Scaladoc: fix crash when processing extends call (scala#17260)

Fixes scala#17234

Author: Florian3k

scaladoc-testcases/src/tests/extendsCall.scala

@@ -0,0 +1,6 @@
+package tests
+package extendsCall
+
+class Impl() extends Base(Seq.empty, c = "-") //expected: class Impl() extends Base
+
+class Base(val a: Seq[String], val b: String = "", val c: String = "") //expected: class Base(val a: Seq[String], val b: String, val c: String)

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

@@ -64,14 +64,18 @@ trait ClassLikeSupport:
     signatureOnly: Boolean = false,
     modifiers: Seq[Modifier] = classDef.symbol.getExtraModifiers(),
   ): Member =
-    def unpackTreeToClassDef(tree: Tree): ClassDef = tree match
-      case tree: ClassDef => tree
-      case TypeDef(_, tbt: TypeBoundsTree) => unpackTreeToClassDef(tbt.tpe.typeSymbol.tree)
-      case TypeDef(_, tt: TypeTree) => unpackTreeToClassDef(tt.tpe.typeSymbol.tree)
-      case c: Apply =>
-        c.symbol.owner.tree.symbol.tree match
+    def unpackTreeToClassDef(tree: Tree): ClassDef =
+      def unpackApply(a: Apply) =
+        a.symbol.owner.tree match
           case tree: ClassDef => tree
-      case tt: TypeTree => unpackTreeToClassDef(tt.tpe.typeSymbol.tree)
+
+      tree match
+        case tree: ClassDef => tree
+        case TypeDef(_, tbt: TypeBoundsTree) => unpackTreeToClassDef(tbt.tpe.typeSymbol.tree)
+        case TypeDef(_, tt: TypeTree) => unpackTreeToClassDef(tt.tpe.typeSymbol.tree)
+        case c: Apply => unpackApply(c)
+        case Block(_, c: Apply) => unpackApply(c)
+        case tt: TypeTree => unpackTreeToClassDef(tt.tpe.typeSymbol.tree)
 
     def signatureWithName(s: dotty.tools.scaladoc.Signature): dotty.tools.scaladoc.Signature =
       s match

scaladoc/test/dotty/tools/scaladoc/signatures/TranslatableSignaturesTestCases.scala

@@ -108,3 +108,5 @@ class ImplicitMembers extends SignatureTest(
 )
 
 class NonScala3Parent extends SignatureTest("nonScala3Parent", SignatureTest.all)
+
+class ExtendsCall extends SignatureTest("extendsCall", SignatureTest.all)