improvement: Suggest to add using as a code action

This should add the code action to both Metals and Intellij.

I will try to go over the existing rewrites to see if we can add more actions easily.

Fixes #23071

Author: tgodzik

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

@@ -424,12 +424,17 @@ trait NoDisambiguation extends Message:
   withoutDisambiguation()
 
 /** The fallback `Message` containing no explanation and having no `kind` */
-final class NoExplanation(msgFn: Context ?=> String)(using Context) extends Message(ErrorMessageID.NoExplanationID) {
+final class NoExplanation(msgFn: Context ?=> String, actions: List[CodeAction] = List.empty)(using Context) extends Message(ErrorMessageID.NoExplanationID) {
   def msg(using Context): String = msgFn
   def explain(using Context): String = ""
   val kind: MessageKind = MessageKind.NoKind
 
+  override def actions(using Context): List[CodeAction] = actions
+
   override def toString(): String = msg
+
+  def withActions(actions: CodeAction*): NoExplanation =
+    new NoExplanation(msgFn, actions.toList)
 }
 
 /** The extractor for `NoExplanation` can be used to check whether any error

compiler/src/dotty/tools/dotc/typer/Migrations.scala

@@ -21,6 +21,8 @@ import NameKinds.ContextBoundParamName
 import rewrites.Rewrites.patch
 import util.Spans.Span
 import rewrites.Rewrites
+import dotty.tools.dotc.rewrites.Rewrites.ActionPatch
+import dotty.tools.dotc.util.SourcePosition
 
 /** A utility trait containing source-dependent deprecation messages
  *  and migrations.
@@ -139,14 +141,23 @@ trait Migrations:
       val rewriteMsg =
         if hasParentheses then
           Message.rewriteNotice("This code", mversion.patchFrom)
-        else
-          ""
-      report.errorOrMigrationWarning(
+        else ""
+      val message =
         em"""Implicit parameters should be provided with a `using` clause.$rewriteMsg
-            |To disable the warning, please use the following option: 
+            |To disable the warning, please use the following option:
             |  "-Wconf:msg=Implicit parameters should be provided with a `using` clause:s"
-            |""", 
-        pt.args.head.srcPos, mversion)
+            |"""
+      val codeAction = CodeAction(
+        title = "Add `using` clause",
+        description = None,
+        patches = List(ActionPatch(pt.args.head.startPos.sourcePos, "using "))
+      )
+      val withActions = message.withActions(codeAction)
+      report.errorOrMigrationWarning(
+        withActions,
+        pt.args.head.srcPos,
+        mversion
+      )
       if hasParentheses && mversion.needsPatch then
         patch(Span(pt.args.head.span.start), "using ")
   end implicitParams

compiler/test/dotty/tools/dotc/reporting/CodeActionTest.scala

@@ -54,6 +54,19 @@ class CodeActionTest extends DottyTest:
          |""".stripMargin
       )
 
+  @Test def addUsingClause =
+    checkCodeAction(
+      """|object Test:
+         |  def foo(implicit a: Int) = a
+         |  foo(123)
+         |""".stripMargin,
+      "Add `using` clause",
+      """|object Test:
+         |  def foo(implicit a: Int) = a
+         |  foo(using 123)
+         |""".stripMargin
+      )
+
   @Test def insertMissingCases =
     checkCodeAction(
       code =

tests/neg/i22440.check

@@ -3,5 +3,5 @@
   |            ^
   |            Implicit parameters should be provided with a `using` clause.
   |            This code can be rewritten automatically under -rewrite -source 3.7-migration.
-  |            To disable the warning, please use the following option: 
+  |            To disable the warning, please use the following option:
   |              "-Wconf:msg=Implicit parameters should be provided with a `using` clause:s"

tests/warn/i22440.check

@@ -3,5 +3,5 @@
   |            ^
   |            Implicit parameters should be provided with a `using` clause.
   |            This code can be rewritten automatically under -rewrite -source 3.7-migration.
-  |            To disable the warning, please use the following option: 
+  |            To disable the warning, please use the following option:
   |              "-Wconf:msg=Implicit parameters should be provided with a `using` clause:s"

tests/warn/i22731.check

@@ -3,11 +3,11 @@
   |        ^^^^^^^^
   |        Implicit parameters should be provided with a `using` clause.
   |        This code can be rewritten automatically under -rewrite -source 3.7-migration.
-  |        To disable the warning, please use the following option: 
+  |        To disable the warning, please use the following option:
   |          "-Wconf:msg=Implicit parameters should be provided with a `using` clause:s"
 -- Warning: tests/warn/i22731.scala:7:6 --------------------------------------------------------------------------------
 7 |  foo { () => 43 } // warn
   |      ^^^^^^^^^^^^
   |      Implicit parameters should be provided with a `using` clause.
-  |      To disable the warning, please use the following option: 
+  |      To disable the warning, please use the following option:
   |        "-Wconf:msg=Implicit parameters should be provided with a `using` clause:s"