Implement getScaladoc2Type without using tree show

Showing the tree or type does not return a reliable representation. The
only way to create this correctly is be creating a custom printer that
prints in the required format.

Author: nicolasstucki

scaladoc/src/dotty/tools/scaladoc/tasty/Scaladoc2AnchorCreator.scala

@@ -7,10 +7,66 @@ import scala.util.matching.Regex
 
 object Scaladoc2AnchorCreator:
 
-  def getScaladoc2Type(using Quotes)(t: reflect.Tree) =
-    import reflect.*
-    val regex = t match
-      case d: DefDef =>  "def"
-      case t: TypeDef => "type"
-      case v: ValDef =>  "val|var"
-    t.show(using Printer.TreeShortCode).split(regex, 2)(1).replace(" ","")
+  def getScaladoc2Type(using Quotes)(sym: quotes.reflect.Symbol) = signatureAnchor(sym)
+
+  /** Creates the signature anchor
+   *
+   *  - `X` for a `type X ...`
+   *  - `x:X` for a `val x: X`
+   *  - `f[U1,...](x1:T1,...)(impliciti1:U1,impliciti2:U2,...)...:R` for a `def f[U1, ...](x1: T1, ...)(implicit i1: U1, i2: U2...)...: R`
+   *
+   *  Types are printed without their paths. No spaces are printed in the output.
+   */
+  private def signatureAnchor(using Quotes)(sym: quotes.reflect.Symbol): String =
+    import quotes.reflect.*
+    def signatureType(tp: quotes.reflect.TypeRepr): String =
+      tp match
+        case mt @ MethodType(paramNames, paramTypes, res) =>
+          val implicitPrefix = if mt.isImplicit then "implicit " else ""
+          val closeClause = res match
+            case _: MethodOrPoly => ")"
+            case _ => "):"
+          paramNames.zip(paramTypes.map(signatureType))
+            .map((name, tpe) => s"$implicitPrefix$name:$tpe")
+            .mkString("(", ",", closeClause) + signatureType(res)
+        case PolyType(paramNames, paramBounds, res) =>
+          val closeClause = res match
+            case _: MethodOrPoly => "]"
+            case _ => "]:"
+          paramNames.zip(paramBounds.map(signatureType))
+            .map((name, tpe) => s"$name$tpe")
+            .mkString("[", ",", closeClause) + signatureType(res)
+        case TypeLambda(paramNames, paramBounds, res) =>
+          paramNames.zip(paramBounds.map(signatureType))
+            .map((name, tpe) => s"$name$tpe")
+            .mkString("[", ",", "]") + "=>" + signatureType(res)
+        case ByNameType(tp) =>
+          ":" + signatureType(tp)
+        case TypeBounds(low, hi) =>
+          val lowBound = if low =:= defn.NothingClass.typeRef then "" else ">:" + signatureType(low)
+          val hiBound = if low =:= defn.AnyClass.typeRef then "" else "<:" + signatureType(hi)
+          lowBound + hiBound
+        case tp: ParamRef =>
+          tp.binder match
+            case binder: MethodType => binder.paramNames(tp.paramNum) + ".type"
+            case binder: PolyType => binder.paramNames(tp.paramNum)
+            case binder: LambdaType => binder.paramNames(tp.paramNum)
+        case AppliedType(tycon, args) =>
+          args.map {
+            case tp: TypeBounds => "_" + signatureType(tp)
+            case tp => signatureType(tp)
+          }.mkString(signatureType(tycon) + "[", ",", "]")
+        case tp: AnnotatedType =>
+          signatureType(tp.underlying) + "@" + tp.annotation.symbol.owner.name
+        case tp: ThisType =>
+          signatureType(tp.tref) + ".this"
+        case tp: TypeRef =>
+          tp.name
+        case tp =>
+          // TODO handle other cases without using show (show does not have a stable representation)
+          tp.show(using Printer.TypeReprShortCode).replace(" ","")
+
+    sym match
+      case sym if sym.isType => sym.name
+      case sym if sym.flags.is(Flags.Method) => sym.name + signatureType(sym.info)
+      case sym => sym.name + ":" + signatureType(sym.info)

scaladoc/src/dotty/tools/scaladoc/tasty/SymOps.scala

@@ -235,7 +235,7 @@ class SymOpsWithLinkCache:
       def constructPathForScaladoc2: String =
         val l = escapeUrl(location.mkString("/"))
         val scaladoc2Anchor = if anchor.isDefined then {
-          "#" + getScaladoc2Type(sym.tree)
+          "#" + getScaladoc2Type(sym)
         } else ""
         docURL + l + extension + scaladoc2Anchor