Merge pull request #2534 from dotty-staging/fix-#2533

Fix #2533: Fold refinement with error info to error

Author: smarter

compiler/src/dotty/tools/dotc/typer/TypeAssigner.scala

@@ -465,7 +465,8 @@ trait TypeAssigner {
     def addRefinement(parent: Type, refinement: Tree): Type = {
       val rsym = refinement.symbol
       val rinfo = if (rsym is Accessor) rsym.info.resultType else rsym.info
-      RefinedType(parent, rsym.name, rinfo)
+      if (rinfo.isError) rinfo
+      else RefinedType(parent, rsym.name, rinfo)
     }
     val refined = (parent.tpe /: refinements)(addRefinement)
     tree.withType(RecType.closeOver(rt => refined.substThis(refineCls, RecThis(rt))))

tests/neg/i2533.scala

@@ -0,0 +1,3 @@
+object Foo {
+  def test(f: { type A = A }): Int = ??? // error
+}