Update proposals/NNNN-global-actor-isolated-types-usability.md

simanerush · rjmccall · web-flow · commit 669f1d1196f5 · 2024-04-02T07:51:43.000-07:00
Co-authored-by: John McCall &lt;rjmccall@gmail.com&gt;
diff --git a/proposals/NNNN-global-actor-isolated-types-usability.md b/proposals/NNNN-global-actor-isolated-types-usability.md
@@ -48,7 +48,9 @@ func test() {
 }
 ```
 
-In the above code, the closure is global-actor-isolated, so it cannot be called concurrently. The compiler should be able to infer the `@Sendable` attribute. Because of the same reason, globally isolated closures should be allowed to capture non-`Sendable` values.
+Requiring both a global actor attribute and `@Sendable` creates an unfortunate pile-up of attributes, and it would be better for Swift to just infer `@Sendable` from the global actor attribute.
+
+Because a globally-isolated closure cannot be called concurrently, it's safe for it to capture non-`Sendable` values even if it's implicitly `@Sendable`.  Such values just need to be transferred to the global actor's region (if they aren't there already).  This also applies to closures that are isolated to a specific actor reference.
 
 
 Finally, the current diagnostic for a global-actor-isolated subclass of a non-isolated superclass is too restrictive:

Original file line number	Diff line number	Diff line change
`@@ -48,7 +48,9 @@ func test() {`
`48`	`48`	`}`
`49`	`49`	```
`50`	`50`
`51`		-In the above code, the closure is global-actor-isolated, so it cannot be called concurrently. The compiler should be able to infer the `@Sendable` attribute. Because of the same reason, globally isolated closures should be allowed to capture non-`Sendable` values.
	`51`	+Requiring both a global actor attribute and `@Sendable` creates an unfortunate pile-up of attributes, and it would be better for Swift to just infer `@Sendable` from the global actor attribute.
	`52`	`+`
	`53`	+Because a globally-isolated closure cannot be called concurrently, it's safe for it to capture non-`Sendable` values even if it's implicitly `@Sendable`. Such values just need to be transferred to the global actor's region (if they aren't there already). This also applies to closures that are isolated to a specific actor reference.
`52`	`54`
`53`	`55`
`54`	`56`	`Finally, the current diagnostic for a global-actor-isolated subclass of a non-isolated superclass is too restrictive:`