2 files changed, 15 insertions, 1 deletions
diff --git a/src/test/java/org/shedlang/compiler/ast/UntypedFunctionDefinitionNodeMatcher.java b/src/test/java/org/shedlang/compiler/ast/UntypedFunctionDefinitionNodeMatcher.java
index 775cf5f5..0a52482d 100644
--- a/src/test/java/org/shedlang/compiler/ast/UntypedFunctionDefinitionNodeMatcher.java
+++ b/src/test/java/org/shedlang/compiler/ast/UntypedFunctionDefinitionNodeMatcher.java
@@ -32,7 +32,7 @@ public class UntypedFunctionDefinitionNodeMatcher extends MatcherBuilder<Untyped
         return with(has("body", x -> x.body(), body));
     }
 
-    public UntypedFunctionDefinitionNodeMatcher withEffect(Matcher<Optional<UntypedTypeLevelExpressionNode>> effect) {
+    public UntypedFunctionDefinitionNodeMatcher withEffect(Matcher<Optional<? extends UntypedTypeLevelExpressionNode>> effect) {
         return with(has("effect", x -> x.effect(), effect));
     }
 
diff --git a/src/test/java/org/shedlang/compiler/parser/ParserFunctionDefinitionTests.java b/src/test/java/org/shedlang/compiler/parser/ParserFunctionDefinitionTests.java
index 34c50065..80ecb5b2 100644
--- a/src/test/java/org/shedlang/compiler/parser/ParserFunctionDefinitionTests.java
+++ b/src/test/java/org/shedlang/compiler/parser/ParserFunctionDefinitionTests.java
@@ -26,4 +26,18 @@ public class ParserFunctionDefinitionTests {
                 .withBody(isSequence())
         );
     }
+    @Test
+    public void canParseFunctionWithEffect() {
+        var source = """
+            fun f() ! Io -> Unit {
+            }""";
+
+        var node = parseString(source, Parser::parseNamespaceStatement);
+
+        assertThat(
+            node,
+            isUntypedFunctionDefinitionNode()
+                .withEffect(isOptionalOf(isUntypedTypeLevelReferenceNode("Io")))
+        );
+    }
 }