From 2430188225c1f8889362a673f759ba7c559c20f5 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Pawe=C5=82=20Per=C5=82akowski?=
 <17816164+Perl99@users.noreply.github.com>
Date: Fri, 5 Sep 2025 14:51:37 +0200
Subject: [PATCH 1/2] Improve symbol order in completions provided by the
 presentation compiler

Extension methods that are not in the same file are placed after all Product methods and even after extension methods like "ensuring". This PR penalizes the following methods, so that they are no longer at the top of the suggestions:
- scala.Product.*
- scala.Equals.*
- scala.Predef.ArrowAssoc.*
- scala.Predef.Ensuring.*
- scala.Predef.StringFormat.*
- scala.Predef.nn
- scala.Predef.runtimeChecked

Resolves https://github.com/scalameta/metals/issues/7642
---
 .../tools/pc/completions/Completions.scala    | 22 +++++++++-
 .../completion/CompletionExtensionSuite.scala | 41 +++++++++++++++++++
 .../pc/tests/completion/CompletionSuite.scala | 18 ++++----
 3 files changed, 70 insertions(+), 11 deletions(-)

diff --git a/presentation-compiler/src/main/dotty/tools/pc/completions/Completions.scala b/presentation-compiler/src/main/dotty/tools/pc/completions/Completions.scala
index 61a93dc1bccb..2f5a46d19a86 100644
--- a/presentation-compiler/src/main/dotty/tools/pc/completions/Completions.scala
+++ b/presentation-compiler/src/main/dotty/tools/pc/completions/Completions.scala
@@ -766,6 +766,13 @@ class Completions(
     ).flatMap(_.alternatives.map(_.symbol)).toSet
   )
 
+  private lazy val EqualsClass: ClassSymbol = requiredClass("scala.Equals")
+  private lazy val ArrowAssocClass: ClassSymbol = requiredClass("scala.Predef.ArrowAssoc")
+  private lazy val EnsuringClass: ClassSymbol = requiredClass("scala.Predef.Ensuring")
+  private lazy val StringFormatClass: ClassSymbol = requiredClass("scala.Predef.StringFormat")
+  private lazy val nnMethod: Symbol = defn.ScalaPredefModule.requiredMethod("nn")
+  private lazy val runtimeCheckedMethod: Symbol = defn.ScalaPredefModule.requiredMethod("runtimeChecked")
+
   private def isNotLocalForwardReference(sym: Symbol)(using Context): Boolean =
     !sym.isLocalToBlock ||
       !sym.srcPos.isAfter(completionPos.originalCursorPosition) ||
@@ -784,6 +791,17 @@ class Completions(
       (sym.isField && !isJavaClass && !isModuleOrClass) || sym.getter != NoSymbol
     catch case _ => false
 
+    def isInheritedFromScalaLibrary(sym: Symbol) =
+      sym.owner == defn.AnyClass || 
+        sym.owner == defn.ObjectClass ||
+        sym.owner == defn.ProductClass ||
+        sym.owner == EqualsClass ||
+        sym.owner == ArrowAssocClass ||
+        sym.owner == EnsuringClass ||
+        sym.owner == StringFormatClass ||
+        sym == nnMethod ||
+        sym == runtimeCheckedMethod
+
     def symbolRelevance(sym: Symbol): Int =
       var relevance = 0
       // symbols defined in this file are more relevant
@@ -801,7 +819,7 @@ class Completions(
         case _ =>
 
       // symbols whose owner is a base class are less relevant
-      if sym.owner == defn.AnyClass || sym.owner == defn.ObjectClass
+      if isInheritedFromScalaLibrary(sym)
       then relevance |= IsInheritedBaseMethod
       // symbols not provided via an implicit are more relevant
       if sym.is(Implicit) ||
@@ -813,7 +831,7 @@ class Completions(
       // accessors of case class members are more relevant
       if !sym.is(CaseAccessor) then relevance |= IsNotCaseAccessor
       // public symbols are more relevant
-      if !sym.isPublic then relevance |= IsNotCaseAccessor
+      if !sym.isPublic then relevance |= IsNotPublic
       // synthetic symbols are less relevant (e.g. `copy` on case classes)
       if sym.is(Synthetic) && !sym.isAllOf(EnumCase) then
         relevance |= IsSynthetic
diff --git a/presentation-compiler/test/dotty/tools/pc/tests/completion/CompletionExtensionSuite.scala b/presentation-compiler/test/dotty/tools/pc/tests/completion/CompletionExtensionSuite.scala
index b41084af4a8e..16535381165c 100644
--- a/presentation-compiler/test/dotty/tools/pc/tests/completion/CompletionExtensionSuite.scala
+++ b/presentation-compiler/test/dotty/tools/pc/tests/completion/CompletionExtensionSuite.scala
@@ -437,3 +437,44 @@ class CompletionExtensionSuite extends BaseCompletionSuite:
          |""".stripMargin,
       assertSingleItem = false
     )
+
+  @Test def `extension-for-case-class` =
+    check(
+      """|case class Bar():
+         |  def baz(): Unit = ???
+         |
+         |object Bar:
+         |  extension (f: Bar)
+         |    def qux: Unit = ???
+         |
+         |object Main:
+         |  val _ = Bar().@@
+         |""".stripMargin,
+      """|baz(): Unit
+         |copy(): Bar
+         |qux: Unit
+         |asInstanceOf[X0]: X0
+         |canEqual(that: Any): Boolean
+         |equals(x$0: Any): Boolean
+         |getClass[X0 >: Bar](): Class[? <: X0]
+         |hashCode(): Int
+         |isInstanceOf[X0]: Boolean
+         |productArity: Int
+         |productElement(n: Int): Any
+         |productElementName(n: Int): String
+         |productElementNames: Iterator[String]
+         |productIterator: Iterator[Any]
+         |productPrefix: String
+         |synchronized[X0](x$0: X0): X0
+         |toString(): String
+         |->[B](y: B): (Bar, B)
+         |ensuring(cond: Boolean): Bar
+         |ensuring(cond: Bar => Boolean): Bar
+         |ensuring(cond: Boolean, msg: => Any): Bar
+         |ensuring(cond: Bar => Boolean, msg: => Any): Bar
+         |nn: `?1`.type
+         |runtimeChecked: `?2`.type
+         |formatted(fmtstr: String): String
+         |→[B](y: B): (Bar, B)
+         | """.stripMargin
+    )
diff --git a/presentation-compiler/test/dotty/tools/pc/tests/completion/CompletionSuite.scala b/presentation-compiler/test/dotty/tools/pc/tests/completion/CompletionSuite.scala
index 4dad18a78181..c02d217e45d9 100644
--- a/presentation-compiler/test/dotty/tools/pc/tests/completion/CompletionSuite.scala
+++ b/presentation-compiler/test/dotty/tools/pc/tests/completion/CompletionSuite.scala
@@ -109,18 +109,9 @@ class CompletionSuite extends BaseCompletionSuite:
          |tabulate[A](n: Int)(f: Int => A): List[A]
          |unapplySeq[A](x: List[A] @uncheckedVariance): UnapplySeqWrapper[A]
          |unfold[A, S](init: S)(f: S => Option[(A, S)]): List[A]
-         |->[B](y: B): (List.type, B)
-         |ensuring(cond: Boolean): List.type
-         |ensuring(cond: List.type => Boolean): List.type
-         |ensuring(cond: Boolean, msg: => Any): List.type
-         |ensuring(cond: List.type => Boolean, msg: => Any): List.type
          |fromSpecific(from: Any)(it: IterableOnce[Nothing]): List[Nothing]
          |fromSpecific(it: IterableOnce[Nothing]): List[Nothing]
-         |nn: List.type
-         |runtimeChecked scala.collection.immutable
          |toFactory(from: Any): Factory[Nothing, List[Nothing]]
-         |formatted(fmtstr: String): String
-         |→[B](y: B): (List.type, B)
          |iterableFactory[A]: Factory[A, List[A]]
          |asInstanceOf[X0]: X0
          |equals(x$0: Any): Boolean
@@ -129,6 +120,15 @@ class CompletionSuite extends BaseCompletionSuite:
          |isInstanceOf[X0]: Boolean
          |synchronized[X0](x$0: X0): X0
          |toString(): String
+         |->[B](y: B): (List.type, B)
+         |ensuring(cond: Boolean): List.type
+         |ensuring(cond: List.type => Boolean): List.type
+         |ensuring(cond: Boolean, msg: => Any): List.type
+         |ensuring(cond: List.type => Boolean, msg: => Any): List.type
+         |nn: List.type
+         |runtimeChecked scala.collection.immutable
+         |formatted(fmtstr: String): String
+         |→[B](y: B): (List.type, B)
          |""".stripMargin
     )
 

From 20c8a3282ec29ad2944320e6da54abf8a0f158f2 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Pawe=C5=82=20Per=C5=82akowski?=
 <17816164+Perl99@users.noreply.github.com>
Date: Fri, 12 Sep 2025 15:22:41 +0200
Subject: [PATCH 2/2] Review fix

---
 .../src/main/dotty/tools/pc/completions/Completions.scala    | 5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/presentation-compiler/src/main/dotty/tools/pc/completions/Completions.scala b/presentation-compiler/src/main/dotty/tools/pc/completions/Completions.scala
index 2f5a46d19a86..72b65b3cadb9 100644
--- a/presentation-compiler/src/main/dotty/tools/pc/completions/Completions.scala
+++ b/presentation-compiler/src/main/dotty/tools/pc/completions/Completions.scala
@@ -15,6 +15,7 @@ import dotty.tools.dotc.ast.untpd
 import dotty.tools.dotc.core.Comments.Comment
 import dotty.tools.dotc.core.Constants.Constant
 import dotty.tools.dotc.core.Contexts.*
+import dotty.tools.dotc.core.Decorators.toTermName
 import dotty.tools.dotc.core.Denotations.SingleDenotation
 import dotty.tools.dotc.core.Flags
 import dotty.tools.dotc.core.Flags.*
@@ -770,8 +771,8 @@ class Completions(
   private lazy val ArrowAssocClass: ClassSymbol = requiredClass("scala.Predef.ArrowAssoc")
   private lazy val EnsuringClass: ClassSymbol = requiredClass("scala.Predef.Ensuring")
   private lazy val StringFormatClass: ClassSymbol = requiredClass("scala.Predef.StringFormat")
-  private lazy val nnMethod: Symbol = defn.ScalaPredefModule.requiredMethod("nn")
-  private lazy val runtimeCheckedMethod: Symbol = defn.ScalaPredefModule.requiredMethod("runtimeChecked")
+  private lazy val nnMethod: Symbol = defn.ScalaPredefModule.info.member("nn".toTermName).symbol
+  private lazy val runtimeCheckedMethod: Symbol = defn.ScalaPredefModule.info.member("runtimeChecked".toTermName).symbol
 
   private def isNotLocalForwardReference(sym: Symbol)(using Context): Boolean =
     !sym.isLocalToBlock ||