Fix perfect forwarding in TypedAllocator::allocate.
#2008
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alexmccord
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TypedAllocator::allocate.
hgoldstein
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Sep 26, 2025
# New Solver * Avoid bidirectional inference always forcing constraints for simple code such as the example below. Fixes #2017. ```luau type Suit = "Hearts" | "Spades" | "Clubs" | "Diamonds" local getSuits(): { Suit } return { "Hearts", "Spades", "Clubs", "Diamonds" } end ``` * Iterating over an empty pack, such as in the below example, should error but still allow type inference to complete. ```luau local function foo() end -- has type `() -> ()` for _ in foo() do end -- Errors, as you can't iterate over `()`, but type inference still completes. ``` * Implement arity based overload selection: this allows for overloaded functions with generics to more consistently infer reasonable results. For example: ```luau -- This code no longer errors as we determine that the first overload to -- table.insert is what the author intended. table.insert({} :: { any }, 42) ``` * Allow the`table` type to be a subtype of generic tables. This means code like the following no longer raises a type error: ```luau local function doSomething(t: unknown) if type(t) == "table" then -- Prior we would error as `table` is not a subtype of a generic table -- Also works with `pairs` and similar builtin functions. local foo, bar = next(t) end end ``` * Descend into intersection types when performing bidirectional inference, this allows us to correctly bidirectionally infer code like: ```luau type A = { foo: "a" } type B = { bar: "b" } type AB = A & B -- No longer errors as the literals "a" and "b" will be inferred to be their singleton types. local t: AB = { foo = "a", bar = "b" } ``` * #2008 * Fix intersections between table types and extern types to preserve intersections when either type contains an indexer, fixing a regression introduced when trying to refine table and extern types more precisely: ```luau function f(obj: { [any]: any }, functionName: string) if typeof(obj) == "userdata" then -- No longer errors as we still have a `class & { [any]: any }` rather than a `class` local _ = obj[functionName] end end ``` * Separated recursion limits for different parts of the new solver. No immediate changes, but this creates more tools to tamp down on stack overflows without affecting other subsystems. # Runtime * Implement "stackless" `pcall` / `xpcall` in yieldable contexts: this lets recursive calls to `pcall` nest further, erroring at the Luau call stack limit (20000 calls as of this writing) rather than the C call stack limit (200 calls as of this writing) --- Co-authored-by: Ariel Weiss <aaronweiss@roblox.com> Co-authored-by: Hunter Goldstein <hgoldstein@roblox.com> Co-authored-by: Sora Kanosue <skanosue@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> --------- Co-authored-by: Varun Saini <61795485+vrn-sn@users.noreply.github.com> Co-authored-by: Alexander Youngblood <ayoungblood@roblox.com> Co-authored-by: Menarul Alam <malam@roblox.com> Co-authored-by: Aviral Goel <agoel@roblox.com> Co-authored-by: Vighnesh <vvijay@roblox.com> Co-authored-by: Vyacheslav Egorov <vegorov@roblox.com> Co-authored-by: Ariel Weiss <aaronweiss@roblox.com> Co-authored-by: Andy Friesen <afriesen@roblox.com>
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The original wasn't actually allowing universal references and if you have a datatype with a deleted copy constructor, the template substitution would fail here. This lets me use
TypedAllocatorfor some type that isn't copyable. I doubt there would be any performance difference due to copy elision anyway.