# What's changed?
- Record the location of properties for table types (closes#802)
- Implement stricter UTF-8 validations as per the RFC
(https://github.com/luau-lang/rfcs/pull/1)
- Implement `buffer` as a new type in both the old and new solvers.
- Changed errors produced by some `buffer` builtins to be a bit more
generic to avoid platform-dependent error messages.
- Fixed a bug where `Unifier` would copy some persistent types, tripping
some internal assertions.
- Type checking rules on relational operators is now a little bit more
lax.
- Improve dead code elimination for some `if` statements with complex
always-false conditions
## New type solver
- Dataflow analysis now generates phi nodes on exit of branches.
- Dataflow analysis avoids producing a new definition for locals or
properties that are not owned by that loop.
- If a function parameter has been constrained to `never`, report errors
at all uses of that parameter within that function.
- Switch to using the new `Luau::Set` to replace `std::unordered_set` to
alleviate some poor allocation characteristics which was negatively
affecting overall performance.
- Subtyping can now report many failing reasons instead of just the
first one that we happened to find during the test.
- Subtyping now also report reasons for type pack mismatches.
- When visiting `if` statements or expressions, the resulting context
are the common terms in both branches.
## Native codegen
- Implement support for `buffer` builtins to its IR for x64 and A64.
- Optimized `table.insert` by not inserting a table barrier if it is
fastcalled with a constant.
## 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: Arseny Kapoulkine <arseny@roblox.com>
Co-authored-by: Aviral Goel <agoel@roblox.com>
Co-authored-by: Lily Brown <lbrown@roblox.com>
Co-authored-by: Vyacheslav Egorov <vegorov@roblox.com>
# What's changed?
* Fixed a bug in type cloning by maintaining persistent types.
* We now parse imprecise integer literals to report the imprecision as a
warning to developers.
* Add a compiler flag to specify the name of the statistics output file.
### New type solver
* Renamed `ConstraintGraphBuilder` to `ConstraintGenerator`
* LValues now take into account the type being assigned during
constraint generation.
* Normalization performance has been improved by 33% by replacing the an
internal usage of `std::unordered_set` with `DenseHashMap`.
* Normalization now has a helper to identify types that are equivalent
to `unknown`, which is being used to fix some bugs in subtyping.
* Uses of the old unifier in the new type solver have been eliminated.
* Improved error explanations for subtyping errors in `TypeChecker2`.
### Native code generation
* Expanded some of the statistics recorded during compilation to include
the number of instructions and blocks.
* Introduce instruction and block count limiters for controlling what
bytecode is translated into native code.
* Implement code generation for byteswap instruction.
### 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: Lily Brown <lbrown@roblox.com>
### What's Changed
- Improve readability of unions and intersections by limiting the number
of elements of those types that can be presented on a single line (gated
under `FFlag::LuauToStringSimpleCompositeTypesSingleLine`)
- Adds a new option to the compiler `--record-stats` to record and
output compilation statistics
- `if...then...else` expressions are now optimized into `AND/OR` form
when possible.
### VM
- Add a new `buffer` type to Luau based on the [buffer
RFC](https://github.com/Roblox/luau/pull/739) and additional C API
functions to work with it; this release does not include the library.
- Internal C API to work with string buffers has been updated to align
with Lua version more closely
### Native Codegen
- Added support for new X64 instruction (rev) and new A64 instruction
(bswap) in the assembler
- Simplified the way numerical loop condition is translated to IR
### New Type Solver
- Operator inference now handled by type families
- Created a new system called `Type Paths` to explain why subtyping
tests fail in order to improve the quality of error messages.
- Systematic changes to implement Data Flow analysis in the new solver
(`Breadcrumb` removed and replaced with `RefinementKey`)
---
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: Lily Brown <lbrown@roblox.com>
Co-authored-by: Vighnesh Vijay <vvijay@roblox.com>
Co-authored-by: Vyacheslav Egorov <vegorov@roblox.com>
---------
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>
Co-authored-by: Aaron Weiss <aaronweiss@roblox.com>
Co-authored-by: Alexander McCord <amccord@roblox.com>
Co-authored-by: Aviral Goel <agoel@roblox.com>
# New Type Solver
- Implement bidirectional type inference for higher order functions so
that we can provide a more precise type improving the autocomplete's
human factors.
- We seal all tables, so we changed the stringification to make it a
little lighter on users.
- Fixed a case of array-out-of-bound access.
- Type families no longer depends on `TxnLog` and `Unifier`.
- Type refinements now waits until the free types are sufficiently
solved.
# Native Code Generation
- Remove cached slot lookup for `executeSETTABLEKS` function because it
is a fallback in the event of a cache miss, making the cached slot
lookup redundant.
- Optimized repeated array lookups, e.g. `a[3]` in `a[3] = a[3] / 2` is
done once.
# Misc
- On some platforms, it is necessary to use `gmtime_s` with the
arguments reversed to get the current time. You can now define
`DOCTEST_CONFIG_USE_GMTIME_S` to build and run unit tests on those
platforms.
---------
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>
Co-authored-by: Aaron Weiss <aaronweiss@roblox.com>
* Rerun clang-format on the code
* Fix the variance on indexer result subtyping. This fixes some issues
with inconsistent error reporting.
* Fix a bug in the normalization logic for intersections of strings
New Type Solver
* New overload selection logic
* Subtype tests now correctly treat a generic as its upper bound within
that generic's scope
* Semantic subtyping for negation types
* Semantic subtyping between strings and compatible table types like
`{lower: (string) -> string}`
* Further work toward finalizing our new subtype test
* Correctly generalize module-scope symbols
Native Codegen
* Lowering statistics for assembly
* Make executable allocation size/limit configurable without a rebuild.
Use `FInt::LuauCodeGenBlockSize` and `FInt::LuauCodeGenMaxTotalSize`.
---------
Co-authored-by: Arseny Kapoulkine <arseny.kapoulkine@gmail.com>
Co-authored-by: Vyacheslav Egorov <vegorov@roblox.com>
Co-authored-by: Lily Brown <lbrown@roblox.com>
* Fix a use-after-free bug in the new type cloning algorithm
* Tighten up the type of `coroutine.wrap`. It is now `<A..., R...>(f:
(A...) -> R...) -> ((A...) -> R...)`
* Break `.luaurc` out into a separate library target `Luau.Config`. This
makes it easier for applications to reason about config files without
also depending on the type inference engine.
* Move typechecking limits into `FrontendOptions`. This allows embedders
more finely-grained control over autocomplete's internal time limits.
* Fix stability issue with debugger onprotectederror callback allowing
break in non-yieldable contexts
New solver:
* Initial work toward [Local Type
Inference](0e1082108f/rfcs/local-type-inference.md)
* Introduce a new subtyping test. This will be much nicer than the old
test because it is completely separate both from actual type inference
and from error reporting.
Native code generation:
* Added function to compute iterated dominance frontier
* Optimize barriers in SET_UPVALUE when tag is known
* Cache lua_State::global in a register on A64
* Optimize constant stores in A64 lowering
* Track table array size state to optimize array size checks
* Add split tag/value store into a VM register
* Check that spills can outlive the block only in specific conditions
---------
Co-authored-by: Arseny Kapoulkine <arseny.kapoulkine@gmail.com>
Co-authored-by: Vyacheslav Egorov <vegorov@roblox.com>
* Better indentation in multi-line type mismatch error messages
* Error message clone can no longer cause a stack overflow (when
typechecking with retainFullTypeGraphs set to false); fixes
https://github.com/Roblox/luau/issues/975
* `string.format` with %s is now ~2x faster on strings smaller than 100
characters
Native code generation:
* All VM side exits will block return to the native execution of the
current function to preserve correctness
* Fixed executable page allocation on Apple platforms when using
hardened runtime
* Added statistics for code generation (no. of functions compiler,
memory used for different areas)
* Fixed issue with function entry type checks performed more that once
in some functions
* 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>
* Added support for async typechecking cancellation using a token passed
through frontend options
* Added luaC_enumheap for building debug tools that need a graph of Luau
heap
In our new typechecker:
* Errors or now suppressed when checking property lookup of
error-suppressing unions
In our native code generation (jit):
* Fixed unhandled value type in NOT_ANY lowering
* Fast-call tag checks will exit to VM on failure, instead of relying on
a native fallback
* Added vector type to the type information
* Eliminated redundant direct jumps across dead blocks
* Debugger APIs are now disabled for call frames executing natively
* Implemented support for unwind registration on macOS 14
* Fixed indexing table intersections using `x["prop"]` syntax:
https://github.com/Roblox/luau/pull/971
* Add console output codepage for Windows:
https://github.com/Roblox/luau/pull/967
* Added `Frontend::parse` for a fast source graph preparation
* luau_load should check GC
* Work toward a type-diff system for nicer error messages
New Solver
* Correctly suppress errors in more cases
* Further improvements to typechecking of function calls and return
statements
* Crash fixes
* Propagate refinements drawn from the condition of a while loop into
the loop body
JIT
* Fix accidental bailout for math.frexp/modf/sign in A64
* Work toward bringing type annotation info in
* Do not propagate Luau IR constants of wrong type into load
instructions
* CHECK_SAFEENV exits to VM on failure
* Implement error handling in A64 reg allocator
* Inline the string.len builtin
* Do not enter native code of a function if arguments don’t match
---------
Co-authored-by: Arseny Kapoulkine <arseny.kapoulkine@gmail.com>
Co-authored-by: Vyacheslav Egorov <vegorov@roblox.com>
Lots of things going on this week:
* Fix a crash that could occur in the presence of a cyclic union. We
shouldn't be creating cyclic unions, but we shouldn't be crashing when
they arise either.
* Minor cleanup of `luau_precall`
* Internal change to make L->top handling slightly more uniform
* Optimize SETGLOBAL & GETGLOBAL fallback C functions.
* https://github.com/Roblox/luau/pull/929
* The syntax to the `luau-reduce` commandline tool has changed. It now
accepts a script, a command to execute, and an error to search for. It
no longer automatically passes the script to the command which makes it
a lot more flexible. Also be warned that it edits the script it is
passed **in place**. Do not point it at something that is not in source
control!
New solver
* Switch to a greedier but more fallible algorithm for simplifying union
and intersection types that are created as part of refinement
calculation. This has much better and more predictable performance.
* Fix a constraint cycle in recursive function calls.
* Much improved inference of binary addition. Functions like `function
add(x, y) return x + y end` can now be inferred without annotations. We
also accurately typecheck calls to functions like this.
* Many small bugfixes surrounding things like table indexers
* Add support for indexers on class types. This was previously added to
the old solver; we now add it to the new one for feature parity.
JIT
* https://github.com/Roblox/luau/pull/931
* Fuse key.value and key.tt loads for CEHCK_SLOT_MATCH in A64
* Implement remaining aliases of BFM for A64
* Implement new callinfo flag for A64
* Add instruction simplification for int->num->int conversion chains
* Don't even load execdata for X64 calls
* Treat opcode fallbacks the same as manually written fallbacks
---------
Co-authored-by: Arseny Kapoulkine <arseny.kapoulkine@gmail.com>
Co-authored-by: Vyacheslav Egorov <vegorov@roblox.com>
* `ClassType` can now have an indexer defined on it. This allows custom
types to be used in `t[x]` expressions.
* Fixed search for closest executable breakpoint line. Previously,
breakpoints might have been skipped in `else` blocks at the end of a
function
* Fixed how unification is performed for two optional types `a? <: b?`,
previously it might have unified either 'a' or 'b' with 'nil'. Note that
this fix is not enabled by default yet (see the list in
`ExperimentalFlags.h`)
In the new type solver, a concept of 'Type Families' has been
introduced.
Type families can be thought of as type aliases with custom type
inference/reduction logic included with them.
For example, we can have an `Add<T, U>` type family that will resolve
the type that is the result of adding two values together.
This will help type inference to figure out what 'T' and 'U' might be
when explicit type annotations are not provided.
In this update we don't define any type families, but they will be added
in the near future.
It is also possible for Luau embedders to define their own type families
in the global/environment scope.
Other changes include:
* Fixed scope used to find out which generic types should be included in
the function generic type list
* Fixed a crash after cyclic bound types were created during unification
And in native code generation (jit):
* Use of arm64 target on M1 now requires macOS 13
* Entry into native code has been optimized. This is especially
important for coroutine call/pcall performance as they involve going
through a C call frame
* LOP_LOADK(X) translation into IR has been improved to enable type
tag/constant propagation
* arm64 can use integer immediate values to synthesize floating-point
values
* x64 assembler removes duplicate 64bit numbers from the data section to
save space
* Linux `perf` can now be used to profile native Luau code (when running
with --codegen-perf CLI argument)
* Added a limit on how many instructions the Compiler can safely produce
(reported by @TheGreatSageEqualToHeaven)
C++ API Changes:
* With work started on read-only and write-only properties,
`Property::type` member variable has been replaced with `TypeId type()`
and `setType(TypeId)` functions.
* New `LazyType` unwrap callback now has a `void` return type, all
that's required from the callback is to write into `unwrapped` field.
In our work on the new type solver, the following issues were fixed:
* Work has started to support https://github.com/Roblox/luau/pull/77 and
https://github.com/Roblox/luau/pull/79
* Refinements are no longer applied on l-values, removing some
false-positive errors
* Improved overload resolution against expected result type
* `Frontend::prepareModuleScope` now works in the new solver
* Cofinite strings are now comparable
And these are the changes in native code generation (JIT):
* Fixed MIN_NUM and MAX_NUM constant fold when one of the arguments is
NaN
* Added constant folding for number conversions and bit operations
* Value spilling and rematerialization is now supported on arm64
* Improved FASTCALL2K IR generation to support second argument constant
* Added value numbering and load/store propagation optimizations
* Added STORE_VECTOR on arm64, completing the IR lowering on this target
* Work toward affording parallel type checking
* The interface to `LazyType` has changed:
* `LazyType` now takes a second callback that is passed the `LazyType&`
itself. This new callback is responsible for populating the field
`TypeId LazyType::unwrapped`. Multithreaded implementations should
acquire a lock in this callback.
* Modules now retain their `humanReadableNames`. This reduces the number
of cases where type checking has to call back to a `ModuleResolver`.
* https://github.com/Roblox/luau/pull/902
* Add timing info to the Luau REPL compilation output
We've also fixed some bugs and crashes in the new solver as we march
toward readiness.
* Thread ICEs (Internal Compiler Errors) back to the Frontend properly
* Refinements are no longer applied to lvalues
* More miscellaneous stability improvements
Lots of activity in the new JIT engine:
* Implement register spilling/restore for A64
* Correct Luau IR value restore location tracking
* Fixed use-after-free in x86 register allocator spill restore
* Use btz for bit tests
* Finish branch assembly support for A64
* Codesize and performance improvements for A64
* The bit32 library has been implemented for arm and x64
---------
Co-authored-by: Arseny Kapoulkine <arseny.kapoulkine@gmail.com>
Co-authored-by: Vyacheslav Egorov <vegorov@roblox.com>
* `table.sort` was improved further. It now guarentees N*log(N) time
complexity in the worst case.
* Fix https://github.com/Roblox/luau/issues/880
We are also working on fixing final bugs and crashes in the new type
solver.
On the CodeGen front we have a few things going on:
* We have a smarter register allocator for the x86 JIT
* We lower more instructions on arm64
* The vector constructor builtin is now translated to IR
---------
Co-authored-by: Arseny Kapoulkine <arseny.kapoulkine@gmail.com>
Co-authored-by: Vyacheslav Egorov <vegorov@roblox.com>
All of our changes this week have been focused on the new type solver
and the JIT.
As we march toward feature parity with the old solver, we've tightened
up a bunch of lingering issues with overload resolution, unsealed
tables, and type normalization. We've also fixed a bunch of crashes and
assertion failures in the new solver.
On the JIT front, we've started work on an A64 backend, improved the IR
analysis in a bunch of cases, and implemented assembly generation for
the builtin functions `type()` and `typeof()`.
---------
Co-authored-by: Arseny Kapoulkine <arseny.kapoulkine@gmail.com>
Co-authored-by: Vyacheslav Egorov <vegorov@roblox.com>
* Fix a bug where reading a property from an unsealed table caused
inference to improperly infer the existence of that property.
* Fix#827
We have also made a lot of progress on the new solver and the JIT. Both
projects are still in the process of being built out. Neither are ready
for general use yet.
We are mostly working to tighten up how the new solver handles
refinements and updates to unsealed tables to bring it up to the same
level as the old solver.
---------
Co-authored-by: Arseny Kapoulkine <arseny.kapoulkine@gmail.com>
Co-authored-by: Vyacheslav Egorov <vegorov@roblox.com>
Having the location where the table type is defined is useful for
tracking other info such as documentation comments, or pointing back
through "Go To Definition" functionality etc.
This adds in the required info
* 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
}```
* Support `["prop"]` syntax on class definitions in definition files.
(#704)
* Improve type checking performance for complex overloaded functions
* Fix rare cases of incorrect stack traces for out of memory errors at
runtime
- 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
