Merge pull request #3680 from dotty-staging/fix-error-types

Fixes related to ErrorType appearing in other types

Author: odersky

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

@@ -185,12 +185,16 @@ trait TypeOps { this: Context => // TODO: Make standalone object.
           tp1.rebind(approximateOr(tp1.parent, tp2))
         case tp1: TypeProxy if !isClassRef(tp1) =>
           orDominator(tp1.superType | tp2)
+        case err: ErrorType =>
+          err
         case _ =>
           tp2 match {
             case tp2: RecType =>
               tp2.rebind(approximateOr(tp1, tp2.parent))
             case tp2: TypeProxy if !isClassRef(tp2) =>
               orDominator(tp1 | tp2.superType)
+            case err: ErrorType =>
+              err
             case _ =>
               val commonBaseClasses = tp.mapReduceOr(_.baseClasses)(intersect)
               val doms = dominators(commonBaseClasses, Nil)

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

@@ -411,6 +411,8 @@ trait TypeAssigner {
           if (sameLength(argTypes, paramNames)) pt.instantiate(argTypes)
           else wrongNumberOfTypeArgs(fn.tpe, pt.typeParams, args, tree.pos)
         }
+      case err: ErrorType =>
+        err
       case _ =>
         //println(i"bad type: $fn: ${fn.symbol} / ${fn.symbol.isType} / ${fn.symbol.info}") // DEBUG
         errorType(err.takesNoParamsStr(fn, "type "), tree.pos)

compiler/test-resources/repl/errmsgs

@@ -68,3 +68,7 @@ scala> while (((  foo ))) {}
 1 | while (((  foo ))) {}
   |            ^^^
   |            not found: foo
+scala> val a: iDontExist = 1
+1 | val a: iDontExist = 1
+  |        ^^^^^^^^^^
+  |        not found: type iDontExist

tests/neg/errorTypes.scala

@@ -0,0 +1,11 @@
+object Test {
+  val x: iDontExist = 1 // error: not found: type iDontExist
+
+  val y = x.asInstanceOf[Int] // No error reported (was: value asInstanceOf does not take type parameters)
+
+  val a: iDontExist | Int = 1 // error: not found: type iDontExist
+  val a2 = a.isInstanceOf[Int] // No error (used to crash)
+
+  val b: iDontExist & Int = 1 // error: not found: type iDontExist
+  val b2 = a.isInstanceOf[Int] // No error (worked before too)
+}