Hey folks, another week means another Luau release! This one features a
number of bug fixes in the New Type Solver including improvements to
user-defined type functions and a bunch of work to untangle some of the
outstanding issues we've been seeing with constraint solving not
completing in real world use. We're also continuing to make progress on
crashes and other problems that affect the stability of fragment
autocomplete, as we work towards delivering consistent, low-latency
autocomplete for any editor environment.
## New Type Solver
- Fix a bug in user-defined type functions where `print` would
incorrectly insert `\1` a number of times.
- Fix a bug where attempting to refine an optional generic with a type
test will cause a false positive type error (fixes#1666)
- Fix a bug where the `refine` type family would not skip over
`*no-refine*` discriminants (partial resolution for #1424)
- Fix a constraint solving bug where recursive function calls would
consistently produce cyclic constraints leading to incomplete or
inaccurate type inference.
- Implement `readparent` and `writeparent` for class types in
user-defined type functions, replacing the incorrectly included `parent`
method.
- Add initial groundwork (under a debug flag) for eager free type
generalization, moving us towards further improvements to constraint
solving incomplete errors.
## Fragment Autocomplete
- Ease up some assertions to improve stability of mixed-mode use of the
two type solvers (i.e. using Fragment Autocomplete on a type graph
originally produced by the old type solver)
- Resolve a bug with type compatibility checks causing internal compiler
errors in autocomplete.
## Lexer and Parser
- Improve the accuracy of the roundtrippable AST parsing mode by
correctly placing closing parentheses on type groupings.
- Add a getter for `offset` in the Lexer by @aduermael in #1688
- Add a second entry point to the parser to parse an expression,
`parseExpr`
## 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: James McNellis <jmcnellis@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>
---------
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>
Co-authored-by: Vighnesh <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
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>
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## General
- Fix a parsing bug related to the starting position of function names.
- Rename Luau's `Table` struct to `LuaTable`.
## New Solver
- Add support for generics in user-defined type functions
([RFC](https://rfcs.luau.org/support-for-generic-function-types-in-user-defined-type-functions.html)).
- Provide a definition of `math.lerp` to the typechecker.
- Implement error suppression in `string.format`.
- Fixes#1587.
- Ensure function call discriminant types are always filled when
resolving `FunctionCallConstraint`.
---
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: Vyacheslav Egorov <vegorov@roblox.com>
benchmark / callgrind (map[branch:main name:luau-lang/benchmark-data], ubuntu-22.04) (push) Has been cancelled
build / macos (push) Has been cancelled
build / macos-arm (push) Has been cancelled
build / ubuntu (push) Has been cancelled
build / windows (Win32) (push) Has been cancelled
build / windows (x64) (push) Has been cancelled
build / coverage (push) Has been cancelled
build / web (push) Has been cancelled
release / macos (push) Has been cancelled
release / ubuntu (push) Has been cancelled
release / windows (push) Has been cancelled
release / web (push) Has been cancelled
# General
All code has been re-formatted by `clang-format`; this is not
mechanically enforced, so Luau may go out-of-sync over the course of the
year.
# New Solver
* Track free types interior to a block of code on `Scope`, which should
reduce the number of free types that remain un-generalized after type
checking is complete (e.g.: less errors like `'a <: number is
incompatible with number`).
# Autocomplete
* Fragment autocomplete now does *not* provide suggestions within
comments (matching non-fragment autocomplete behavior).
* Autocomplete now respects iteration and recursion limits (some hangs
will now early exit with a "unification too complex error," some crashes
will now become internal complier exceptions).
# Runtime
* Add a limit to how many Luau codegen slot nodes addresses can be in
use at the same time (fixes#1605, fixes#1558).
* Added constant folding for vector arithmetic (fixes#1553).
* Added support for `buffer.readbits` and `buffer.writebits` (see:
https://github.com/luau-lang/rfcs/pull/18).
---
Co-authored-by: Aaron Weiss <aaronweiss@roblox.com>
Co-authored-by: David Cope <dcope@roblox.com>
Co-authored-by: Hunter Goldstein <hgoldstein@roblox.com>
Co-authored-by: Vighnesh Vijay <vvijay@roblox.com>
Co-authored-by: Vyacheslav Egorov <vegorov@roblox.com>
benchmark / callgrind (map[branch:main name:luau-lang/benchmark-data], ubuntu-22.04) (push) Has been cancelled
build / macos (push) Has been cancelled
build / macos-arm (push) Has been cancelled
build / ubuntu (push) Has been cancelled
build / windows (Win32) (push) Has been cancelled
build / windows (x64) (push) Has been cancelled
build / coverage (push) Has been cancelled
build / web (push) Has been cancelled
release / macos (push) Has been cancelled
release / ubuntu (push) Has been cancelled
release / windows (push) Has been cancelled
release / web (push) Has been cancelled
## New Solver
* Type functions should be able to signal whether or not irreducibility
is due to an error
* Do not generate extra expansion constraint for uninvoked user-defined
type functions
* Print in a user-defined type function reports as an error instead of
logging to stdout
* Many e-graphs bugfixes and performance improvements
* Many general bugfixes and improvements to the new solver as a whole
* Fixed issue with used-defined type functions not being able to call
each other
* Infer types of globals under new type solver
## Fragment Autocomplete
* Miscellaneous fixes to make interop with the old solver better
## Runtime
* Support disabling specific built-in functions from being fast-called
or constant-evaluated (Closes#1538)
* New compiler option `disabledBuiltins` accepts a list of library
function names like "tonumber" or "math.cos"
* Added constant folding for vector arithmetic
* Added constant propagation and type inference for vector globals
(Fixes#1511)
* New compiler option `librariesWithKnownMembers` accepts a list of
libraries for members of which a request for constant value and/or type
will be made
* `libraryMemberTypeCb` callback is called to get the type of a global,
return one of the `LuauBytecodeType` values. 'boolean', 'number',
'string' and 'vector' type are supported.
* `libraryMemberConstantCb` callback is called to setup the constant
value of a global. To set a value, C API `luau_set_compile_constant_*`
or C++ API `setCompileConstant*` functions should be used.
---
Co-authored-by: Aaron Weiss <aaronweiss@roblox.com>
Co-authored-by: Andy Friesen <afriesen@roblox.com>
Co-authored-by: Aviral Goel <agoel@roblox.com>
Co-authored-by: Daniel Angel <danielangel@roblox.com>
Co-authored-by: Jonathan Kelaty <jkelaty@roblox.com>
Co-authored-by: Hunter Goldstein <hgoldstein@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: Aaron Weiss <aaronweiss@roblox.com>
Co-authored-by: Alexander McCord <amccord@roblox.com>
Co-authored-by: Andy Friesen <afriesen@roblox.com>
Co-authored-by: Aviral Goel <agoel@roblox.com>
Co-authored-by: David Cope <dcope@roblox.com>
Co-authored-by: Lily Brown <lbrown@roblox.com>
Co-authored-by: Vyacheslav Egorov <vegorov@roblox.com>
Co-authored-by: Junseo Yoo <jyoo@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: Varun Saini <vsaini@roblox.com>
Co-authored-by: Andrew Miranti <amiranti@roblox.com>
Co-authored-by: Shiqi Ai <sai@roblox.com>
Co-authored-by: Yohoo Lin <yohoo@roblox.com>
Co-authored-by: Daniel Angel <danielangel@roblox.com>
Co-authored-by: Jonathan Kelaty <jkelaty@roblox.com>
### What's new
* Light update this week, mostly fast flag cleanups.
### New Solver
* Rename flag to enable new solver from
`DebugLuauDeferredConstraintResolution` to `LuauSolverV2`
* Added support for magic functions for the new type checker (as opposed
to the type inference component)
* Improved handling of `string.format` with magic function improvements
* Cleaning up some of the reported errors by the new type checker
* Minor refactoring of `TypeChecker2.cpp` that happens to make the diff
very hard to read.
---
### Internal Contributors
Co-authored-by: Aaron Weiss <aaronweiss@roblox.com>
Co-authored-by: Andy Friesen <afriesen@roblox.com>
Co-authored-by: Vighnesh Vijay <vvijay@roblox.com>
Co-authored-by: Vyacheslav Egorov <vegorov@roblox.com>
---------
Co-authored-by: Alexander McCord <amccord@roblox.com>
Co-authored-by: Andy Friesen <afriesen@roblox.com>
Co-authored-by: Vighnesh <vvijay@roblox.com>
Co-authored-by: Aviral Goel <agoel@roblox.com>
Co-authored-by: David Cope <dcope@roblox.com>
Co-authored-by: Lily Brown <lbrown@roblox.com>
Co-authored-by: Vyacheslav Egorov <vegorov@roblox.com>
Co-authored-by: Junseo Yoo <jyoo@roblox.com>
### What's new
* Fixed many of the false positive errors in indexing of table unions
and table intersections
* It is now possible to run custom checks over Luau AST during
typechecking by setting `customModuleCheck` in `FrontendOptions`
* Fixed codegen issue on arm, where number->vector cast could corrupt
that number value for the next time it's read
### New Solver
* `error` type now behaves as the bottom type during subtyping checks
* Fixed the scope that is used in subtyping with generic types
* Fixed `astOriginalCallTypes` table often used by LSP to match the old
solver
---
### Internal Contributors
Co-authored-by: Aaron Weiss <aaronweiss@roblox.com>
Co-authored-by: Andy Friesen <afriesen@roblox.com>
Co-authored-by: Vighnesh Vijay <vvijay@roblox.com>
Co-authored-by: Vyacheslav Egorov <vegorov@roblox.com>
New Solver
* Fix some type inference issues surrounding updates to upvalues eg
```luau
local x = 0
function f()
x = x + 1
end
```
* User-defined type function progress
* Bugfixes for normalization of negated class types. eg `SomeClass &
(class & ~SomeClass)`
* Fixes to subtyping between tables and the top `table` type.
---------
Co-authored-by: Aaron Weiss <aaronweiss@roblox.com>
Co-authored-by: Vighnesh <vvijay@roblox.com>
Co-authored-by: Aviral Goel <agoel@roblox.com>
Co-authored-by: David Cope <dcope@roblox.com>
Co-authored-by: Vyacheslav Egorov <vegorov@roblox.com>
Co-authored-by: Junseo Yoo <jyoo@roblox.com>
# What's Changed?
- Code refactoring with a new clang-format
- More bug fixes / test case fixes in the new solver
## New Solver
- More precise telemetry collection of `any` types
- Simplification of two completely disjoint tables combines them into a
single table that inherits all properties / indexers
- Refining a `never & <anything>` does not produce type family types nor
constraints
- Silence "inference failed to complete" error when it is the only error
reported
---
### Internal Contributors
Co-authored-by: Aaron Weiss <aaronweiss@roblox.com>
Co-authored-by: Andy Friesen <afriesen@roblox.com>
Co-authored-by: Dibri Nsofor <dnsofor@roblox.com>
Co-authored-by: Jeremy Yoo <jyoo@roblox.com>
Co-authored-by: Vighnesh Vijay <vvijay@roblox.com>
Co-authored-by: Vyacheslav Egorov <vegorov@roblox.com>
---------
Co-authored-by: Aaron Weiss <aaronweiss@roblox.com>
Co-authored-by: Alexander McCord <amccord@roblox.com>
Co-authored-by: Andy Friesen <afriesen@roblox.com>
Co-authored-by: Vighnesh <vvijay@roblox.com>
Co-authored-by: Aviral Goel <agoel@roblox.com>
Co-authored-by: David Cope <dcope@roblox.com>
Co-authored-by: Lily Brown <lbrown@roblox.com>
Co-authored-by: Vyacheslav Egorov <vegorov@roblox.com>
# What's Changed?
- Telemetry support for usage of any type in old/new solver
- Bug fixes and flag removals with the new solver
## New Solver
- Fixed constraint ordering bug to infer types more accurately
- Improved inferring a call to `setmetatable()`
## VM
- Restored global metatable lookup for `typeof` on lightuserdata to fix
unintentional API change (Fixes#1335)
---
### Internal Contributors
Co-authored-by: Aaron Weiss <aaronweiss@roblox.com>
Co-authored-by: Alexander McCord <amccord@roblox.com>
Co-authored-by: Andy Friesen <afriesen@roblox.com>
Co-authored-by: Dibri Nsofor <dnsofor@roblox.com>
Co-authored-by: Jeremy Yoo <jyoo@roblox.com>
Co-authored-by: Vighnesh Vijay <vvijay@roblox.com>
Co-authored-by: Vyacheslav Egorov <vegorov@roblox.com>
---------
Co-authored-by: Aaron Weiss <aaronweiss@roblox.com>
Co-authored-by: Alexander McCord <amccord@roblox.com>
Co-authored-by: Andy Friesen <afriesen@roblox.com>
Co-authored-by: Vighnesh <vvijay@roblox.com>
Co-authored-by: Aviral Goel <agoel@roblox.com>
Co-authored-by: David Cope <dcope@roblox.com>
Co-authored-by: Lily Brown <lbrown@roblox.com>
Co-authored-by: Vyacheslav Egorov <vegorov@roblox.com>
