Fix #5332: Catch recursion in memberNames

Author: odersky

compiler/src/dotty/tools/dotc/core/SymDenotations.scala

@@ -1779,16 +1779,22 @@ object SymDenotations {
     def computeMemberNames(keepOnly: NameFilter)(implicit onBehalf: MemberNames, ctx: Context): Set[Name] = {
       var names = Set[Name]()
       def maybeAdd(name: Name) = if (keepOnly(thisType, name)) names += name
-      for (p <- classParents)
-        for (name <- p.classSymbol.asClass.memberNames(keepOnly))
-          maybeAdd(name)
-      val ownSyms =
-        if (keepOnly eq implicitFilter)
-          if (this is Package) Iterator.empty
-          else info.decls.iterator filter (_ is Implicit)
-        else info.decls.iterator
-      for (sym <- ownSyms) maybeAdd(sym.name)
-      names
+      try {
+        for (p <- classParents)
+          for (name <- p.classSymbol.asClass.memberNames(keepOnly))
+            maybeAdd(name)
+        val ownSyms =
+          if (keepOnly eq implicitFilter)
+            if (this is Package) Iterator.empty
+            else info.decls.iterator filter (_ is Implicit)
+          else info.decls.iterator
+        for (sym <- ownSyms) maybeAdd(sym.name)
+        names
+      }
+      catch {
+        case ex: Throwable =>
+          handleRecursive("member names", i"of $this", ex)
+      }
     }
 
     override final def fullNameSeparated(kind: QualifiedNameKind)(implicit ctx: Context): Name = {

tests/neg/i5332.scala

@@ -0,0 +1,5 @@
+
+object O{
+  type T[R] = X
+  class X extends T[Int] // error
+}