We have lots of new changes for you!
# What's Changed
## General
- We updated Luau's license year to 2025!
- We fixed a bug where large amounts of errors were being printed when
deep intersections of unions error.
## Require-by-String
This release introduces the `Luau.Require` library, which exposes the
runtime semantics of require-by-string, including support for the new
`@self` alias described in [this
RFC](https://github.com/luau-lang/rfcs/pull/109).
The library operates on a virtualized filesystem, allowing consumers to
specify navigation rules without assuming a filesystem context.
Documentation in `Require.h` explains how to enable the library, and the
`setupState` function in Repl.cpp demonstrates how we've integrated it
into the luau CLI tool. Note that the interface in `Require.h` is
written in C, which enables any application written in a language with a
C foreign-function interface to link against this library and enable
require-by-string. This makes it straightforward for any application
embedding Luau to support require-by-string, provided that it defines or
operates within an environment resembling a virtual filesystem.
The core navigation semantics of require-by-string have additionally
been pulled into the `Luau.RequireNavigator` library. While
`Luau.Require` internally depends on `Luau.RequireNavigator`, the latter
does not depend on the Luau VM. This library provides an interface for
inspecting require-by-string's navigation behavior and therefore serves
as a useful dependency for static tooling. Documentation for
`Luau.RequireNavigator` is available in `RequireNavigator.h`.
## Autocomplete
- We fixed a memory leak in fragment autocomplete!
## New Solver And Old Solver
- We've found a infinite iteration error over a type pack. We added a
way to detect this error and throw an `InternalCompileError` instead.
- We fix `table.freeze` not accounting for the first argument not
getting type stated. We fall back to regular inference instead.
- We fix a crash in the old solver with `length_error`.
- We fix a crash in the new solver stemming from generalization
reentrancy. Now we correctly generalize interior free types that do not
appear in a function signature.
- We fix a nil refinement. (Fixes
https://github.com/luau-lang/luau/issues/1687 and
https://github.com/luau-lang/luau/issues/1451)
### Internal Contributors
Co-authored-by: Andy Friesen <afriesen@roblox.com>
Co-authored-by: Hunter Goldstein <hgoldstein@roblox.com>
Co-authored-by: Talha Pathan <tpathan@roblox.com>
Co-authored-by: Varun Saini <vsaini@roblox.com>
Co-authored-by: Vighnesh Vijay <vvijay@roblox.com>
Co-authored-by: Vyacheslav Egorov <vegorov@roblox.com>
Full Changelog: https://github.com/luau-lang/luau/compare/0.668...0.669
---------
Co-authored-by: Hunter Goldstein <hgoldstein@roblox.com>
Co-authored-by: Varun Saini <61795485+vrn-sn@users.noreply.github.com>
Co-authored-by: Alexander Youngblood <ayoungblood@roblox.com>
Co-authored-by: Aviral Goel <agoel@roblox.com>
Co-authored-by: Vighnesh <vvijay@roblox.com>
Co-authored-by: Vyacheslav Egorov <vegorov@roblox.com>
Co-authored-by: Ariel Weiss <aaronweiss@roblox.com>
After a very auspicious release last week, we have a new bevy of changes
for you!
## What's Changed
### Deprecated Attribute
This release includes an implementation of the `@deprecated` attribute
proposed in [this
RFC](https://rfcs.luau.org/syntax-attribute-functions-deprecated.html).
It relies on the new type solver to propagate deprecation information
from function and method AST nodes to the corresponding type objects.
These objects are queried by a linter pass when it encounters local,
global, or indexed variables, to issue deprecation warnings. Uses of
deprecated functions and methods in recursion are ignored. To support
deprecation of class methods, the parser has been extended to allow
attribute declarations on class methods. The implementation does not
support parameters, so it is not currently possible for users to
customize deprecation messages.
### General
- Add a limit for normalization of function types.
### New Type Solver
- Fix type checker to accept numbers as concat operands (Fixes#1671).
- Fix user-defined type functions failing when used inside type
aliases/nested calls (Fixes#1738, Fixes#1679).
- Improve constraint generation for overloaded functions (in part thanks
to @vvatheus in #1694).
- Improve type inference for indexers on table literals, especially when
passing table literals directly as a function call argument.
- Equate regular error type and intersection with a negation of an error
type.
- Avoid swapping types in 2-part union when RHS is optional.
- Use simplification when doing `~nil` refinements.
- `len<>` now works on metatables without `__len` function.
### AST
- Retain source information for `AstTypeUnion` and
`AstTypeIntersection`.
### Transpiler
- Print attributes on functions.
### Parser
- Allow types in indexers to begin with string literals by @jackdotink
in #1750.
### Autocomplete
- Evaluate user-defined type functions in ill-formed source code to
provide autocomplete.
- Fix the start location of functions that have attributes.
- Implement better fragment selection.
### Internal Contributors
Co-authored-by: Andy Friesen <afriesen@roblox.com>
Co-authored-by: Ariel Weiss <aaronweiss@roblox.com>
Co-authored-by: Aviral Goel <agoel@roblox.com>
Co-authored-by: Hunter Goldstein <hgoldstein@roblox.com>
Co-authored-by: Sora Kanosue <skanosue@roblox.com>
Co-authored-by: Talha Pathan <tpathan@roblox.com>
Co-authored-by: Varun Saini <vsaini@roblox.com>
Co-authored-by: Vighnesh Vijay <vvijay@roblox.com>
Co-authored-by: Vyacheslav Egorov <vegorov@roblox.com>
**Full Changelog**:
https://github.com/luau-lang/luau/compare/0.666...0.667
---------
Co-authored-by: Hunter Goldstein <hgoldstein@roblox.com>
Co-authored-by: Varun Saini <61795485+vrn-sn@users.noreply.github.com>
Co-authored-by: Menarul Alam <malam@roblox.com>
Co-authored-by: Aviral Goel <agoel@roblox.com>
Co-authored-by: Vighnesh <vvijay@roblox.com>
Co-authored-by: Vyacheslav Egorov <vegorov@roblox.com>
Co-authored-by: Ariel Weiss <aaronweiss@roblox.com>
Another week, another release. Happy spring! 🌷
## New Type Solver
- Add typechecking and autocomplete support for user-defined type
functions!
- Improve the display of type paths, making type mismatch errors far
more human-readable.
- Enhance various aspects of the `index` type function: support function
type metamethods, fix crashes involving cyclic metatables, and forward
`any` types through the type function.
- Fix incorrect subtyping results involving the `buffer` type.
- Fix crashes related to typechecking anonymous functions in nonstrict
mode.
## AST
- Retain source information for type packs, functions, and type
functions.
- Introduce `AstTypeOptional` to differentiate `T?` from `T | nil` in
the AST.
- Prevent the transpiler from advancing before tokens when the AST has
errors.
## Autocomplete
- Introduce demand-based cloning and better module isolation for
fragment autocomplete, leading to a substantial speedup in performance.
- Guard against recursive unions in `autocompleteProps`.
## Miscellaneous
- #1720 (thank you!)
## Internal Contributors
Co-authored-by: Andy Friesen <afriesen@roblox.com>
Co-authored-by: Ariel Weiss <aaronweiss@roblox.com>
Co-authored-by: Hunter Goldstein <hgoldstein@roblox.com>
Co-authored-by: Talha Pathan <tpathan@roblox.com>
Co-authored-by: Vighnesh Vijay <vvijay@roblox.com>
Co-authored-by: Vyacheslav Egorov <vegorov@roblox.com>
## What's new
This update brings improvements to the new type solver, roundtrippable
AST parsing mode and closes multiple issues reported in this repository.
* `require` dependency tracing for non-string requires now supports `()`
groups in expressions and types as well as an ability to type annotate a
value with a `typeof` of a different module path
* Fixed rare misaligned memory access in Compiler/Typechecker on 32 bit
platforms (Closes#1572)
## New Solver
* Fixed crash/UB in subtyping of type packs (Closes#1449)
* Fixed incorrect type errors when calling `debug.info` (Closes#1534
and Resolves#966)
* Fixed incorrect boolean and string equality comparison result in
user-defined type functions (Closes#1623)
* Fixed incorrect class types being produced in user-defined type
functions when multiple classes share the same name (Closes#1639)
* Improved bidirectional typechecking for table literals containing
elements that have not been solved yet (Closes#1641)
## Roundtrippable AST
* Added source information for `AstStatTypeAlias`
* Fixed an issue with `AstTypeGroup` node (added in #1643) producing
invalid AST json. Contained type is now named 'inner' instead of 'type'
* Fixed end location of the `do ... end` statement
---
Internal Contributors:
Co-authored-by: Hunter Goldstein <hgoldstein@roblox.com>
Co-authored-by: Talha Pathan <tpathan@roblox.com>
Co-authored-by: Varun Saini <vsaini@roblox.com>
Co-authored-by: Vighnesh Vijay <vvijay@roblox.com>
Co-authored-by: Vyacheslav Egorov <vegorov@roblox.com>
# General
- Additional logging enabled for fragment autocomplete.
## Roundtrippable AST
- Add a new `AstNode`, `AstGenericType`
- Retain source information for `AstExprTypeAssertion`
## New Type Solver
- New non-strict mode will report unknown symbol errors, e.g
```
foo = 5
local wrong1 = foob <- issue warning
```
- Fixed a bug where new non-strict mode failed to visit large parts of
the program.
- We now infer the types of unnanotated local variables in statements
with multiple assignments, e.g. `local x: "a", y, z = "a", f()`
- Fixed bugs in constraint dispatch ordering.
- Fixed a bug that caused an infinite loop between `Subtyping`,
`OverloadResolution`, and `Type Function Reduction`, by preventing calls
to `Type Function Reduction` being re-entrant.
- Fixed a crash in bidirectional type inference caused by asserting read
and write properties on a type that was readonly.
## Runtime
- Fix a stack overflow caused by `luaL_checkstack` consuming stack space
even if the function fails to reserve memory.
- Using '%c' with a 0 value in Luau string.format will append a '\0'.
Resolves https://github.com/luau-lang/luau/issues/1650
## Miscellaneous
- Miscellaneous small bugfixes for the new solver.
**Full Changelog**:
https://github.com/luau-lang/luau/compare/0.660...0.661
----
Co-authored-by: Ariel Weiss <aaronweiss@roblox.com>
Co-authored-by: Hunter Goldstein <hgoldstein@roblox.com>
Co-authored-by: Talha Pathan <tpathan@roblox.com>
Co-authored-by: Varun Saini <vsaini@roblox.com>
Co-authored-by: Vighnesh Vijay <vvijay@roblox.com>
Co-authored-by: Vyacheslav Egorov <vegorov@roblox.com>
---------
Co-authored-by: Hunter Goldstein <hgoldstein@roblox.com>
Co-authored-by: Varun Saini <61795485+vrn-sn@users.noreply.github.com>
Co-authored-by: Alexander Youngblood <ayoungblood@roblox.com>
Co-authored-by: Menarul Alam <malam@roblox.com>
Co-authored-by: Aviral Goel <agoel@roblox.com>
# General
This release introduces initial work on a Roundtrippable AST for Luau,
and numerous fixes to the new type solver, runtime, and fragment
autocomplete.
## Roundtrippable AST
To support tooling around source code transformations, we are extending
the parser to retain source information so that we can re-emit the
initial source code exactly as the author wrote it. We have made
numerous changes to the Transpiler, added new AST types such as
`AstTypeGroup`, and added source information to AST nodes such as
`AstExprInterpString`, `AstExprIfElse`, `AstTypeTable`,
`AstTypeReference`, `AstTypeSingletonString`, and `AstTypeTypeof`.
## New Type Solver
* Implement `setmetatable` and `getmetatable` type functions.
* Fix handling of nested and recursive union type functions to prevent
the solver from getting stuck.
* Free types in both old and new solver now have an upper and lower
bound to resolve mixed mode usage of the solvers in fragment
autocomplete.
* Fix infinite recursion during normalization of cyclic tables.
* Add normalization support for intersections of subclasses with negated
superclasses.
## Runtime
* Fix compilation error in Luau buffer bit operations for big-endian
machines.
## Miscellaneous
* Add test and bugfixes to fragment autocomplete.
* Fixed `clang-tidy` warnings in `Simplify.cpp`.
**Full Changelog**:
https://github.com/luau-lang/luau/compare/0.659...0.660
---
Co-authored-by: Ariel Weiss <aaronweiss@roblox.com>
Co-authored-by: Hunter Goldstein <hgoldstein@roblox.com>
Co-authored-by: Talha Pathan <tpathan@roblox.com>
Co-authored-by: Varun Saini <vsaini@roblox.com>
Co-authored-by: Vighnesh Vijay <vvijay@roblox.com>
Co-authored-by: Vyacheslav Egorov <vegorov@roblox.com>
---------
Co-authored-by: Hunter Goldstein <hgoldstein@roblox.com>
Co-authored-by: Varun Saini <61795485+vrn-sn@users.noreply.github.com>
Co-authored-by: Alexander Youngblood <ayoungblood@roblox.com>
Co-authored-by: Menarul Alam <malam@roblox.com>
