0.655

What's Changed

• Convert Luau heap dumps to Chrome heap snapshots by @jkelaty-rbx in #1554

New Solver

• Type functions should be able to signal whether or not irreducibility is due to an error
• Do not generate extra expansion constraint for uninvoked user-defined type functions
• Print in a user-defined type function reports as an error instead of logging to stdout
• Many e-graphs bugfixes and performance improvements
• Many general bugfixes and improvements to the new solver as a whole
• Fixed issue with used-defined type functions not being able to call each other
• Infer types of globals under new type solver

Fragment Autocomplete

• Miscellaneous fixes to make interop with the old solver better

Runtime

• Support disabling specific built-in functions from being fast-called or constant-evaluated (Closes #1538)
  • New compiler option disabledBuiltins accepts a list of library function names like "tonumber" or "math.cos"
• Added constant folding for vector arithmetic
• Added constant propagation and type inference for vector globals (Fixes #1511)
  • New compiler option librariesWithKnownMembers accepts a list of libraries for members of which a request for constant value and/or type will be made
  • libraryMemberTypeCb callback is called to get the type of a global, return one of the LuauBytecodeType values. 'boolean', 'number', 'string' and 'vector' type are supported.
  • libraryMemberConstantCb callback is called to setup the constant value of a global. To set a value, C API luau_set_compile_constant_* or C++ API setCompileConstant* functions should be used.

New Contributors

• @jkelaty-rbx made their first contribution in #1554

Full Changelog: 0.654...0.655

What's changed

---

Co-authored-by: Aaron Weiss aaronweiss@roblox.com
Co-authored-by: Andy Friesen afriesen@roblox.com
Co-authored-by: Aviral Goel agoel@roblox.com
Co-authored-by: Daniel Angel danielangel@roblox.com
Co-authored-by: Jonathan Kelaty jkelaty@roblox.com
Co-authored-by: Hunter Goldstein hgoldstein@roblox.com
Co-authored-by: Varun Saini vsaini@roblox.com
Co-authored-by: Vighnesh Vijay vvijay@roblox.com
Co-authored-by: Vyacheslav Egorov vegorov@roblox.com

0.654

What's Changed?

• Support dead store elimination for STORE_VECTOR instruction
• Fix parser hang when a separator is used between Luau class
  declaration properties
• Provide properties and metatable for built-in vector type definition
  to fix type errors
• Fix Fragment Autocomplete to ensure correct parentheses insertion
  behavior.
• Add support for 'thread' and 'buffer' primitive types in user-defined
  type functions

---

Co-authored-by: Andy Friesen afriesen@roblox.com
Co-authored-by: Hunter Goldstein hgoldstein@roblox.com
Co-authored-by: Vighnesh Vijay vvijay@roblox.com
Co-authored-by: Vyacheslav Egorov vegorov@roblox.com

New Contributors

• @Ramdoys made their first contribution in #1532

Full Changelog: 0.653...0.654

0.653

What's Changed?

• Optimized the vector dot product by up to 24%
• Allow for x/y/z/X/Y/Z vector field access by registering a vector metatable
  with an __index method (Fixes #1521)
• Fixed a bug preventing consistent recovery from parse errors in table types
• Optimized k*n and k+n when types are known
• Allow fragment autocomplete to handle cases like the automatic insertion of
  parens, keywords, strings, etc., while maintaining a correct relative positioning

New Solver

• Allow for nil assignment to tables and classes with indexers

---

Internal Contributors:

Co-authored-by: Aaron Weiss aaronweiss@roblox.com
Co-authored-by: Andy Friesen afriesen@roblox.com
Co-authored-by: Aviral Goel agoel@roblox.com
Co-authored-by: Hunter Goldstein hgoldstein@roblox.com
Co-authored-by: Varun Saini vsaini@roblox.com
Co-authored-by: Vighnesh Vijay vvijay@roblox.com
Co-authored-by: Vyacheslav Egorov vegorov@roblox.com

Full Changelog: 0.652...0.653

0.652

What's Changed

• Add support for mixed-mode type checking, which allows modules checked
  in the old type solver to be checked and autocompleted by the new one.
• Generalize RequireResolver to support require-by-string semantics in
  luau-analyze.
• Fix a bug in incremental autocomplete where DefIds associated with
  index expressions were not correctly picked up.
• Fix a bug that prevented "complex" types in generic parameters (for
  example, local x: X<(() -> ())?>).
• CodeGen: Rewrite dot product lowering using a dedicated IR instruction by @zeux in #1512
• Fix mesh-normal-vector benchmark array access by @zeux in #1514
• Remove noexcepts from Config by @vrn-sn in #1523

Issues fixed

• #1507
• #1518

New Contributors

• @vrn-sn made their first contribution in #1523

Full Changelog: 0.651...0.652

---

Internal Contributors:

Co-authored-by: Aaron Weiss aaronweiss@roblox.com
Co-authored-by: Andy Friesen afriesen@roblox.com
Co-authored-by: Hunter Goldstein hgoldstein@roblox.com
Co-authored-by: Varun Saini vsaini@roblox.com
Co-authored-by: Vighnesh Vijay vvijay@roblox.com

0.651

What's Changed

• Fragment Autocomplete: a new API allows for type checking a small fragment of code against an existing file, significantly speeding up autocomplete performance in large files.
• Requiring a path with a ".lua" or ".luau" extension will now have a bespoke error suggesting to remove said extension.
• Fixes a bug in which whether two Luau::Symbols are equal depends on whether the new solver is enabled.
• Fix definition module name & location by @checkraisefold in #1495
• Pre-populate/duplicate check class definitions (new solver) by @checkraisefold in #1493
• Set the defining module even when the new solver cloned the type. by @aatxe in #1506
• Replace old site urls by @Barocena in #1505

New Solver

• E-Graphs have landed: this is an ongoing approach to make the new type solver simplify types in a more consistent and principled manner, based on similar work (see: https://egraphs-good.github.io/).
• Adds support for exporting / local user type functions (previously they were always exported).
• Fixes a set of bugs in which the new solver will fail to complete inference for simple expressions with just literals and operators.

General Updates

New Contributors

• @checkraisefold made their first contribution in #1495
• @Barocena made their first contribution in #1505

Full Changelog: 0.650...651

---

Internal Contributors:

Co-authored-by: Aaron Weiss aaronweiss@roblox.com
Co-authored-by: Andy Friesen afriesen@roblox.com
Co-authored-by: David Cope dcope@roblox.com
Co-authored-by: Hunter Goldstein hgoldstein@roblox.com
Co-authored-by: Varun Saini vsaini@roblox.com
Co-authored-by: Vighnesh Vijay vvijay@roblox.com
Co-authored-by: Vyacheslav Egorov vegorov@roblox.com

0.650

What's Changed

• New vector library! See https://rfcs.luau.org/vector-library.html for details
• Replace the use of non-portable strnlen with memchr. strnlen is not part of any C or C++ standard.
• Introduce lua_newuserdatataggedwithmetatable for faster tagged userdata creation of userdata with metatables registered with lua_setuserdatametatable

Old Solver

• It used to be the case that a module's result type would unconditionally be inferred to be any if it imported any module that participates in any import cycle. This is now fixed.

New Solver

• Improve inference of table.freeze: We now infer read-only properties on tables after they have been frozen.
• We now correctly flag cases where string.format is called with 0 arguments.
• Fix a bug in user-defined type functions where table properties could be lost if the table had a metatable
• Reset the random number seed for each evaluation of a type function
• We now retry subtyping arguments if it failed due to hidden variadics.

---

Internal Contributors

Co-authored-by: Aaron Weiss aaronweiss@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: Hunter Goldstein hgoldstein@roblox.com
Co-authored-by: Vyacheslav Egorov vegorov@roblox.com

Full Changelog: 0.649...0.650

0.649

What's new?

• More progress on the upcoming analysis API for fragment type inference.
• Fix a bug in type normalization where intersection did not appropriately respect resource limits (affects new and old type solvers).
• Allow type normalization to track cyclic pairs of types in inhabitance checks.
• Fix a bug in the old type solver where Unifier did not necessarily live long enough.
• Check the coroutine stack size before resuming in the Luau VM.

New Type Solver

• Add support for typestating table.freeze and updated its behavior to transform the given table types into being marked read-only for all of its properties. More to come here for indexers when we add support for read-only indexers.
• Fix #1453 by adding a missing arity check to string.format.
• Fix a crash when editing caused by invalid AST states not being visited properly by the type solver.
• Fix a crash in type simplification caused by missing follow calls.

---

Internal Contributors:

Co-authored-by: Aaron Weiss aaronweiss@roblox.com
Co-authored-by: Andy Friesen afriesen@roblox.com
Co-authored-by: Hunter Goldstein hgoldstein@roblox.com
Co-authored-by: Vighnesh Vijay vvijay@roblox.com
Co-authored-by: Vyacheslav Egorov vegorov@roblox.com

0.648

What's new

• Added math.map function to the standard library, based on RFC for math.map
• FileResolver can provide an implementation of getRequireSuggestions to provide auto-complete suggestions for require-by-string

New Solver

• In user-defined type functions, readproperty and writeproperty will return nil instead of erroring if property is not found
• Fixed incorrect scope of variadic arguments in the data-flow graph
• Fixed multiple assertion failures

---

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

Full Changelog: 0.647...0.648

0.647

What's Changed

• Rename type field of AstStatTypeAlias in JSON Encoder by @Dekkonot in #1461
• Support function attributes in luau-ast by @Dekkonot in #1466
• Fix an old solver crash that occurs in the presence of cyclic requires()

New Solver

• Improvements to Luau user-defined type function library
• Avoid asserting on unexpected metatable types
• Properties in user defined type functions should have a consistent iteration order - in this case it is insertion ordering

Runtime

• Track VM allocations for telemetry

---

Co-authored-by: Aaron Weiss aaronweiss@roblox.com
Co-authored-by: Andy Friesen afriesen@roblox.com
Co-authored-by: Hunter Goldstein hgoldstein@roblox.com
Co-authored-by: James McNellis jmcnellis@roblox.com
Co-authored-by: Varun Saini vsaini@roblox.com
Co-authored-by: Vighnesh Vijay vvijay@roblox.com
Co-authored-by: Vyacheslav Egorov vegorov@roblox.com

Full Changelog: 0.646...0.647

0.646

What's Changed?

• 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 luau-lang/rfcs#56 for details.

New Solver

• Fix many crashes in the new solver (thanks you for your bug reports!)
• 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

Full Changelog: 0.645...0.646