--- /dev/null
+import "StandardLibrary"
+
+mapping relation Foo String String
+
+rule DoIt where
+ @when
+ Foo ?a ?b
+
+ @to
+ Foo ?b "c"
+
+main = transformation OneShotForward where
+ Foo "a" "b"
+--
+10:9-10:11: Cannot resolve the variable ?b using the source patterns.
\ No newline at end of file