0.596

What's Changed

• Support Control Flow type Refinements for "break" and "continue" statements by @AmberGraceSoftware in #1004
• 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
• Generate SHL/SHR/SAR/rotates with immediate operands in X64
• Removed redundant case re-check in table lookup fallback

New Contributors

• @AmberGraceSoftware made their first contribution in #1004

Full Changelog: 0.595...0.596

0.595

What's new

• 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
• Demo site: case sensitive highlighting by @Someon1e in #1040

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.

New Contributors

• @Someon1e made their first contribution in #1040

Full Changelog: 0.594...0.595

0.594

Analysis Changes

• Fixed generic variadic function unification succeeding when it should have reported an error

Other Changes

• Fixed Frontend::markDirty not working on modules that were not typechecked yet
• Fix build & test conformance issues on mingw32/gcc and mingw64/clang by @jdpatdiscord in #1023
• Update syntax.md by @zeux in #1035

New Type Solver

• Implemented semantic subtyping check for function types

Native Code Generation

• Improved performance of numerical loops with a constant step
• Simplified IR for bit32.extract calls extracting first/last bits
• Improved performance of NaN checks

0.593

Floor division operator //

Luau now supports floor division operator //; by default it works on numbers and is equivalent to math.floor(a / b), but it can also be overridden for other types using __idiv metamethod. The operator has the same syntax and semantics as // in Lua 5.3; see #832 for full RFC.

Analysis Changes

• Autocomplete now shows end within do blocks
• Restore BraceType when using Lexer::lookahead (fixes #1019)

New Type Solver

• Enhance subtyping tests to support metatables, string singletons, and class types

Native Codegen

• Fixed clobbering of non-volatile xmm registers on Windows
• Optimize redundant table slot lookups
• Improve value propagation optimizations to work across basic blocks in some cases
• Implemented IR translation of table.insert builtin
• Fixed mmap error handling on macOS/Linux

0.592

Analysis Changes

• Improved parsing error messages
• Fixed crash on null pointer access in unification (fixes #1017)

Other Changes

• AST queries at position where function name is will now return AstExprLocal
• Lexer performance has been slightly improved
• Fixed incorrect string singleton autocomplete suggestions (fixes #858)
• Native code support is enabled by default and native=1 (make)/LUAU_NATIVE (CMake)/-DLUA_CUSTOM_EXECUTION configuration is no longer required

New Type Solver

• New subtyping check can now handle generic functions and tables (including those that contain cycles)

Native Codegen

• Loops with non-numeric parameters are now handled by VM to streamline native code
• Array size check can be optimized away in SETLIST
• On failure, CodeGen::compile returns a reason
• Fixed clobbering of non-volatile xmm registers on Windows

0.591

What's Changed

• LinterConfig.h: add missing stdint.h include by @xgqt in #1010
• 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 a stability issue with debugger debugprotectederror callback allowing break in non-yieldable contexts

New Type Solver

• Initial work toward Local Type Inference
• 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

New Contributors

• @xgqt made their first contribution in #1010

Full Changelog: 0.590...0.591

0.590

Analysis Changes

• 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 #975

Runtime Changes

• string.format with %s is now ~2x faster on strings smaller than 100 characters

Other Changes

• Use const char* const* over const char** by @LoganDark in #1005
• Add luau-compile to .gitignore by @j-hui in #995

Native Codegen

• 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

New Contributors

• @j-hui made their first contribution in #995

Full Changelog: 0.589...0.590

0.589

Analysis Changes

• 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.

Runtime Changes

• 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.

Other changes

• Add dark theme by @Someon1e in #991
• Fix some EBNF cases in grammar.md by @cassanof in #999

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

New Contributors

• @cassanof made their first contribution in #999

Full Changelog: 0.588...0.589

0.588

Analysis and Autocomplete Changes

• Luau::autocomplete no longer performs typechecking internally, make sure to run Frontend::check before performing autocomplete requests
• Autocomplete string suggestions without "" are now only suggested inside the ""
• Autocomplete suggestions now include function (anonymous autofilled) key with a full suggestion for the function expression (with arguments included) stored in AutocompleteEntry::insertText
• AutocompleteEntry::indexedWithSelf is provided for function call suggestions made with :
• Cyclic modules now see each other type exports as any to prevent memory use-after-free (similar to module return type)

Runtime Changes

• Updated inline/loop unroll cost model to better handle assignments (Fixes #978)
• math.noise speed was improved by ~30%
• table.concat speed was improved by ~5-7%
• tonumber and tostring now have fastcall paths that execute ~1.5x and ~2.5x faster respectively (Fixes #777)
• Fixed crash in luaL_typename when index refers to a non-existing value
• Fixed potential out of memory scenario when using string.sub or string.char in a loop
• Fixed behavior of some fastcall builtins when called without arguments under -O2 to match original functions
• Support for native code execution in VM is now enabled by default (note: native code still has to be generated explicitly)
• CodeGen::compile now accepts CodeGen_OnlyNativeModules flag. When set, only modules that have a --!native hot-comment at the top will be compiled to native code

Other Changes

• HATRA 23 paper by @asajeffrey in #979
• README.md: Add Gentoo Linux to listed distributions by @MagelessMayhem in #976
• docs: Document return value for table.remove by @zeux in #987
• Improve demo site by @Someon1e in #990

New Type Solver

• Generic type packs are no longer considered to be variadic during unification
• Timeout and cancellation now works in new solver
• Fixed false positive errors around 'table' and 'function' type refinements
• Table literals now use covariant unification rules. This is sound since literal has no type specified and has no aliases
• Fixed issues with blocked types escaping the constraint solver
• Fixed more places where error messages that should've been suppressed were still reported
• Fixed errors when iterating over a top table type

JIT

• 'DebugLuauAbortingChecks' flag is now supported on A64
• LOP_NEWCLOSURE has been translated to IR

New Contributors

• @MagelessMayhem made their first contribution in #976
• @Someon1e made their first contribution in #990

0.584

What's Changed

• 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

New Type Solver

• Errors are now suppressed when checking property lookup of error-suppressing unions

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