# 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>
* 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
A pretty small changelist this week:
* When type inference fails to find any matching overload for a
function, we were declining to commit any changes to the type graph at
all. This was resulting in confusing type errors in certain cases. Now,
when a matching overload cannot be found, we always commit to the first
overload we tried.
JIT
* Fix missing variadic register invalidation in FALLBACK_GETVARARGS
* Add a missing null pointer check for the result of luaT_gettm
---------
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)
* 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>
* 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
- Fix rare type checking bugs with invalid generic types escaping the
module scope
- Fix type checking of variadic type packs in certain cases
- Implement type normalization, which resolves a large set of various
issues with unions/intersections in type checker
- Improve parse errors for trailing commas in function calls and type
lists
- Reduce profiling skew when using --profile with very high frequencies
- Improve performance of `lua_getinfo` (`debug.info`, `debug.traceback`
and profiling overhead are now 20% faster/smaller)
- Improve performance of polymorphic comparisons (1-2% lift on some
benchmarks)
- Improve performance of closure creation (1-2% lift on some benchmarks)
- Improve string comparison performance (4% lift on string sorting)
- 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
- Fix DeprecatedGlobal warning text in cases when the global is deprecated without a suggested alternative
- Fix an off-by-one error in type error text for incorrect use of string.format
- Reduce stack consumption further during parsing, hopefully eliminating stack overflows during parsing/compilation for good
- Mark interpolated string support as experimental (requires --fflags=LuauInterpolatedStringBaseSupport to enable)
- Simplify garbage collection treatment of upvalues, reducing cache misses during sweeping stage and reducing the cost of upvalue assignment (SETUPVAL); supersedes #643
- Simplify garbage collection treatment of sleeping threads
- Simplify sweeping of alive threads, reducing cache misses during sweeping stage
- Simplify management of string buffers, removing redundant linked list operations
- Rework transaction log used for type checking which should result in more robust type checking internals with fewer bugs
- Reduce the amount of memory consumed by type checker on large module graphs
- Type checker now errors on attempts to change the type of imported module fields
- The return type of newproxy is now any (fixes#296)
- Implement new number printing algorithm (Schubfach) which makes tostring() produce precise (round-trippable) and short decimal output up to 10x faster
- Fix lua_Debug::linedefined to point to the line with the function definition instead of the first statement (fixes#265)
- Fix minor bugs in Tab completion in Repl
- Repl now saves/restores command history in ~/.luau_history
This doesn't contain all changes for 507 yet but we might want to do the
Luau 0.507 release a bit earlier to end the year sooner.
Changes:
- Type ascription (::) now permits casts between related types in both directions, allowing to refine or loosen the type (RFC #56)
- Fix type definition for tonumber to return number? since the input string isn't guaranteed to contain a valid number
- Fix type refinements for field access via []
- Many stability fixes for type checker
- Provide extra information in error messages for type mismatches in more cases
- Improve performance of type checking for large unions when union members are string literals
- Add coverage reporting support to Repl (--coverage command line argument) and lua_getcoverage C API
- Work around code signing issues during Makefile builds on macOS
- Improve performance of truthiness checks in some cases, particularly on Apple M1, resulting in 10-25% perf gains on qsort benchmark depending on the CPU/compiler
- Fix support for little-endian systems; IBM s390x here we go!
- Improve error recovery during type checking
- Initial (not fully complete) implementation for singleton types (RFC RFC: Singleton types #37)
- Implement a C-friendly interface for compiler (luacode.h)
- Remove C++ features from lua.h (removed default arguments from luau_load and lua_pushcfunction)
- Fix lua_breakpoint behavior when enabled=false
- Implement coroutine.close (RFC RFC: coroutine.close #88)
Note, this introduces small breaking changes in lua.h:
- luau_load env argument is now required, pass an extra 0
- lua_pushcfunction now must be called with 3 arguments; if you were calling it with 2 arguments, pass an extra NULL; if you were calling it with 4, use lua_pushcclosure.
These changes are necessary to make sure lua.h can be used from pure C - the future release will make it possible by adding an option to luaconf.h to change function name mangling to be C-compatible. We don't anticipate breaking the FFI interface in the future, but this change was necessary to restore C compatibility.
Closes#121Fixes#213
