From daee3e1c695795d60dcef6380cf388c5d41de5e5 Mon Sep 17 00:00:00 2001
From: Albert Meltzer <7529386+kitbellew@users.noreply.github.com>
Date: Sun, 6 Oct 2024 20:00:17 -0700
Subject: [PATCH] ConvertToNewScala3Syntax: remove `:_`/`@_` as unit

---
 .../rewrite/ConvertToNewScala3Syntax.scala    | 23 +++++++++++++++----
 .../src/test/resources/scala3/Vararg.stat     | 14 +----------
 .../test/scala/org/scalafmt/FormatTests.scala |  2 +-
 3 files changed, 20 insertions(+), 19 deletions(-)

diff --git a/scalafmt-core/shared/src/main/scala/org/scalafmt/rewrite/ConvertToNewScala3Syntax.scala b/scalafmt-core/shared/src/main/scala/org/scalafmt/rewrite/ConvertToNewScala3Syntax.scala
index 2395d18e7c..cc45cb6bf1 100644
--- a/scalafmt-core/shared/src/main/scala/org/scalafmt/rewrite/ConvertToNewScala3Syntax.scala
+++ b/scalafmt-core/shared/src/main/scala/org/scalafmt/rewrite/ConvertToNewScala3Syntax.scala
@@ -34,7 +34,16 @@ private class ConvertToNewScala3Syntax(implicit val ftoks: FormatTokens)
       style: ScalafmtConfig,
   ): Option[Replacement] = Option {
     val flag = style.rewrite.scala3.newSyntax
-    def left = ftoks.prevNonComment(ft).left
+    def pft = ftoks.prevNonComment(ft)
+    def left = pft.left
+
+    def removeAndClaimUnderscore(): Replacement = {
+      val nft = ftoks.nextNonCommentAfter(ft)
+      if (nft.right.is[Token.Underscore]) removeToken(nft.idx :: Nil) else null
+    }
+    def removeUnderscoreIfPreviousRemoved(): Replacement =
+      if (session.isRemovedOnLeft(pft, ok = true)) removeToken else null
+
     ft.right match {
 
       case _: Token.LeftParen if flag.control && dialect.allowQuietSyntax =>
@@ -47,15 +56,19 @@ private class ConvertToNewScala3Syntax(implicit val ftoks: FormatTokens)
 
       case _: Token.Colon
           if flag.deprecated && dialect.allowPostfixStarVarargSplices =>
+        // trick: to get "*", just remove ":" and "_"
         ft.meta.rightOwner match {
-          case t: Term.Repeated if isSimpleRepeated(t) => removeToken // trick: to get "*", just remove ":" and "_"
+          case t: Term.Repeated if isSimpleRepeated(t) =>
+            removeAndClaimUnderscore()
+          case Pat.Bind(_, _: Pat.SeqWildcard) => removeAndClaimUnderscore()
           case _ => null
         }
 
       case _: Token.At
           if flag.deprecated && dialect.allowPostfixStarVarargSplices =>
+        // trick: to get "*", just remove "@" and "_"
         ft.meta.rightOwner match {
-          case Pat.Bind(_, _: Pat.SeqWildcard) => removeToken // trick: to get "*", just remove "@" and "_"
+          case Pat.Bind(_, _: Pat.SeqWildcard) => removeAndClaimUnderscore()
           case _ => null
         }
 
@@ -68,10 +81,10 @@ private class ConvertToNewScala3Syntax(implicit val ftoks: FormatTokens)
                 t.parent.is[Type.ArgClause] => replaceTokenIdent("?", ft.right)
           case t: Term.Repeated
               if dialect.allowPostfixStarVarargSplices && isSimpleRepeated(t) =>
-            removeToken // see above, under Colon
+            removeUnderscoreIfPreviousRemoved()
           case t: Pat.SeqWildcard
               if dialect.allowPostfixStarVarargSplices &&
-                t.parent.is[Pat.Bind] => removeToken // see above, under At
+                t.parent.is[Pat.Bind] => removeUnderscoreIfPreviousRemoved()
           case _ => null
         }
 
diff --git a/scalafmt-tests/shared/src/test/resources/scala3/Vararg.stat b/scalafmt-tests/shared/src/test/resources/scala3/Vararg.stat
index 58d40e039e..c4b2818d53 100644
--- a/scalafmt-tests/shared/src/test/resources/scala3/Vararg.stat
+++ b/scalafmt-tests/shared/src/test/resources/scala3/Vararg.stat
@@ -32,23 +32,11 @@ node match {
     false
 }
 >>>
-test does not parse: [dialect scala3] illegal start of simple pattern
-          Node3(TERMREFpkg, Seq("scala.annotation.internal"), zxc),
-          children:*
-        )
-        ^
-      ) =>
-    children.filterNot(_.tag == IMPORT).exists {
-      case Node3(TYPEDEF, Seq("SourceFile"), _) => true
-====== full result: ======
 node match {
   case Node3(
         PACKAGE,
         _,
-        Seq(
-          Node3(TERMREFpkg, Seq("scala.annotation.internal"), zxc),
-          children:*
-        )
+        Seq(Node3(TERMREFpkg, Seq("scala.annotation.internal"), zxc), children*)
       ) =>
     children.filterNot(_.tag == IMPORT).exists {
       case Node3(TYPEDEF, Seq("SourceFile"), _) => true
diff --git a/scalafmt-tests/shared/src/test/scala/org/scalafmt/FormatTests.scala b/scalafmt-tests/shared/src/test/scala/org/scalafmt/FormatTests.scala
index bb4cd62974..cc9b150f1e 100644
--- a/scalafmt-tests/shared/src/test/scala/org/scalafmt/FormatTests.scala
+++ b/scalafmt-tests/shared/src/test/scala/org/scalafmt/FormatTests.scala
@@ -137,7 +137,7 @@ class FormatTests extends FunSuite with CanRunTests with FormatAssertions {
   override def afterAll(): Unit = {
     logger.debug(s"Total explored: ${Debug.explored}")
     if (!onlyUnit && !onlyManual)
-      assertEquals(Debug.explored, 1785581, "total explored")
+      assertEquals(Debug.explored, 1785622, "total explored")
     val results = debugResults.result()
     // TODO(olafur) don't block printing out test results.
     // I don't want to deal with scalaz's Tasks :'(