Make errors are not swept under the carpet

Typer#ensureReported's comment outlines an example where errors
could go unreported, resulting in error trees after typer without
any reported error messages. This commit makes sure that at least
one error is reported if a tree node has an error type.

Fixes #1802.

1 files changed, 5 insertions, 6 deletions

diff --git a/compiler/src/dotty/tools/dotc/typer/Dynamic.scala b/compiler/src/dotty/tools/dotc/typer/Dynamic.scala
index b5ace87d3..4039c8b81 100644
--- a/compiler/src/dotty/tools/dotc/typer/Dynamic.scala
+++ b/compiler/src/dotty/tools/dotc/typer/Dynamic.scala
@@ -11,6 +11,7 @@ import dotty.tools.dotc.core.Names.Name
 import dotty.tools.dotc.core.StdNames._
 import dotty.tools.dotc.core.Types._
 import dotty.tools.dotc.core.Decorators._
+import ErrorReporting._
 
 object Dynamic {
   def isDynamicMethod(name: Name): Boolean =
@@ -41,10 +42,9 @@ trait Dynamic { self: Typer with Applications =>
       def isNamedArg(arg: untpd.Tree): Boolean = arg match { case NamedArg(_, _) => true; case _ => false }
       val args = tree.args
       val dynName = if (args.exists(isNamedArg)) nme.applyDynamicNamed else nme.applyDynamic
-      if (dynName == nme.applyDynamicNamed && untpd.isWildcardStarArgList(args)) {
-        ctx.error("applyDynamicNamed does not support passing a vararg parameter", tree.pos)
-        tree.withType(ErrorType)
-      } else {
+      if (dynName == nme.applyDynamicNamed && untpd.isWildcardStarArgList(args))
+        errorTree(tree, "applyDynamicNamed does not support passing a vararg parameter")
+      else {
         def namedArgTuple(name: String, arg: untpd.Tree) = untpd.Tuple(List(Literal(Constant(name)), arg))
         def namedArgs = args.map {
           case NamedArg(argName, arg) => namedArgTuple(argName.toString, arg)
@@ -89,8 +89,7 @@ trait Dynamic { self: Typer with Applications =>
       case TypeApply(Select(qual, name), targs) if !isDynamicMethod(name) =>
         typedDynamicAssign(qual, name, targs)
       case _ =>
-        ctx.error("reassignment to val", tree.pos)
-        tree.withType(ErrorType)
+        errorTree(tree, "reassignment to val")
     }
   }