Mark CanThrow @experimental

Author: odersky

library/src-bootstrapped/scala/CanThrow.scala

@@ -1,19 +1,22 @@
 package scala
 import language.experimental.erasedDefinitions
-import annotation.implicitNotFound
+import annotation.{implicitNotFound, experimental}
 
 /** An ability class that allows to throw exception `E`. When used with the
  *  experimental.saferExceptions feature, a `throw Ex()` expression will require
  *  a given of class `CanThrow[Ex]` to be available.
  */
+@experimental
 @implicitNotFound("The ability to throw exception ${E} is missing.\nThe ability can be provided by one of the following:\n - A using clause `(using CanThrow[${E}])`\n - A `canThrow` clause in a result type such as `X canThrow ${E}`\n - an enclosing `try` that catches ${E}")
 erased class CanThrow[-E <: Exception]
 
 /** A helper type to allow syntax like
  *
  *    def f(): T canThrow Ex
  */
+@experimental
 infix type canThrow[R, +E <: Exception] = CanThrow[E] ?=> R
 
+@experimental
 object unsafeExceptions:
   given canThrowAny: CanThrow[Exception] = ???

library/src/scala/runtime/stdLibPatches/language.scala

@@ -50,12 +50,14 @@ object language:
 
     /** Experimental support for using indentation for arguments
      */
+    @compileTimeOnly("`fewerBraces` can only be used at compile time in import statements")
     object fewerBraces
 
     /** Experimental support for typechecked exception capabilities
      *
      *  @see [[https://dotty.epfl.ch/docs/reference/experimental/canthrow]]
      */
+    @compileTimeOnly("`saferExceptions` can only be used at compile time in import statements")
     object saferExceptions
 
   end experimental