined if non-generic)
        outerTypeParameters: TypeParameter[];      // Outer type parameters (undefined if none)
        localTypeParameters: TypeParameter[];      // Local type parameters (undefined if none)
        thisType: TypeParameter;                   // The "this" type (undefined if none)
        /* @internal */
        resolvedBaseConstructorType?: Type;        // Resolved base constructor type of class
        /* @internal */
        resolvedBaseTypes: ObjectType[];           // Resolved base types
    }

    export interface InterfaceTypeWithDeclaredMembers extends InterfaceType {
        declaredProperties: Symbol[];              // Declared members
        declaredCallSignatures: Signature[];       // Declared call signatures
        declaredConstructSignatures: Signature[];  // Declared construct signatures
        declaredStringIndexType: Type;             // Declared string index type
        declaredNumberIndexType: Type;             // Declared numeric index type
    }

    // Type references (TypeFlags.Reference). When a class or interface has type parameters or
    // a "this" type, references to the class or interface are made using type references. The
    // typeArguments property specififes the types to substitute for the type parameters of the
    // class or interface and optionally includes an extra element that specifies the type to
    // substitute for "this" in the resulting instantiation. When no extra argument is present,
    // the type reference itself is substituted for "this". The typeArguments property is undefined
    // if the class or interface has no type parameters and the reference isn't specifying an
    // explicit "this" argument.
    export interface TypeReference extends ObjectType {
        target: GenericType;    // Type reference target
        typeArguments: Type[];  // Type reference type arguments (undefined if none)
    }

    // Generic class and interface types
    export interface GenericType extends InterfaceType, TypeReference {
        /* @internal */
        instantiations: Map<TypeReference>;   // Generic instantiation cache
    }

    export interface TupleType extends ObjectType {
        elementTypes: Type[];  // Element types
    }

    export interface UnionOrIntersectionType extends Type {
        types: Type[];                    // Constituent types
        /* @internal */
        reducedType: Type;                // Reduced union type (all subtypes removed)
        /* @internal */
        resolvedProperties: SymbolTable;  // Cache of resolved properties
    }

    export interface UnionType extends UnionOrIntersectionType { }

    export interface IntersectionType extends UnionOrIntersectionType { }

    /* @internal */
    // An instantiated anonymous type has a target and a mapper
    export interface AnonymousType extends ObjectType {
        target?: AnonymousType;  // Instantiation target
        mapper?: TypeMapper;     // Instantiation mapper
    }

    /* @internal */
    // Resolved object, union, or intersection type
    export interface ResolvedType extends ObjectType, UnionOrIntersectionType {
        members: SymbolTable;              // Properties by name
        properties: Symbol[];              // Properties
        callSignatures: Signature[];       // Call signatures of type
        constructSignatures: Signature[];  // Construct signatures of type
        stringIndexType?: Type;            // String index type
        numberIndexType?: Type;            // Numeric index type
    }

    /* @internal */
    // Object literals are initially marked fresh. Freshness disappears following an assignment,
    // before a type assertion, or when when an object literal's type is widened. The regular
    // version of a fresh type is identical except for the TypeFlags.FreshObjectLiteral flag.
    export interface FreshObjectLiteralType extends ResolvedType {
        regularType: ResolvedType;  // Regular version of fresh type
    }

    // Just a place to cache element types of iterables and iterators
    /* @internal */
    export interface IterableOrIteratorType extends ObjectType, UnionType {
        iterableElementType?: Type;
        iteratorElementType?: Type;
    }

    // Type parameters (TypeFlags.TypeParameter)
    export interface TypeParameter extends Type {
        constraint: Type;        // Constraint
        /* @internal */
        target?: TypeParameter;  // Instantiation target
        /* @internal */
        mapper?: TypeMapper;     // Instantiation mapper
    }

    export const enum SignatureKind {
        Call,
        Construct,
    }

    export interface Signature {
        declaration: SignatureDeclaration;  // Originating declaration
        typeParameters: TypeParameter[];    // Type parameters (undefined if non-generic)
        parameters: Symbol[];               // Parameters
        typePredicate?: TypePredicate;      // Type predicate
        /* @internal */
        resolvedReturnType: Type;           // Resolved return type
        /* @internal */
        minArgumentCount: number;           // Number of non-optional parameters
        /* @internal */
        hasRestParameter: boolean;          // True if last parameter is rest parameter
        /* @internal */
        hasStringLiterals: boolean;         // True if specialized
        /* @internal */
        target?: Signature;                 // Instantiation target
        /* @internal */
        mapper?: TypeMapper;                // Instantiation mapper
        /* @internal */
        unionSignatures?: Signature[];      // Underlying signatures of a union signature
        /* @internal */
        erasedSignatureCache?: Signature;   // Erased version of signature (deferred)
        /* @internal */
        isolatedSignatureType?: ObjectType; // A manufactured type that just contains the signature for purposes of signature comparison
    }

    export const enum IndexKind {
        String,
        Number,
    }

    /* @internal */
    export interface TypeMapper {
        (t: TypeParameter): Type;
        instantiations?: Type[];    // Cache of instantiations created using this type mapper.
        context?: InferenceContext; // The inference context this mapper was created from.
                                    // Only inference mappers have this set (in createInferenceMapper).
                                    // The identity mapper and regular instantiation mappers do not need it.
    }

    /* @internal */
    export interface TypeInferences {
        primary: Type[];    // Inferences made directly to a type parameter
        secondary: Type[];  // Inferences made to a type parameter in a union type
        isFixed: boolean;   // Whether the type parameter is fixed, as defined in section 4.12.2 of the TypeScript spec
                            // If a type parameter is fixed, no more inferences can be made for the type parameter
    }

    /* @internal */
    export interface InferenceContext {
        typeParameters: TypeParameter[];    // Type parameters for which inferences are made
        inferUnionTypes: boolean;           // Infer union types for disjoint candidates (otherwise undefinedType)
        inferences: TypeInferences[];       // Inferences made for each type parameter
        inferredTypes: Type[];              // Inferred type for each type parameter
        failedTypeParameterIndex?: number;  // Index of type parameter for which inference failed
        // It is optional because in contextual signature instantiation, nothing fails
    }

    export interface DiagnosticMessage {
        key: string;
        category: DiagnosticCategory;
        code: number;
        message: string;
    }

    /**
     * A linked list of formatted diagnostic messages to be used as part of a multiline message.
     * It is built from the bottom up, leaving the head to be the "main" diagnostic.
     * While it seems that DiagnosticMessageChain is structurally similar to DiagnosticMessage,
     * the difference is that messages are all preformatted in DMC.
     */
    export interface DiagnosticMessageChain {
        messageText: string;
        category: DiagnosticCategory;
        code: number;
        next?: DiagnosticMessageChain;
    }

    export interface Diagnostic {
        file: SourceFile;
        start: number;
        length: number;
        messageText: string | DiagnosticMessageChain;
        category: DiagnosticCategory;
        code: number;
    }

    export enum DiagnosticCategory {
        Warning,
        Error,
        Message,
    }

    export const enum ModuleResolutionKind {
        Classic  = 1,
        NodeJs  = 2
    }

    export interface CompilerOptions {
        allowNonTsExtensions?: boolean;
        charset?: string;
        declaration?: boolean;
        diagnostics?: boolean;
        emitBOM?: boolean;
        help?: boolean;
        init?: boolean;
        inlineSourceMap?: boolean;
        inlineSources?: boolean;
        jsx?: JsxEmit;
        listFiles?: boolean;
        locale?: string;
        mapRoot?: string;
        module?: ModuleKind;
        newLine?: NewLineKind;
        noEmit?: boolean;
        noEmitHelpers?: boolean;
        noEmitOnError?: boolean;
        noErrorTruncation?: boolean;
        noImplicitAny?: boolean;
        noLib?: boolean;
        noResolve?: boolean;
        out?: string;
        outFile?: string;
        outDir?: string;
        preserveConstEnums?: boolean;
        /* @internal */ pretty?: DiagnosticStyle;
        project?: string;
        removeComments?: boolean;
        rootDir?: string;
        sourceMap?: boolean;
        sourceRoot?: string;
        suppressExcessPropertyErrors?: boolean;
        suppressImplicitAnyIndexErrors?: boolean;
        target?: ScriptTarget;
        version?: boolean;
        watch?: boolean;
        isolatedModules?: boolean;
        experimentalDecorators?: boolean;
        emitDecoratorMetadata?: boolean;
        moduleResolution?: ModuleResolutionKind;
        allowUnusedLabels?: boolean;
        allowUnreachableCode?: boolean;
        noImplicitReturns?: boolean;
        noFallthroughCasesInSwitch?: boolean;
        forceConsistentCasingInFileNames?: boolean;
        /* @internal */ stripInternal?: boolean;

        // Skip checking lib.d.ts to help speed up tests.
        /* @internal */ skipDefaultLibCheck?: boolean;

        [option: string]: string | number | boolean;
    }

    export const enum ModuleKind {
        None = 0,
        CommonJS = 1,
        AMD = 2,
        UMD = 3,
        System = 4,
        ES6 = 5,
        ES2015 = ES6,
    }

    export const enum JsxEmit {
        None = 0,
        Preserve = 1,
        React = 2
    }

    export const enum NewLineKind {
        CarriageReturnLineFeed = 0,
        LineFeed = 1,
    }

    export interface LineAndCharacter {
        line: number;
        /*
         * This value denotes the character position in line and is different from the 'column' because of tab characters.
         */
        character: number;
    }

    export const enum ScriptTarget {
        ES3 = 0,
        ES5 = 1,
        ES6 = 2,
        ES2015 = ES6,
        Latest = ES6,
    }

    export const enum LanguageVariant {
        Standard,
        JSX,
    }

    /* @internal */
    export const enum DiagnosticStyle {
        Simple,
        Pretty,
    }

    export interface ParsedCommandLine {
        options: CompilerOptions;
        fileNames: string[];
        errors: Diagnostic[];
    }

    /* @internal */
    export interface CommandLineOptionBase {
        name: string;
        type: string | Map<number>;         // "string", "number", "boolean", or an object literal mapping named values to actual values
        isFilePath?: boolean;               // True if option value is a path or fileName
        shortName?: string;                 // A short mnemonic for convenience - for instance, 'h' can be used in place of 'help'
        description?: DiagnosticMessage;    // The message describing what the command line switch does
        paramType?: DiagnosticMessage;      // The name to be used for a non-boolean option's parameter
        experimental?: boolean;
    }

    /* @internal */
    export interface CommandLineOptionOfPrimitiveType extends CommandLineOptionBase {
        type: string;                   // "string" | "number" | "boolean"
    }

    /* @internal */
    export interface CommandLineOptionOfCustomType extends CommandLineOptionBase {
        type: Map<number>;             // an object literal mapping named values to actual values
        error: DiagnosticMessage;      // The error given when the argument does not fit a customized 'type'
    }

    /* @internal */
    export type CommandLineOption = CommandLineOptionOfCustomType | CommandLineOptionOfPrimitiveType;

    /* @internal */
    export const enum CharacterCodes {
        nullCharacter = 0,
        maxAsciiCharacter = 0x7F,

        lineFeed = 0x0A,              // \n
        carriageReturn = 0x0D,        // \r
        lineSeparator = 0x2028,
        paragraphSeparator = 0x2029,
        nextLine = 0x0085,

        // Unicode 3.0 space characters
        space = 0x0020,   // " "
        nonBreakingSpace = 0x00A0,   //
        enQuad = 0x2000,
        emQuad = 0x2001,
        enSpace = 0x2002,
        emSpace = 0x2003,
        threePerEmSpace = 0x2004,
        fourPerEmSpace = 0x2005,
        sixPerEmSpace = 0x2006,
        figureSpace = 0x2007,
        punctuationSpace = 0x2008,
        thinSpace = 0x2009,
        hairSpace = 0x200A,
        zeroWidthSpace = 0x200B,
        narrowNoBreakSpace = 0x202F,
        ideographicSpace = 0x3000,
        mathematicalSpace = 0x205F,
        ogham = 0x1680,

        _ = 0x5F,
        $ = 0x24,

        _0 = 0x30,
        _1 = 0x31,
        _2 = 0x32,
        _3 = 0x33,
        _4 = 0x34,
        _5 = 0x35,
        _6 = 0x36,
        _7 = 0x37,
        _8 = 0x38,
        _9 = 0x39,

        a = 0x61,
        b = 0x62,
        c = 0x63,
        d = 0x64,
        e = 0x65,
        f = 0x66,
        g = 0x67,
        h = 0x68,
        i = 0x69,
        j = 0x6A,
        k = 0x6B,
        l = 0x6C,
        m = 0x6D,
        n = 0x6E,
        o = 0x6F,
        p = 0x70,
        q = 0x71,
        r = 0x72,
        s = 0x73,
        t = 0x74,
        u = 0x75,
        v = 0x76,
        w = 0x77,
        x = 0x78,
        y = 0x79,
        z = 0x7A,

        A = 0x41,
        B = 0x42,
        C = 0x43,
        D = 0x44,
        E = 0x45,
        F = 0x46,
        G = 0x47,
        H = 0x48,
        I = 0x49,
        J = 0x4A,
        K = 0x4B,
        L = 0x4C,
        M = 0x4D,
        N = 0x4E,
        O = 0x4F,
        P = 0x50,
        Q = 0x51,
        R = 0x52,
        S = 0x53,
        T = 0x54,
        U = 0x55,
        V = 0x56,
        W = 0x57,
        X = 0x58,
        Y = 0x59,
        Z = 0x5a,

        ampersand = 0x26,             // &
        asterisk = 0x2A,              // *
        at = 0x40,                    // @
        backslash = 0x5C,             // \
        backtick = 0x60,              // `
        bar = 0x7C,                   // |
        caret = 0x5E,                 // ^
        closeBrace = 0x7D,            // }
        closeBracket = 0x5D,          // ]
        closeParen = 0x29,            // )
        colon = 0x3A,                 // :
        comma = 0x2C,                 // ,
        dot = 0x2E,                   // .
        doubleQuote = 0x22,           // "
        equals = 0x3D,                // =
        exclamation = 0x21,           // !
        greaterThan = 0x3E,           // >
        hash = 0x23,                  // #
        lessThan = 0x3C,              // <
        minus = 0x2D,                 // -
        openBrace = 0x7B,             // {
        openBracket = 0x5B,           // [
        openParen = 0x28,             // (
        percent = 0x25,               // %
        plus = 0x2B,                  // +
        question = 0x3F,              // ?
        semicolon = 0x3B,             // ;
        singleQuote = 0x27,           // '
        slash = 0x2F,                 // /
        tilde = 0x7E,                 // ~

        backspace = 0x08,             // \b
        formFeed = 0x0C,              // \f
        byteOrderMark = 0xFEFF,
        tab = 0x09,                   // \t
        verticalTab = 0x0B,           // \v
    }

    export interface ModuleResolutionHost {
        fileExists(fileName: string): boolean;
        // readFile function is used to read arbitrary text files on disk, i.e. when resolution procedure needs the content of 'package.json'
        // to determine location of bundled typings for node module 
        readFile(fileName: string): string;
    }

    export interface ResolvedModule {
        resolvedFileName: string;
        /*
         * Denotes if 'resolvedFileName' is isExternalLibraryImport and thus should be proper external module:
         * - be a .d.ts file 
         * - use top level imports\exports
         * - don't use tripleslash references
         */
        isExternalLibraryImport?: boolean;
    }

    export interface ResolvedModuleWithFailedLookupLocations {
        resolvedModule: ResolvedModule;
        failedLookupLocations: string[];
    }

    export interface CompilerHost extends ModuleResolutionHost {
        getSourceFile(fileName: string, languageVersion: ScriptTarget, onError?: (message: string) => void): SourceFile;
        getCancellationToken?(): CancellationToken;
        getDefaultLibFileName(options: CompilerOptions): string;
        writeFile: WriteFileCallback;
        getCurrentDirectory(): string;
        getCanonicalFileName(fileName: string): string;
        useCaseSensitiveFileNames(): boolean;
        getNewLine(): string;

        /*
         * CompilerHost must either implement resolveModuleNames (in case if it wants to be completely in charge of 
         * module name resolution) or provide implementation for methods from ModuleResolutionHost (in this case compiler 
         * will appply built-in module resolution logic and use members of ModuleResolutionHost to ask host specific questions).
         * If resolveModuleNames is implemented then implementation for members from ModuleResolutionHost can be just 
         * 'throw new Error("NotImplemented")'  
         */
        resolveModuleNames?(moduleNames: string[], containingFile: string): ResolvedModule[];
    }

    export interface TextSpan {
        start: number;
        length: number;
    }

    export interface TextChangeRange {
        span: TextSpan;
        newLength: number;
    }

    /* @internal */
    export interface DiagnosticCollection {
        // Adds a diagnostic to this diagnostic collection.
        add(diagnostic: Diagnostic): void;

        // Gets all the diagnostics that aren't associated with a file.
        getGlobalDiagnostics(): Diagnostic[];

        // If fileName is provided, gets all the diagnostics associated with that file name.
        // Otherwise, returns all the diagnostics (global and file associated) in this colletion.
        getDiagnostics(fileName?: string): Diagnostic[];

        // Gets a count of how many times this collection has been modified.  This value changes
        // each time 'add' is called (regardless of whether or not an equivalent diagnostic was
        // already in the collection).  As such, it can be used as a simple way to tell if any
        // operation caused diagnostics to be returned by storing and comparing the return value
        // of this method before/after the operation is performed.
        getModificationCount(): number;

        /* @internal */ reattachFileDiagnostics(newFile: SourceFile): void;
    }
}