fix: [SemanticDB] Emit symbol-info and occ for anon class

fix #15852

This commit enables ExtractSemanticDB to emit SymbolInformation and
SymbolOccurrence of anonymous classes.

e.g.

```scala
trait Foo:
  def foo: String

val foo1: Foo = new Foo { def foo: String = ??? }
val foo2: Foo = new { def foo: String = ??? }
```

While Scala2 semanticdb-plugin emit symbols for the anonymous class.

Lack of the symbol information / occurrence led Metals not being able to
find those anonymous classes as implementations by `go-to-implementation` from `trait Foo`.

Author: tanishiking

compiler/src/dotty/tools/dotc/semanticdb/ExtractSemanticDB.scala

@@ -81,7 +81,9 @@ class ExtractSemanticDB extends Phase:
     private def excludeDef(sym: Symbol)(using Context): Boolean =
       !sym.exists
       || sym.isLocalDummy
-      || sym.is(Synthetic)
+      // basically do not register synthetic symbols, except anonymous class
+      // `new Foo { ... }`
+      || (sym.is(Synthetic) && !sym.isAnonymousClass)
       || sym.isSetter
       || sym.isOldStyleImplicitConversion(forImplicitClassOnly = true)
       || sym.owner.isGivenInstanceSummoner
@@ -178,7 +180,7 @@ class ExtractSemanticDB extends Phase:
                 if !excludeChildren(tree.symbol) then
                   traverseChildren(tree)
             }
-            if !excludeDef(tree.symbol) && tree.span.hasLength then
+            if !excludeDef(tree.symbol) && (tree.span.hasLength || tree.symbol.isAnonymousClass) then
               registerDefinition(tree.symbol, tree.nameSpan, symbolKinds(tree), tree.source)
               val privateWithin = tree.symbol.privateWithin
               if privateWithin.exists then
@@ -355,7 +357,7 @@ class ExtractSemanticDB extends Phase:
       else
         Span(span.start)
 
-      if namePresentInSource(sym, span, treeSource) then
+      if namePresentInSource(sym, span, treeSource) || sym.isAnonymousClass then
         registerOccurrence(sname, finalSpan, SymbolOccurrence.Role.DEFINITION, treeSource)
       if !sym.is(Package) then
         registerSymbol(sym, symkinds)

compiler/src/dotty/tools/dotc/semanticdb/Scala3.scala

@@ -43,7 +43,6 @@ object Scala3:
         if content.lift(span.end - 1).exists(_ == '`') then
           (span.start + 1, span.end - 1)
         else (span.start, span.end)
-      // println(s"${start}, $end")
       val nameInSource = content.slice(start, end).mkString
       // for secondary constructors `this`
       desig match

tests/semanticdb/expect/Advanced.expect.scala

@@ -11,8 +11,8 @@ class C/*<-advanced::C#*/[T/*<-advanced::C#[T]*/] {
 
 class Structural/*<-advanced::Structural#*/ {
   def s1/*<-advanced::Structural#s1().*/: { val x/*<-local0*/: Int/*->scala::Int#*/ } = ???/*->scala::Predef.`???`().*/
-  def s2/*<-advanced::Structural#s2().*/: { val x/*<-local1*/: Int/*->scala::Int#*/ } = new { val x/*<-local2*/: Int/*->scala::Int#*/ = ???/*->scala::Predef.`???`().*/ }
-  def s3/*<-advanced::Structural#s3().*/: { def m/*<-local6*/(x/*<-local5*/: Int/*->scala::Int#*/): Int/*->scala::Int#*/ } = new { def m/*<-local8*/(x/*<-local7*/: Int/*->scala::Int#*/): Int/*->scala::Int#*/ = ???/*->scala::Predef.`???`().*/ }
+  def s2/*<-advanced::Structural#s2().*/: { val x/*<-local1*/: Int/*->scala::Int#*/ } = /*<-local3*/new { val x/*<-local2*/: Int/*->scala::Int#*/ = ???/*->scala::Predef.`???`().*/ }
+  def s3/*<-advanced::Structural#s3().*/: { def m/*<-local6*/(x/*<-local5*/: Int/*->scala::Int#*/): Int/*->scala::Int#*/ } = /*<-local9*/new { def m/*<-local8*/(x/*<-local7*/: Int/*->scala::Int#*/): Int/*->scala::Int#*/ = ???/*->scala::Predef.`???`().*/ }
   def s4/*<-advanced::Structural#s4().*/(a/*<-advanced::Structural#s4().(a)*/: Int/*->scala::Int#*/): { val x/*<-local11*/: Int/*->scala::Int#*/ } = ???/*->scala::Predef.`???`().*/
   trait T/*<-advanced::Structural#T#*/[A/*<-advanced::Structural#T#[A]*/] { val foo/*<-advanced::Structural#T#foo.*/: { type B/*<-local12*/ = A/*->advanced::Structural#T#[A]*/ } = ???/*->scala::Predef.`???`().*/; def bar/*<-advanced::Structural#T#bar().*/(b/*<-advanced::Structural#T#bar().(b)*/: foo/*->advanced::Structural#T#foo.*/.B/*->local12*/) = () } // from tests/pos/t8177e.scala
 }

tests/semanticdb/expect/Anonymous.expect.scala

@@ -16,5 +16,10 @@ class Anonymous/*<-example::Anonymous#*/ {
   }
 
   trait Foo/*<-example::Anonymous#Foo#*/
-  val foo/*<-example::Anonymous#foo.*/ = new Foo/*->example::Anonymous#Foo#*/ {}
+  val foo/*<-example::Anonymous#foo.*/ = /*<-local1*/new Foo/*->example::Anonymous#Foo#*/ {}
+
+  trait Bar/*<-example::Anonymous#Bar#*/:
+    def bar/*<-example::Anonymous#Bar#bar().*/: String/*->scala::Predef.String#*/
+  val bar1/*<-example::Anonymous#bar1.*/: Bar/*->example::Anonymous#Bar#*/ = /*<-local4*/new Bar/*->example::Anonymous#Bar#*/ { def bar/*<-local3*/: String/*->scala::Predef.String#*/ = ???/*->scala::Predef.`???`().*/ }
+  val bar2/*<-example::Anonymous#bar2.*/: Bar/*->example::Anonymous#Bar#*/ = /*<-local7*/new { def bar/*<-local6*/: String/*->scala::Predef.String#*/ = ???/*->scala::Predef.`???`().*/ }
 }

tests/semanticdb/expect/Anonymous.scala

@@ -17,4 +17,9 @@ class Anonymous {
 
   trait Foo
   val foo = new Foo {}
+
+  trait Bar:
+    def bar: String
+  val bar1: Bar = new Bar { def bar: String = ??? }
+  val bar2: Bar = new { def bar: String = ??? }
 }

tests/semanticdb/expect/Classes.expect.scala

@@ -46,7 +46,7 @@ class C12/*<-classes::C12#*/ {
 }
 
 object N/*<-classes::N.*/ {
-  val anonClass/*<-classes::N.anonClass.*/ = new C7/*->classes::C7#*/(42) {
+  val anonClass/*<-classes::N.anonClass.*/ = /*<-local1*/new C7/*->classes::C7#*/(42) {
     val local/*<-local0*/ = ???/*->scala::Predef.`???`().*/
   }
   val anonFun/*<-classes::N.anonFun.*/ = List/*->scala::package.List.*/(1).map/*->scala::collection::immutable::List#map().*/ { i/*<-local3*/ =>

tests/semanticdb/expect/Traits.expect.scala

@@ -6,7 +6,7 @@ trait T/*<-traits::T#*/ {
 
 sealed trait U/*<-traits::U#*/
 object U/*<-traits::U.*/ {
-  def u/*<-traits::U.u().*/: U/*->traits::U#*/ = new U/*->traits::U#*/ {}
+  def u/*<-traits::U.u().*/: U/*->traits::U#*/ = /*<-local0*/new U/*->traits::U#*/ {}
 }
 
 class C/*<-traits::C#*/

tests/semanticdb/expect/semanticdb-Types.expect.scala

@@ -62,9 +62,9 @@ object Test/*<-types::Test.*/ {
     val compoundType1/*<-types::Test.C#compoundType1.*/: { def k/*<-local0*/: Int/*->scala::Int#*/ } = ???/*->scala::Predef.`???`().*/
     val compoundType2/*<-types::Test.C#compoundType2.*/: M/*->types::Test.M#*/ with N/*->types::Test.N#*/ = ???/*->scala::Predef.`???`().*/
     val compoundType3/*<-types::Test.C#compoundType3.*/: M/*->types::Test.M#*/ with N/*->types::Test.N#*/ { def k/*<-local1*/: Int/*->scala::Int#*/ } = ???/*->scala::Predef.`???`().*/
-    val compoundType4/*<-types::Test.C#compoundType4.*/ = new { def k/*<-local2*/: Int/*->scala::Int#*/ = ???/*->scala::Predef.`???`().*/ }
-    val compoundType5/*<-types::Test.C#compoundType5.*/ = new M/*->types::Test.M#*/ with N/*->types::Test.N#*/
-    val compoundType6/*<-types::Test.C#compoundType6.*/ = new M/*->types::Test.M#*/ with N/*->types::Test.N#*/ { def k/*<-local7*/: Int/*->scala::Int#*/ = ???/*->scala::Predef.`???`().*/ }
+    val compoundType4/*<-types::Test.C#compoundType4.*/ = /*<-local3*/new { def k/*<-local2*/: Int/*->scala::Int#*/ = ???/*->scala::Predef.`???`().*/ }
+    val compoundType5/*<-types::Test.C#compoundType5.*/ = /*<-local5*/new M/*->types::Test.M#*/ with N/*->types::Test.N#*/
+    val compoundType6/*<-types::Test.C#compoundType6.*/ = /*<-local8*/new M/*->types::Test.M#*/ with N/*->types::Test.N#*/ { def k/*<-local7*/: Int/*->scala::Int#*/ = ???/*->scala::Predef.`???`().*/ }
 
     val annType1/*<-types::Test.C#annType1.*/: T/*->types::T#*/ @ann(42) = ???/*->scala::Predef.`???`().*/
     val annType2/*<-types::Test.C#annType2.*/: T/*->types::T#*/ @ann1/*->types::ann1#*/ @ann2/*->types::ann2#*/ = ???/*->scala::Predef.`???`().*/

tests/semanticdb/metac.expect

@@ -49,7 +49,7 @@ Uri => Advanced.scala
 Text => empty
 Language => Scala
 Symbols => 60 entries
-Occurrences => 132 entries
+Occurrences => 134 entries
 Synthetics => 4 entries
 
 Symbols:
@@ -139,6 +139,7 @@ Occurrences:
 [13:6..13:8): s2 <- advanced/Structural#s2().
 [13:16..13:17): x <- local1
 [13:19..13:22): Int -> scala/Int#
+[13:27..13:27): <- local3
 [13:37..13:38): x <- local2
 [13:40..13:43): Int -> scala/Int#
 [13:46..13:49): ??? -> scala/Predef.`???`().
@@ -147,6 +148,7 @@ Occurrences:
 [14:18..14:19): x <- local5
 [14:21..14:24): Int -> scala/Int#
 [14:27..14:30): Int -> scala/Int#
+[14:35..14:35): <- local9
 [14:45..14:46): m <- local8
 [14:47..14:48): x <- local7
 [14:50..14:53): Int -> scala/Int#
@@ -357,15 +359,20 @@ Schema => SemanticDB v4
 Uri => Anonymous.scala
 Text => empty
 Language => Scala
-Symbols => 14 entries
-Occurrences => 30 entries
+Symbols => 23 entries
+Occurrences => 47 entries
 Synthetics => 2 entries
 
 Symbols:
-example/Anonymous# => class Anonymous extends Object { self: Anonymous & Anonymous => +6 decls }
+example/Anonymous# => class Anonymous extends Object { self: Anonymous & Anonymous => +9 decls }
+example/Anonymous#Bar# => trait Bar extends Object { self: Bar => +2 decls }
+example/Anonymous#Bar#`<init>`(). => primary ctor <init> (): Bar
+example/Anonymous#Bar#bar(). => abstract method bar => String
 example/Anonymous#Foo# => trait Foo extends Object { self: Foo => +1 decls }
 example/Anonymous#Foo#`<init>`(). => primary ctor <init> (): Foo
 example/Anonymous#`<init>`(). => primary ctor <init> (): Anonymous
+example/Anonymous#bar1. => val method bar1 Bar
+example/Anonymous#bar2. => val method bar2 Bar
 example/Anonymous#foo. => val method foo Foo
 example/Anonymous#locally(). => method locally [typeparam A ](param x: A): A
 example/Anonymous#locally().(x) => param x: A
@@ -376,6 +383,10 @@ example/Anonymous#m1().[T][_] => type _
 example/Anonymous#m2(). => method m2 => Map[_, List[_] forSome { type _  }] forSome { type _  }
 local0 => val local x: Function1[Int, Int]
 local1 => final class $anon extends Object with Foo { self: $anon => +1 decls }
+local3 => method bar => String <: example/Anonymous#Bar#bar().
+local4 => final class $anon extends Object with Bar { self: $anon => +2 decls }
+local6 => method bar => String <: example/Anonymous#Bar#bar().
+local7 => final class $anon extends Object with Bar { self: $anon => +2 decls }
 
 Occurrences:
 [0:8..0:15): example <- example/
@@ -407,7 +418,24 @@ Occurrences:
 [14:29..14:32): ??? -> scala/Predef.`???`().
 [17:8..17:11): Foo <- example/Anonymous#Foo#
 [18:6..18:9): foo <- example/Anonymous#foo.
+[18:12..18:12): <- local1
 [18:16..18:19): Foo -> example/Anonymous#Foo#
+[20:8..20:11): Bar <- example/Anonymous#Bar#
+[21:8..21:11): bar <- example/Anonymous#Bar#bar().
+[21:13..21:19): String -> scala/Predef.String#
+[22:6..22:10): bar1 <- example/Anonymous#bar1.
+[22:12..22:15): Bar -> example/Anonymous#Bar#
+[22:18..22:18): <- local4
+[22:22..22:25): Bar -> example/Anonymous#Bar#
+[22:32..22:35): bar <- local3
+[22:37..22:43): String -> scala/Predef.String#
+[22:46..22:49): ??? -> scala/Predef.`???`().
+[23:6..23:10): bar2 <- example/Anonymous#bar2.
+[23:12..23:15): Bar -> example/Anonymous#Bar#
+[23:18..23:18): <- local7
+[23:28..23:31): bar <- local6
+[23:33..23:39): String -> scala/Predef.String#
+[23:42..23:45): ??? -> scala/Predef.`???`().
 
 Synthetics:
 [10:2..10:9):locally => *[Unit]
@@ -446,7 +474,7 @@ Uri => Classes.scala
 Text => empty
 Language => Scala
 Symbols => 109 entries
-Occurrences => 113 entries
+Occurrences => 114 entries
 Synthetics => 2 entries
 
 Symbols:
@@ -664,6 +692,7 @@ Occurrences:
 [43:101..43:104): ??? -> scala/Predef.`???`().
 [47:7..47:8): N <- classes/N.
 [48:6..48:15): anonClass <- classes/N.anonClass.
+[48:18..48:18): <- local1
 [48:22..48:24): C7 -> classes/C7#
 [49:8..49:13): local <- local0
 [49:16..49:19): ??? -> scala/Predef.`???`().
@@ -3430,7 +3459,7 @@ Uri => Traits.scala
 Text => empty
 Language => Scala
 Symbols => 13 entries
-Occurrences => 12 entries
+Occurrences => 13 entries
 
 Symbols:
 local0 => final class $anon extends Object with U { self: $anon => +1 decls }
@@ -3455,6 +3484,7 @@ Occurrences:
 [7:7..7:8): U <- traits/U.
 [8:6..8:7): u <- traits/U.u().
 [8:9..8:10): U -> traits/U#
+[8:13..8:13): <- local0
 [8:17..8:18): U -> traits/U#
 [11:6..11:7): C <- traits/C#
 [12:6..12:7): V <- traits/V#
@@ -4522,7 +4552,7 @@ Uri => semanticdb-Types.scala
 Text => empty
 Language => Scala
 Symbols => 144 entries
-Occurrences => 225 entries
+Occurrences => 228 entries
 Synthetics => 1 entries
 
 Symbols:
@@ -4780,13 +4810,16 @@ Occurrences:
 [63:41..63:44): Int -> scala/Int#
 [63:49..63:52): ??? -> scala/Predef.`???`().
 [64:8..64:21): compoundType4 <- types/Test.C#compoundType4.
+[64:24..64:24): <- local3
 [64:34..64:35): k <- local2
 [64:37..64:40): Int -> scala/Int#
 [64:43..64:46): ??? -> scala/Predef.`???`().
 [65:8..65:21): compoundType5 <- types/Test.C#compoundType5.
+[65:24..65:24): <- local5
 [65:28..65:29): M -> types/Test.M#
 [65:35..65:36): N -> types/Test.N#
 [66:8..66:21): compoundType6 <- types/Test.C#compoundType6.
+[66:24..66:24): <- local8
 [66:28..66:29): M -> types/Test.M#
 [66:35..66:36): N -> types/Test.N#
 [66:43..66:44): k <- local7