vala: Type check for errors require an error expression

Fixes https://gitlab.gnome.org/GNOME/vala/issues/362

1 files changed, 6 insertions, 0 deletions

diff --git a/vala/valatypecheck.vala b/vala/valatypecheck.vala
index 904311d54..3674b5c45 100644
--- a/vala/valatypecheck.vala
+++ b/vala/valatypecheck.vala
@@ -116,6 +116,12 @@ public class Vala.TypeCheck : Expression {
 			return false;
 		}
 
+		if (type_reference is ErrorType && !(expression.value_type is ErrorType)) {
+			Report.error (expression.source_reference, "`%s' must be an error".printf (expression.to_string ()));
+			error = true;
+			return false;
+		}
+
 		if (context.profile == Profile.GOBJECT && type_reference.has_type_arguments ()) {
 			Report.warning (_data_type.source_reference, "Type argument list has no effect");
 		}