Make CanThrow a SharedCapability

Author: odersky

library/src/scala/CanThrow.scala

@@ -8,7 +8,7 @@ import annotation.{implicitNotFound, experimental, capability}
  */
 @experimental
 @implicitNotFound("The capability to throw exception ${E} is missing.\nThe capability can be provided by one of the following:\n - Adding a using clause `(using CanThrow[${E}])` to the definition of the enclosing method\n - Adding `throws ${E}` clause after the result type of the enclosing method\n - Wrapping this piece of code with a `try` block that catches ${E}")
-erased class CanThrow[-E <: Exception] extends caps.Capability
+erased class CanThrow[-E <: Exception] extends caps.SharedCapability
 
 @experimental
 object unsafeExceptions:

tests/pos-custom-args/captures/erased-methods.scala

@@ -7,14 +7,14 @@ class Ex2 extends Exception("Ex2")
 class Ex3 extends Exception("Ex3")
 
 def foo8a(i: Int) =
-  (erased xx1: CanThrow[Ex2]^) ?=> throw new Ex2
+  (erased xx1: CanThrow[Ex2]) ?=> throw new Ex2
 
 def foo9a(i: Int)
-  : (erased x$0: CanThrow[Ex3]^)
-    ?=> (erased x$1: CanThrow[Ex2]^)
-    ?=> (erased x$2: CanThrow[Ex1]^)
+  : (erased x$0: CanThrow[Ex3])
+    ?=> (erased x$1: CanThrow[Ex2])
+    ?=> (erased x$2: CanThrow[Ex1])
     ?=> Unit
-  = (erased x$1: CanThrow[Ex3]^)
-     ?=> (erased x$2: CanThrow[Ex2]^)
-     ?=> (erased x$3: CanThrow[Ex1]^)
+  = (erased x$1: CanThrow[Ex3])
+     ?=> (erased x$2: CanThrow[Ex2])
+     ?=> (erased x$3: CanThrow[Ex1])
      ?=> throw new Ex3