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Update syntax-metatable-type-annotation.md

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Alexander McCord 2022-03-01 14:59:04 -08:00 • committed by GitHub
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rfcs/syntax-metatable-type-annotation.md
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@ -169,6 +169,10 @@ setmetatable({
})
```
Another issue is the unfortunate wart in syntax with bounded quantification, for example if we want a generic to only range over types that defines a `__add` metamethod: (using invented notation) `<a: setmetatable({}, {__add: (a, a) -> a})>(a) -> a`.
This syntax also exposes an opportunity to write things like `setmetatable(Instance, { ... })` where `Instance` is a class type variable, forcing us to write in more code that produces a type error on nonsensical use of `setmetatable`.
### 2: `setmetatable<>`
```lua
@ -181,7 +185,7 @@ It still does not grant us any syntax to return the metatable of the type, or `n
This option would mean `withmetatable<>` and `getmetatable<>` are the first exported types in Luau's prelude, which is not something that we want to do at this time.
This option has the same issue as `setmetatable()` on formatting.
This option has the same issue as `setmetatable()` on formatting, unfortunate quirk in syntax with bounded quantification, and requires dealing with edge cases where `T` is not a table.
### 3: `{ @metatable {} }` (status quo when performing `Luau::toString`)