Add extension information in extension function pages

Author: pikinier20

scala3doc/src/dotty/dokka/translators/ScalaContentBuilder.scala

@@ -248,6 +248,14 @@ class ScalaPageContentBuilder(
 
     def signature(d: Documentable) = addChildren(signatureProvider.signature(d).asScala.toList)
 
+    private def buildSignature(d: Documentable, s: Signature) = signatureProvider.asInstanceOf[ScalaSignatureProvider].signature(d, s)
+
+    def signature(d: Documentable, s: Signature) = addChild(buildSignature(d, s))
+
+    def inlineSignature(d: Documentable, s: Signature) = addChildren(
+      buildSignature(d, s).getChildren.asScala.toSeq
+    )
+
     def defaultHeaders = List(
       contentForDRIs(
         dris = mainDRI,

scala3doc/src/dotty/dokka/translators/ScalaPageCreator.scala

@@ -317,12 +317,20 @@ class ScalaPageCreator(
             case _ => withNamedTags
           }
 
+          val withExtensionInformation = d.kind match {
+            case Kind.Extension(on) => 
+              val sourceSets = d.getSourceSets.asScala.toSet
+              withCompanion.cell(sourceSets = sourceSets)(_.text("Extension"))
+                .cell(sourceSets = sourceSets)(_.text(s"This function is an extension on (${on.name}: ").inlineSignature(d, on.signature).text(")"))
+            case _ => withCompanion
+          }
+
           d match
-            case null => withCompanion
+            case null => withExtensionInformation
             case m: Member =>
               sourceLinks.pathTo(m).fold(withCompanion){ link =>
                 val sourceSets = m.getSourceSets.asScala.toSet
-                withCompanion.cell(sourceSets = sourceSets)(_.text("Source"))
+                withExtensionInformation.cell(sourceSets = sourceSets)(_.text("Source"))
                   .cell(sourceSets = sourceSets)(_.resolvedLink("(source)", link))
               }
         }

scala3doc/src/dotty/dokka/translators/ScalaSignatureProvider.scala

@@ -31,6 +31,11 @@ class ScalaSignatureProvider(contentConverter: CommentsToContentConverter, logge
     def driLink(text: String, dri: DRI): SignatureBuilder = ContentNodeBuilder(builder.driLink(text, dri))
   }
 
+  def signature(d: Documentable, s: Signature) = signatureContent(d){ builder => 
+    val res = ContentNodeBuilder(builder).signature(s)
+    res.asInstanceOf[ContentNodeBuilder].builder
+  }
+
   override def signature(documentable: Documentable) =
     JList(signatureContent(documentable){ builder =>
       val withAnnotations = ContentNodeBuilder(builder).annotationsBlock(documentable)