mirror of
https://github.com/luau-lang/luau.git
synced 2024-12-13 05:20:38 +00:00
96 lines
3 KiB
Markdown
96 lines
3 KiB
Markdown
---
|
|
layout: single
|
|
title: "Luau Recap: November 2022"
|
|
---
|
|
|
|
While the team is busy to bring some bigger things in the future, we have made some small improvements this month.
|
|
|
|
[Cross-posted to the [Roblox Developer Forum](https://devforum.roblox.com/t/luau-recap-november-2022/).]
|
|
|
|
## Analysis improvements
|
|
|
|
We have improved tagged union type refinements to only include unhandled type cases in the `else` branch of the `if` statement:
|
|
|
|
```lua
|
|
type Ok<T> = { tag: "ok", value: T }
|
|
type Err = { tag: "error", msg: string }
|
|
type Result<T> = Ok<T> | Err
|
|
|
|
function unwrap<T>(r: Result<T>): T?
|
|
if r.tag == "ok" then
|
|
return r.value
|
|
else
|
|
-- Luau now understands that 'r' here can only be the 'Err' part
|
|
print(r.msg)
|
|
return nil
|
|
end
|
|
end
|
|
```
|
|
|
|
For better inference, we updated the definition of `Enum.SomeType:GetEnumItems()` to return `{Enum.SomeType}` instead of common `{EnumItem}` and the return type of `next` function now includes the possibility of key being `nil`.
|
|
|
|
Finally, if you use `and` operator on non-boolean values, `boolean` type will no longer be added by the type inference:
|
|
|
|
```lua
|
|
local function f1(a: number?)
|
|
-- 'x' is still a 'number?' and doesn't become 'boolean | number'
|
|
local x = a and 5
|
|
end
|
|
```
|
|
|
|
## Error message improvements
|
|
|
|
We now give an error when built-in types are being redefined:
|
|
|
|
```lua
|
|
type string = number -- Now an error: Redefinition of type 'string'
|
|
```
|
|
|
|
We also had a parse error missing in case you forgot your default type pack parameter value. We accepted the following code silently without raising an issue:
|
|
|
|
```lua
|
|
type Foo<T... = > = nil -- Now an error: Expected type, got '>'
|
|
```
|
|
|
|
Error about function argument count mismatch no longer points at the last argument, but instead at the function in question.
|
|
So, instead of:
|
|
|
|
```lua
|
|
function myfunction(a: number, b:number) end
|
|
myfunction(123)
|
|
~~~
|
|
```
|
|
|
|
We now highlight this:
|
|
|
|
```lua
|
|
function myfunction(a: number, b:number) end
|
|
myfunction(123)
|
|
~~~~~~~~~~
|
|
```
|
|
|
|
If you iterate over a table value that could also be `nil`, you get a better explanation in the error message:
|
|
|
|
```lua
|
|
local function f(t: {number}?)
|
|
for i,v in t do -- Value of type {number}? could be nil
|
|
--...
|
|
end
|
|
end
|
|
```
|
|
Previously it was `Cannot call non-function {number}?` which was confusing.
|
|
|
|
And speaking of confusing, some of you might have seen an error like `Type 'string' could not be converted into 'string'`.
|
|
|
|
This was caused by Luau having both a primitive type `string` and a table type coming from `string` library. Since the way you can get the type of the `string` library table is by using `typeof(string)`, the updated error message will mirror that and report `Type 'string' could not be converted into 'typeof(string)'`.
|
|
|
|
|
|
Parsing now recovers with a more precise error message if you forget a comma in table constructor spanning multiple lines:
|
|
|
|
```lua
|
|
local t = {
|
|
a = 1
|
|
b = 2 -- Expected ',' after table constructor element
|
|
c = 3 -- Expected ',' after table constructor element
|
|
}
|
|
```
|