From a08c3409b8ca0ac335f1ffd0f200f1be372859fa Mon Sep 17 00:00:00 2001
From: vegorov-rbx <75688451+vegorov-rbx@users.noreply.github.com>
Date: Mon, 31 Jul 2023 13:02:24 -0700
Subject: [PATCH] Luau Recap: July 2023 (#993)

If this does make it to the Roblox forum, I think I will cut intro about
new type solver and JIT.


[Rendered](https://github.com/vegorov-rbx/luau/blob/post-recap-july-2023/docs/_posts/2023-07-28-luau-recap-july-2023.md)


[Preview](https://vegorov-rbx.github.io/luau/2023/07/28/luau-recap-july-2023.html)
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+---
+layout: single
+title:  "Luau Recap: July 2023"
+---
+
+Our team is still spending a lot of time working on upcoming replacement for our type inference engine as well as working on native code generation to improve runtime performance.
+
+However, we also worked on unrelated improvements during this time that are summarized here.
+
+[Cross-posted to the [Roblox Developer Forum](https://devforum.roblox.com/t/luau-recap-july-2023/).]
+
+## Analysis improvements
+
+Indexing table intersections using `x["prop"]` syntax has been fixed and no longer reports a false positive error:
+
+```lua
+type T = { foo: string } & { bar: number }
+local x: T = { foo = "1", bar = 2 }
+
+local y = x["bar"] -- This is no longer an error
+```
+
+Generic `T...` type is now convertible to `...any` variadic parameter.
+
+This solves issues people had with variadic functions and variadic argument:
+
+```lua
+local function foo(...: any)
+    print(...)
+end
+
+local function bar<T...>(...: T...)
+    foo(...) -- This is no longer an error
+end
+```
+
+We have also improved our general typechecking performance by ~17% and by additional ~30% in modules with complex types.
+
+Other fixes include:
+
+* Fixed issue with type `T?` not being convertible to `T | T` or `T?` which could've generated confusing errors
+* Return type of `os.date` is now inferred as `DateTypeResult` when argument is "*t" or "!*t"
+
+## Runtime improvements
+
+Out-of-memory exception handling has been improved.
+`xpcall` handlers will now actually be called with a "not enough memory" string and whatever string/object they return will be correctly propagated.
+
+Other runtime improvements we've made:
+
+* Performance of `table.sort` was improved further. It now guarantees N*log(N) time complexity in the worst case
+* Performance of `table.concat` was improved by ~5-7%
+* Performance of `math.noise` was improved by ~30%
+* Inlining of functions is now possible even when they used to compute their own arguments
+* Improved logic for determining whether inlining a function or unrolling a loop is profitable
+
+## Autocomplete improvements
+
+An issue with exported types not being suggested is now fixed.
+
+## Debugger improvements
+
+We have fixed the search for the closest executable breakpoint line.
+
+Previously, breakpoints might have been skipped in `else` blocks at the end of a function.
+This simplified example shows the issue:
+
+```lua
+local function foo(isIt)
+    if isIt then
+        print("yes")
+    else
+        -- When 'true' block exits the function, breakpoint couldn't be placed here
+        print("no")
+    end
+end
+```
+
+## Thanks
+
+A very special thanks to all of our open source contributors:
+
+* [Petri Häkkinen](https://github.com/petrihakkinen)
+* [JohnnyMorganz](https://github.com/JohnnyMorganz)
+* [Gael](https://github.com/TheGreatSageEqualToHeaven)
+* [Jan](https://github.com/Jan200101)
+* [Alex Orlenko](https://github.com/khvzak)
+* [mundusnine](https://github.com/mundusnine)
+* [Ben Mactavsin](https://github.com/BenMactavsin)
+* [RadiatedExodus](https://github.com/RealEthanPlayzDev)
+* [Lodinu Kalugalage](https://github.com/imlodinu)
+* [MagelessMayhem](https://github.com/MagelessMayhem)
+* [Someon1e](https://github.com/Someon1e)