0.729

General

• Introduced DenseHash2; this is based on LLVM's recent improvements to their own dense hash table implementation, detailed in this blog post. We hope for this to entirely replace DenseHash as, for our workloads, it is as-good or better than DenseHash, supports erasing elements, and does not require elements to be default constructible, meaning some uses of std::unordered_map can now be DenseHashMap.
• Document luau-compile -t flag in the help message by @ssobkowski in #2455
• fix: add missing AstExprConstantInteger visitor to AstJsonEncoder by @spxnso in #2442

Parser

• Parser: reject duplicated binary prefixes by @bytexenon in #2461

Analysis

• Fixed inference of higher order generic functions when, themselves, used with generic functions:

local function identity<T>(t: T)
    return t
end
-- Prior, `result` is of type `T?` and we error on `42` claiming its not of type `T`.
-- Now there are no errors and `result` is of type `number?`
local ok, result = pcall(identity, 42)

• Fixed a class of internal compiler errors that could occur when nesting type-state-ing functions:

local tbl = {}
-- In some cases we would throw an exception like "CG: AstExprLocal came before its declaration?"
setmetatable(tbl, setmetatable(tbl, {}))

• Indexing into refinements against any should now preserve the any-ness of the original value:

-- Prior the first two return statements would raise a type
-- checking error, as we'd claim they were `~nil`, dropping
-- the `*error-type*` part.
local function keyExtractor(item: any, index: number): string
    if typeof(item) == "table" and item.key ~= nil then
        return item.key
    end
    if typeof(item) == "table" and item.id ~= nil then
        return item.id
    end
    return tostring(index)
end

• Fix @deprecated attribute not propagating on anonymous functions in new solver by @JohnnyMorganz in #2332
• Track the local binding that a prefixed type reference is linked to by @JohnnyMorganz in #2334
• Add a luaL_checkudatatagged and lua_getuserdataname by @PhoenixWhitefire in #2483
• __tostring for type by @PhoenixWhitefire in #2525
• Correct types.singleton using lua_typename instead of luaL_typename by @PhoenixWhitefire in #2506

Runtime

• Fixed a garbage collection issue with lua_registeruserdatadirectfieldget, where depending on the GC phase, we may erroneously consider an allocated dispatch table to be unreachable.
• NCG: When replacing an instruction, we now more consistently attempt to substitute it with a precomputed value. E.g., if we replace an IR instruction with one that has already been computed, we can potentially emit a STORE rather than said instruction and an additional STORE.

New Contributors

• @spxnso made their first contribution in #2442
• @ssobkowski made their first contribution in #2455

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Co-authored-by: Andy Friesen afriesen@roblox.com
Co-authored-by: Annie Tang annietang@roblox.com
Co-authored-by: Hunter Goldstein hgoldstein@roblox.com
Co-authored-by: Ilya Rezvov irezvov@roblox.com
Co-authored-by: Thomas Schollenberger tschollenberger@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: 0.728...0.729