From 016eb9f9fa4128300fb9401baf46370d8577f62c Mon Sep 17 00:00:00 2001
From: Katarzyna Marek <kasia@marek.net>
Date: Fri, 8 Sep 2023 13:24:57 +0200
Subject: [PATCH 01/11] bugfix: highlight for enum type params

[Cherry-picked e08c70e9332a4193f6267ce16741d9fee8b8105b]
---
 .../src/main/dotty/tools/pc/PcCollector.scala | 35 +++++++++++-
 .../highlight/DocumentHighlightSuite.scala    | 57 ++++++++++++++++---
 2 files changed, 82 insertions(+), 10 deletions(-)

diff --git a/presentation-compiler/src/main/dotty/tools/pc/PcCollector.scala b/presentation-compiler/src/main/dotty/tools/pc/PcCollector.scala
index 274b0704674d..fda62cbb25e4 100644
--- a/presentation-compiler/src/main/dotty/tools/pc/PcCollector.scala
+++ b/presentation-compiler/src/main/dotty/tools/pc/PcCollector.scala
@@ -111,6 +111,33 @@ abstract class PcCollector[T](
   end adjust
 
   def symbolAlternatives(sym: Symbol) =
+    def member(parent: Symbol) = parent.info.member(sym.name).symbol
+    def primaryConstructorTypeParam(owner: Symbol) =
+      for
+        typeParams <- owner.primaryConstructor.paramSymss.headOption
+        param <- typeParams.find(_.name == sym.name)
+        if (param.isType)
+      yield param
+    def additionalForEnumTypeParam(enumClass: Symbol) =
+      if enumClass.is(Flags.Enum) then
+        val enumOwner =
+          if enumClass.is(Flags.Case)
+          then
+            Option.when(member(enumClass).is(Flags.Synthetic))(
+              enumClass.maybeOwner.companionClass
+            )
+          else Some(enumClass)
+        enumOwner.toSet.flatMap { enumOwner =>
+          val symsInEnumCases = enumOwner.children.toSet.flatMap(enumCase =>
+            if member(enumCase).is(Flags.Synthetic)
+            then primaryConstructorTypeParam(enumCase)
+            else None
+          )
+          val symsInEnumOwner =
+            primaryConstructorTypeParam(enumOwner).toSet + member(enumOwner)
+          symsInEnumCases ++ symsInEnumOwner
+        }
+      else Set.empty
     val all =
       if sym.is(Flags.ModuleClass) then
         Set(sym, sym.companionModule, sym.companionModule.companion)
@@ -129,7 +156,11 @@ abstract class PcCollector[T](
         ) ++ sym.allOverriddenSymbols.toSet
       // type used in primary constructor will not match the one used in the class
       else if sym.isTypeParam && sym.owner.isPrimaryConstructor then
-        Set(sym, sym.owner.owner.info.member(sym.name).symbol)
+        Set(sym, member(sym.maybeOwner.maybeOwner))
+          ++ additionalForEnumTypeParam(sym.maybeOwner.maybeOwner)
+      else if sym.isTypeParam then
+        primaryConstructorTypeParam(sym.maybeOwner).toSet
+          ++ additionalForEnumTypeParam(sym.maybeOwner) + sym
       else Set(sym)
     all.filter(s => s != NoSymbol && !s.isError)
   end symbolAlternatives
@@ -409,7 +440,7 @@ abstract class PcCollector[T](
          * All select statements such as:
          * val a = hello.<<b>>
          */
-        case sel: Select 
+        case sel: Select
           if sel.span.isCorrect && filter(sel) &&
             !isForComprehensionMethod(sel) =>
           occurrences + collect(
diff --git a/presentation-compiler/test/dotty/tools/pc/tests/highlight/DocumentHighlightSuite.scala b/presentation-compiler/test/dotty/tools/pc/tests/highlight/DocumentHighlightSuite.scala
index 4bf04ed1d0af..6ed5d6c636e3 100644
--- a/presentation-compiler/test/dotty/tools/pc/tests/highlight/DocumentHighlightSuite.scala
+++ b/presentation-compiler/test/dotty/tools/pc/tests/highlight/DocumentHighlightSuite.scala
@@ -758,8 +758,8 @@ class DocumentHighlightSuite extends BaseDocumentHighlightSuite:
         |  }
         |}""".stripMargin
     )
-  
-  @Test def `for-comp-map` = 
+
+  @Test def `for-comp-map` =
     check(
       """|object Main {
          |  val x = List(1).<<m@@ap>>(_ + 1)
@@ -770,7 +770,7 @@ class DocumentHighlightSuite extends BaseDocumentHighlightSuite:
          |""".stripMargin,
     )
 
-  @Test def `for-comp-map1` = 
+  @Test def `for-comp-map1` =
     check(
       """|object Main {
          |  val x = List(1).<<m@@ap>>(_ + 1)
@@ -782,7 +782,7 @@ class DocumentHighlightSuite extends BaseDocumentHighlightSuite:
          |""".stripMargin,
     )
 
-  @Test def `for-comp-foreach` = 
+  @Test def `for-comp-foreach` =
     check(
       """|object Main {
          |  val x = List(1).<<for@@each>>(_ => ())
@@ -793,7 +793,7 @@ class DocumentHighlightSuite extends BaseDocumentHighlightSuite:
          |""".stripMargin,
     )
 
-  @Test def `for-comp-withFilter` = 
+  @Test def `for-comp-withFilter` =
     check(
       """|object Main {
          |  val x = List(1).<<with@@Filter>>(_ => true)
@@ -805,7 +805,7 @@ class DocumentHighlightSuite extends BaseDocumentHighlightSuite:
          |""".stripMargin,
     )
 
-  @Test def `for-comp-withFilter1` = 
+  @Test def `for-comp-withFilter1` =
     check(
       """|object Main {
          |  val x = List(1).withFilter(_ => true).<<m@@ap>>(_ + 1)
@@ -817,7 +817,7 @@ class DocumentHighlightSuite extends BaseDocumentHighlightSuite:
          |""".stripMargin,
     )
 
-  @Test def `for-comp-flatMap1` = 
+  @Test def `for-comp-flatMap1` =
     check(
       """|object Main {
          |  val x = List(1).<<flat@@Map>>(_ => List(1))
@@ -830,7 +830,7 @@ class DocumentHighlightSuite extends BaseDocumentHighlightSuite:
          |""".stripMargin,
     )
 
-  @Test def `for-comp-flatMap2` = 
+  @Test def `for-comp-flatMap2` =
     check(
       """|object Main {
          |  val x = List(1).withFilter(_ => true).<<flat@@Map>>(_ => List(1))
@@ -1102,3 +1102,44 @@ class DocumentHighlightSuite extends BaseDocumentHighlightSuite:
          |val alpha = MyOption.<<MySome>>(1)
          |""".stripMargin,
     )
+
+  @Test def `type-params-in-enum` =
+    check(
+      """|enum MyOption[+<<A@@A>>]:
+         |  case MySome(value: <<AA>>)
+         |  case MyNone
+         |""".stripMargin,
+    )
+
+  @Test def `type-params-in-enum2` =
+    check(
+      """|enum MyOption[+<<AA>>]:
+         |  case MySome(value: <<A@@A>>)
+         |  case MyNone
+         |""".stripMargin,
+    )
+
+  @Test def `type-params-in-enum3` =
+    check(
+      """|enum MyOption[<<AA>>](v: <<AA>>):
+         |  def get: <<A@@A>> = ???
+         |  case MySome[AA](value: AA) extends MyOption[Int](1)
+         |""".stripMargin,
+    )
+
+  @Test def `type-params-in-enum4` =
+    check(
+      """|enum MyOption[+<<AA>>]:
+         |  def get: <<A@@A>> = ???
+         |  case MySome(value: <<AA>>)
+         |  case MyNone
+         |""".stripMargin,
+    )
+
+  @Test def `type-params-in-enum5` =
+    check(
+      """|enum MyOption[AA]:
+         |  def get: AA = ???
+         |  case MySome[<<AA>>](value: <<A@@A>>) extends MyOption[Int]
+         |""".stripMargin,
+    )

From 931cb921bff1796181151e5407a765462b65761a Mon Sep 17 00:00:00 2001
From: Katarzyna Marek <kasia@marek.net>
Date: Tue, 25 Apr 2023 13:56:14 +0200
Subject: [PATCH 02/11] bugfix: in semanticdb make synthetic apply
 disambiguator consistent with Scala 2 implementation

[Cherry-picked 7a44b59d8f733356d8050e8d122e933b7cac2813]
---
 .../semanticdb/SemanticSymbolBuilder.scala    |  2 +-
 .../semanticdb/expect/CaseClass.expect.scala  |  7 +++
 tests/semanticdb/expect/CaseClass.scala       |  7 +++
 tests/semanticdb/metac.expect                 | 53 +++++++++++++++++++
 4 files changed, 68 insertions(+), 1 deletion(-)
 create mode 100644 tests/semanticdb/expect/CaseClass.expect.scala
 create mode 100644 tests/semanticdb/expect/CaseClass.scala

diff --git a/compiler/src/dotty/tools/dotc/semanticdb/SemanticSymbolBuilder.scala b/compiler/src/dotty/tools/dotc/semanticdb/SemanticSymbolBuilder.scala
index c7b0dfd437db..0b92ebddb02c 100644
--- a/compiler/src/dotty/tools/dotc/semanticdb/SemanticSymbolBuilder.scala
+++ b/compiler/src/dotty/tools/dotc/semanticdb/SemanticSymbolBuilder.scala
@@ -84,7 +84,7 @@ class SemanticSymbolBuilder:
         else
           decls0
       end decls
-      val alts = decls.filter(_.isOneOf(Method | Mutable)).toList.reverse
+      val alts = decls.filter(_.isOneOf(Method | Mutable)).toList.reverse.partition(!_.is(Synthetic)).toList.flatten
       def find(filter: Symbol => Boolean) = alts match
         case notSym :: rest if !filter(notSym) =>
           val idx = rest.indexWhere(filter).ensuring(_ >= 0)
diff --git a/tests/semanticdb/expect/CaseClass.expect.scala b/tests/semanticdb/expect/CaseClass.expect.scala
new file mode 100644
index 000000000000..d0c509855c70
--- /dev/null
+++ b/tests/semanticdb/expect/CaseClass.expect.scala
@@ -0,0 +1,7 @@
+package caseclass
+
+case class CaseClass/*<-caseclass::CaseClass#*/(int1/*<-caseclass::CaseClass#int1.*/: Int/*->scala::Int#*/, int2/*<-caseclass::CaseClass#int2.*/: Int/*->scala::Int#*/)
+
+object CaseClass/*<-caseclass::CaseClass.*/:
+  def apply/*<-caseclass::CaseClass.apply().*/(int/*<-caseclass::CaseClass.apply().(int)*/: Int/*->scala::Int#*/): CaseClass/*->caseclass::CaseClass#*/ = CaseClass/*->caseclass::CaseClass.*/(int/*->caseclass::CaseClass.apply().(int)*/, 0)
+  def apply/*<-caseclass::CaseClass.apply(+1).*/(): CaseClass/*->caseclass::CaseClass#*/ = CaseClass/*->caseclass::CaseClass.*/(0, 0)
diff --git a/tests/semanticdb/expect/CaseClass.scala b/tests/semanticdb/expect/CaseClass.scala
new file mode 100644
index 000000000000..576678112353
--- /dev/null
+++ b/tests/semanticdb/expect/CaseClass.scala
@@ -0,0 +1,7 @@
+package caseclass
+
+case class CaseClass(int1: Int, int2: Int)
+
+object CaseClass:
+  def apply(int: Int): CaseClass = CaseClass(int, 0)
+  def apply(): CaseClass = CaseClass(0, 0)
diff --git a/tests/semanticdb/metac.expect b/tests/semanticdb/metac.expect
index e456b192e015..ee63e6c3d0df 100644
--- a/tests/semanticdb/metac.expect
+++ b/tests/semanticdb/metac.expect
@@ -477,6 +477,59 @@ Occurrences:
 [4:4..4:7): bar <- angiven/AnonymousGiven$package.bar().
 [4:14..4:17): Foo -> angiven/Foo#
 
+expect/CaseClass.scala
+----------------------
+
+Summary:
+Schema => SemanticDB v4
+Uri => CaseClass.scala
+Text => empty
+Language => Scala
+Symbols => 22 entries
+Occurrences => 16 entries
+
+Symbols:
+caseclass/CaseClass# => case class CaseClass extends Object with Product with Serializable { self: CaseClass => +8 decls }
+caseclass/CaseClass#_1(). => method _1 => Int
+caseclass/CaseClass#_2(). => method _2 => Int
+caseclass/CaseClass#`<init>`(). => primary ctor <init> (val param int1: Int, val param int2: Int): CaseClass
+caseclass/CaseClass#`<init>`().(int1) => val param int1: Int
+caseclass/CaseClass#`<init>`().(int2) => val param int2: Int
+caseclass/CaseClass#copy$default$1(). => method copy$default$1 => Int @uncheckedVariance
+caseclass/CaseClass#copy$default$2(). => method copy$default$2 => Int @uncheckedVariance
+caseclass/CaseClass#copy(). => method copy (param int1: Int, param int2: Int): CaseClass
+caseclass/CaseClass#copy().(int1) => param int1: Int
+caseclass/CaseClass#copy().(int2) => param int2: Int
+caseclass/CaseClass#int1. => val method int1 Int
+caseclass/CaseClass#int2. => val method int2 Int
+caseclass/CaseClass. => final object CaseClass extends Object { self: CaseClass.type => +5 decls }
+caseclass/CaseClass.apply(). => method apply (param int: Int): CaseClass
+caseclass/CaseClass.apply().(int) => param int: Int
+caseclass/CaseClass.apply(+1). => method apply (): CaseClass
+caseclass/CaseClass.apply(+2). => method apply (param int1: Int, param int2: Int): CaseClass
+caseclass/CaseClass.apply(+2).(int1) => param int1: Int
+caseclass/CaseClass.apply(+2).(int2) => param int2: Int
+caseclass/CaseClass.unapply(). => method unapply (param x$1: CaseClass): CaseClass
+caseclass/CaseClass.unapply().(x$1) => param x$1: CaseClass
+
+Occurrences:
+[0:8..0:17): caseclass <- caseclass/
+[2:11..2:20): CaseClass <- caseclass/CaseClass#
+[2:21..2:25): int1 <- caseclass/CaseClass#int1.
+[2:27..2:30): Int -> scala/Int#
+[2:32..2:36): int2 <- caseclass/CaseClass#int2.
+[2:38..2:41): Int -> scala/Int#
+[4:7..4:16): CaseClass <- caseclass/CaseClass.
+[5:6..5:11): apply <- caseclass/CaseClass.apply().
+[5:12..5:15): int <- caseclass/CaseClass.apply().(int)
+[5:17..5:20): Int -> scala/Int#
+[5:23..5:32): CaseClass -> caseclass/CaseClass#
+[5:35..5:44): CaseClass -> caseclass/CaseClass.
+[5:45..5:48): int -> caseclass/CaseClass.apply().(int)
+[6:6..6:11): apply <- caseclass/CaseClass.apply(+1).
+[6:15..6:24): CaseClass -> caseclass/CaseClass#
+[6:27..6:36): CaseClass -> caseclass/CaseClass.
+
 expect/Classes.scala
 --------------------
 

From ff12f9a4def5c8c6c1f83af668541ca2c9831dd0 Mon Sep 17 00:00:00 2001
From: Jamie Thompson <bishbashboshjt@gmail.com>
Date: Fri, 14 Jul 2023 12:33:39 +0200
Subject: [PATCH 03/11] reduce some warnings in semanticdb tests

[Cherry-picked bef7a4a81a2af9420fbbe3819ad028ef004c7aee]
---
 tests/semanticdb/expect/Enums.expect.scala  |  2 +-
 tests/semanticdb/expect/Enums.scala         |  2 +-
 tests/semanticdb/expect/Givens.expect.scala |  3 +-
 tests/semanticdb/expect/Givens.scala        |  3 +-
 tests/semanticdb/metac.expect               | 49 +++++++++++++--------
 5 files changed, 36 insertions(+), 23 deletions(-)

diff --git a/tests/semanticdb/expect/Enums.expect.scala b/tests/semanticdb/expect/Enums.expect.scala
index 3e1dc9087db7..404dd14b07d2 100644
--- a/tests/semanticdb/expect/Enums.expect.scala
+++ b/tests/semanticdb/expect/Enums.expect.scala
@@ -46,7 +46,7 @@ object Enums/*<-_empty_::Enums.*/:
   enum <:</*<-_empty_::Enums.`<:<`#*/[-A/*<-_empty_::Enums.`<:<`#[A]*/, B/*<-_empty_::Enums.`<:<`#[B]*/]:
     case Refl/*<-_empty_::Enums.`<:<`.Refl#*/[C/*<-_empty_::Enums.`<:<`.Refl#[C]*/]() extends (C/*->_empty_::Enums.`<:<`.Refl#[C]*/ <:</*->_empty_::Enums.`<:<`#*/ C/*->_empty_::Enums.`<:<`.Refl#[C]*/)
 
-  object <:</*<-_empty_::Enums.`<:<`.*/ :
+  object `<:</*<-_empty_::Enums.`<:<`.*/`:
     given [T/*<-_empty_::Enums.`<:<`.`given_<:<_T_T`().[T]*/]: (T/*->_empty_::Enums.`<:<`.`given_<:<_T_T`().[T]*/ <:</*->_empty_::Enums.`<:<`#*/ T/*->_empty_::Enums.`<:<`.`given_<:<_T_T`().[T]*/) = Refl/*->_empty_::Enums.`<:<`.Refl.*/()
 
   extension [A/*<-_empty_::Enums.unwrap().[A]*/, B/*<-_empty_::Enums.unwrap().[B]*/](opt/*<-_empty_::Enums.unwrap().(opt)*/: Option/*->scala::Option#*/[A/*->_empty_::Enums.unwrap().[A]*/]) def unwrap/*<-_empty_::Enums.unwrap().*/(using ev/*<-_empty_::Enums.unwrap().(ev)*/: A/*->_empty_::Enums.unwrap().[A]*/ <:</*->_empty_::Enums.`<:<`#*/ Option/*->scala::Option#*/[B/*->_empty_::Enums.unwrap().[B]*/]): Option/*->scala::Option#*/[B/*->_empty_::Enums.unwrap().[B]*/] = ev/*->_empty_::Enums.unwrap().(ev)*/ match
diff --git a/tests/semanticdb/expect/Enums.scala b/tests/semanticdb/expect/Enums.scala
index be7e2d6ce5cb..7647c9cafeb7 100644
--- a/tests/semanticdb/expect/Enums.scala
+++ b/tests/semanticdb/expect/Enums.scala
@@ -46,7 +46,7 @@ object Enums:
   enum <:<[-A, B]:
     case Refl[C]() extends (C <:< C)
 
-  object <:< :
+  object `<:<`:
     given [T]: (T <:< T) = Refl()
 
   extension [A, B](opt: Option[A]) def unwrap(using ev: A <:< Option[B]): Option[B] = ev match
diff --git a/tests/semanticdb/expect/Givens.expect.scala b/tests/semanticdb/expect/Givens.expect.scala
index 5d7a9f5dc798..8ee82a419435 100644
--- a/tests/semanticdb/expect/Givens.expect.scala
+++ b/tests/semanticdb/expect/Givens.expect.scala
@@ -22,6 +22,7 @@ object Givens/*<-a::b::Givens.*/:
     def empty/*<-a::b::Givens.given_Monoid_String.empty().*/ = ""
     extension (x/*<-a::b::Givens.given_Monoid_String.combine().(x)*/: String/*->scala::Predef.String#*/) def combine/*<-a::b::Givens.given_Monoid_String.combine().*/(y/*<-a::b::Givens.given_Monoid_String.combine().(y)*/: String/*->scala::Predef.String#*/) = x/*->a::b::Givens.given_Monoid_String.combine().(x)*/ +/*->java::lang::String#`+`().*/ y/*->a::b::Givens.given_Monoid_String.combine().(y)*/
 
-  inline given int2String/*<-a::b::Givens.int2String().*/: Conversion/*->scala::Conversion#*/[Int/*->scala::Int#*/, String/*->scala::Predef.String#*/] = _.toString/*->scala::Any#toString().*/
+  inline given int2String/*<-a::b::Givens.int2String().*/: Conversion/*->scala::Conversion#*/[Int/*->scala::Int#*/, String/*->scala::Predef.String#*/] with
+    def apply/*<-a::b::Givens.int2String#apply().*/(x/*<-a::b::Givens.int2String#apply().(x)*/: Int/*->scala::Int#*/): String/*->scala::Predef.String#*/ = x/*->a::b::Givens.int2String#apply().(x)*/.toString/*->scala::Any#toString().*/
 
   def foo/*<-a::b::Givens.foo().*/[A/*<-a::b::Givens.foo().[A]*/](using A/*<-a::b::Givens.foo().(A)*/: Monoid/*->a::b::Givens.Monoid#*/[A/*->a::b::Givens.foo().[A]*/]): A/*->a::b::Givens.foo().[A]*/ = A/*->a::b::Givens.foo().(A)*/.combine/*->a::b::Givens.Monoid#combine().*/(A/*->a::b::Givens.foo().(A)*/.empty/*->a::b::Givens.Monoid#empty().*/)(A/*->a::b::Givens.foo().(A)*/.empty/*->a::b::Givens.Monoid#empty().*/)
diff --git a/tests/semanticdb/expect/Givens.scala b/tests/semanticdb/expect/Givens.scala
index 819d70cfadca..f0a56e624d5d 100644
--- a/tests/semanticdb/expect/Givens.scala
+++ b/tests/semanticdb/expect/Givens.scala
@@ -22,6 +22,7 @@ object Givens:
     def empty = ""
     extension (x: String) def combine(y: String) = x + y
 
-  inline given int2String: Conversion[Int, String] = _.toString
+  inline given int2String: Conversion[Int, String] with
+    def apply(x: Int): String = x.toString
 
   def foo[A](using A: Monoid[A]): A = A.combine(A.empty)(A.empty)
diff --git a/tests/semanticdb/metac.expect b/tests/semanticdb/metac.expect
index ee63e6c3d0df..00727163fda4 100644
--- a/tests/semanticdb/metac.expect
+++ b/tests/semanticdb/metac.expect
@@ -486,7 +486,7 @@ Uri => CaseClass.scala
 Text => empty
 Language => Scala
 Symbols => 22 entries
-Occurrences => 16 entries
+Occurrences => 17 entries
 
 Symbols:
 caseclass/CaseClass# => case class CaseClass extends Object with Product with Serializable { self: CaseClass => +8 decls }
@@ -515,6 +515,7 @@ caseclass/CaseClass.unapply().(x$1) => param x$1: CaseClass
 Occurrences:
 [0:8..0:17): caseclass <- caseclass/
 [2:11..2:20): CaseClass <- caseclass/CaseClass#
+[2:20..2:20): <- caseclass/CaseClass#`<init>`().
 [2:21..2:25): int1 <- caseclass/CaseClass#int1.
 [2:27..2:30): Int -> scala/Int#
 [2:32..2:36): int2 <- caseclass/CaseClass#int2.
@@ -1285,7 +1286,7 @@ Occurrences:
 [46:28..46:29): C -> _empty_/Enums.`<:<`.Refl#[C]
 [46:30..46:33): <:< -> _empty_/Enums.`<:<`#
 [46:34..46:35): C -> _empty_/Enums.`<:<`.Refl#[C]
-[48:9..48:12): <:< <- _empty_/Enums.`<:<`.
+[48:10..48:13): <:< <- _empty_/Enums.`<:<`.
 [49:11..49:12): T <- _empty_/Enums.`<:<`.`given_<:<_T_T`().[T]
 [49:16..49:17): T -> _empty_/Enums.`<:<`.`given_<:<_T_T`().[T]
 [49:18..49:21): <:< -> _empty_/Enums.`<:<`#
@@ -1636,12 +1637,12 @@ Schema => SemanticDB v4
 Uri => Givens.scala
 Text => empty
 Language => Scala
-Symbols => 29 entries
-Occurrences => 66 entries
+Symbols => 33 entries
+Occurrences => 72 entries
 Synthetics => 3 entries
 
 Symbols:
-a/b/Givens. => final object Givens extends Object { self: Givens.type => +12 decls }
+a/b/Givens. => final object Givens extends Object { self: Givens.type => +13 decls }
 a/b/Givens.Monoid# => trait Monoid [typeparam A ] extends Object { self: Monoid[A] => +4 decls }
 a/b/Givens.Monoid#[A] => typeparam A 
 a/b/Givens.Monoid#`<init>`(). => primary ctor <init> [typeparam A ](): Monoid[A]
@@ -1659,7 +1660,11 @@ a/b/Givens.given_Monoid_String.combine().(y) => param y: String
 a/b/Givens.given_Monoid_String.empty(). => method empty => String <: a/b/Givens.Monoid#empty().
 a/b/Givens.goodbye1. => val method goodbye1 String
 a/b/Givens.hello1. => val method hello1 String
-a/b/Givens.int2String(). => final implicit given inline macro int2String => Conversion[Int, String]
+a/b/Givens.int2String# => implicit given class int2String extends Conversion[Int, String] { self: int2String => +2 decls }
+a/b/Givens.int2String#`<init>`(). => primary ctor <init> (): int2String
+a/b/Givens.int2String#apply(). => method apply (param x: Int): String <: scala/Conversion#apply()., scala/Function1#apply().
+a/b/Givens.int2String#apply().(x) => param x: Int
+a/b/Givens.int2String(). => final implicit given inline macro int2String => int2String
 a/b/Givens.sayGoodbye(). => method sayGoodbye [typeparam B ](param any: B): String
 a/b/Givens.sayGoodbye().(any) => param any: B
 a/b/Givens.sayGoodbye().[B] => typeparam B 
@@ -1723,21 +1728,27 @@ Occurrences:
 [22:55..22:56): y -> a/b/Givens.given_Monoid_String.combine().(y)
 [24:15..24:25): int2String <- a/b/Givens.int2String().
 [24:27..24:37): Conversion -> scala/Conversion#
+[24:27..24:27): <- a/b/Givens.int2String#`<init>`().
 [24:38..24:41): Int -> scala/Int#
 [24:43..24:49): String -> scala/Predef.String#
-[24:55..24:63): toString -> scala/Any#toString().
-[26:6..26:9): foo <- a/b/Givens.foo().
-[26:10..26:11): A <- a/b/Givens.foo().[A]
-[26:19..26:20): A <- a/b/Givens.foo().(A)
-[26:22..26:28): Monoid -> a/b/Givens.Monoid#
-[26:29..26:30): A -> a/b/Givens.foo().[A]
-[26:34..26:35): A -> a/b/Givens.foo().[A]
-[26:38..26:39): A -> a/b/Givens.foo().(A)
-[26:40..26:47): combine -> a/b/Givens.Monoid#combine().
-[26:48..26:49): A -> a/b/Givens.foo().(A)
-[26:50..26:55): empty -> a/b/Givens.Monoid#empty().
-[26:57..26:58): A -> a/b/Givens.foo().(A)
-[26:59..26:64): empty -> a/b/Givens.Monoid#empty().
+[25:8..25:13): apply <- a/b/Givens.int2String#apply().
+[25:14..25:15): x <- a/b/Givens.int2String#apply().(x)
+[25:17..25:20): Int -> scala/Int#
+[25:23..25:29): String -> scala/Predef.String#
+[25:32..25:33): x -> a/b/Givens.int2String#apply().(x)
+[25:34..25:42): toString -> scala/Any#toString().
+[27:6..27:9): foo <- a/b/Givens.foo().
+[27:10..27:11): A <- a/b/Givens.foo().[A]
+[27:19..27:20): A <- a/b/Givens.foo().(A)
+[27:22..27:28): Monoid -> a/b/Givens.Monoid#
+[27:29..27:30): A -> a/b/Givens.foo().[A]
+[27:34..27:35): A -> a/b/Givens.foo().[A]
+[27:38..27:39): A -> a/b/Givens.foo().(A)
+[27:40..27:47): combine -> a/b/Givens.Monoid#combine().
+[27:48..27:49): A -> a/b/Givens.foo().(A)
+[27:50..27:55): empty -> a/b/Givens.Monoid#empty().
+[27:57..27:58): A -> a/b/Givens.foo().(A)
+[27:59..27:64): empty -> a/b/Givens.Monoid#empty().
 
 Synthetics:
 [12:17..12:25):sayHello => *[Int]

From 7823d4264d9ad3c33f195aa5962199c61e39c7c8 Mon Sep 17 00:00:00 2001
From: Katarzyna Marek <kasia@marek.net>
Date: Fri, 15 Sep 2023 10:48:14 +0200
Subject: [PATCH 04/11] Add missing span to extension method select

[Cherry-picked fe4a6855efb1e59e050f3ebf00cfd91a32675eec]
---
 .../dotty/tools/dotc/inlines/Inliner.scala    |  2 +-
 .../dotty/tools/dotc/typer/Applications.scala |  2 +-
 .../tools/dotc/typer/ErrorReporting.scala     |  3 +-
 .../dotty/tools/dotc/typer/Implicits.scala    | 12 +++---
 .../tools/dotc/typer/ImportSuggestions.scala  |  2 +-
 .../dotty/tools/dotc/typer/ProtoTypes.scala   | 39 ++++++++++---------
 .../src/dotty/tools/dotc/typer/Typer.scala    | 10 ++---
 .../tests/definition/PcDefinitionSuite.scala  | 10 +++++
 .../highlight/DocumentHighlightSuite.scala    | 31 +++++++++++++++
 .../tools/pc/tests/hover/HoverTypeSuite.scala | 12 ++++++
 .../semanticdb/expect/Extension.expect.scala  |  9 +++++
 tests/semanticdb/expect/Extension.scala       |  9 +++++
 tests/semanticdb/metac.expect                 | 26 +++++++++++--
 13 files changed, 130 insertions(+), 37 deletions(-)

diff --git a/compiler/src/dotty/tools/dotc/inlines/Inliner.scala b/compiler/src/dotty/tools/dotc/inlines/Inliner.scala
index 29d6a5365978..66a83c66b5f8 100644
--- a/compiler/src/dotty/tools/dotc/inlines/Inliner.scala
+++ b/compiler/src/dotty/tools/dotc/inlines/Inliner.scala
@@ -771,7 +771,7 @@ class Inliner(val call: tpd.Tree)(using Context):
 
     override def typedSelect(tree: untpd.Select, pt: Type)(using Context): Tree = {
       val locked = ctx.typerState.ownedVars
-      val qual1 = typed(tree.qualifier, shallowSelectionProto(tree.name, pt, this))
+      val qual1 = typed(tree.qualifier, shallowSelectionProto(tree.name, pt, this, tree.nameSpan))
       val resNoReduce = untpd.cpy.Select(tree)(qual1, tree.name).withType(tree.typeOpt)
       val reducedProjection = reducer.reduceProjection(resNoReduce)
       if reducedProjection.isType then
diff --git a/compiler/src/dotty/tools/dotc/typer/Applications.scala b/compiler/src/dotty/tools/dotc/typer/Applications.scala
index 19af6b02c25d..09daa429a08f 100644
--- a/compiler/src/dotty/tools/dotc/typer/Applications.scala
+++ b/compiler/src/dotty/tools/dotc/typer/Applications.scala
@@ -959,7 +959,7 @@ trait Applications extends Compatibility {
             val resultType =
               if !originalResultType.isRef(defn.ObjectClass) then originalResultType
               else AvoidWildcardsMap()(proto.resultType.deepenProtoTrans) match
-                case SelectionProto(nme.asInstanceOf_, PolyProto(_, resTp), _, _) => resTp
+                case SelectionProto(nme.asInstanceOf_, PolyProto(_, resTp), _, _, _) => resTp
                 case resTp if isFullyDefined(resTp, ForceDegree.all) => resTp
                 case _ => defn.ObjectType
             val methType = MethodType(proto.typedArgs().map(_.tpe.widen), resultType)
diff --git a/compiler/src/dotty/tools/dotc/typer/ErrorReporting.scala b/compiler/src/dotty/tools/dotc/typer/ErrorReporting.scala
index 339d1f2f7bc6..2da934c6013a 100644
--- a/compiler/src/dotty/tools/dotc/typer/ErrorReporting.scala
+++ b/compiler/src/dotty/tools/dotc/typer/ErrorReporting.scala
@@ -8,6 +8,7 @@ import Types._, ProtoTypes._, Contexts._, Decorators._, Denotations._, Symbols._
 import Implicits._, Flags._, Constants.Constant
 import Trees._
 import NameOps._
+import util.Spans.NoSpan
 import util.SrcPos
 import config.Feature
 import reporting._
@@ -266,7 +267,7 @@ object ErrorReporting {
       else
         val add = suggestImports(
           ViewProto(qualType.widen,
-            SelectionProto(tree.name, WildcardType, NoViewsAllowed, privateOK = false)))
+            SelectionProto(tree.name, WildcardType, NoViewsAllowed, privateOK = false, NoSpan)))
         if add.isEmpty then ""
         else ", but could be made available as an extension method." ++ add
     end selectErrorAddendum
diff --git a/compiler/src/dotty/tools/dotc/typer/Implicits.scala b/compiler/src/dotty/tools/dotc/typer/Implicits.scala
index 29a35ccbdac0..3872d0dd79d0 100644
--- a/compiler/src/dotty/tools/dotc/typer/Implicits.scala
+++ b/compiler/src/dotty/tools/dotc/typer/Implicits.scala
@@ -75,7 +75,7 @@ object Implicits:
    *  method with the selecting name? False otherwise.
    */
   def hasExtMethod(tp: Type, expected: Type)(using Context) = expected match
-    case selProto @ SelectionProto(selName: TermName, _, _, _) =>
+    case selProto @ SelectionProto(selName: TermName, _, _, _, _) =>
       tp.memberBasedOnFlags(selName, required = ExtensionMethod).exists
     case _ =>
       false
@@ -437,7 +437,7 @@ object Implicits:
     def clarify(tp: Type)(using Context): Type = tp
 
     final protected def qualify(using Context): String = expectedType match {
-      case SelectionProto(name, mproto, _, _) if !argument.isEmpty =>
+      case SelectionProto(name, mproto, _, _, _) if !argument.isEmpty =>
         i"provide an extension method `$name` on ${argument.tpe}"
       case NoType =>
         if (argument.isEmpty) i"match expected type"
@@ -842,8 +842,8 @@ trait Implicits:
       NoMatchingImplicitsFailure
     else {
       def adjust(to: Type) = to.stripTypeVar.widenExpr match {
-        case SelectionProto(name, memberProto, compat, true) =>
-          SelectionProto(name, memberProto, compat, privateOK = false)
+        case SelectionProto(name, memberProto, compat, true, nameSpan) =>
+          SelectionProto(name, memberProto, compat, privateOK = false, nameSpan)
         case tp => tp
       }
 
@@ -1137,10 +1137,10 @@ trait Implicits:
               pt, locked)
           }
           pt match
-            case selProto @ SelectionProto(selName: TermName, mbrType, _, _) =>
+            case selProto @ SelectionProto(selName: TermName, mbrType, _, _, nameSpan) =>
 
               def tryExtension(using Context) =
-                extMethodApply(untpd.Select(untpdGenerated, selName), argument, mbrType)
+                extMethodApply(untpd.Select(untpdGenerated, selName).withSpan(nameSpan), argument, mbrType)
 
               def tryConversionForSelection(using Context) =
                 val converted = tryConversion
diff --git a/compiler/src/dotty/tools/dotc/typer/ImportSuggestions.scala b/compiler/src/dotty/tools/dotc/typer/ImportSuggestions.scala
index 70addd442100..a21a94aab271 100644
--- a/compiler/src/dotty/tools/dotc/typer/ImportSuggestions.scala
+++ b/compiler/src/dotty/tools/dotc/typer/ImportSuggestions.scala
@@ -237,7 +237,7 @@ trait ImportSuggestions:
           // don't suggest things that are imported by default
 
       def extensionImports = pt match
-        case ViewProto(argType, SelectionProto(name: TermName, _, _, _)) =>
+        case ViewProto(argType, SelectionProto(name: TermName, _, _, _, _)) =>
           roots.flatMap(extensionMethod(_, name, argType))
         case _ =>
           Nil
diff --git a/compiler/src/dotty/tools/dotc/typer/ProtoTypes.scala b/compiler/src/dotty/tools/dotc/typer/ProtoTypes.scala
index bde279c582e6..31cca0301d7f 100644
--- a/compiler/src/dotty/tools/dotc/typer/ProtoTypes.scala
+++ b/compiler/src/dotty/tools/dotc/typer/ProtoTypes.scala
@@ -19,6 +19,7 @@ import util.SourceFile
 import TypeComparer.necessarySubType
 
 import scala.annotation.internal.sharable
+import dotty.tools.dotc.util.Spans.{NoSpan, Span}
 
 object ProtoTypes {
 
@@ -165,7 +166,7 @@ object ProtoTypes {
    *
    *       [ ].name: proto
    */
-  abstract case class SelectionProto(name: Name, memberProto: Type, compat: Compatibility, privateOK: Boolean)
+  abstract case class SelectionProto(name: Name, memberProto: Type, compat: Compatibility, privateOK: Boolean, nameSpan: Span)
   extends CachedProxyType with ProtoType with ValueTypeOrProto {
 
     /** Is the set of members of this type unknown, in the sense that we
@@ -230,9 +231,9 @@ object ProtoTypes {
 
     def underlying(using Context): Type = WildcardType
 
-    def derivedSelectionProto(name: Name, memberProto: Type, compat: Compatibility)(using Context): SelectionProto =
-      if ((name eq this.name) && (memberProto eq this.memberProto) && (compat eq this.compat)) this
-      else SelectionProto(name, memberProto, compat, privateOK)
+    def derivedSelectionProto(name: Name, memberProto: Type, compat: Compatibility, nameSpan: Span)(using Context): SelectionProto =
+      if ((name eq this.name) && (memberProto eq this.memberProto) && (compat eq this.compat) && (nameSpan == this.nameSpan)) this
+      else SelectionProto(name, memberProto, compat, privateOK, nameSpan)
 
     override def isErroneous(using Context): Boolean =
       memberProto.isErroneous
@@ -240,14 +241,14 @@ object ProtoTypes {
     override def unusableForInference(using Context): Boolean =
       memberProto.unusableForInference
 
-    def map(tm: TypeMap)(using Context): SelectionProto = derivedSelectionProto(name, tm(memberProto), compat)
+    def map(tm: TypeMap)(using Context): SelectionProto = derivedSelectionProto(name, tm(memberProto), compat, nameSpan)
     def fold[T](x: T, ta: TypeAccumulator[T])(using Context): T = ta(x, memberProto)
 
     override def deepenProto(using Context): SelectionProto =
-      derivedSelectionProto(name, memberProto.deepenProto, compat)
+      derivedSelectionProto(name, memberProto.deepenProto, compat, nameSpan)
 
     override def deepenProtoTrans(using Context): SelectionProto =
-      derivedSelectionProto(name, memberProto.deepenProtoTrans, compat)
+      derivedSelectionProto(name, memberProto.deepenProtoTrans, compat, nameSpan)
 
     override def computeHash(bs: Hashable.Binders): Int = {
       val delta = (if (compat eq NoViewsAllowed) 1 else 0) | (if (privateOK) 2 else 0)
@@ -268,12 +269,12 @@ object ProtoTypes {
     }
   }
 
-  class CachedSelectionProto(name: Name, memberProto: Type, compat: Compatibility, privateOK: Boolean)
-  extends SelectionProto(name, memberProto, compat, privateOK)
+  class CachedSelectionProto(name: Name, memberProto: Type, compat: Compatibility, privateOK: Boolean, nameSpan: Span)
+  extends SelectionProto(name, memberProto, compat, privateOK, nameSpan)
 
   object SelectionProto {
-    def apply(name: Name, memberProto: Type, compat: Compatibility, privateOK: Boolean)(using Context): SelectionProto = {
-      val selproto = new CachedSelectionProto(name, memberProto, compat, privateOK)
+    def apply(name: Name, memberProto: Type, compat: Compatibility, privateOK: Boolean, nameSpan: Span)(using Context): SelectionProto = {
+      val selproto = new CachedSelectionProto(name, memberProto, compat, privateOK, nameSpan)
       if (compat eq NoViewsAllowed) unique(selproto) else selproto
     }
   }
@@ -281,11 +282,11 @@ object ProtoTypes {
   /** Create a selection proto-type, but only one level deep;
    *  treat constructors specially
    */
-  def shallowSelectionProto(name: Name, tp: Type, typer: Typer)(using Context): TermType =
+  def shallowSelectionProto(name: Name, tp: Type, typer: Typer, nameSpan: Span)(using Context): TermType =
     if (name.isConstructorName) WildcardType
     else tp match
-      case tp: UnapplyFunProto => new UnapplySelectionProto(name)
-      case tp => SelectionProto(name, IgnoredProto(tp), typer, privateOK = true)
+      case tp: UnapplyFunProto => new UnapplySelectionProto(name, nameSpan)
+      case tp => SelectionProto(name, IgnoredProto(tp), typer, privateOK = true, nameSpan)
 
   /** A prototype for expressions [] that are in some unspecified selection operation
    *
@@ -295,12 +296,12 @@ object ProtoTypes {
    *  operation is further selection. In this case, the expression need not be a value.
    *  @see checkValue
    */
-  @sharable object AnySelectionProto extends SelectionProto(nme.WILDCARD, WildcardType, NoViewsAllowed, true)
+  @sharable object AnySelectionProto extends SelectionProto(nme.WILDCARD, WildcardType, NoViewsAllowed, true, NoSpan)
 
-  @sharable object SingletonTypeProto extends SelectionProto(nme.WILDCARD, WildcardType, NoViewsAllowed, true)
+  @sharable object SingletonTypeProto extends SelectionProto(nme.WILDCARD, WildcardType, NoViewsAllowed, true, NoSpan)
 
   /** A prototype for selections in pattern constructors */
-  class UnapplySelectionProto(name: Name) extends SelectionProto(name, WildcardType, NoViewsAllowed, true)
+  class UnapplySelectionProto(name: Name, nameSpan: Span) extends SelectionProto(name, WildcardType, NoViewsAllowed, true, nameSpan)
 
   trait ApplyingProto extends ProtoType   // common trait of ViewProto and FunProto
   trait FunOrPolyProto extends ProtoType: // common trait of PolyProto and FunProto
@@ -599,7 +600,7 @@ object ProtoTypes {
     def isMatchedBy(tp: Type, keepConstraint: Boolean)(using Context): Boolean =
       ctx.typer.isApplicableType(tp, argType :: Nil, resultType) || {
         resType match {
-          case selProto @ SelectionProto(selName: TermName, mbrType, _, _) =>
+          case selProto @ SelectionProto(selName: TermName, mbrType, _, _, _) =>
             ctx.typer.hasExtensionMethodNamed(tp, selName, argType, mbrType)
               //.reporting(i"has ext $tp $name $argType $mbrType: $result")
           case _ =>
@@ -921,7 +922,7 @@ object ProtoTypes {
       }
       approxOr
     case tp: SelectionProto =>
-      tp.derivedSelectionProto(tp.name, wildApprox(tp.memberProto, theMap, seen, internal), NoViewsAllowed)
+      tp.derivedSelectionProto(tp.name, wildApprox(tp.memberProto, theMap, seen, internal), NoViewsAllowed, tp.nameSpan)
     case tp: ViewProto =>
       tp.derivedViewProto(
           wildApprox(tp.argType, theMap, seen, internal),
diff --git a/compiler/src/dotty/tools/dotc/typer/Typer.scala b/compiler/src/dotty/tools/dotc/typer/Typer.scala
index 34940d2f5277..c18a369207a5 100644
--- a/compiler/src/dotty/tools/dotc/typer/Typer.scala
+++ b/compiler/src/dotty/tools/dotc/typer/Typer.scala
@@ -752,7 +752,7 @@ class Typer(@constructorOnly nestingLevel: Int = 0) extends Namer
     record("typedSelect")
 
     def typeSelectOnTerm(using Context): Tree =
-      val qual = typedExpr(tree.qualifier, shallowSelectionProto(tree.name, pt, this))
+      val qual = typedExpr(tree.qualifier, shallowSelectionProto(tree.name, pt, this, tree.nameSpan))
       typedSelect(tree, pt, qual).withSpan(tree.span).computeNullable()
 
     def javaSelectOnType(qual: Tree)(using Context) =
@@ -782,7 +782,7 @@ class Typer(@constructorOnly nestingLevel: Int = 0) extends Namer
       tryAlternatively(typeSelectOnTerm)(fallBack)
 
     if (tree.qualifier.isType) {
-      val qual1 = typedType(tree.qualifier, shallowSelectionProto(tree.name, pt, this))
+      val qual1 = typedType(tree.qualifier, shallowSelectionProto(tree.name, pt, this, tree.nameSpan))
       assignType(cpy.Select(tree)(qual1, tree.name), qual1)
     }
     else if (ctx.isJava && tree.name.isTypeName)
@@ -3442,7 +3442,7 @@ class Typer(@constructorOnly nestingLevel: Int = 0) extends Namer
         then
           Some(adapt(tree, pt, locked))
         else
-          val selProto = SelectionProto(name, pt, NoViewsAllowed, privateOK = false)
+          val selProto = SelectionProto(name, pt, NoViewsAllowed, privateOK = false, tree.nameSpan)
           if selProto.isMatchedBy(qual.tpe) || tree.hasAttachment(InsertedImplicitOnQualifier) then
             None
           else
@@ -3467,7 +3467,7 @@ class Typer(@constructorOnly nestingLevel: Int = 0) extends Namer
       (tree: untpd.Select, pt: Type, mbrProto: Type, qual: Tree, locked: TypeVars, compat: Compatibility, inSelect: Boolean)
       (using Context): Tree =
 
-    def selectionProto = SelectionProto(tree.name, mbrProto, compat, privateOK = inSelect)
+    def selectionProto = SelectionProto(tree.name, mbrProto, compat, privateOK = inSelect, tree.nameSpan)
 
     def tryExtension(using Context): Tree =
       val altImports = new mutable.ListBuffer[TermRef]()
@@ -3897,7 +3897,7 @@ class Typer(@constructorOnly nestingLevel: Int = 0) extends Namer
        *  function prototype `(...)R`. Otherwise `pt`.
        */
       def ptWithoutRedundantApply: Type = pt.revealIgnored match
-        case SelectionProto(nme.apply, mpt, _, _) =>
+        case SelectionProto(nme.apply, mpt, _, _, _) =>
           mpt.revealIgnored match
             case fpt: FunProto => fpt
             case _ => pt
diff --git a/presentation-compiler/test/dotty/tools/pc/tests/definition/PcDefinitionSuite.scala b/presentation-compiler/test/dotty/tools/pc/tests/definition/PcDefinitionSuite.scala
index 4869cdf0fa3b..2b49d2db3f08 100644
--- a/presentation-compiler/test/dotty/tools/pc/tests/definition/PcDefinitionSuite.scala
+++ b/presentation-compiler/test/dotty/tools/pc/tests/definition/PcDefinitionSuite.scala
@@ -401,3 +401,13 @@ class PcDefinitionSuite extends BasePcDefinitionSuite:
          |
          |""".stripMargin
     )
+
+  @Test def `implicit-extension` =
+    check(
+      """|class MyIntOut(val value: Int)
+         |object MyIntOut:
+         |  extension (i: MyIntOut) def <<uneven>> = i.value % 2 == 1
+         |
+         |val a = MyIntOut(1).un@@even
+         |""".stripMargin,
+    )
diff --git a/presentation-compiler/test/dotty/tools/pc/tests/highlight/DocumentHighlightSuite.scala b/presentation-compiler/test/dotty/tools/pc/tests/highlight/DocumentHighlightSuite.scala
index 6ed5d6c636e3..0ed40c6c537f 100644
--- a/presentation-compiler/test/dotty/tools/pc/tests/highlight/DocumentHighlightSuite.scala
+++ b/presentation-compiler/test/dotty/tools/pc/tests/highlight/DocumentHighlightSuite.scala
@@ -1143,3 +1143,34 @@ class DocumentHighlightSuite extends BaseDocumentHighlightSuite:
          |  case MySome[<<AA>>](value: <<A@@A>>) extends MyOption[Int]
          |""".stripMargin,
     )
+
+  @Test def `implicit-extension` =
+    check(
+      """|class MyIntOut(val value: Int)
+         |object MyIntOut:
+         |  extension (i: MyIntOut) def <<uneven>> = i.value % 2 == 1
+         |
+         |val a = MyIntOut(1)
+         |val m = a.<<un@@even>>
+         |""".stripMargin,
+    )
+
+  @Test def `implicit-extension-2` =
+    check(
+      """|class MyIntOut(val value: Int)
+         |object MyIntOut:
+         |  extension (i: MyIntOut) def <<uneven>>(u: Int) = i.value % 2 == 1
+         |
+         |val a = MyIntOut(1).<<un@@even>>(3)
+         |""".stripMargin,
+    )
+
+  @Test def `implicit-extension-infix` =
+    check(
+      """|class MyIntOut(val value: Int)
+         |object MyIntOut:
+         |  extension (i: MyIntOut) def <<++>>(u: Int) = i.value + u
+         |
+         |val a = MyIntOut(1) <<+@@+>> 3
+         |""".stripMargin,
+    )
diff --git a/presentation-compiler/test/dotty/tools/pc/tests/hover/HoverTypeSuite.scala b/presentation-compiler/test/dotty/tools/pc/tests/hover/HoverTypeSuite.scala
index 12c3a7be584f..984066fb7803 100644
--- a/presentation-compiler/test/dotty/tools/pc/tests/hover/HoverTypeSuite.scala
+++ b/presentation-compiler/test/dotty/tools/pc/tests/hover/HoverTypeSuite.scala
@@ -355,3 +355,15 @@ class HoverTypeSuite extends BaseHoverSuite:
       """|val ddd: Int
          |""".stripMargin.hover,
     )
+
+  @Test def `infix-extension` =
+    check(
+      """|class MyIntOut(val value: Int)
+         |object MyIntOut:
+         |  extension (i: MyIntOut) def uneven = i.value % 2 == 1
+         |
+         |val a = MyIntOut(1).un@@even
+         |""".stripMargin,
+      """|extension (i: MyIntOut) def uneven: Boolean
+         |""".stripMargin.hover,
+    )
diff --git a/tests/semanticdb/expect/Extension.expect.scala b/tests/semanticdb/expect/Extension.expect.scala
index b40e965d4885..f6f76b17b698 100644
--- a/tests/semanticdb/expect/Extension.expect.scala
+++ b/tests/semanticdb/expect/Extension.expect.scala
@@ -16,3 +16,12 @@ extension (s/*<-ext::Extension$package.readInto().(s)*/: String/*->scala::Predef
 
 trait Functor/*<-ext::Functor#*/[F/*<-ext::Functor#[F]*/[_]]:
   extension [T/*<-ext::Functor#map().[T]*/](t/*<-ext::Functor#map().(t)*/: F/*->ext::Functor#[F]*/[T/*->ext::Functor#map().[T]*/]) def map/*<-ext::Functor#map().*/[U/*<-ext::Functor#map().[U]*/](f/*<-ext::Functor#map().(f)*/: T/*->ext::Functor#map().[T]*/ => U/*->ext::Functor#map().[U]*/): F/*->ext::Functor#[F]*/[U/*->ext::Functor#map().[U]*/]
+
+opaque type Deck/*<-ext::Extension$package.Deck#*/ = Long/*->scala::Long#*/
+object Deck/*<-ext::Extension$package.Deck.*/:
+  extension (data/*<-ext::Extension$package.Deck.fooSize().(data)*/: Deck/*->ext::Extension$package.Deck#*/)
+    def fooSize/*<-ext::Extension$package.Deck.fooSize().*/: Int/*->scala::Int#*/ = ???/*->scala::Predef.`???`().*/
+
+object DeckUsage/*<-ext::DeckUsage.*/:
+  val deck/*<-ext::DeckUsage.deck.*/: Deck/*->ext::Extension$package.Deck#*/ = ???/*->scala::Predef.`???`().*/
+  deck/*->ext::DeckUsage.deck.*/.fooSize/*->ext::Extension$package.Deck.fooSize().*/
diff --git a/tests/semanticdb/expect/Extension.scala b/tests/semanticdb/expect/Extension.scala
index c204b1ff7fcc..76a012e4b758 100644
--- a/tests/semanticdb/expect/Extension.scala
+++ b/tests/semanticdb/expect/Extension.scala
@@ -16,3 +16,12 @@ extension (s: String)
 
 trait Functor[F[_]]:
   extension [T](t: F[T]) def map[U](f: T => U): F[U]
+
+opaque type Deck = Long
+object Deck:
+  extension (data: Deck)
+    def fooSize: Int = ???
+
+object DeckUsage:
+  val deck: Deck = ???
+  deck.fooSize
diff --git a/tests/semanticdb/metac.expect b/tests/semanticdb/metac.expect
index 00727163fda4..d8aa1e39abef 100644
--- a/tests/semanticdb/metac.expect
+++ b/tests/semanticdb/metac.expect
@@ -1450,12 +1450,18 @@ Schema => SemanticDB v4
 Uri => Extension.scala
 Text => empty
 Language => Scala
-Symbols => 26 entries
-Occurrences => 52 entries
+Symbols => 32 entries
+Occurrences => 66 entries
 Synthetics => 1 entries
 
 Symbols:
-ext/Extension$package. => final package object ext extends Object { self: ext.type => +6 decls }
+ext/DeckUsage. => final object DeckUsage extends Object { self: DeckUsage.type => +2 decls }
+ext/DeckUsage.deck. => val method deck Deck
+ext/Extension$package. => final package object ext extends Object { self: ext.type { opaque type Deck  } => +9 decls }
+ext/Extension$package.Deck# => opaque type Deck 
+ext/Extension$package.Deck. => final object Deck extends Object { self: Deck.type => +2 decls }
+ext/Extension$package.Deck.fooSize(). => method fooSize (param data: Deck): Int
+ext/Extension$package.Deck.fooSize().(data) => param data: Deck
 ext/Extension$package.`#*#`(). => method #*# (param s: String)(param i: Int): Tuple2[String, Int]
 ext/Extension$package.`#*#`().(i) => param i: Int
 ext/Extension$package.`#*#`().(s) => param s: String
@@ -1535,6 +1541,20 @@ Occurrences:
 [17:44..17:45): U -> ext/Functor#map().[U]
 [17:48..17:49): F -> ext/Functor#[F]
 [17:50..17:51): U -> ext/Functor#map().[U]
+[19:12..19:16): Deck <- ext/Extension$package.Deck#
+[19:19..19:23): Long -> scala/Long#
+[20:7..20:11): Deck <- ext/Extension$package.Deck.
+[21:13..21:17): data <- ext/Extension$package.Deck.fooSize().(data)
+[21:19..21:23): Deck -> ext/Extension$package.Deck#
+[22:8..22:15): fooSize <- ext/Extension$package.Deck.fooSize().
+[22:17..22:20): Int -> scala/Int#
+[22:23..22:26): ??? -> scala/Predef.`???`().
+[24:7..24:16): DeckUsage <- ext/DeckUsage.
+[25:6..25:10): deck <- ext/DeckUsage.deck.
+[25:12..25:16): Deck -> ext/Extension$package.Deck#
+[25:19..25:22): ??? -> scala/Predef.`???`().
+[26:2..26:6): deck -> ext/DeckUsage.deck.
+[26:7..26:14): fooSize -> ext/Extension$package.Deck.fooSize().
 
 Synthetics:
 [14:46..14:61):summon[Read[T]] => *(x$2)

From 95b6ff2dac4d8771cba74295c34ddfea4cc4f085 Mon Sep 17 00:00:00 2001
From: Lorenzo Gabriele <lorenzolespaul@gmail.com>
Date: Tue, 19 Sep 2023 15:32:37 +0200
Subject: [PATCH 05/11] Avoid flattening `List` of `List`s

[Cherry-picked c39d260042332803259563110603521ed6381db6]
---
 .../tools/dotc/transform/CheckUnused.scala     | 18 +++++++++++++-----
 1 file changed, 13 insertions(+), 5 deletions(-)

diff --git a/compiler/src/dotty/tools/dotc/transform/CheckUnused.scala b/compiler/src/dotty/tools/dotc/transform/CheckUnused.scala
index f40993314257..a3dbbfb202e7 100644
--- a/compiler/src/dotty/tools/dotc/transform/CheckUnused.scala
+++ b/compiler/src/dotty/tools/dotc/transform/CheckUnused.scala
@@ -561,11 +561,19 @@ object CheckUnused:
         else
           Nil
       val warnings =
-        List(sortedImp, sortedLocalDefs, sortedExplicitParams, sortedImplicitParams,
-                  sortedPrivateDefs, sortedPatVars, unsetLocalDefs, unsetPrivateDefs).flatten.sortBy { s =>
-        val pos = s.pos.sourcePos
-        (pos.line, pos.column)
-      }
+        val unsorted =
+          sortedImp :::
+          sortedLocalDefs :::
+          sortedExplicitParams :::
+          sortedImplicitParams :::
+          sortedPrivateDefs :::
+          sortedPatVars :::
+          unsetLocalDefs :::
+          unsetPrivateDefs
+        unsorted.sortBy { s =>
+          val pos = s.pos.sourcePos
+          (pos.line, pos.column)
+        }
       UnusedResult(warnings.toSet)
     end getUnused
     //============================ HELPERS ====================================

From 473656b472c91053c66b7271a0298e35794eef3c Mon Sep 17 00:00:00 2001
From: Lorenzo Gabriele <lorenzolespaul@gmail.com>
Date: Tue, 19 Sep 2023 15:44:14 +0200
Subject: [PATCH 06/11] Remove redundant `.toList` call on a `List`

Co-authored-by: Nicolas Stucki <nicolas.stucki@gmail.com>

[Cherry-picked 0c04c2e5206e8e5ade2cc8c31efb394803e62e28]
---
 compiler/src/dotty/tools/MainGenericRunner.scala | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/compiler/src/dotty/tools/MainGenericRunner.scala b/compiler/src/dotty/tools/MainGenericRunner.scala
index 6f4366a00b77..0a5a1b191a44 100644
--- a/compiler/src/dotty/tools/MainGenericRunner.scala
+++ b/compiler/src/dotty/tools/MainGenericRunner.scala
@@ -148,7 +148,7 @@ object MainGenericRunner {
     case (o @ javaOption(striped)) :: tail =>
       processArgs(tail, settings.withJavaArgs(striped).withScalaArgs(o))
     case (o @ scalaOption(_*)) :: tail =>
-      val remainingArgs = (CommandLineParser.expandArg(o) ++ tail).toList
+      val remainingArgs = CommandLineParser.expandArg(o) ++ tail
       processArgs(remainingArgs, settings)
     case (o @ colorOption(_*)) :: tail =>
       processArgs(tail, settings.withScalaArgs(o))

From b5e560b50c391c88e9ecabd27cc9e162d75fa7e1 Mon Sep 17 00:00:00 2001
From: Lorenzo Gabriele <lorenzolespaul@gmail.com>
Date: Tue, 19 Sep 2023 15:48:18 +0200
Subject: [PATCH 07/11] Avoid creating a List to initialize fields

[Cherry-picked c3377d4900cba307d291fc56e39187431fc9aa7a]
---
 compiler/src/dotty/tools/dotc/core/Definitions.scala | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/compiler/src/dotty/tools/dotc/core/Definitions.scala b/compiler/src/dotty/tools/dotc/core/Definitions.scala
index 2f60d5f4d3cb..c76b6423548c 100644
--- a/compiler/src/dotty/tools/dotc/core/Definitions.scala
+++ b/compiler/src/dotty/tools/dotc/core/Definitions.scala
@@ -2130,8 +2130,10 @@ class Definitions {
     this.initCtx = ctx
     if (!isInitialized) {
       // force initialization of every symbol that is synthesized or hijacked by the compiler
-      val forced =
-        syntheticCoreClasses ++ syntheticCoreMethods ++ ScalaValueClasses() :+ JavaEnumClass
+      syntheticCoreClasses
+      syntheticCoreMethods
+      JavaEnumClass
+      // end force initialization
       isInitialized = true
     }
     addSyntheticSymbolsComments

From bf4e4ebd510180429f6bd429c0fe6477af6ae094 Mon Sep 17 00:00:00 2001
From: Lorenzo Gabriele <lorenzolespaul@gmail.com>
Date: Wed, 20 Sep 2023 12:01:46 +0200
Subject: [PATCH 08/11] Add back `ScalaValueClasses()` initialization

The call to `apply` perform side effects that need to be executed

[Cherry-picked 240e95ae148189c46ce990d0d71db968f7cffe63]
---
 compiler/src/dotty/tools/dotc/core/Definitions.scala | 1 +
 1 file changed, 1 insertion(+)

diff --git a/compiler/src/dotty/tools/dotc/core/Definitions.scala b/compiler/src/dotty/tools/dotc/core/Definitions.scala
index c76b6423548c..953f91459eda 100644
--- a/compiler/src/dotty/tools/dotc/core/Definitions.scala
+++ b/compiler/src/dotty/tools/dotc/core/Definitions.scala
@@ -2132,6 +2132,7 @@ class Definitions {
       // force initialization of every symbol that is synthesized or hijacked by the compiler
       syntheticCoreClasses
       syntheticCoreMethods
+      ScalaValueClasses()
       JavaEnumClass
       // end force initialization
       isInitialized = true

From 53794f1fa237e3f5d631de04e59a7592ed51ab8f Mon Sep 17 00:00:00 2001
From: Jakub Ciesluk <323892@uwr.edu.pl>
Date: Thu, 21 Sep 2023 10:50:44 +0200
Subject: [PATCH 09/11] bugfix: Incorrect semanticdb span on Selectable

Semanticdb range on selectDynamic in `foo.bar` previously contained `.bar` instead of `bar`

[Cherry-picked 5df5855ac5099363583e43751e16cd1808880c78]
---
 compiler/src/dotty/tools/dotc/ast/Trees.scala |  2 +-
 .../dotc/semanticdb/ExtractSemanticDB.scala   | 11 +--
 tests/semanticdb/expect/Givens.expect.scala   |  6 +-
 .../expect/ImplicitConversion.expect.scala    |  6 +-
 .../expect/StructuralTypes.expect.scala       | 22 +++++
 tests/semanticdb/expect/StructuralTypes.scala | 22 +++++
 tests/semanticdb/metac.expect                 | 87 ++++++++++++++++---
 7 files changed, 132 insertions(+), 24 deletions(-)
 create mode 100644 tests/semanticdb/expect/StructuralTypes.expect.scala
 create mode 100644 tests/semanticdb/expect/StructuralTypes.scala

diff --git a/compiler/src/dotty/tools/dotc/ast/Trees.scala b/compiler/src/dotty/tools/dotc/ast/Trees.scala
index 8d19dfdf6743..c202f7ccb523 100644
--- a/compiler/src/dotty/tools/dotc/ast/Trees.scala
+++ b/compiler/src/dotty/tools/dotc/ast/Trees.scala
@@ -455,7 +455,7 @@ object Trees {
         val point = span.point
         if name.toTermName == nme.ERROR then
           Span(point)
-        else if qualifier.span.start > span.start then // right associative
+        else if qualifier.span.start > span.point then // right associative
           val realName = name.stripModuleClassSuffix.lastPart
           Span(span.start, span.start + realName.length, point)
         else
diff --git a/compiler/src/dotty/tools/dotc/semanticdb/ExtractSemanticDB.scala b/compiler/src/dotty/tools/dotc/semanticdb/ExtractSemanticDB.scala
index 5cff105cbaa4..e364bf15ca13 100644
--- a/compiler/src/dotty/tools/dotc/semanticdb/ExtractSemanticDB.scala
+++ b/compiler/src/dotty/tools/dotc/semanticdb/ExtractSemanticDB.scala
@@ -392,15 +392,12 @@ class ExtractSemanticDB extends Phase:
         }).toMap
     end findGetters
 
-    private def selectSpan(tree: Select) =
+    private def selectSpan(tree: Select)(using Context) =
       val end = tree.span.end
       val limit = tree.qualifier.span.end
-      val start =
-        if limit < end then
-          val len = tree.name.toString.length
-          if tree.source.content()(end - 1) == '`' then end - len - 2 else end - len
-        else limit
-      Span(start max limit, end)
+      if limit < end then
+        tree.nameSpan
+      else Span(limit, end)
 
     extension (span: Span)
       private def hasLength: Boolean = span.exists && !span.isZeroExtent
diff --git a/tests/semanticdb/expect/Givens.expect.scala b/tests/semanticdb/expect/Givens.expect.scala
index 8ee82a419435..8cd1ee287096 100644
--- a/tests/semanticdb/expect/Givens.expect.scala
+++ b/tests/semanticdb/expect/Givens.expect.scala
@@ -4,11 +4,11 @@ package b
 object Givens/*<-a::b::Givens.*/:
 
   extension [A/*<-a::b::Givens.sayHello().[A]*/](any/*<-a::b::Givens.sayHello().(any)*/: A/*->a::b::Givens.sayHello().[A]*/)
-    def sayHello/*<-a::b::Givens.sayHello().*/ = s"Hello, I am $any/*->a::b::Givens.sayHello().(any)*/"/*->scala::StringContext#s().*/
+    def sayHello/*<-a::b::Givens.sayHello().*/ = s/*->scala::StringContext#s().*/"Hello, I am $any/*->a::b::Givens.sayHello().(any)*/"
 
   extension [B/*<-a::b::Givens.sayGoodbye().[B]*//*<-a::b::Givens.saySoLong().[B]*/](any/*<-a::b::Givens.sayGoodbye().(any)*//*<-a::b::Givens.saySoLong().(any)*/: B/*->a::b::Givens.sayGoodbye().[B]*//*->a::b::Givens.saySoLong().[B]*/)
-    def sayGoodbye/*<-a::b::Givens.sayGoodbye().*/ = s"Goodbye, from $any/*->a::b::Givens.sayGoodbye().(any)*/"/*->scala::StringContext#s().*/
-    def saySoLong/*<-a::b::Givens.saySoLong().*/ = s"So Long, from $any/*->a::b::Givens.saySoLong().(any)*/"/*->scala::StringContext#s().*/
+    def sayGoodbye/*<-a::b::Givens.sayGoodbye().*/ = s/*->scala::StringContext#s().*/"Goodbye, from $any/*->a::b::Givens.sayGoodbye().(any)*/"
+    def saySoLong/*<-a::b::Givens.saySoLong().*/ = s/*->scala::StringContext#s().*/"So Long, from $any/*->a::b::Givens.saySoLong().(any)*/"
 
   val hello1/*<-a::b::Givens.hello1.*/ = 1.sayHello/*->a::b::Givens.sayHello().*/
   val goodbye1/*<-a::b::Givens.goodbye1.*/ = 1.sayGoodbye/*->a::b::Givens.sayGoodbye().*/
diff --git a/tests/semanticdb/expect/ImplicitConversion.expect.scala b/tests/semanticdb/expect/ImplicitConversion.expect.scala
index 635ffb4d94c9..7c1708ee7617 100644
--- a/tests/semanticdb/expect/ImplicitConversion.expect.scala
+++ b/tests/semanticdb/expect/ImplicitConversion.expect.scala
@@ -21,10 +21,10 @@ class ImplicitConversion/*<-example::ImplicitConversion#*/ {
   val x/*<-example::ImplicitConversion#x.*/: Int/*->scala::Int#*/ = message/*->example::ImplicitConversion#message.*/
 
   // interpolators
-  s"Hello $message/*->example::ImplicitConversion#message.*/ $number/*->example::ImplicitConversion#number.*/"/*->scala::StringContext#s().*/
-  s"""Hello
+  s/*->scala::StringContext#s().*/"Hello $message/*->example::ImplicitConversion#message.*/ $number/*->example::ImplicitConversion#number.*/"
+  s/*->scala::StringContext#s().*/"""Hello
      |$message/*->example::ImplicitConversion#message.*/
-     |$number/*->example::ImplicitConversion#number.*/"""/*->scala::StringContext#s().*/.stripMargin/*->scala::collection::StringOps#stripMargin(+1).*/
+     |$number/*->example::ImplicitConversion#number.*/""".stripMargin/*->scala::collection::StringOps#stripMargin(+1).*/
 
   val a/*<-example::ImplicitConversion#a.*/: Int/*->scala::Int#*/ = char/*->example::ImplicitConversion#char.*/
   val b/*<-example::ImplicitConversion#b.*/: Long/*->scala::Long#*/ = char/*->example::ImplicitConversion#char.*/
diff --git a/tests/semanticdb/expect/StructuralTypes.expect.scala b/tests/semanticdb/expect/StructuralTypes.expect.scala
new file mode 100644
index 000000000000..96c7181d6f10
--- /dev/null
+++ b/tests/semanticdb/expect/StructuralTypes.expect.scala
@@ -0,0 +1,22 @@
+package example
+
+import reflect.Selectable/*->scala::reflect::Selectable.*/.reflectiveSelectable/*->scala::reflect::Selectable.reflectiveSelectable().*/
+
+object StructuralTypes/*<-example::StructuralTypes.*/:
+  type User/*<-example::StructuralTypes.User#*/ = {
+    def name/*<-local0*/: String/*->scala::Predef.String#*/
+    def age/*<-local1*/: Int/*->scala::Int#*/
+    def foo/*<-local3*/(x/*<-local2*/: Int/*->scala::Int#*/): Int/*->scala::Int#*/
+  }
+
+  val user/*<-example::StructuralTypes.user.*/ = null.asInstanceOf/*->scala::Any#asInstanceOf().*/[User/*->example::StructuralTypes.User#*/]
+  user/*->example::StructuralTypes.user.*/.name/*->scala::reflect::Selectable#selectDynamic().*/
+  user/*->example::StructuralTypes.user.*/.age/*->scala::reflect::Selectable#selectDynamic().*/
+  val fooBar/*<-example::StructuralTypes.fooBar.*/ = user/*->example::StructuralTypes.user.*/ foo/*->scala::reflect::Selectable#applyDynamic().*/ 123
+
+  val V/*<-example::StructuralTypes.V.*/: Object/*->java::lang::Object#*/ {
+    def scalameta/*<-local4*/: String/*->scala::Predef.String#*/
+  } = /*<-local6*/new:
+    def scalameta/*<-local5*/ = "4.0"
+  V/*->example::StructuralTypes.V.*/.scalameta/*->scala::reflect::Selectable#selectDynamic().*/
+end StructuralTypes/*->example::StructuralTypes.*/
\ No newline at end of file
diff --git a/tests/semanticdb/expect/StructuralTypes.scala b/tests/semanticdb/expect/StructuralTypes.scala
new file mode 100644
index 000000000000..5d10dbe67224
--- /dev/null
+++ b/tests/semanticdb/expect/StructuralTypes.scala
@@ -0,0 +1,22 @@
+package example
+
+import reflect.Selectable.reflectiveSelectable
+
+object StructuralTypes:
+  type User = {
+    def name: String
+    def age: Int
+    def foo(x: Int): Int
+  }
+
+  val user = null.asInstanceOf[User]
+  user.name
+  user.age
+  val fooBar = user foo 123
+
+  val V: Object {
+    def scalameta: String
+  } = new:
+    def scalameta = "4.0"
+  V.scalameta
+end StructuralTypes
\ No newline at end of file
diff --git a/tests/semanticdb/metac.expect b/tests/semanticdb/metac.expect
index d8aa1e39abef..d2220e2af17a 100644
--- a/tests/semanticdb/metac.expect
+++ b/tests/semanticdb/metac.expect
@@ -193,21 +193,21 @@ Occurrences:
 [27:6..27:9): s1x <- advanced/Test.s1x.
 [27:12..27:13): s -> advanced/Test.s.
 [27:14..27:16): s1 -> advanced/Structural#s1().
-[27:16..27:18): .x -> scala/reflect/Selectable#selectDynamic().
+[27:17..27:18): x -> scala/reflect/Selectable#selectDynamic().
 [28:6..28:8): s2 <- advanced/Test.s2.
 [28:11..28:12): s -> advanced/Test.s.
 [28:13..28:15): s2 -> advanced/Structural#s2().
 [29:6..29:9): s2x <- advanced/Test.s2x.
 [29:12..29:13): s -> advanced/Test.s.
 [29:14..29:16): s2 -> advanced/Structural#s2().
-[29:16..29:18): .x -> scala/reflect/Selectable#selectDynamic().
+[29:17..29:18): x -> scala/reflect/Selectable#selectDynamic().
 [30:6..30:8): s3 <- advanced/Test.s3.
 [30:11..30:12): s -> advanced/Test.s.
 [30:13..30:15): s3 -> advanced/Structural#s3().
 [31:6..31:9): s3x <- advanced/Test.s3x.
 [31:12..31:13): s -> advanced/Test.s.
 [31:14..31:16): s3 -> advanced/Structural#s3().
-[31:16..31:18): .m -> scala/reflect/Selectable#applyDynamic().
+[31:17..31:18): m -> scala/reflect/Selectable#applyDynamic().
 [31:19..31:22): ??? -> scala/Predef.`???`().
 [33:6..33:7): e <- advanced/Test.e.
 [33:14..33:23): Wildcards -> advanced/Wildcards#
@@ -242,7 +242,7 @@ Occurrences:
 [47:11..47:14): foo -> advanced/Test.foo.
 [47:15..47:16): A -> local17
 [47:19..47:22): foo -> advanced/Test.foo.
-[47:22..47:24): .a -> scala/reflect/Selectable#selectDynamic().
+[47:23..47:24): a -> scala/reflect/Selectable#selectDynamic().
 [52:6..52:13): HKClass <- advanced/HKClass#
 [52:13..52:13): <- advanced/HKClass#`<init>`().
 [52:14..52:15): F <- advanced/HKClass#[F]
@@ -1704,8 +1704,8 @@ Occurrences:
 [5:16..5:19): any <- a/b/Givens.sayHello().(any)
 [5:21..5:22): A -> a/b/Givens.sayHello().[A]
 [6:8..6:16): sayHello <- a/b/Givens.sayHello().
+[6:19..6:20): s -> scala/StringContext#s().
 [6:34..6:37): any -> a/b/Givens.sayHello().(any)
-[6:37..6:38): " -> scala/StringContext#s().
 [8:13..8:14): B <- a/b/Givens.sayGoodbye().[B]
 [8:13..8:14): B <- a/b/Givens.saySoLong().[B]
 [8:16..8:19): any <- a/b/Givens.sayGoodbye().(any)
@@ -1713,11 +1713,11 @@ Occurrences:
 [8:21..8:22): B -> a/b/Givens.sayGoodbye().[B]
 [8:21..8:22): B -> a/b/Givens.saySoLong().[B]
 [9:8..9:18): sayGoodbye <- a/b/Givens.sayGoodbye().
+[9:21..9:22): s -> scala/StringContext#s().
 [9:38..9:41): any -> a/b/Givens.sayGoodbye().(any)
-[9:41..9:42): " -> scala/StringContext#s().
 [10:8..10:17): saySoLong <- a/b/Givens.saySoLong().
+[10:20..10:21): s -> scala/StringContext#s().
 [10:37..10:40): any -> a/b/Givens.saySoLong().(any)
-[10:40..10:41): " -> scala/StringContext#s().
 [12:6..12:12): hello1 <- a/b/Givens.hello1.
 [12:17..12:25): sayHello -> a/b/Givens.sayHello().
 [13:6..13:14): goodbye1 <- a/b/Givens.goodbye1.
@@ -1836,12 +1836,12 @@ Occurrences:
 [20:6..20:7): x <- example/ImplicitConversion#x.
 [20:9..20:12): Int -> scala/Int#
 [20:15..20:22): message -> example/ImplicitConversion#message.
+[23:2..23:3): s -> scala/StringContext#s().
 [23:11..23:18): message -> example/ImplicitConversion#message.
 [23:20..23:26): number -> example/ImplicitConversion#number.
-[23:26..23:27): " -> scala/StringContext#s().
+[24:2..24:3): s -> scala/StringContext#s().
 [25:7..25:14): message -> example/ImplicitConversion#message.
 [26:7..26:13): number -> example/ImplicitConversion#number.
-[26:15..26:16): " -> scala/StringContext#s().
 [26:17..26:28): stripMargin -> scala/collection/StringOps#stripMargin(+1).
 [28:6..28:7): a <- example/ImplicitConversion#a.
 [28:9..28:12): Int -> scala/Int#
@@ -3346,6 +3346,73 @@ Occurrences:
 [13:17..13:17): <- selfs/C6#`<init>`().
 [13:27..13:28): B -> selfs/B#
 
+expect/StructuralTypes.scala
+----------------------------
+
+Summary:
+Schema => SemanticDB v4
+Uri => StructuralTypes.scala
+Text => empty
+Language => Scala
+Symbols => 12 entries
+Occurrences => 33 entries
+Synthetics => 4 entries
+
+Symbols:
+example/StructuralTypes. => final object StructuralTypes extends Object { self: StructuralTypes.type => +5 decls }
+example/StructuralTypes.User# => type User  = Object { abstract method foo (param x: Int): Int; abstract method age => Int; abstract method name => String }
+example/StructuralTypes.V. => val method V Object { abstract method scalameta => String }
+example/StructuralTypes.fooBar. => val method fooBar Int
+example/StructuralTypes.user. => val method user User
+local0 => abstract method name => String
+local1 => abstract method age => Int
+local2 => param x: Int
+local3 => abstract method foo (param x: Int): Int
+local4 => abstract method scalameta => String
+local5 => method scalameta => String
+local6 => final class $anon extends Object { self: $anon => +2 decls }
+
+Occurrences:
+[0:8..0:15): example <- example/
+[2:7..2:14): reflect -> scala/reflect/
+[2:15..2:25): Selectable -> scala/reflect/Selectable.
+[2:26..2:46): reflectiveSelectable -> scala/reflect/Selectable.reflectiveSelectable().
+[4:7..4:22): StructuralTypes <- example/StructuralTypes.
+[5:7..5:11): User <- example/StructuralTypes.User#
+[6:8..6:12): name <- local0
+[6:14..6:20): String -> scala/Predef.String#
+[7:8..7:11): age <- local1
+[7:13..7:16): Int -> scala/Int#
+[8:8..8:11): foo <- local3
+[8:12..8:13): x <- local2
+[8:15..8:18): Int -> scala/Int#
+[8:21..8:24): Int -> scala/Int#
+[11:6..11:10): user <- example/StructuralTypes.user.
+[11:18..11:30): asInstanceOf -> scala/Any#asInstanceOf().
+[11:31..11:35): User -> example/StructuralTypes.User#
+[12:2..12:6): user -> example/StructuralTypes.user.
+[12:7..12:11): name -> scala/reflect/Selectable#selectDynamic().
+[13:2..13:6): user -> example/StructuralTypes.user.
+[13:7..13:10): age -> scala/reflect/Selectable#selectDynamic().
+[14:6..14:12): fooBar <- example/StructuralTypes.fooBar.
+[14:15..14:19): user -> example/StructuralTypes.user.
+[14:20..14:23): foo -> scala/reflect/Selectable#applyDynamic().
+[16:6..16:7): V <- example/StructuralTypes.V.
+[16:9..16:15): Object -> java/lang/Object#
+[17:8..17:17): scalameta <- local4
+[17:19..17:25): String -> scala/Predef.String#
+[18:6..18:6): <- local6
+[19:8..19:17): scalameta <- local5
+[20:2..20:3): V -> example/StructuralTypes.V.
+[20:4..20:13): scalameta -> scala/reflect/Selectable#selectDynamic().
+[21:4..21:19): StructuralTypes -> example/StructuralTypes.
+
+Synthetics:
+[12:2..12:6):user => reflectiveSelectable(*)
+[13:2..13:6):user => reflectiveSelectable(*)
+[14:15..14:19):user => reflectiveSelectable(*)
+[20:2..20:3):V => reflectiveSelectable(*)
+
 expect/Synthetic.scala
 ----------------------
 
@@ -3944,7 +4011,7 @@ Occurrences:
 [48:18..48:19): v -> example/ValUsages.v.
 [48:20..48:23): yim -> example/Vals#yim().
 [49:2..49:3): v -> example/ValUsages.v.
-[49:3..49:18): .explicitSetter -> example/Vals#`explicitSetter_=`().
+[49:4..49:18): explicitSetter -> example/Vals#`explicitSetter_=`().
 
 expect/Vararg.scala
 -------------------

From c711f63949c3f84e1c54070449a182100bc5d0d9 Mon Sep 17 00:00:00 2001
From: Jamie Thompson <bishbashboshjt@gmail.com>
Date: Thu, 21 Sep 2023 16:48:13 +0200
Subject: [PATCH 10/11] remove implementation details from enum spec

[Cherry-picked a7d1e3332dbee3588fa1da1f2538d0be8d82b7fe]
---
 docs/_spec/05-classes-and-objects.md | 157 +++++++++++----------------
 1 file changed, 62 insertions(+), 95 deletions(-)

diff --git a/docs/_spec/05-classes-and-objects.md b/docs/_spec/05-classes-and-objects.md
index d777ebfe73e8..cc8d97704a50 100644
--- a/docs/_spec/05-classes-and-objects.md
+++ b/docs/_spec/05-classes-and-objects.md
@@ -904,7 +904,7 @@ Very much like a concrete class definition, an object definition may still conta
 <!-- TODO: Agree with NTs of rest of spec -->
 ```ebnf
 TmplDef   ::=  ‘enum’ EnumDef
-EnumDef   ::=  id ClassConstr [‘extends’ [ConstrApps]] EnumBody
+EnumDef   ::=  id ClassConstr [‘extends’ ConstrApps] EnumBody
 EnumBody  ::=  [nl] ‘{’ [SelfType] EnumStat {semi EnumStat} ‘}’
 EnumStat  ::=  TemplateStat
             |  {Annotation [nl]} {Modifier} EnumCase
@@ -925,18 +925,15 @@ First, some terminology and notational conventions:
 - We use `<...>` for syntactic constructs that in some circumstances might be empty.
 For instance, `<value-params>` represents one or more parameter lists `(´\mathit{ps}_1\,´)...(´\mathit{ps}_n´)` or nothing at all.
 - Enum classes fall into two categories:
-  - _parameterized_ enum classes have at least one of the following:
-     - a type parameter section, denoted as `[´\mathit{tps}\,´]`;
-     - one or more (possibly empty) parameter sections, denoted as `(´\mathit{ps}_1\,´)...(´\mathit{ps}_n´)`.
-  - _unparameterized_ enum classes have no type parameter sections and no parameter sections.
+  - _parameterized_ enum classes have at least one or more (possibly empty) term parameter clauses, denoted as `(´\mathit{ps}_1\,´)...(´\mathit{ps}_n´)`.
+  - _unparameterized_ enum classes have no term parameter clauses, but may optionally have a type parameter clause, denoted as `[´\mathit{tps}\,´]`.
 - Enum cases fall into three categories:
-
-  - _Class cases_ are those cases that are parameterized, either with a type parameter section `[´\mathit{tps}\,´]` or with one or more (possibly empty) parameter sections `(´\mathit{ps}_1\,´)...(´\mathit{ps}_n´)`.
-  - _Simple cases_ are cases of an unparameterized enum that have neither parameters nor an extends clause or body.
+  - _Class enum cases_ are those cases that possibly have a type parameter clause `[´\mathit{tps}\,´]`, and necessarily have one or more (possibly empty) parameter clauses `(´\mathit{ps}_1\,´)...(´\mathit{ps}_n´)`.
+  - _Simple enum cases_ are those cases that have no parameter clauses and no extends clause.
   That is, they consist of a name only.
-  - _Value cases_ are all cases that do not have a parameter section but that do have a (possibly generated) `extends` clause and/or a body.
+  - _Value enum cases_ are those cases that have no parameter clauses but that do have a (possibly generated) `extends` clause.
 
-- Simple cases and value cases are collectively called _singleton cases_.
+- Simple enum cases and value enum cases are collectively called _singleton enum cases_.
 
 ###### Example
 
@@ -970,13 +967,11 @@ enum Option[+T]:
 ### Lowering of Enum Definitions
 
 ###### Summary
-An enum class is represented as a `sealed` class that extends the `scala.reflect.Enum` trait.
+An enum class is represented as a `sealed abstract` class that extends the `scala.reflect.Enum` trait.
 
 Enum cases are represented as follows:
-- a class case is mapped to a `case class`,
-- a singleton case is mapped to a `val` definition, where
-  - Simple cases all share a single implementation class.
-  - Value cases will each be implemented by a unique class.
+- a class enum case is mapped to a `case class` member of enum class' companion object,
+- a singleton enum case is mapped to a `val` member of the enum class' companion object, implemented by a local class definition which may be shared between cases.
 
 ###### Precise rules
 The `scala.reflect.Enum` trait defines a single public method, `ordinal`:
@@ -989,106 +984,119 @@ transparent trait Enum extends Any, Product, Serializable:
 ```
 There are nine desugaring rules.
 Rule (1) desugars enum definitions.
-Rules (2) and (3) desugar simple cases.
-Rules (4) to (6) define `extends` clauses for cases that are missing them.
-Rules (7) to (9) define how such cases with `extends` clauses map into `case class`es or `val`s.
+Rule (2) desugars cases of comma-separated names to simple enum cases.
+Rules (3) to (7) desugar inferrable details of enum cases.
+Rules (8) and (9) define how fully-desugared enum cases map into `case class`es or `val`s.
+Explicit `extends` clauses must be provided in the following cases, where rules (2) to (6) do not apply:
+- any enum case of a parameterized enum,
+- any singleton enum case of an unparameterized enum with non-variant type parameters,
+- any class enum case of an enum with type parameters, where the case also has type parameters.
 
 1.  An `enum` definition
     ```scala
-    enum ´E´ ... { <defs> <cases> }
+    enum ´E´ <type-params> <value-params> { <defs> <cases> }
     ```
     expands to a `sealed abstract` class that extends the `scala.reflect.Enum` trait and an associated companion object that contains the defined cases, expanded according to rules (2 - 8).
     The enum class starts with a compiler-generated import that imports the names `<caseIds>` of all cases so that they can be used without prefix in the class.
     ```scala
-    sealed abstract class ´E´ ... extends <parents> with scala.reflect.Enum {
-        import ´E´.{ <caseIds> }
-        <defs>
+    sealed abstract class ´E´ <type-params> <value-params>
+        extends <parents> with scala.reflect.Enum {
+      import ´E´.{ <caseIds> }
+      <defs>
     }
     object ´E´ { <cases> }
     ```
 
-2. A singleton case consisting of a comma-separated list of enum names
+2. A simple enum case consisting of a comma-separated list of names
    ```scala
    case ´C_1´, ..., ´C_n´
    ```
-   expands to
+   expands to the following simple enum cases
    ```scala
    case ´C_1´; ...; case ´C_n´
    ```
    Any modifiers or annotations on the original case extend to all expanded cases.
-   This result is then further rewritten by either (3 or 4).
+   <p>This result is then further rewritten by either (3 or 4).</p>
 
-3. A singleton case without an extends clause
+3. A simple enum case `´C´` of an unparameterized enum `´E´` without type parameters
    ```scala
    case ´C´
    ```
-   of an unparameterized enum `´E´` expands to the following simple enum case in `´E´`'s companion object:
+  expands to the following value enum case:
    ```scala
-   val ´C´ = $new(n, "C")
+   case ´C´ extends ´E´
    ```
-   Here, `$new` is a private method that creates an instance of ´E´ (see below).
+   This result is then further rewritten with rule (8).
 
-4. A singleton case without an extends clause
+4. A simple enum case  `´C´` of an unparameterized enum `´E´[´\mathit{tps}´]` with type parameters
    ```scala
    case ´C´
    ```
-   of an enum `´E´` with type parameters
+   where `´\mathit{tps}´` are of the following form
    ```scala
    ´\mathit{v}_1´ ´T_1´ >: ´L_1´ <: ´U_1´ ,   ... ,   ´\mathit{v}_n´ ´T_n´ >: ´L_n´ <: ´U_n´      (n > 0)
    ```
-   where each of the variances `´\mathit{v}_i´` is either `'+'` or `'-'`, expands to the following value enum case:
+   and where each of the variances `´\mathit{v}_i´` is either `'+'` or `'-'`, expands to the following value enum case:
    ```scala
    case ´C´ extends ´E´[´B_1´, ..., ´B_n´]
    ```
    where `´B_i´` is `´L_i´` if `´\mathit{v}_i´ = '+'` and `´U_i´` if `´\mathit{v}_i´ = '-'`.
-   This result is then further rewritten with rule (8).
-   **NOTE:** It is not permitted for enums with non-variant type parameters to have singleton cases without an extends clause.
+   <p>This result is then further rewritten with rule (8).</p>
 
-5. A class case without an extends clause
+5. A class enum case with type parameters, but without an extends clause
    ```scala
-   case ´C´ <type-params> <value-params>
+   case ´C´[´\mathit{tps}´](´\mathit{ps}_1\,´)...(´\mathit{ps}_n´)
    ```
-   of an enum `´E´` that does not take type parameters expands to
+   of an unparameterized enum `´E´` without type parameters expands to
    ```scala
-   case ´C´ <type-params> <value-params> extends ´E´
+   case ´C´[´\mathit{tps}´](´\mathit{ps}_1\,´)...(´\mathit{ps}_n´) extends ´E´
    ```
    This result is then further rewritten with rule (9).
 
-6. If `´E´` is an enum with type parameters `´\mathit{tps}´`, a class case with neither type parameters nor an extends clause
+6. A class enum case without type parameters or an extends clause
    ```scala
-   case ´C´ <value-params>
+   case ´C´(´\mathit{ps}_1\,´)...(´\mathit{ps}_n´)
    ```
-   expands to
+   of an unparameterized enum `´E´[´\mathit{tps}´]` with type parameters expands to
    ```scala
-   case ´C´[´\mathit{tps}´] <value-params> extends ´E´[´\mathit{tps}´]
+   case ´C´(´\mathit{ps}_1\,´)...(´\mathit{ps}_n´) extends ´E´[´\mathit{tps}´]
    ```
-   This result is then further rewritten with rule (9).
-   For class cases that have type parameters themselves, an extends clause needs to be given explicitly.
-
+   This result is then further rewritten with rule (7).
 
-7. If `´E´` is an enum with type parameters `´\mathit{tps}´`, a class case without type parameters but with an extends clause
+7. A class enum case without type parameters, but has an extends clause
    ```scala
-   case ´C´ <value-params> extends <parents>
+   case ´C´(´\mathit{ps}_1\,´)...(´\mathit{ps}_n´) extends <parents>
    ```
-   expands to
+   of an enum `´E´[´\mathit{tps}´]` with type parameters expands to
    ```scala
-   case ´C´[´\mathit{tps}´] <value-params> extends <parents>
+   case ´C´[´\mathit{tps}´](´\mathit{ps}_1\,´)...(´\mathit{ps}_n´) extends <parents>
    ```
-   provided at least one of the parameters `´\mathit{tps}´` is mentioned in a parameter type in `<value-params>` or in a type argument in `<parents>`.
+   provided at least one of the parameters `´\mathit{tps}´` is mentioned in a parameter type in `(´\mathit{ps}_1\,´)...(´\mathit{ps}_n´)` or in a type argument in `<parents>`.
+   <br/><br/>
+   This result is then further rewritten with rule (9).
 
-8. A value case
+8. A singleton enum case
    ```scala
    case ´C´ extends <parents>
    ```
    expands to the following `val` definition in `´E´`'s companion object:
    ```scala
-   val ´C´ = new <parents> { <body>; def ordinal = ´\mathit{n}´ }
+   val ´C´ = $factory(_$ordinal = ´\mathit{n}´, $name = "C")
    ```
    where `´\mathit{n}´` is the ordinal number of the case in the companion object, starting from 0.
+   `$factory` is a placeholder that expands its arguments into an expression that produces something equivalent to
+   a new instance of the following (possibly shared) anonymous class:
+   ```scala
+   new <parents> {
+      def ordinal: Int = _$ordinal
+      override def toString: String = $name
+   }
+   ```
    The anonymous class also implements the abstract `Product` methods that it inherits from `Enum`.
+   <br/><br/>
    **NOTE:** It is an error if a value case refers to a type parameter of `´E´` in a type argument within `<parents>`.
 
-9. A class case
+9. A class enum case
    ```scala
    case ´C´ <type-params> <value-params> extends <parents>
    ```
@@ -1099,6 +1107,7 @@ Rules (7) to (9) define how such cases with `extends` clauses map into `case cla
    }
    ```
    where `´\mathit{n}´` is the ordinal number of the case in the companion object, starting from 0.
+   <br/><br/>
    **NOTE:** It is an error if a class case refers to a type parameter of `´E´` in a parameter type in `<type-params>` or `<value-params>` or in a type argument of `<parents>`, unless that parameter is already a type parameter of the case, i.e. the parameter name is defined in `<type-params>`.
 
 ###### Superclass of an enum case
@@ -1131,34 +1140,6 @@ private def $new(_$ordinal: Int, $name: String) =
     override def toString = $name
 ```
 
-
-###### Example
-
-Consider the more complex enumeration `Color`, consisting of value enum cases:
-```scala
-enum Color(val rgb: Int):
-  case Red   extends Color(0xFF0000)
-  case Green extends Color(0x00FF00)
-  case Blue  extends Color(0x0000FF)
-```
-
-The three value cases will expand as follows in the companion of `Color`:
-
-```scala
-val Red = new Color(0xFF0000):
-  def ordinal: Int = 0
-  override def productPrefix: String = "Red"
-  override def toString: String = "Red"
-val Green = new Color(0x00FF00):
-  def ordinal: Int = 1
-  override def productPrefix: String = "Green"
-  override def toString: String = "Green"
-val Blue = new Color(0x0000FF):
-  def ordinal: Int = 2
-  override def productPrefix: String = "Blue"
-  override def toString: String = "Blue"
-```
-
 ### Widening of enum cases post-construction
 The compiler-generated `apply` and `copy` methods of an class enum case
 ```scala
@@ -1176,20 +1157,6 @@ An enum `´E´` (possibly generic) that defines one or more singleton cases, and
    It returns the singleton case value whose identifier is `name`.
    - A method `values` which returns an `Array[´E'´]` of all singleton case values defined by `E`, in the order of their definitions.
 
-### Factory method for simple enum cases
-
-If an enum `´E´` contains at least one simple case, its companion object will define in addition:
-
-  - A private method `$new` which defines a new simple case value with given ordinal number and name.
-  This method can be thought as being defined as follows.
-
-  ```scala
-  private def $new(_$ordinal: Int, $name: String): ´E´ with runtime.EnumValue
-  ```
-  - `$new` returns a new instance of an anonymous class which implements the abstract `Product` methods that it inherits from `Enum`.
-  - if `´E´` inherits from `java.lang.Enum` the anonymous class does not override the `ordinal` or `toString` methods, as these are final in `java.lang.Enum`.
-  Additionally `productPrefix` will delegate to `this.name`.
-
 ### Translation of Java-compatible enums
 
 A Java-compatible enum is an enum that extends `java.lang.Enum`.

From 34093beecd3136c760bd1bf6c92eb851ab247491 Mon Sep 17 00:00:00 2001
From: Jamie Thompson <bishbashboshjt@gmail.com>
Date: Fri, 22 Sep 2023 11:56:50 +0200
Subject: [PATCH 11/11] address review comments

[Cherry-picked 57a0f174762e6009e46c77ba309d33b5301d499d]
---
 docs/_spec/05-classes-and-objects.md | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/docs/_spec/05-classes-and-objects.md b/docs/_spec/05-classes-and-objects.md
index cc8d97704a50..e1d4ace3d81f 100644
--- a/docs/_spec/05-classes-and-objects.md
+++ b/docs/_spec/05-classes-and-objects.md
@@ -970,8 +970,8 @@ enum Option[+T]:
 An enum class is represented as a `sealed abstract` class that extends the `scala.reflect.Enum` trait.
 
 Enum cases are represented as follows:
-- a class enum case is mapped to a `case class` member of enum class' companion object,
-- a singleton enum case is mapped to a `val` member of the enum class' companion object, implemented by a local class definition which may be shared between cases.
+- a class enum case is mapped to a `case class` member of the enum class' companion object,
+- a singleton enum case is mapped to a `val` member of the enum class' companion object, implemented by a local class definition. Whether that local class is shared with other singleton cases, and which ones, is left as an implementation detail.
 
 ###### Precise rules
 The `scala.reflect.Enum` trait defines a single public method, `ordinal`:
@@ -994,7 +994,7 @@ Explicit `extends` clauses must be provided in the following cases, where rules
 
 1.  An `enum` definition
     ```scala
-    enum ´E´ <type-params> <value-params> { <defs> <cases> }
+    enum ´E´ <type-params> <value-params> extends <parents> { <defs> <cases> }
     ```
     expands to a `sealed abstract` class that extends the `scala.reflect.Enum` trait and an associated companion object that contains the defined cases, expanded according to rules (2 - 8).
     The enum class starts with a compiler-generated import that imports the names `<caseIds>` of all cases so that they can be used without prefix in the class.