April 2022 recap (#470)

docs/_posts/2022-05-02-luau-recap-april-2022.md

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+---
+layout: single
+title:  "Luau Recap: April 2022"
+---
+
+Luau is our new language that you can read more about at [https://luau-lang.org](https://luau-lang.org).
+
+[Cross-posted to the [Roblox Developer Forum](https://devforum.roblox.com/t/luau-recap-april-2022/).]
+
+It's been a bit of a quiet month.  We mostly have small optimizations and bugfixes for you.
+
+It is now allowed to define functions on sealed tables that have string indexers.  These functions will be typechecked against the indexer type.  For example, the following is now valid:
+
+```lua
+local a : {[string]: () -> number} = {}
+
+function b.y() return 4 end -- OK
+```
+
+Autocomplete will now provide string literal suggestions for singleton types.  eg
+
+```lua
+local function f(x: "a" | "b") end
+f("_") -- suggest "a" and "b"
+```
+
+Improve error recovery in the case where we encounter a type pack variable in a place where one is not allowed.  eg `type Foo<A...> = { value: A... }`
+
+When code does not pass enough arguments to a variadic function, the error feedback is now better.
+
+For example, the following script now produces a much nicer error message:
+```lua
+type A = { [number]: number }
+type B = { [number]: string }
+
+local a: A = { 1, 2, 3 }
+
+-- ERROR: Type 'A' could not be converted into 'B'
+--     caused by:
+--       Property '[indexer value]' is not compatible. Type 'number' could not be converted into 'string'
+local b: B = a
+```
+
+If the following code were to error because `Hello` was undefined, we would erroneously include the comment in the span of the error.  This is now fixed.
+```lua
+type Foo = Hello -- some comment over here
+```
+
+Fix a crash that could occur when strict scripts have cyclic require() dependencies.
+
+Add an option to autocomplete to cause it to abort processing after a certain amount of time has elapsed.