Language

• Introducing an experimental feature to make tables "exact" by default. See https://github.com/luau-lang/rfcs/pull/11 for full details, but the gist is to differentiate between tables that may have extraneous fields and tables that do not. We believe that this behavior better aligns with user expectations, and allows us to make the type system more predictable.

  :::luau -- This table may have extra fields type Inexact = { x: number, y: number, ... } -- This table does not have extra fields type Exact = { x: number, y: number }

  local : Inexact = { x = 3, y = 4, foo = "spooky" } -- OK! local : Exact = { x = 3, y = 4, foo = "spooky" } -- Not OK!

• if local is still experimental but is moving closer to a full release.

Analysis

• Removed Luau::Set, now entirely subsumed by the new DenseHashSet implementation.
• Fixed an internal error that could occur when processing exceptionally large types ("Internal recursion counter limit exceeded in ReferenceCountInitializer").

• Fixed a bug in function normalization that meant we'd use argument types as return types:

  :::luau function g(x : (() -> string | number) & (() -> number | boolean)) local z : () -> () = x -- This should not be allowed end

Runtime

• Fixed an issue where OOMing during table re-hashing or freezing could leave the underlying table in an unexpected state.
• When dumping bytecode, upvalues are now prefixed with U
• Fixed integer.idiv(x, y) not being floored in some configurations, resulting in differing behavior across the interpreter, NCG backends, and constant folding.
• Add array iteration fast-path to A64 FORGLOOP lowering by @green-real in https://github.com/luau-lang/luau/pull/2683
• Freeze vector metatable in luaL_sandbox if it is set by @PhoenixWhitefire in https://github.com/luau-lang/luau/pull/2583
• Fix optional tagged userdata types not being remapped at load time by @green-real in https://github.com/luau-lang/luau/pull/2699
• Optimize string.split by @gemtool in https://github.com/luau-lang/luau/pull/2981
• Fix x64 regalloc converting a stack spill on reload by @green-real in https://github.com/luau-lang/luau/pull/2987

Etc.

• Add CMake options for four-wide and double-precision vectors. by @xCynDev in https://github.com/luau-lang/luau/pull/2622
• Fix missing direct includes by @Aesthete in https://github.com/luau-lang/luau/pull/2687
• Fix CMake configuration when tests are disabled on MSVC by @mrcjkb in https://github.com/luau-lang/luau/pull/2980

New Contributors

• @xCynDev made their first contribution in https://github.com/luau-lang/luau/pull/2622
• @Aesthete made their first contribution in https://github.com/luau-lang/luau/pull/2687
• @mrcjkb made their first contribution in https://github.com/luau-lang/luau/pull/2980
• @gemtool made their first contribution in https://github.com/luau-lang/luau/pull/2981

Co-authored-by: Andreas Haeberlen andreas.haeberlen@roblox.com Co-authored-by: Andy Friesen afriesen@roblox.com Co-authored-by: Annie Tang annietang@roblox.com Co-authored-by: Ariel Weiss arielweiss@roblox.com Co-authored-by: Hunter Goldstein hgoldstein@roblox.com Co-authored-by: Ilya Rezvov irezvov@roblox.com Co-authored-by: Sora Kanosue skanosue@roblox.com Co-authored-by: Thomas Schollenberger tschollenberger@roblox.com Co-authored-by: Vighnesh Vijay vvijay@roblox.com Co-authored-by: Vyacheslav Egorov vegorov@roblox.com

Full Changelog: https://github.com/luau-lang/luau/compare/0.739...0.740