@lezer/javascript/test/typescript.txt

lezer-based JavaScript grammar

# Undefined and Null Type {"dialect": "ts"}

let x: undefined
let y: null

==>

Script(
  VariableDeclaration(let,VariableDefinition,TypeAnnotation(
    TypeName)),
  VariableDeclaration(let,VariableDefinition,TypeAnnotation(
    NullType(null))))

# Type declaration {"dialect": "ts"}

function foo(a: number, b: "literal" | Map<number, boolean>): RegExp[] {}

==>

Script(FunctionDeclaration(function, VariableDefinition, ParamList(
  VariableDefinition, TypeAnnotation(TypeName),
  VariableDefinition, TypeAnnotation(UnionType(LiteralType(String), LogicOp, ParameterizedType(TypeName, TypeArgList(TypeName, TypeName))))
), TypeAnnotation(ArrayType(TypeName)), Block))

# Type predicate {"dialect": "ts"}

function isFoo(foo: any): foo is Foo { return true }

function assertFoo(foo: any): asserts foo is "string" { return true }

==>

Script(
  FunctionDeclaration(function, VariableDefinition, ParamList(
    VariableDefinition, TypeAnnotation(TypeName)
  ), TypePredicate(VariableName, is, TypeName), Block(ReturnStatement(return, BooleanLiteral))),
  FunctionDeclaration(function,VariableDefinition,ParamList(
    VariableDefinition,TypeAnnotation(TypeName)
  ),TypePredicate(asserts,VariableName,is,LiteralType(String)),Block(ReturnStatement(return,BooleanLiteral))))

# Type alias {"dialect": "ts"}

type Foo<T extends string> = T[]

==>

Script(TypeAliasDeclaration(type, TypeDefinition, TypeParamList(TypeDefinition, extends, TypeName), Equals, ArrayType(TypeName)))

# Enum declaration {"dialect": "ts"}

const enum Type { Red = 1, Blue, Green }

==>

Script(EnumDeclaration(const, enum, TypeDefinition, EnumBody(PropertyName, Equals, Number, PropertyName, PropertyName)))

# Interface declaration {"dialect": "ts"}

interface Foo {
  readonly a: number
  b(arg: string): void
  (call: number): boolean
  new (): Foo
  readonly [x: string]: number
}

==>

Script(InterfaceDeclaration(interface, TypeDefinition, ObjectType(
  PropertyType(readonly, PropertyDefinition, TypeAnnotation(TypeName)),
  MethodType(PropertyDefinition, ParamList(VariableDefinition, TypeAnnotation(TypeName)), TypeAnnotation(VoidType(void))),
  CallSignature(ParamList(VariableDefinition, TypeAnnotation(TypeName)), TypeAnnotation(TypeName)),
  NewSignature(new,ParamList, TypeAnnotation(TypeName)),
  IndexSignature(readonly, PropertyDefinition, TypeAnnotation(TypeName), TypeAnnotation(TypeName)))))

# Call type args {"dialect": "ts"}

foo<number, string>() + new Bar<11>()
x < 10 > 5

==>

Script(
  ExpressionStatement(BinaryExpression(
    CallExpression(InstantiationExpression(VariableName, TypeArgList(TypeName, TypeName)), ArgList),
    ArithOp,
    NewExpression(new, InstantiationExpression(VariableName, TypeArgList(LiteralType(Number))), ArgList))),
  ExpressionStatement(BinaryExpression(BinaryExpression(VariableName, CompareOp, Number), CompareOp, Number)))

# Advanced types {"dialect": "ts"}

let x: typeof X.x | keyof Y & Z["Foo"] | A<string>
let tuple: [a, b]
let f: (x: number) => boolean

==>

Script(
  VariableDeclaration(let, VariableDefinition, TypeAnnotation(
    UnionType(TypeofType(typeof, MemberExpression(VariableName, PropertyName)), LogicOp,
              IntersectionType(KeyofType(keyof, TypeName), LogicOp, IndexedType(TypeName, LiteralType(String))),
              LogicOp, ParameterizedType(TypeName, TypeArgList(TypeName))))),
  VariableDeclaration(let, VariableDefinition, TypeAnnotation(TupleType(TypeName, TypeName))),
  VariableDeclaration(let, VariableDefinition, TypeAnnotation(FunctionSignature(
    ParamList(VariableDefinition, TypeAnnotation(TypeName)), Arrow, TypeName))))

# Prefix union/intersection

let x:
  | A
  | B
  | C
let y: & RegExp & (& Date)

==>

Script(
  VariableDeclaration(let,VariableDefinition,TypeAnnotation(
    UnionType(LogicOp,TypeName,LogicOp,TypeName,LogicOp,TypeName))),
  VariableDeclaration(let,VariableDefinition,TypeAnnotation(
    IntersectionType(LogicOp,TypeName,LogicOp,ParenthesizedType(IntersectionType(LogicOp,TypeName))))))

# Prefix cast {"dialect": "ts"}

<string>foo

==>

Script(ExpressionStatement(PrefixCast(TypeName, VariableName)))

# No prefix cast in JSX {"dialect": "ts jsx"}

<string>foo</string>

==>

Script(ExpressionStatement(JSXElement(
  JSXOpenTag(JSXStartTag, JSXBuiltin(JSXIdentifier), JSXEndTag),
  JSXText,
  JSXCloseTag(JSXStartCloseTag, JSXBuiltin(JSXIdentifier), JSXEndTag))))

# Class definition {"dialect": "ts"}

class Foo<T> extends Bar<T> implements Stuff {
  a: number
  public readonly b: string = "two"
  constructor(readonly x: boolean, public y: number, z: string) {}
  private static blah(): void {}
}

==>

Script(ClassDeclaration(
  class, VariableDefinition, TypeParamList(TypeDefinition),
  extends, VariableName, TypeArgList(TypeName),
  implements TypeName,
  ClassBody(
    PropertyDeclaration(PropertyDefinition, TypeAnnotation(TypeName)),
    PropertyDeclaration(Privacy, readonly, PropertyDefinition, TypeAnnotation(TypeName), Equals, String),
    MethodDeclaration(PropertyDefinition, ParamList(
      readonly, VariableDefinition, TypeAnnotation(TypeName),
      Privacy, VariableDefinition, TypeAnnotation(TypeName),
      VariableDefinition, TypeAnnotation(TypeName)), Block),
    MethodDeclaration(Privacy, static, PropertyDefinition, ParamList, TypeAnnotation(VoidType(void)), Block))))

# Arrow with type params {"dialect": "ts"}

let x = <T>(arg: T): T => arg

==>

Script(VariableDeclaration(let, VariableDefinition, Equals, ArrowFunction(
  TypeParamList(TypeDefinition),
  ParamList(VariableDefinition, TypeAnnotation(TypeName)),
  TypeAnnotation(TypeName),
  Arrow,
  VariableName)))

# Template types {"dialect": "ts"}

type Tmpl<T> = `${string} ${5}` | `one ${Two}`

==>

Script(TypeAliasDeclaration(type, TypeDefinition, TypeParamList(TypeDefinition), Equals,
  UnionType(TemplateType(Interpolation(InterpolationStart,TypeName,InterpolationEnd), Interpolation(InterpolationStart,LiteralType(Number),InterpolationEnd)), LogicOp, TemplateType(Interpolation(InterpolationStart,TypeName,InterpolationEnd)))))

# Extending complex types {"dialect": "ts"}

class Foo extends A.B<Param> {}

==>

Script(ClassDeclaration(class, VariableDefinition,
  extends, MemberExpression(VariableName, PropertyName), TypeArgList(TypeName),
  ClassBody))

# Object type {"dialect": "ts"}

type A = {a: number, b: number}
type B = {a: number; b: number;}

==>

Script(
  TypeAliasDeclaration(type,TypeDefinition,Equals,ObjectType(
    PropertyType(PropertyDefinition,TypeAnnotation(TypeName)),
    PropertyType(PropertyDefinition,TypeAnnotation(TypeName)))),
  TypeAliasDeclaration(type,TypeDefinition,Equals,ObjectType(
    PropertyType(PropertyDefinition,TypeAnnotation(TypeName)),
    PropertyType(PropertyDefinition,TypeAnnotation(TypeName)))))

# Conditional Type {"dialect": "ts"}

type X<T> = T extends E ? number : A

==>

Script(
  TypeAliasDeclaration(type,TypeDefinition,TypeParamList(TypeDefinition),Equals,
    ConditionalType(TypeName,extends,TypeName,LogicOp,TypeName,LogicOp,TypeName)))

# Generic Function Type {"dialect": "ts"}

let f: <T>() => T

==>

Script(
  VariableDeclaration(let,VariableDefinition,TypeAnnotation(
    FunctionSignature(TypeParamList(TypeDefinition),ParamList,Arrow,TypeName))))

# Satisfies operator {"dialect": "ts"}

let x = 1 satisfies number

==>

Script(VariableDeclaration(let,VariableDefinition,Equals,BinaryExpression(Number,satisfies,TypeName)))

# Override modifier on properties {"dialect": "ts"}

class A {
  override accessor a;
  static override b = 1;
  override c = 2;
}

==>

Script(ClassDeclaration(class,VariableDefinition,ClassBody(
  PropertyDeclaration(override,accessor,PropertyDefinition),
  PropertyDeclaration(static,override,PropertyDefinition,Equals,Number),
  PropertyDeclaration(override,PropertyDefinition,Equals,Number))))

# Class extending expression {"dialect": "ts"}

class X extends class {} {}

==>

Script(ClassDeclaration(class,VariableDefinition,extends,ClassExpression(class,ClassBody),ClassBody))

# Declare syntax {"dialect": "ts"}

declare namespace myLib {
  function makeGreeting(s: string): string;
  let numberOfGreetings: number;
}

declare function greet(setting: GreetingSettings): void;

declare class Greeter {
  constructor(greeting: string);
  greeting: string;
  showGreeting(): void;
}

class X {
  declare foo();
  declare bar: number;
}

==>

Script(
  AmbientDeclaration(declare,NamespaceDeclaration(namespace,VariableDefinition,Block(
    FunctionDeclaration(function,VariableDefinition,ParamList(VariableDefinition,TypeAnnotation(TypeName)),
      TypeAnnotation(TypeName)),
    VariableDeclaration(let,VariableDefinition,TypeAnnotation(TypeName))))),
  AmbientDeclaration(declare,AmbientFunctionDeclaration(function,VariableDefinition,
    ParamList(VariableDefinition,TypeAnnotation(TypeName)),TypeAnnotation(VoidType(void)))),
  AmbientDeclaration(declare,ClassDeclaration(class,VariableDefinition,ClassBody(
    MethodDeclaration(PropertyDefinition,ParamList(VariableDefinition,TypeAnnotation(TypeName))),
    PropertyDeclaration(PropertyDefinition,TypeAnnotation(TypeName)),
    MethodDeclaration(PropertyDefinition,ParamList,TypeAnnotation(VoidType(void)))))),
  ClassDeclaration(class,VariableDefinition,ClassBody(
    MethodDeclaration(declare,PropertyDefinition,ParamList),
    PropertyDeclaration(declare,PropertyDefinition,TypeAnnotation(TypeName)))))

# Declare this in a Function {"dialect": "ts"}

function foo(this: User) {}

==>

Script(FunctionDeclaration(function,VariableDefinition,ParamList(this,TypeAnnotation(TypeName)),Block))

# Prefers type parameters to comparison operators {"dialect": "ts jsx"}

let a = useState<string>(1)
return 2

==>

Script(
  VariableDeclaration(let,VariableDefinition,Equals,
    CallExpression(InstantiationExpression(VariableName,TypeArgList(TypeName)),ArgList(Number))),
  ReturnStatement(return,Number))

# Type parameters vs JSX {"dialect": "jsx ts"}

let a = <T extends any>(f) => null
let b = <T,>() => 1

==>

Script(
  VariableDeclaration(let,VariableDefinition,Equals,ArrowFunction(
    TypeParamList(TypeDefinition,extends,TypeName),ParamList(VariableDefinition),Arrow,null)),
  VariableDeclaration(let,VariableDefinition,Equals,ArrowFunction(
    TypeParamList(TypeDefinition),ParamList,Arrow,Number)))

# Destructured parameters in function signature {"dialect": "ts"}

type F = ([a, b]: [number, number]) => void

==>

Script(TypeAliasDeclaration(type,TypeDefinition,Equals,FunctionSignature(
  ParamList(ArrayPattern(VariableDefinition,VariableDefinition),TypeAnnotation(TupleType(TypeName,TypeName))),
  Arrow,
  VoidType(void))))

# Instantiated expression {"dialect": "ts"}

let x = a<b>;

type Foo = Bar<typeof baz<Bug<Quux>>>;

==>

Script(
  VariableDeclaration(let,VariableDefinition,Equals,InstantiationExpression(VariableName,TypeArgList(TypeName))),
  TypeAliasDeclaration(type,TypeDefinition,Equals,ParameterizedType(TypeName,TypeArgList(
    TypeofType(typeof,InstantiationExpression(VariableName,TypeArgList(
      ParameterizedType(TypeName,TypeArgList(TypeName)))))))))

# Not instantiated {"dialect": "ts"}

let x = a<b>c

==>

Script(VariableDeclaration(let,VariableDefinition,Equals,BinaryExpression(
  BinaryExpression(VariableName,CompareOp,VariableName),CompareOp,VariableName)))

# Allows computed properties in types {"dialect": "ts"}

interface X {
  [Symbol.iterator](): Iterator<number>
  [1]: string
}

==>

Script(InterfaceDeclaration(interface,TypeDefinition,ObjectType(
  MethodType(MemberExpression(VariableName,PropertyName),ParamList,
    TypeAnnotation(ParameterizedType(TypeName,TypeArgList(TypeName)))),
  PropertyType(Number,TypeAnnotation(TypeName)))))