Roadmap.md

This page outlines specific features and fixes that are scheduled or planned for given releases. The 6-month roadmaps that outlines focus areas of work can be viewed for

• January to June 2021 (current)
• January to December 2020
• July to December 2019
• January to June 2019

• Feature already available in typescript@next

Future

• Investigate nominal typing support
• Flattening declarations
• Implement ES Decorator proposal
• Investigate Ambient, Deprecated, and Conditional decorators
• Investigate partial type argument inference
• Quick fix to Scaffold local @types packages
• Investigate error messages in haiku or iambic pentameter
• Decorators for function expressions/arrow functions

5.0 (March 2023)

See the 5.0 Iteration Plan for more details.

• Standard ECMAScript Decorators
• const Type Parameters
• --moduleResolution bundler
• extends Support for Multiple tsconfig.json Files
• Declaration Files for non-JavaScript Files with --allowArbitraryExtensions
• export type *
• --verbatimModuleSyntax
• @satisfies JSDoc Tag in JavaScript
• @overload JSDoc Tag in JavaScript
• Unification Between Numeric and Literal enums
• Toggling Certain Compiler-Specific Flags Under --build
• Flag Deprecations
• Improved in Checks Under --noUncheckedIndexedAccess
• Editor Support for Case-Sensitive Import Sorting
• Editor Support for Exhaustive switch/case Snippet Completions
• Virtual File System Support for TSServer
• Optimizations
  • Migrate to Modules
  • Node Monomorphization
  • Symbol Monomorphization
  • Identifier Size Reduction
  • Printer Caching
  • Limited TDZ Avoidance

4.9 (November 2022)

See the 4.9 Iteration Plan for more details.

• Narrowing Checks for Unknown Properties with the in Operator
• satisfies operator
• Auto-accessors in classes
• Forbidden Equality Checks Against NaN
• File Watching Defaults Using to File-System Events
• "Remove Imports" Command for Editors
• Go-to-Definition on return Keywords
• Optimizations
  • forEachChild as a Jump Table
  • visitEachChild as a Jump Table
  • Lazily Intersect and Normalize Substitution Type Constraints

4.8 (August 2022)

See the 4.8 Iteration Plan for more details.

• Improved Narrowing on Generics and Intersection Reduction
• Improved Inference for infer Types in Template String Types
• --build, --watch, and --incremental Performance Improvements
• Errors When Comparing Object and Array Literals
• Improved Inference from Binding Patterns
• Resilient File-Watching During Large File Changes
• Find-All-References Performance Improvements

4.7 (May 2022)

See the 4.7 Iteration Plan for more details.

• --module and --moduleResolution options node16 and nodenext
• Control Flow and Class Initialization Checks for Computed Properties
• Instantiation Expressions
• Improved Inference Between Function-Initialized Properties and Methods
• extends Constraints on infer Type Variables
• Optional Variance Annotations
• moduleSuffixes Option For Resolution
• resolution-mode for /// <reference types="..." /> Directives
• resolution-mode for import type
• Allow typeof on #private Fields
• Object Method Snippet Completions
• Grouping-Aware Organize Imports
• Go to Source Definition/JavaScript Implementation

4.6 (February 2022)

See the 4.6 Iteration Plan for more details.

• Narrowing for Variables Destructured from Discriminated Unions
• Relaxed Checks on Code Before super()
• Improved Recursion Depth Checks
• Indexed Access Inference Improvements
• --target es2022
• Syntax and Binding Errors in JavaScript Files
• Release of @typescript/analyze-trace

4.5 (November 2021)

See the 4.5 Iteration Plan for more details.

• lib Overrides from node_modules
• Awaited and Promise Function Improvements
• Tail Recursive Evaluation of Conditional Types
• Template String Discriminants
• --module es2022
• Controls for Import Elision via --preserveValueImports
• type Modifiers on Import Names
• in Checks on #private Fields
• Import Assertions
• Speed Improvements on Windows/Mac via realpathSync.native
• Snippet Completions for Subclass Methods
• Snippet Completions for JSX Attributes
• Better Editor Support for Unresolved Types

4.4 (August 2021)

See the 4.4 Iteration Plan for more details.

• Control Flow Analysis of Aliased Conditions
• Generalized index signatures
• Strict optional property checks with --strictOptionalProperties
• Use unknown for try/catch variables with --useUnknownInCatchVariables
• Updated --help descriptions
• Inlay Hints
• High-Confidence Suggestions in Unchecked JavaScript
• Quick Fix to Declare Missing Properties on Objects

4.3 (May 2021)

See the 4.3 Iteration Plan for more details.

• Separate "write" types
• --noImplicitOverride and the override keyword
• Template string type inference and compatibility improvements
• Contextual Narrowing for Generics
• Infer template string types when contextually typed
• ECMAScript #private Methods/Statics/Accessors
• static Index Signatures
• Editor support for @link tags
• Investigate auto-import improvements
  • Complete import statements through auto-imports
• Support Go-to-Definition on Relative Non-JS/TS Files

4.2 (February 2021)

See the 4.2 Iteration Plan for more details.

• Leading/middle rest elements in tuple types
• Smarter Type Alias Printing and Emit
• Template Literal Types for Template String Expressions
• --noPropertyAccessFromIndexSignature
• abstract constructor types
• Smarter unused local analysis in destructuring
• --explainFiles to understand why files have been included in a program
• Declare missing helper function

4.1. (November 2020)

See the 4.1 Iteration Plan for more details

• Template literal types and mapped type 'as' clauses
• Recursive Conditional Types
• Pedantic Index Signature Checks (--noUncheckedIndexedAccess)
• export * as default
• Aliased this in JavaScript functions
• Editor support for /** @see */ tags
• Semantic Highlighting API

4.0 (August 2020)

See the 4.0 Iteration Plan for more details.

• Variadic Tuple Types
• Labeled Tuple Elements
• Class Property Inference from Constructors
• Short-Circuiting Assignment Operators
• unknown on catch Clause Bindings
• Lightweight Editor Mode
• Improved Auto-Import
• Editor support for /** @deprecated */ tags
• Refactoring Discoverability (ideas)
• Refactorings
  • Convert to Optional Chaining and Coalescing

3.9 (May 2020)

See the 3.9 Iteration Plan for more details.

• Fix Inference in Promise.all
• Type-Checking Speedups
  • microsoft/TypeScript#36576
  • microsoft/TypeScript#36590
  • microsoft/TypeScript#36607
  • microsoft/TypeScript#36622
  • microsoft/TypeScript#36754
  • microsoft/TypeScript#36696
• // @ts-expect-error Comments
• Uncalled Function Checks in Conditionals
• Support for CommonJS Auto-Imports
• Preserved Newlines in Refactorings/Quick Fixes
• Editor Support for Solution-Style tsconfig.json Files
• Editor Support for Multi-Project Symbol Navigation
• Quick Fixes to
  • Correct Cases of Missing Return Expressions
  • Declare a private method
  • Declare a private property

3.8 (February 2020)

See the 3.8 Iteration Plan for more details.

• Type-Only Imports and Exports
• New export * as ns Syntax
• Top-Level Await
• Private Fields
• JSDoc @public/@private/@protected Modifiers
• JSDoc @readonly Modifier
• Improved File Watching and watchOptions
• "Fast and Loose" Incremental Checking
• Editor Support for Call Hierarchy View

3.7 (November 2019)

See the 3.7 Iteration Plan for more details.

• Optional Chaining
• Nullish Coalescing
• Assertions in Control Flow Analysis
• Recursive Type References
• Allow allowJs and declaration to be used together
• Uncalled Function Checks
• --declaration and --isolatedModules
• Flattened Property/Method Reporting
• --declaration and --allowJs
• Editor Functionality/APIs
  • Build-Free Editing for Project References
  • Auto-inserted await for completions
  • Quick fix to convert const to let
  • Semicolon Formatting Preferences

3.6 (August 2019)

See the 3.6 Iteration Plan for more details.

• Strongly typed iterators and generators
• More accurate array spreads
• Improved UX around Promises
• Semicolon-aware auto-imports

3.5 (May 2019)

See the 3.5 Iteration Plan for more details.

• Higher order inferences for constructor functions
• Easier assignment to discriminated unions
• Change default constraint for type parameters from {} to unknown
• Improved checking of indexed access types
• The Omit helper type
• APIs for composite projects (--build mode)
• --allowUmdGlobalAccess to use UMD globals from modules
• --noEmitOnError with --isolatedModules
• Speed improvements in --incremental and --build
  • Caching module resolution results
  • Caching results of parsing tsconfig.json
• Sorted/prioritized completions
• Smart Select API
• Refactoring to extract type

3.4 (March 2019)

See the 3.4 Iteration Plan for more details.

• Higher order function type inference
• --incremental builds with .tsbuildinfo files
• Improved support for read-only arrays and tuples
• Const contexts for literal expressions
• globalThis
• Refactorings to...
  • Convert to "named" parameters

3.3 (January 2019)

• Relaxed rules on methods of union types
• File-incremental builds in --build --watch mode for composite projects

3.2 (November 2018)

• Strict bind, call, and apply methods on functions
• Allow non-unit types in union discriminants
• Generic spread expressions in object literals
• Generic object rest variables and parameters
• Type-checking support for BigInt
• Configuration inheritance through node packages
• Supporting Object.defineProperty property assignments in JS
• Support printing the implied configuration object to the console with --showConfig
• Improved formatting and indentation for lists and chained calls
• Quick fixes to...
  • Add intermediate unknown type assertions
  • Add missing new keyword
  • Infer types from usage outside of noImplicitAny
  • Infer JSDoc types from usage

3.1 (September 2018)

• Mapped tuple and array types
• Property assignments on function declarations
• typesVersions redirects
• Error UX improvements
• Refactorings to...
  • Rename files from import/export paths
  • Convert from Promise#then/catch to async/await

3.0 (July 2018)

• Support for project references/composite projects
• Tuples in rest parameters and spread expressions
• New unknown top type
• /// <reference lib="..." /> reference directives
• Support for defaultProps and propTypes in React JSX elements
• Error UX improvements
  • Related error spans
  • Improved message quality and suggestions
• Refactors to...
  • Convert named imports to namespace imports and back
  • Add or remove braces from arrow function
• Quick fixes to...
  • Remove unused labels
  • Remove unreachable code
• Outlining spans for JSX expressions
• Auto-closing JSX tags

2.9 (May 2018)

• Support number and symbol named properties with keyof and mapped types
• Support for passing generics to JSX elements
• Support for passing generics to tagged template calls
• Allow import(...)-ing types at any location
• --pretty error output by default
• Support for import.meta
• New --resolveJsonModule
• Declaration source maps and code navigation via them
• Show suggestion diagnostics for open files
• Show unused declarations as suggestions
• Support setting quote style in quick fixes and refactorings
• New Rename File command
• Refactors to...
  • Move to a new file
  • Convert property to getter/setter
• Quick fix to...
  • Convert require to import in .ts files
  • Install @types/node for built-in node modules

2.8 (March 2018)

• Conditional types
• Type inference in conditional types
• Predefined conditional types in lib.d.ts
• Improved control over mapped type modifiers
• Improved keyof with intersection types
• New --emitDeclarationOnly
• Better handling for namespace-patterns in .js files
• Support for per-file JSX pragmas
• New Organize imports command
• Quick fix for uninitialized class properties

2.7 (January 2018)

• Support for properties named with const-declared symbols
• Strict property initialization checks in classes
• Definite assignment assertions
• Improved type inference for object literals
• Improved handling of structurally identical classes
• Fixed length tuples
• Type guards inferred from in operator
• Numeric separators
• Support for import d from "cjs" form CommonJS modules with --esModuleInterop
• Apply all quick fixes in a file
• Refactors to convert CommonJS module to ES6 module
• Support for incremental builder compiler API
• Quick fix to add missing async keyword
• Completion list preselects suggested item based on context
• Completion list includes this., brackets, and curlies for JSX

2.6 (October 2017)

• Strict function types
• Support for JSX Fragments
• Cached tagged template objects in modules
• Include localized diagnostics in npm
• Suppress errors in .ts files using // @ts-ignore comments
• Speed improvements to --watch
• Automatic imports from completion lists
• Refactors to...
  • Extract constants/locals in refactorings
  • Convert JSDoc type annotations to TypeScript
• Quick fixes to...
  • Infer from usage on noImplicitAny errors
  • Invoke uncalled decorators
  • Install from @types
• Support outlining for // #regions

2.5 (August 2017)

• Assertion/cast JSDoc syntax in checkJs mode
• Refactoring to extract functions & methods
• Optional catch binding
• Quick fixes to...
  • correct references to types of properties
  • correct uses of JSDoc types to TypeScript types

2.4 (June 2017)

• Infer from generic function return types
• Contextual generic function types
• Stricter generic signature checks
• Covariant checking for callback parameters
• String valued members in enums
• Weak type detection
• ES dynamic import() expressions
• Refactoring support in Language Service API
  • Refactor ES5 function to ES6 class in .js files
• Suggestions and quick fixes for spelling corrections in error messages

2.3 (April 2017)

• Generator support for ES3/ES5
• Asynchronous iterators
• Generic defaults
• Controlling this in methods of object literals through contextual type
• JSX stateless components overload resolution
• JSX children checking
• New --strict master option
• Report errors in .js files with new --checkJs
• Enhanced tsc --init output
• Language Service Extensibility

2.2 (February 2017)

• Mixin classes
• Allow deriving from object and intersection types
• Support for new.target
• Improved checking of nullable operands in expressions
• Update __extends to use Object.setPrototypeOf
• Allow property (dotted) access for types with string index signatures
• Support for JSX spread children
• New --jsx react-native
• Support for the object type.
• More Quick Fixes!
  • Add missing imports
  • Implement interface/abstract class members
  • Remove unused declarations
  • Add missing this.
  • Add missing property declaration

2.1 (December 2016)

• Switch to a transformation-based emitter
• async/await support for ES5/ES3
• Support for external helpers library
• Static types for dynamically named properties (keyof T and T[K])
• Mapped types (e.g. { [P in K]: T[P] })
• Support ESNext object property spread and rest
• Better inference for literal types
• Use returned values from super calls as 'this'
• Control flow analysis for implicit any variables
• Control flow analysis for array construction
• Narrow string and number types in literal equality checks
• Contextual typing of partially annotated signatures
• Normalize union/intersection type combinations
• New --jsxFactory
• New --alwaysStrict
• Support for --target ES2016, --target ES2017 and --target ESNext
• Configuration inheritance
• Go to implementation support
• Completions in imports and triple-slash reference paths
• Quick fixes support in language service API
• Untyped (implicit-any) imports

2.0

• Non-nullable types
• Control flow based type analysis
• Discriminated union types
• Improved definition file acquisition
• Specifying this types for functions
• Type guards on property access
• Readonly properties and index signatures
• Use path mappings in module resolution
• Shorthand ambient module declarations and wildcard matching in module names
• Implicit index signatures
• Support private and protected constructors
• Support abstract properties
• Optional properties in classes
• The never type
• --skipLibCheck compiler option
• Support for declaration output folder using --declarationDir
• Glob support in tsconfig.json
• Improve lib.d.ts modularity and new --lib support
• Support for UMD module definitions
• Trailing Commas in Function Param Lists
• Support for jsdoc @typedef for JS files
• Completion lists for string literals
• Module name in imports allow .js extension
• Support 'target:es5' with 'module:es6'
• Flag unused declarations with --noUnusedLocals and --noUnusedParameters
• Number, boolean, and Enum literal types

1.8

• Allow JavaScript in TypeScript compilations with --allowjs
• Allow captured let/const in loops
• Flag unreachable code
• Concatenate module output with --outFile
• Accept comments in tsconfig.json
• Stylize error messages in terminal output with --pretty
• Support for --outFile with named pipes, sockets, and special devices
• Support computed property with literal names
• String literal types
• Stateless Functional Components in JSX
• Improved union/intersection type inference
• Support for F-Bounded Polymorphism
• Support full path for -project/-p parameter
• Extract type information from JSDoc in js files
• Support for default import interop with SystemJS using --allowSyntheticDefaultImports
• Recognize prototype assignments in JavaScript files
• Augmenting global/module scope from other modules
• Use tsconfig.json as higher priority source of configuration in Visual Studio
• this-based type guards
• Support for custom JSX factories using --reactNamespace
• Improved checking of for-in statements
• Colorization of JSX code in VS 2015
• Publish official TypeScript NuGet packages

1.7

• ES7 exponentiation operator
• Polymorphic this type
• Support --module with --target es6
• Support for decorators when targeting ES3
• async/await support for ES6 (Node v4)
• Improved checking of destructuring with literal initializers

1.6

• ES6 Generators
• Local types
• Generic type aliases
• Expressions in class extends clauses
• Class expressions
• exclude property in tsconfig.json
• User defined type guard functions
• External module resolution enhancements
• JSX support
• Intersection types
• abstract classes and methods
• Strict object literal assignment checking
• Declaration merging for classes and interfaces
• New --init

1.5

• Support for Destructuring
• Support for Spread Operator
• Support for ES6 Modules
• Support for for..of
• Support for ES6 Unicode specification
• Support for Symbols
• Support for Computed properties
• Support for tsconfig.json files
• Support for let and const in ES3/ES5
• Support for tagged templates in ES3/ES5
• Expose a new editor interface through TS Server
• Support for ES7 Decorators proposal
• Support for Decorator type metadata
• New --rootDir
• New ts.transpile API
• Support --module umd
• Support --module system
• New --noEmitHelpers
• New --inlineSourceMap
• New --inlineSources
• New --newLine
• New --isolatedModules
• Support for new namespace keyword
• Support for tsconfig.json in Visual Studio 2015
• Improved template literal highlighting in Visual Studio 2013

1.4

• Support for Union Types and Type Guards
• New --noEmitOnError
• New --target ES6
• Support for Let and Const
• Support for Template Literals
• Library typings for ES6
• Support for Const enums
• Export Language Service public API

1.3

• Language service re-write to target new compiler
• Support for protected members in classes
• Support for Tuple Types