Replace scala.quoted.qctx with scala.quoted.reflect

[nicolasstucki]

The only reason we added qctx was to have a simple way to access the reflection in context using qctx.reflect. There are no other uses of this method. It is much simpler for users if they a provided with the method reflect that those the same as qctx.reflect. The name qctx is also a bit obscure and is not that simple to identify in the API.

To use reflection inside a method

def f(using QuoteContext) = { // or (using qctx: QuoteContext)
-   import qctx.reflect._ // equivalent to import qctx.reflect._
+   import reflect._ // equivalent to import qctx.reflect._
  ...
}

or to use reflection in the signature of a method

- def f(using QuoteContext)(tree: qctx.reflect.Tree): qctx.reflect.Position = ...
+ def f(using QuoteContext)(tree: reflect.Tree): reflect.Position = ...

[liufengyun]

Is the Scala 3 feature going to stay? The worry I have is that either Scala 3 drops the feature or it makes Scala 3 difficult to drop the feature.

[nicolasstucki]

Which feature?

[liufengyun]

Which feature?

I mean the following:

def reflect(using qctx: QuoteContext): qctx.reflect.type = qctx.reflect

[smarter]

I don't understand how this works, reflect is a def so it's not stable, and we're only supposed to allow import from stable prefixes unless something changed? (Also when I see import reflect._ I would assume it's about scala.reflect).

[smarter]

#10295

[nicolasstucki]

That def returns a stable path and it is that path that is taken into account for the stability.

def reflect(using q: QuoteContext): q.reflect.type = q.reflect

def f(using q: QuoteContext)
  // reflect.Tree   ==>    reflect(q).Tree   ==>   q.reflect.Tree
  import reflect.Tree

[nicolasstucki]

Is the Scala 3 feature going to stay? The worry I have is that either Scala 3 drops the feature or it makes Scala 3 difficult to drop the feature.

Which feature?

I mean the following:

def reflect(using qctx: QuoteContext): qctx.reflect.type = qctx.reflect

We need to support that, it is equivalent to a more concrete version of summon.

inline def summon[T](using x: T): x.type = x

If we would drop the feature we would have to remove summon.

[liufengyun]

What about #10295 ? There is no precedent in the language where we can import an unstable prefix. Or at least, with inline and checks?

Meanwhile, it seems to me that import qctx.reflect._ is better than import reflect._, as the former tells some information about the relationship between qctx and reflect, while the latter makes me wonder what's the magic behind.