docs: add in a few docs in the newly added classes

Author: ckipp01

compiler/src/dotty/tools/dotc/reporting/CodeAction.scala

@@ -2,6 +2,13 @@ package dotty.tools.dotc.reporting
 
 import dotty.tools.dotc.rewrites.Rewrites.ActionPatch
 
+/** A representation of a code action / fix that can be used by tooling to
+  * apply a fix to their code.
+  *
+  * @param title The title of the fix, often showed to a user in their editor.
+  * @param description An optional description of the fix.
+  * @param patches The patches that this fix contains.
+  */
 case class CodeAction(
   title: String,
   description: java.util.Optional[String],

compiler/src/dotty/tools/dotc/reporting/Message.scala

@@ -414,6 +414,9 @@ abstract class Message(val errorId: ErrorMessageID)(using Context) { self =>
    */
   def showAlways = false
 
+  /** A list of actions attatched to this message to address the issue this
+    * message represents.
+    */
   def actions(using Context): java.util.List[CodeAction] =
     java.util.Collections.emptyList
 

compiler/src/dotty/tools/dotc/rewrites/Rewrites.scala

@@ -20,6 +20,14 @@ object Rewrites {
     def delta = replacement.length - (span.end - span.start)
   }
 
+  /** A special type of Patch that instead of just a span, contains the
+    * full SourcePosition. This is useful when being used by
+    * [[dotty.tools.dotc.reporting.CodeAction]] or if the patch doesn't
+    * belong to the same file that the actual issue it's addressing is in.
+    *
+    * @param srcPos The SourcePosition of the patch.
+    * @param replacement The Replacement that should go in that position.
+    */
   case class ActionPatch(srcPos: SourcePosition, replacement: String)
 
   private class Patches(source: SourceFile) {

sbt-bridge/src/dotty/tools/xsbt/Problem.java

@@ -69,6 +69,10 @@ public List<xsbti.Action> actions() {
     if (_actions.isEmpty()) {
       return java.util.Collections.emptyList();
     } else {
+      // Same as with diagnosticCode, we need to ensure we don't create the actual
+      // Action until we are here to ensure that when using an older version of sbt/zinc
+      // with the new versions of the compiler, this doesn't blow up because this is
+      // never getting called.
       return _actions
               .stream()
               .map(action -> new Action(action.title(), action.description(), toWorkspaceEdit(action.patches())))