fix(language): disallow error predicate assertions

We don't process error predicate assertions in ModelInitializer, so let's forbid
them entirely.

1 files changed, 5 insertions, 0 deletions

diff --git a/subprojects/language/src/main/java/tools/refinery/language/validation/ProblemValidator.java b/subprojects/language/src/main/java/tools/refinery/language/validation/ProblemValidator.java
index aef1e71d..ace9f3dd 100644
--- a/subprojects/language/src/main/java/tools/refinery/language/validation/ProblemValidator.java
+++ b/subprojects/language/src/main/java/tools/refinery/language/validation/ProblemValidator.java
@@ -504,6 +504,11 @@ public class ProblemValidator extends AbstractProblemValidator {
                         acceptError(message, assertion, ProblemPackage.Literals.ABSTRACT_ASSERTION__RELATION, 0,
                                         SHADOW_RELATION_ISSUE);
                 }
+                if (ProblemUtil.isError(relation)) {
+                        var message = "Assertions for error predicates are not supported.";
+                        acceptError(message, assertion, ProblemPackage.Literals.ABSTRACT_ASSERTION__RELATION, 0,
+                                        UNSUPPORTED_ASSERTION_ISSUE);
+                }
                 int argumentCount = assertion.getArguments().size();
                 checkArity(assertion, ProblemPackage.Literals.ABSTRACT_ASSERTION__RELATION, argumentCount);
         }