0.608

Old Solver:


• Fix a bug in the old solver where a user could use the keyword typeof as the name of a type alias.
• Fix stringification of scientific notation to omit a trailing decimal place when not followed by a digit e.g. 1.e+20 -> 1e+20

New Solver

• Continuing work on the New non-strict mode
• Introduce keyof and rawkeyof type function for acquiring the type of all keys in a table or class (luau-lang/rfcs#16)

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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: Vyacheslav Egorov vegorov@roblox.com
Co-authored-by: Vighnesh Vijay vvijay@roblox.com

0.607

What's changed?

• Fix up the std::iterator_traits definitions for some Luau data structures.
• Replace some of the usages of std::unordered_set and std::unordered_map with Luau-provided data structures to increase performance and reduce overall number of heap allocations.
• Update some of the documentation links in comments throughout the codebase to correctly point to the moved repository.
• Expanded JSON encoder for AST to support singleton types.
• Fixed a bug in luau-analyze where exceptions in the last module being checked during multithreaded analysis would not be rethrown.

New type solver

• Introduce a refine type family to handle deferred refinements during type inference, replacing the old RefineConstraint.
• Continued work on the implementation of type states, fixing some known bugs/blockers.
• Added support for variadic functions in new non-strict mode, enabling broader support for builtins and the Roblox API.

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: Vyacheslav Egorov vegorov@roblox.com

0.606

New Solver

• Improvements to data flow analysis

Native Code Generation

• Block limit is now per-function instead of per-module

Full Changelog: 0.605...0.606

0.605

What's Changed

• Include module name for definitions files by @JohnnyMorganz in #861
• Add SUBRK and DIVRK bytecode instructions to bytecode v5 by @zeux in #1115
• Added --vector-lib, --vector-ctor and --vector-type options to luau-compile to support code with vectors
• Experimental implementation of Require by String with Relative Paths and Require by String with Aliases RFCs with support for paths and aliases arrays in .luaurc file. This implementation is under an experimental flag and will be finalized in the upcoming releases.

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

New Contributors

• @WheretIB made their first contribution in #1119
• @menarulalam made their first contribution in #1123

Full Changelog: 0.604...0.605

0.604

What's Changed

• Add #include <algorithm> to fix building with gcc 14 by @kostadinsh in #1104
• Optimize vector literals by storing them in the constant table by @petrihakkinen in #1096

New Solver

• New algorithm for inferring the types of locals that have no annotations. This
  algorithm is very conservative by default, but is augmented with some control
  flow awareness to handle most common scenarios.
• Fix bugs in type inference of tables
• Improve performance of by switching out standard C++ containers for DenseHashMap
• Infrastructure to support clearer error messages in strict mode

Native Code Generation

• Fix a lowering issue with buffer.writeu8 and 0x80-0xff values: A constant
  argument wasn't truncated to the target type range and that causes an
  assertion failure in build.mov.
• Store full lightuserdata value in loop iteration protocol lowering

New Contributors

• @kostadinsh made their first contribution in #1104

Full Changelog: 0.603...0.604

0.603

What's changed?

• Record the location of properties for table types (closes #802)
• Implement stricter UTF-8 validations as per the RFC (luau-lang/rfcs#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.

0.602

What's changed?

• Fixed a bug in type cloning by maintaining persistent types.
• We now detect imprecise integer literals and flag the imprecision as a lint warning.
• Parsing is now up to 10% faster due to improved inlining.

New type solver

• 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.

Native code generation

• Introduce instruction and block count limiters for controlling what bytecode is translated into native code.
• Implement code generation for bit32.byteswap.
• Marginally speed up method calls for tables via : in some cases.

0.601

What's changed

• bit32.byteswap added by @Dekkonot (RFC)
• Buffer library implementation (RFC)
• Fixed a missing stdint.h include by @xgqt
• Fixed parser limiter for recursive type annotations being kind of weird (fixes #645)

Native Codegen

• Fixed a pair of issues when lowering bit32.extract
• Fixed a narrow edge case that could result in an infinite loop without an interruption
• Fixed a negative array out-of-bounds access issue
• Temporarily reverted linear block predecessor value propagation

New type solver

• We now type check assignments to annotated variables
• Fixed some test cases under local type inference
• Moved isPending checks for type families to improve performance
• Optimized our process for testing if a free type is sufficiently solved

0.600

Analysis

• Improve readability of unions and intersections by limiting the number of elements of those types that can be presented on a single line

Runtime

• if...then...else expressions are now optimized into AND/OR form when possible.
• Add a new buffer type to Luau based on the buffer RFC and additional C API functions to work with it; this release does not include the library.
• C API to work with string buffers has been updated to align with Lua version more closely

Native Codegen

• Simplified the way numerical loop condition is translated to IR

New Type Solver

• Operator inference is 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.
• Progress towards implementing Data Flow analysis in the new solver

0.599

What's Changed

• Improve POSIX compliance in CLI/FileUtils.cpp by @SamuraiCrow #1064
• AstStat*::hasEnd is deprecated; use AstStatBlock::hasEnd instead
• Added a lint for common misuses of the # operator
• Linter now issues deprecated diagnostics for some uses of getfenv and setfenv
• Fixed a case where we included a trailing space in some error stringifications

Compiler

• Do not do function analysis in -O2 on self functions to make compilation faster
• Improve detection of invalid repeat..until expressions vs continue #1065

New Type Solver

• We now cache subtype test results to improve performance
• Improved operator inference mechanics (aka type families)
• Further work towards type states
• Work towards new non-strict mode continues

Native Codegen

• Instruction last use locations should follow the order in which blocks are lowered

New Contributors

• @SamuraiCrow made their first contribution in #1064

Full Changelog: 0.598...0.599