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@menarulalam menarulalam commented Jun 20, 2025

What's Changed?

We've been hard at work fixing bugs and introducing new features!

VM

  • Include constant-folding information in Luau cost model for inlining and loop unrolling
    • ~1% improvement in compile times

New Type Solver

if foo.bar then
    -- Prior to this release, this would be `typeof(foo) & { bar: ~(false?) }
    -- Now, this is `typeof(foo) & { read bar: ~(false?) }
end
  • The type function keyof should respect the empty string as a property, as in:
-- equivalent to type Foo =""
type Foo = keyof<{ [""]: number }>
  • Descend into literals to report subtyping errors for function calls: this both improves bidirectional inference and makes errors more specific. Before, the error reporting for a table with incorrect members passed to a function would cite the entire table, but now it only cites the members that are incorrectly typed.
  • Fixes a case where intersecting two tables without any common properties would create never, instead of a table with both of their properties.

Internal Contributors

Co-authored-by: Ariel Weiss aaronweiss@roblox.com
Co-authored-by: Hunter Goldstein hgoldstein@roblox.com
Co-authored-by: James McNellis jmcnellis@roblox.com
Co-authored-by: Sora Kanosue skanosue@roblox.com
Co-authored-by: Talha Pathan tpathan@roblox.com
Co-authored-by: Vighnesh Vijay vvijay@roblox.com
Co-authored-by: Vyacheslav Egorov vegorov@roblox.com

hgoldstein and others added 30 commits January 10, 2025 09:13
Note: Fixed conflicts by hand in:
- Analysis/src/ConstraintGenerator.cpp
- CodeGen/src/OptimizeConstProp.cpp
- VM/src/lmathlib.cpp
- tests/Conformance.test.cpp
a03c92095f6 #unflagged CLI-141149 Added lua_clonetable (#97902)
d66c43f36aa #flagged CLI-140903: Do not crash on duplicate keys in table literals (#97833)
8a2687f1690 #nonprod Luau: fix a test configuration issue breaking OSS CI. (#97878)
7add6d9dde9 #nojira CI-debugger revert #unflagged CLI-132461 Luau: refactor subtyping to also include the generic mapping it came up with. (#97872)
0c731fd3cc4 #flag-removal Clip `LuauNewSolverVisitErrorExprLvalues` (#96942)
2fe783b9615 #unflagged CLI-132461 Luau: refactor subtyping to also include the generic mapping it came up with. (#97803)
0cc41a0afae #unflagged CLI-141053 Luau buffer readbits/writebits implementation for big endian machines (#97826)
ae50bf04f99 #nonprod CLI-140027 Simplify require-by-string path resolution, fix bug when running CLI tools on unprefixed path (#97468)
77004599a6f #flag-removal Cleanup Luau VM and Compiler flags (#97799)
86777e269dd #flag-removal Remove LuauUserTypeFunPrintToError, LuauUserTypeFunNoExtraConstraint, LuauUserTypeFunUpdateAllEnvs, LuauUserTypeFunThreadBuffer and LuauUserTypeFunExportedAndLocal (#97624)
349b133fdc4 #nojira CI-debugger revert #unflagged CLI-132461 Luau: refactor subtyping to also include the generic mapping it came up with. (#97759)
2e820646ffa #flagged CLI-139615: Treat user defined type functions as opaque in eqSatSimplify (#96897)
c0845205e37 #flag-removal CLI-140688 Clean up `FFlagLuauIntersectNormalsNeedsToTrackResourceLimits` as `true`. (#97719)
3e07876a043 #flagged CLI-140571: Track interior free table types generated during constraint solving (#97498)
199b558dc36 #unflagged CLI-132461 Luau: refactor subtyping to also include the generic mapping it came up with. (#95646)
fd9255f62d3 #nonprod CLI-140762 unittest for fragment ac crash (#97669)
e9c710e017f #flag-removal FFlagLuauStoreCommentsForDefinitionFiles (#93359)
b184b940d55 CLI-140702 #unflagged Fix most clang-tidy warnings in TypeChecker2 (#97604)
1fc857f1bb3 CLI-140489 #unflagged Fix a potential hash collision bug in StringCache. (#97539)
58f62f900a2 #nonprod Some new unit testing macros for Luau tests. (#97336)
ab43a354b25 #flag-removal Remove LuauVectorMetatable and LuauVectorDefinitionsExtra (#97528)
c4c28694390 #flagged CLI-140485 Do not retain the Def/RefinementKey arenas when retainFullTypeGraphs is false (#97422)
This test fails due to a bad interaction when `FFlagLuauStoreCSTData` is
enabled, whilst `FFlagLexerFixInterpStringStart` is disabled.
The OSS test suite, when run with `--fflags=true`, enables all
flags starting with a `Luau` prefix, but does not enable any other flag.

To resolve this, we explicitly enable both fflags for the failing
interpolated string test cases. As a consequence, we technically lose
the check that these tests pass when all flags are disabled.
andyfriesen and others added 25 commits May 9, 2025 16:08
\# General

* Expose an optional `get_alias` API as an alternative to `get_config` in Luau.Require and Luau.RequireNavigator.
* Improve the Luau CLI's virtual filesystem implementation to fix bugs related to `init.luau`. Fixes #1816

\# New Type Solver

* Avoid double reporting errors when erroneous arguments are provided to
  type functions.
* Fix some instances of unresovable cyclic type functions in loops by only considering the first loop cycles. This results in some type inference inaccuracies when the type of a variable in loop through multiple iterations. Fixes #1413.
* Better generalize free types that have meaningful lower and upper bounds, especially for table indexers.
* Instead of highling the entire table, we now report more specific errors when assigning or returning table literal types.
* Inference for functions with generic type packs is greatly improved.
* Fix some internal compiler exceptions when using type-stating functions like `table.freeze` in `if _ then _ else _` expressions and short circuiting binary operations.
* More consistently simplify unions of primitive types, especially in array-like and dictionary-like tables.
* Fix a crash when type checking an erroneous type alias containing `typeof` with a type assertion expression, as in:
  ```
  type MyTable = {}
  -- This will error at type checking time as it's a duplicate
  type MyTable = typeof(setmetatable(SomeTable :: {}, SomeMetaTable));
  ```
* Fix a crash when inferring the type of an index expression where the indexee is invalid (e.g. `nil`).

\# Runtime
* Avoid throwing an exception from `luau_load` if we run out of memory.
* Type functions are no longer compiled and included in bytecode.
* Fix some instances of Luau C API functions reading invalid debug information (generally when the first or last instruction of a block was being inspected).
* Avoid potential signed integer overflow when doing bounds checks on tables.
* Support 16 byte aligned userdata objects when system allocation alignment is also 16 bytes
@menarulalam menarulalam marked this pull request as ready for review June 20, 2025 22:17
@menarulalam menarulalam merged commit 8fe64db into master Jun 20, 2025
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Type refinements should not apply to lvalues. Type state prevents table key from being changed in new solver
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