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, 3 insertions, 3 deletions

diff --git a/compiler/src/dotty/tools/dotc/typer/Applications.scala b/compiler/src/dotty/tools/dotc/typer/Applications.scala
index 4203ab9b2..da0a59c7b 100644
--- a/compiler/src/dotty/tools/dotc/typer/Applications.scala
+++ b/compiler/src/dotty/tools/dotc/typer/Applications.scala
@@ -561,7 +561,7 @@ trait Applications extends Compatibility { self: Typer with Dynamic =>
       var typedArgs = typedArgBuf.toList
       def app0 = cpy.Apply(app)(normalizedFun, typedArgs) // needs to be a `def` because typedArgs can change later
       val app1 =
-        if (!success) app0.withType(ErrorType)
+        if (!success) app0.withType(UnspecifiedErrorType)
         else {
           if (!sameSeq(args, orderedArgs)) {
             // need to lift arguments to maintain evaluation order in the
@@ -654,7 +654,7 @@ trait Applications extends Compatibility { self: Typer with Dynamic =>
         }
 
       fun1.tpe match {
-        case ErrorType => untpd.cpy.Apply(tree)(fun1, tree.args).withType(ErrorType)
+        case err: ErrorType => untpd.cpy.Apply(tree)(fun1, tree.args).withType(err)
         case TryDynamicCallType => typedDynamicApply(tree, pt)
         case _ =>
           tryEither {
@@ -918,7 +918,7 @@ trait Applications extends Compatibility { self: Typer with Dynamic =>
       case tp =>
         val unapplyErr = if (tp.isError) unapplyFn else notAnExtractor(unapplyFn)
         val typedArgsErr = args mapconserve (typed(_, defn.AnyType))
-        cpy.UnApply(tree)(unapplyErr, Nil, typedArgsErr) withType ErrorType
+        cpy.UnApply(tree)(unapplyErr, Nil, typedArgsErr) withType unapplyErr.tpe
     }
   }