Allow selectDynamic and applyDynamic to be extension methods #17106
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sjrd
reviewed
Mar 15, 2023
| @@ -186,7 +186,7 @@ trait Dynamic { | |||
| // ($qual: Selectable).$selectorName("$name") | |||
| val base = | |||
| untpd.Apply( | |||
| untpd.TypedSplice(selectable.select(selectorName)).withSpan(fun.span), | |||
| untpd.Select(untpd.TypedSplice(selectable), selectorName).withSpan(fun.span), | |||
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That will indeed allow extension methods, but won't it also allow all sorts of other things? Like recursive structural lookups and insertion of implicit conversions? That seems too much (especially the recursive structural lookup).
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It will allow implicit conversions, and that's intentional. It will allow recursive structural lookup if selectDynamic is defined in the structural type. But I think that's a weird corner case, and I also see nothing wrong to support it.
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EDIT: That should have been applyDynamic.
odersky
changed the title
Allow selectDynamic and applyDynamic to be an extension methods when dispatching structurally. Fixes scala#17100
Given
```scala
trait Sel extends Dynamic
extension (s: Sel)
def selectDynamic(name: String) = ???
```
the following worked:
```scala
val sel = new Sel {}
val foo = sel.foo
```
but the following didn't:
```scala
val sel2 = (new Sel {}).asInstanceOf[Sel{ def foo: String }]
val foo2 = sel2.foo
```
The problem was that we recognized a structural dispatch and then required
the qualifier to be an instance of `Selectable`. But in fact, `Dynamic`
works just as well, and the mechanism is the same. It's just that
`Dynamic` is less type safe then `Selectable`.
prolativ
approved these changes
Mar 17, 2023
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Allow selectDynamic and applyDynamic to be extension methods when dispatching structurally.
Fixes #17100