Update generic-constraints.md

fixed grammatical errors

docs/generic-constraints.md

@@ -2,7 +2,7 @@
 ## Summary
 Introduce syntax to extend/constrain the type of a generic.
 ## Motivation
-Luau currently does not provide a way in order to constrain the type of a generic without direct assertions, and even so, would not properly infer the right type.
+Luau currently does not provide a way in order to constrain the type of a generic.
 ```luau
 local qux = { foo = 10, bar = "string" }
 
@@ -15,12 +15,14 @@ local foo = getProperty( qux, "foo" )
 local bar = getProperty( qux, "bar" )
 -- bar: number | string
 ```
-This is wrong! We would expect foo to be a number, with bar being a string.
-In the following snippet, it is impossible to tell whether or not the key variable is the same as the one being used to index T in the callback.
+Type interference believes that either value could be a number or string as keyof<T> is too broad.
+
 ```luau
 local function callbackProperty<T>( object: T, key: keyof<T>, callback: (index<T, keyof<T>>) -> () )
 ....
 ```
+It is impossible to tell whether or not the key variable is the same as the one being used to index T in the callback, and thus Luau infers that it could be a number | string.
+
 ## Design
 The design of this would take inspiration from TypeScript's `extends`, where instead of the additional keyword, we would use `&`.
 ```luau
@@ -36,7 +38,6 @@ local bar = getProperty( qux, "bar" )
 -- bar: string
 ```
 This would correctly infer the type of the each key's value.
-The following snippet would also thus be correctly inferred.
 ```luau
 local qux = { foo = 10, bar = "string" }
 
@@ -48,7 +49,9 @@ callbackProperty( qux, "foo", function( foo )
   -- foo: number -- this is expected!
 end)
 ```
-An alternative syntax could be the following, but does not satisfy current requirements about `:` only being used inside `()` and `{}`, and personally does not look as good.
+This would also be correctly inferred as index<T, K> would correctly result in the type of the field.
+
+An alternative syntax could use `:` instead of `&`. However, this would not match the current semantics of `:` and using `&` implies a union of types.
 ```luau
 local function getProperty<T, K: keyof<T>>( object: T, key: K ) .... end
 local function callbackProperty<T, K: keyof<T>>( object: T, key: K, callback: (index<T, K>) -> () ) .... end
@@ -58,4 +61,4 @@ local function callbackProperty<T, K: keyof<T>>( object: T, key: K, callback: (i
 - Adding an extra use to `&` could make its usage more confusing to novices.
 ## Alternatives
 - Don't do this; this would make it impossible for functions like above to be able to be inferred correctly. Just let people explicitly type their variables instead of inferring types. This makes code more verbose and would likely not allow for full optimization.
-- Use overloaded functions as previously mentioned, but this wouldn't allow the usage of a generic, would require users to add a new overload for each key.
+- Use overloaded functions as previously mentioned, but this would not allow the usage of a generic, and would thus require users to add a new overload for each key.