Fix issue with macro results having unexpected source switches

Problem seems to have been derived from the fact that we would only
remap the source of the outermost tree inserted in a Hole, instead of
going through the whole tree inserted there. This meant that when
inserting `Block` with `Imports` in the contents, the Block node would
have a new source assigned (causing a source change encoded in the
TASTy), and all contents would still have the previous source assigned
(causing more source changes encoded).

Now we reassign sources to nodes recursively, meaning that only
the outermost node has a source change assigned in TASTy.

Author: jchyb

compiler/src/dotty/tools/dotc/quoted/PickledQuotes.scala

@@ -115,8 +115,16 @@ object PickledQuotes {
 
               // We need to make sure a hole is created with the source file of the surrounding context, even if
               // it filled with contents a different source file.
-              if filled.source == ctx.source then filled
-              else filled.cloneIn(ctx.source).withSpan(tree.span)
+              val sourceReassigner = new TreeMapWithImplicits {
+                override def transform(innerTree: tpd.Tree)(using Context) = {
+                  innerTree match
+                    case EmptyTree => innerTree // cannot change span of EmptyTree
+                    case _ =>
+                      if innerTree.source == tree.source then innerTree
+                      else super.transform(innerTree.cloneIn(tree.source).withSpan(tree.span))
+                }
+              }
+              sourceReassigner.transform(filled)
             else
               // For backwards compatibility with 3.0.x and 3.1.x
               // In 3.2.0+ all these holes are handled by `spliceTypes` before we call `spliceTerms`.

scaladoc-testcases/src/tests/i22265/macro.scala

@@ -0,0 +1,13 @@
+import scala.quoted._
+
+object TestBuilder:
+  // transparent is needed
+  transparent inline def apply(inline expr: Unit): Any =
+    ${ TestBuilder.processTests('expr) }
+
+  def processTests(using Quotes)(body: Expr[Unit]): Expr[Any] =
+    import quotes.reflect._
+    body.asTerm match {
+      case Inlined(_, _, bindings) =>
+        '{ ${bindings.asExpr}; () }
+    }

scaladoc-testcases/src/tests/i22265/main.scala

@@ -0,0 +1,4 @@
+object breaks {
+  TestBuilder:
+    import List.empty
+}