# General Updates
* Fix some cases where documentation symbols would not be available when
mouseovering at certain positions in the code
* Scaffolding to help embedders have more control over how `typeof(x)`
refines types
* Refinements to require-by-string semantics. See
https://github.com/luau-lang/rfcs/pull/56 for details.
* Fix for https://github.com/luau-lang/luau/issues/1405
# New Solver
* Fix many crashes (thanks you for your bug reports!)
* Type functions can now call each other
* Type functions all evaluate in a single VM. This should improve
typechecking performance and reduce memory use.
* `export type function` is now forbidden and fails with a clear error
message
* Type functions that access locals in the surrounding environment are
now properly a parse error
* You can now use `:setindexer(types.never, types.never)` to delete an
indexer from a table type.
# Internal Contributors
Co-authored-by: Aaron Weiss <aaronweiss@roblox.com>
Co-authored-by: Hunter Goldstein <hgoldstein@roblox.com>
Co-authored-by: Varun Saini <vsaini@roblox.com>
Co-authored-by: Vyacheslav Egorov <vegorov@roblox.com>
In this update, we continue to improve the overall stability of the new
type solver. We're also shipping some early bits of two new features,
one of the language and one of the analysis API: user-defined type
functions and an incremental typechecking API.
If you use the new solver and want to use all new fixes included in this
release, you have to reference an additional Luau flag:
```c++
LUAU_DYNAMIC_FASTINT(LuauTypeSolverRelease)
```
And set its value to `645`:
```c++
DFInt::LuauTypeSolverRelease.value = 645; // Or a higher value for future updates
```
## New Solver
* Fix a crash where scopes are incorrectly accessed cross-module after
they've been deallocated by appropriately zeroing out associated scope
pointers for free types, generic types, table types, etc.
* Fix a crash where we were incorrectly caching results for bound types
in generalization.
* Eliminated some unnecessary intermediate allocations in the constraint
solver and type function infrastructure.
* Built some initial groundwork for an incremental typecheck API for use
by language servers.
* Built an initial technical preview for [user-defined type
functions](https://rfcs.luau-lang.org/user-defined-type-functions.html),
more work still to come (including calling type functions from other
type functions), but adventurous folks wanting to experiment with it can
try it out by enabling `FFlag::LuauUserDefinedTypeFunctionsSyntax` and
`FFlag::LuauUserDefinedTypeFunction` in their local environment. Special
thanks to @joonyoo181 who built up all the initial infrastructure for
this during his internship!
## Miscellaneous changes
* Fix a compilation error on Ubuntu (fixes#1437)
---
Internal Contributors:
Co-authored-by: Aaron Weiss <aaronweiss@roblox.com>
Co-authored-by: Hunter Goldstein <hgoldstein@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: 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
* 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 Changed?
- Variety of bugfixes in the new solver
## New Solver
- Fix an issue where we would hit a recursion limit when applying long
chains of type refinements.
- Weaken the types of `table.freeze` and `table.clone` in the new solver
so we can accept common code patterns like `local a = table.freeze({x=5,
x=0})` at the expense of accepting code like `table.freeze(true)`.
- Don't warn when the # operator is used on a value of type never
## VM
- Fix a bug in lua_resume where too many values might be removed from
stack when resume throws an error
---
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: 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>
# 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?
- Mostly stability and bugfixes with the new solver.
## New Solver
- Typechecking with the new solver should respect the no-check hot
comment.
- Record type alias locations and property locations of table
assignments
- Maintain location information for exported table types
- Stability fixes for normalization
- Report internal constraint solver errors.
---
### 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: 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>
### What's new
* A bug in exception handling in GCC(11/12/13) on MacOS prevents our
test suite from running.
* Parser now supports leading `|` or `&` when declaring `Union` and
`Intersection` types (#1286)
* We now support parsing of attributes on functions as described in the
[rfc](https://github.com/luau-lang/rfcs/pull/30)
* With this change, expressions such as `local x = @native function(x)
return x+1 end` and `f(@native function(x) return x+1 end)` are now
valid.
* Added support for `@native` attribute - we can now force native
compilation of individual functions if the `@native` attribute is
specified before the `function` keyword (works for lambdas too).
### New Solver
* Many fixes in the new solver for crashes and instability
* Refinements now use simplification and not normalization in a specific
case of two tables
* Assume that compound assignments do not change the type of the
left-side operand
* Fix error that prevented Class Methods from being overloaded
### VM
* Updated description of Garbage Collector invariant
---
### 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: Aviral Goel <agoel@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>
### What's new
* Implemented parsing logic for attributes
* Added `lua_setuserdatametatable` and `lua_getuserdatametatable` C API
methods for a faster userdata metatable fetch compared to
`luaL_getmetatable`. Note that metatable reference has to still be
pinned in memory!
### New Solver
* Further improvement to the assignment inference logic
* Fix many bugs surrounding constraint dispatch order
### Native Codegen
* Add IR lowering hooks for custom host userdata types
* Add IR to create new tagged userdata objects
* Remove outdated NativeState
---
### 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: Aviral Goel <agoel@roblox.com>
Co-authored-by: Vighnesh Vijay <vvijay@roblox.com>
Co-authored-by: Vyacheslav Egorov <vegorov@roblox.com>
### What's new?
* Remove a case of unsound `table.move` optimization
* Add Luau stack slot reservations that were missing in REPL (fixes
#1273)
### New Type Solver
* Assignments have been completely reworked to fix a case of cyclic
constraint dependency
* When indexing, if the fresh type's upper bound already contains a
compatible indexer, do not add another upper bound
* Distribute type arguments over all type families sans `eq`, `keyof`,
`rawkeyof`, and other internal type families
* Fix a case where `buffers` component weren't read in two places (fixes
#1267)
* Fix a case where things that constitutes a strong ref were slightly
incorrect
* Fix a case where constraint dependencies weren't setup wrt `for ...
in` statement
### Native Codegen
* Fix an optimization that splits TValue store only when its value and
its tag are compatible
* Implement a system to plug additional type information for custom host
userdata types
---
### 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: Vighnesh Vijay <vvijay@roblox.com>
Co-authored-by: Vyacheslav Egorov <vegorov@roblox.com>
---------
Co-authored-by: Aaron Weiss <aaronweiss@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?
### New Type Solver
- Unification of two fresh types no longer binds them together.
- Replaced uses of raw `emplace` with `emplaceType` to catch cyclic
bound types when they are created.
- `SetIndexerConstraint` is blocked until the indexer result type is not
blocked.
- Fix a case where a blocked type got past the constraint solver.
- Searching for free types should no longer traverse into `ClassType`s.
- Fix a corner case that could result in the non-testable type `~{}`.
- Fix incorrect flagging when `any` was a parameter of some checked
function in nonstrict type checker.
- `IterableConstraint` now consider tables without `__iter` to be
iterables.
### Native Code Generation
- Improve register type info lookup by program counter.
- Generate type information for locals and upvalues
---
### 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: James McNellis <jmcnellis@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: 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?
* Improved the actual message for the type errors for `cannot call
non-function` when attempting to call a union of functions/callable
tables. The error now correctly explains the issue is an inability to
determine the return type of the call in this situation.
* Resolve an issue where tables and metatables were not correctly being
cloned during instantiation (fixes#1176).
* Refactor `luaM_getnextgcopage` to `luaM_getnextpage` (generally
removing `gco` prefix where appropriate).
* Optimize `table.move` between tables for large ranges of elements.
* Reformat a bunch of code automatically using `clang-format`.
### New Type Solver
* Clean up minimally-used or unused constraints in the constraint solver
(`InstantiationConstraint`, `SetOpConstraint`,
`SingletonOrTopTypeConstraint`).
* Add a builtin `singleton` type family to replace
`SingletonOrTopTypeConstraint` when inferring refinements.
* Fixed a crash involving type path reasoning by recording when type
family reduction has taken place in the path.
* Improved constraint ordering by blocking on unreduced types families
that are not yet proven uninhabitable.
* Improved the handling of `SetIndexerConstraints` for both better
inference quality and to resolve crashes.
* Fix a crash when normalizing cyclic unions of intersections.
* Fix a crash when normalizing an intersection with the negation of
`unknown`.
* Fix a number of crashes caused by missing `follow` calls on `TypeId`s.
* Changed type family reduction to correctly use a semantic notion of
uninhabited types, rather than checking for `never` types specifically.
* Refactor the `union` and `intersect` type families to be variadic.
### Native Code Generation
* Improve translation for userdata key get/set and userdata/vector
namecall.
* Provide `[top level]` and `[anonymous]` as function names to
`FunctionStats` as appropriate when no function name is available.
* Disable unwind support on Android platforms since it is unsupported.
*
---
### 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: Aviral Goel <agoel@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>
# What's Changed
## New Type Solver
- Many fixes to crashes, assertions, and hangs
- Binary type family aliases now have a default parameter
- Added a debug check for unsolved types escaping the constraint solver
- Overloaded functions are no longer inferred
- Unification creates additional subtyping constraints for blocked types
- Attempt to guess the result type for type families that are too large
to resolve timely
## Native Code Generation
- Fixed `IrCmd::CHECK_TRUTHY` lowering in a specific case
- Detailed compilation errors are now supported
- More work on the new allocator
---
# 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: James McNellis <jmcnellis@roblox.com>
Co-authored-by: Lily Brown <lbrown@roblox.com>
Co-authored-by: Vyacheslav Egorov <vegorov@roblox.com>
Co-authored-by: Vighnesh Vijay <vvijay@roblox.com>
# What's changed
### Debugger
* Values after a 'continue' statement should not be accessible by
debugger in the 'until' condition
### New Type Solver
* Many fixes to crashes and hangs
* Better bidirectional inference of table literal expressions
### Native Code Generation
* Initial steps toward a shared code allocator
---
### Internal Contributors
Co-authored-by: Aaron Weiss <aaronweiss@roblox.com>
Co-authored-by: Lily Brown <lbrown@roblox.com>
Co-authored-by: Vyacheslav Egorov <vegorov@roblox.com>
# What's Changed
* Add a compiler hint to improve Luau memory allocation inlining
### New Type Solver
* Added a system for recommending explicit type annotations to users in
cases where we've inferred complex generic types with type families.
* Marked string library functions as `@checked` for use in new
non-strict mode.
* Fixed a bug with new non-strict mode where we would incorrectly report
arity mismatches when missing optional arguments.
* Implement an occurs check for unifications that would produce
self-recursive types.
* Fix bug where overload resolution would fail when applied to
non-overloaded functions.
* Fix bug that caused the subtyping to report an error whenever a
generic was instantiated in an invariant context.
* Fix crash caused by `SetPropConstraint` not blocking properly.
### Native Code Generation
* Implement optimization to eliminate dead stores
* Optimize vector ops for X64 when the source is computed (thanks,
@zeux!)
* Use more efficient lowering for UNM_* (thanks, @zeux!)
---
### 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: David Cope <dcope@roblox.com>
Co-authored-by: Lily Brown <lbrown@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>
# What's changed?
* Check interrupt handler inside the pattern match engine to eliminate
potential for programs to hang during string library function execution.
* Allow iteration over table properties to pass the old type solver.
### Native Code Generation
* Use in-place memory operands for math library operations on x64.
* Replace opaque bools with separate enum classes in IrDump to improve
code maintainability.
* Translate operations on inferred vectors to IR.
* Enable support for debugging native-compiled functions in Roblox
Studio.
### New Type Solver
* Rework type inference for boolean and string literals to introduce
bounded free types (bounded below by the singleton type, and above by
the primitive type) and reworked primitive type constraint to decide
which is the appropriate type for the literal.
* Introduce `FunctionCheckConstraint` to handle bidirectional
typechecking for function calls, pushing the expected parameter types
from the function onto the arguments.
* Introduce `union` and `intersect` type families to compute deferred
simplified unions and intersections to be employed by the constraint
generation logic in the new solver.
* Implement support for expanding the domain of local types in
`Unifier2`.
* Rework type inference for iteration variables bound by for in loops to
use local types.
* Change constraint blocking logic to use a set to prevent accidental
re-blocking.
* Add logic to detect missing return statements in functions.
### 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: Aviral Goel <agoel@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>
- Implemented [Require by String with Relative
Paths](https://github.com/luau-lang/rfcs/blob/master/docs/new-require-by-string-semantics.md)
RFC
- Implemented [Require by String with
Aliases](https://github.com/luau-lang/rfcs/blob/master/docs/require-by-string-aliases.md)
RFC with support for `paths` and `alias` arrays in .luarc
- Added SUBRK and DIVRK bytecode instructions to speed up
constant-number and constant/number operations
- Added `--vector-lib`, `--vector-ctor` and `--vector-type` options to
luau-compile to support code with vectors
New Solver
- Correctness fixes to subtyping
- Improvements to dataflow analysis
Native Code Generation
- Added bytecode analysis pass to predict type tags used in operations
- Fixed rare cases of numerical loops being generated without an
interrupt instruction
- Restored optimization data propagation into the linear block
- Duplicate buffer length checks are optimized away
Miscellaneous
- Small performance improvements to new non-strict mode
- Introduced more scripts for fuzzing Luau and processing the results,
including fuzzer build support for CMake
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: 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>
- Cleaned up `FFlag::FixFindBindingAtFunctionName`,
`FFlag::LuauNormalizeBlockedTypes`, `FFlag::LuauPCallDebuggerFix`
- Added support for break and continue into control flow analysis
- The old type unification engine will now report a more fine-grained
error at times, indicating that type normalization in particular failed
# New Type Solver
- Refactor of Unifier2, the new unification implementation for Luau
- Completed MVP of new unification implementation
- Dramatically simplified overload selection logic
- Type family reduction can now apply sooner to free types that have
been solved
- Subtyping now supports table indexers
- Generalization now replaces bad generics with unknown
# Native Code Generation
- Reduce stack spills caused by FINDUPVAL and STORE_TAG
- Improve Generate SHL/SHR/SAR/rotates with immediate operands in X64
- Removed redundant case re-check in table lookup fallback
---------
Co-authored-by: Arseny Kapoulkine <arseny.kapoulkine@gmail.com>
Co-authored-by: Vyacheslav Egorov <vegorov@roblox.com>
Co-authored-by: Andy Friesen <afriesen@roblox.com>
Co-authored-by: Lily Brown <lbrown@roblox.com>
* Progress toward a diffing algorithm for types. We hope that this will
be useful for writing clearer error messages.
* Add a missing recursion limiter in `Unifier::tryUnifyTables`. This was
causing a crash in certain situations.
* Luau heap graph enumeration improvements:
* Weak references are not reported
* Added tag as a fallback name of non-string table links
* Included top Luau function information in thread name to understand
where thread might be suspended
* Constant folding for `math.pi` and `math.huge` at -O2
* Optimize `string.format` and `%*`
* This change makes string interpolation 1.5x-2x faster depending on the
number and type of formatted components, assuming a few are using
primitive types, and reduces associated GC pressure.
New type checker:
* Initial work toward tracking the upper and lower bounds of types
accurately.
Native code generation (JIT):
* Add IrCmd::CHECK_TRUTHY for improved assert fast-calls
* Do not compute type map for modules without types
* Capture metatable+readonly state for NEW_TABLE IR instructions
* Replace JUMP_CMP_ANY with CMP_ANY and existing JUMP_EQ_INT
* Add support for exits to VM with reentry lock in VmExit
---------
Co-authored-by: Arseny Kapoulkine <arseny.kapoulkine@gmail.com>
Co-authored-by: Vyacheslav Egorov <vegorov@roblox.com>
* Fixed gcc warning about uninitialized `std::optional`
* Fixed inlining of functions when they are used to compute their own
arguments
In the new type solver:
* Type families that are not part of a function signature cannot be
resolved at instantiation time and will now produce an error. This will
be relaxed in the future when we get constraint clauses on function
signatures (internally)
* `never` type is now comparable
* Improved typechecking of `for..in` statements
* Fixed checks for number type in `Add` type family
* Performance was improved, with particularly large gains on large
projects
And in native code generation (jit):
* We eliminated the call instruction overhead when native code support
is enabled in the VM
* Small optimizations to arm64 lowering
* Reworked LOP_GETIMPORT handling to reduce assembly code size
* Fixed non-deterministic binary output
* Fixed bad code generation caused by incorrect SSA to VM register links
invalidation
---------
Co-authored-by: Arseny Kapoulkine <arseny.kapoulkine@gmail.com>
Co-authored-by: Andy Friesen <afriesen@roblox.com>
* `Luau.Analyze.CLI` now has experimental support for concurrent type
checking. Use the option `-jN` where `N` is the number of threads to
spawn.
* Improve typechecking performance by ~17% by making the function
`Luau::follow` much more efficient.
* Tighten up the type of `os.date`
* Removed `ParseOptions::allowTypeAnnotations` and
`ParseOptions::supportContinueStatement`
New solver
* Improve the reliability of function overload resolution
* More work toward supporting parallel type checking
* Fix a bug in inference of `==` and `~=` which would erroneously infer
that the operands were `boolean`
* Better error reporting when `for...in` loops are used incorrectly.
CodeGen
* Fix unwind registration when libunwind is used on Linux
* Fixed replaced IR instruction use count
* Convert X64 unwind info generation to standard prologue
* Implement A64 unwind info support for Dwarf2
* Live in/out data for linear blocks is now created
* Add side-exit VM register requirements to the IR dump
* Reuse ConstPropState between block chains
* Remove redundant base update
---------
Co-authored-by: Arseny Kapoulkine <arseny.kapoulkine@gmail.com>
Co-authored-by: Vyacheslav Egorov <vegorov@roblox.com>
Once again, all of our changes this week are for new type solver and the
JIT.
In the new type solver, we fixed cyclic type alias handling and multiple
stability issues.
In the JIT, our main progress was for arm64, where, after lowering 36%
of instructions, we start seeing first Luau functions executing
natively.
For x64, we performed code cleanup and refactoring to allow for future
optimizations.
* A small subset of control-flow refinements have been added to
recognize type options that are unreachable after a
conditional/unconditional code block. (Fixes
https://github.com/Roblox/luau/issues/356).
Some examples:
```lua
local function f(x: string?)
if not x then return end
-- x is 'string' here
end
```
Throwing calls like `error` or `assert(false)` instead of 'return' are
also recognized.
Existing complex refinements like type/typeof and tagged union checks
are expected to work, among others.
To enable this feature, `LuauTinyControlFlowAnalysis` exclusion has to
be removed from `ExperimentalFlags.h`.
If will become enabled unconditionally in the near future.
* Linter has been integrated into the typechecker analysis so that
type-aware lint warnings can work in any mode
`Frontend::lint` methods were deprecated, `Frontend::check` has to be
used instead with `runLintChecks` option set.
Resulting lint warning are located inside `CheckResult`.
* Fixed large performance drop and increased memory consumption when
array is filled at an offset (Fixes
https://github.com/Roblox/luau/issues/590)
* Part of [Type error suppression
RFC](https://github.com/Roblox/luau/blob/master/rfcs/type-error-suppression.md)
was implemented making subtyping checks with `any` type transitive.
---
In our work on the new type-solver:
* `--!nocheck` mode no longer reports type errors
* New solver will not be used for `--!nonstrict` modules until all
issues with strict mode typechecking are fixed
* Added control-flow aware type refinements mentioned earlier
In native code generation:
* `LOP_NAMECALL` has been translated to IR
* `type` and `typeof` builtin fastcalls have been translated to
IR/assembly
* Additional steps were taken towards arm64 support
* Fix#817
* Fix#850
* Optimize math.floor/ceil/round with SSE4.1
* Results in a ~7-9% speedup on the math-cordic benchmark.
* Optimized table.sort.
* table.sort is now ~4.1x faster (when not using a predicate) and ~2.1x
faster when using a simple predicate. Performance may improve further in
the future.
* Reorganize the memory ownership of builtin type definitions.
* This is a small initial step toward affording parallel typechecking.
The new type solver is coming along nicely. We are working on fixing
crashes and bugs.
A few major changes to native codegen landed this week:
* Fixed lowering of Luau IR mod instruction when first argument is a
constant
* Added VM register data-flow/capture analysis
* Fixed issues with optimizations in unreachable blocks
---------
Co-authored-by: Arseny Kapoulkine <arseny.kapoulkine@gmail.com>
Co-authored-by: Vyacheslav Egorov <vegorov@roblox.com>
* Fixed rare use-after-free in analysis during table unification
A lot of work these past months went into two new Luau components:
* A near full rewrite of the typechecker using a new deferred constraint
resolution system
* Native code generation for AoT/JiT compilation of VM bytecode into x64
(avx)/arm64 instructions
Both of these components are far from finished and we don't provide
documentation on building and using them at this point.
However, curious community members expressed interest in learning about
changes that go into these components each week, so we are now listing
them here in the 'sync' pull request descriptions.
---
New typechecker can be enabled by setting
DebugLuauDeferredConstraintResolution flag to 'true'.
It is considered unstable right now, so try it at your own risk.
Even though it already provides better type inference than the current
one in some cases, our main goal right now is to reach feature parity
with current typechecker.
Features which improve over the capabilities of the current typechecker
are marked as '(NEW)'.
Changes to new typechecker:
* Regular for loop index and parameters are now typechecked
* Invalid type annotations on local variables are ignored to improve
autocomplete
* Fixed missing autocomplete type suggestions for function arguments
* Type reduction is now performed to produce simpler types to be
presented to the user (error messages, custom LSPs)
* Internally, complex types like '((number | string) & ~(false?)) |
string' can be produced, which is just 'string | number' when simplified
* Fixed spots where support for unknown and never types was missing
* (NEW) Length operator '#' is now valid to use on top table type, this
type comes up when doing typeof(x) == "table" guards and isn't available
in current typechecker
---
Changes to native code generation:
* Additional math library fast calls are now lowered to x64: math.ldexp,
math.round, math.frexp, math.modf, math.sign and math.clamp
* Fixed unions of `nil` types displaying as `?`
* Internal normalization now handles class types which can make
previously failing (incorrectly) sub-typing checks to succeed
* Reduce the stack utilization of type checking.
* Improve the error message that's reported when a delimiting comma is
missing from a table literal. eg
```lua
local t = {
first = 1
second = 2
}```
* Reoptimized math.min/max/bit32 builtins assuming at least 2 arguments are used (1-2% lift on some benchmarks)
* Type errors that mention function types no longer have redundant parenthesis around return type
* Luau REPL now supports --compile=remarks which displays the source code with optimization remarks embedded as comments
* Builtin calls are slightly faster when called with 1-2 arguments (~1% improvement in some benchmarks)
- Type aliases can no longer override primitive types; attempts to do
that will result in a type error
- Fix misleading type error messages for mismatches in expression list
length during assignment
- Fix incorrect type name display in certain cases
- setmetatable/getmetatable are now ~2x faster
- tools/perfstat.py can be used to display statistics about profiles
captured via --profile switch
- Improve ComparisonPrecedence lint suggestions for three-way comparisons (X < Y < Z)
- Improve type checking stability
- Improve location information for errors when parsing invalid type annotations
- Compiler now generates bytecode version 3 in all configurations
- Improve performance of comparisons against numeric constants on AArch64
* Fix free Luau type being fully overwritten by 'any' and causing UAF
* Fix lua_clonefunction implementation replacing top instead of pushing
* Falsey values other than false can now narrow refinements
* Fix lua_getmetatable, lua_getfenv not waking thread up
* FIx a case where lua_objlen could push a new string without thread wakeup or GC
* Moved Luau math and bit32 definitions to definition file
* Improve Luau parse recovery of incorrect return type token
* Run clang-format
* Contains a preliminary implementation of deferred constraint resolution
* Reduce stack usage by some recursive functions
* Fix a bug when smartCloning a BoundTypeVar
* Remove some GC related flags from VM
