Introduce UntypedFunctionSignatureNode

8 files changed, 267 insertions, 350 deletions

diff --git a/src/test/java/org/shedlang/compiler/ast/untyped/UntypedFunctionDefinitionNodeMatcher.java b/src/test/java/org/shedlang/compiler/ast/untyped/UntypedFunctionDefinitionNodeMatcher.java
index f50056f0..d3d1e962 100644
--- a/src/test/java/org/shedlang/compiler/ast/untyped/UntypedFunctionDefinitionNodeMatcher.java
+++ b/src/test/java/org/shedlang/compiler/ast/untyped/UntypedFunctionDefinitionNodeMatcher.java
@@ -6,8 +6,6 @@ import org.shedlang.compiler.testing.MatcherBuilder;
 import org.shedlang.compiler.types.Visibility;
 import org.zwobble.precisely.Matcher;
 
-import java.util.Optional;
-
 import static org.zwobble.precisely.Matchers.equalTo;
 import static org.zwobble.precisely.Matchers.has;
 
@@ -30,26 +28,20 @@ public class UntypedFunctionDefinitionNodeMatcher extends MatcherBuilder<Untyped
         return new UntypedFunctionDefinitionNodeMatcher(submatchers);
     }
 
-    public UntypedFunctionDefinitionNodeMatcher withBody(Matcher<UntypedBlockNode> body) {
-        return with(has("body", x -> x.body(), body));
+    public UntypedFunctionDefinitionNodeMatcher withSignature(
+        Matcher<? super UntypedFunctionSignatureNode> signature
+    ) {
+        return with(has("signature", x -> x.signature(), signature));
     }
 
-    public UntypedFunctionDefinitionNodeMatcher withEffect(Matcher<Optional<? extends UntypedTypeLevelExpressionNode>> effect) {
-        return with(has("effect", x -> x.effect(), effect));
+    public UntypedFunctionDefinitionNodeMatcher withBody(Matcher<UntypedBlockNode> body) {
+        return with(has("body", x -> x.body(), body));
     }
 
     public UntypedFunctionDefinitionNodeMatcher withName(String name) {
         return with(has("name", x -> x.name(), equalTo(name)));
     }
 
-    public UntypedFunctionDefinitionNodeMatcher withParams(Matcher<UntypedParamsNode> params) {
-        return with(has("params", x -> x.params(), params));
-    }
-
-    public UntypedFunctionDefinitionNodeMatcher withReturnType(Matcher<UntypedTypeLevelExpressionNode> returnType) {
-        return with(has("returnType", x -> x.returnType(), returnType));
-    }
-
     public UntypedFunctionDefinitionNodeMatcher withVisibility(Visibility visibility) {
         return with(has("visibility", x -> x.visibility(), equalTo(visibility)));
     }
diff --git a/src/test/java/org/shedlang/compiler/ast/untyped/UntypedFunctionExpressionNodeMatcher.java b/src/test/java/org/shedlang/compiler/ast/untyped/UntypedFunctionExpressionNodeMatcher.java
index f5c8d161..434d79e6 100644
--- a/src/test/java/org/shedlang/compiler/ast/untyped/UntypedFunctionExpressionNodeMatcher.java
+++ b/src/test/java/org/shedlang/compiler/ast/untyped/UntypedFunctionExpressionNodeMatcher.java
@@ -5,8 +5,6 @@ import org.pcollections.PVector;
 import org.shedlang.compiler.testing.MatcherBuilder;
 import org.zwobble.precisely.Matcher;
 
-import java.util.Optional;
-
 import static org.zwobble.precisely.Matchers.has;
 
 public class UntypedFunctionExpressionNodeMatcher extends MatcherBuilder<
@@ -36,19 +34,13 @@ public class UntypedFunctionExpressionNodeMatcher extends MatcherBuilder<
         return new UntypedFunctionExpressionNodeMatcher(submatchers);
     }
 
-    public UntypedFunctionExpressionNodeMatcher withBody(Matcher<UntypedBlockNode> body) {
-        return with(has("body", x -> x.body(), body));
-    }
-
-    public UntypedFunctionExpressionNodeMatcher withEffect(Matcher<Optional<? extends UntypedTypeLevelExpressionNode>> effect) {
-        return with(has("effect", x -> x.effect(), effect));
-    }
-
-    public UntypedFunctionExpressionNodeMatcher withParams(Matcher<UntypedParamsNode> params) {
-        return with(has("params", x -> x.params(), params));
+    public UntypedFunctionExpressionNodeMatcher withSignature(
+        Matcher<? super UntypedFunctionSignatureNode> signature
+    ) {
+        return with(has("signature", x -> x.signature(), signature));
     }
 
-    public UntypedFunctionExpressionNodeMatcher withReturnType(Matcher<UntypedTypeLevelExpressionNode> returnType) {
-        return with(has("returnType", x -> x.returnType(), returnType));
+    public UntypedFunctionExpressionNodeMatcher withBody(Matcher<UntypedBlockNode> body) {
+        return with(has("body", x -> x.body(), body));
     }
 }
diff --git a/src/test/java/org/shedlang/compiler/ast/untyped/UntypedFunctionSignatureNodeMatcher.java b/src/test/java/org/shedlang/compiler/ast/untyped/UntypedFunctionSignatureNodeMatcher.java
new file mode 100644
index 00000000..d799245b
--- /dev/null
+++ b/src/test/java/org/shedlang/compiler/ast/untyped/UntypedFunctionSignatureNodeMatcher.java
@@ -0,0 +1,50 @@
+package org.shedlang.compiler.ast.untyped;
+
+import org.pcollections.Empty;
+import org.pcollections.PVector;
+import org.shedlang.compiler.testing.MatcherBuilder;
+import org.zwobble.precisely.Matcher;
+
+import java.util.Optional;
+
+import static org.zwobble.precisely.Matchers.has;
+
+public class UntypedFunctionSignatureNodeMatcher extends MatcherBuilder<
+    UntypedFunctionSignatureNode,
+    UntypedFunctionSignatureNode,
+    UntypedFunctionSignatureNodeMatcher
+> {
+    public static UntypedFunctionSignatureNodeMatcher empty() {
+        return new UntypedFunctionSignatureNodeMatcher(Empty.vector());
+    }
+
+    public UntypedFunctionSignatureNodeMatcher(
+        PVector<Matcher<? super UntypedFunctionSignatureNode>> submatchers
+    ) {
+        super(submatchers);
+    }
+
+    @Override
+    protected Class<UntypedFunctionSignatureNode> expectedType() {
+        return UntypedFunctionSignatureNode.class;
+    }
+
+    @Override
+    protected UntypedFunctionSignatureNodeMatcher create(
+        PVector<Matcher<? super UntypedFunctionSignatureNode>> submatchers
+    ) {
+        return new UntypedFunctionSignatureNodeMatcher(submatchers);
+    }
+
+    public UntypedFunctionSignatureNodeMatcher withEffect(Matcher<Optional<? extends UntypedTypeLevelExpressionNode>> effect) {
+        return with(has("effect", x -> x.effect(), effect));
+    }
+
+    public UntypedFunctionSignatureNodeMatcher withParams(Matcher<UntypedParamsNode> params) {
+        return with(has("params", x -> x.params(), params));
+    }
+
+    public UntypedFunctionSignatureNodeMatcher withReturnType(Matcher<UntypedTypeLevelExpressionNode> returnType) {
+        return with(has("returnType", x -> x.returnType(), returnType));
+    }
+}
diff --git a/src/test/java/org/shedlang/compiler/ast/untyped/UntypedNodeMatchers.java b/src/test/java/org/shedlang/compiler/ast/untyped/UntypedNodeMatchers.java
index 0d4940e8..1a7f0611 100644
--- a/src/test/java/org/shedlang/compiler/ast/untyped/UntypedNodeMatchers.java
+++ b/src/test/java/org/shedlang/compiler/ast/untyped/UntypedNodeMatchers.java
@@ -127,6 +127,10 @@ public class UntypedNodeMatchers {
         );
     }
 
+    public static UntypedFunctionSignatureNodeMatcher isUntypedFunctionSignatureNode() {
+        return UntypedFunctionSignatureNodeMatcher.empty();
+    }
+
     public static UntypedFunctionTypeNodeMatcher isUntypedFunctionTypeNode() {
         return UntypedFunctionTypeNodeMatcher.empty();
     }
diff --git a/src/test/java/org/shedlang/compiler/parser/ParserFunctionDefinitionTests.java b/src/test/java/org/shedlang/compiler/parser/ParserFunctionDefinitionTests.java
index 431ef6d0..9c3148a3 100644
--- a/src/test/java/org/shedlang/compiler/parser/ParserFunctionDefinitionTests.java
+++ b/src/test/java/org/shedlang/compiler/parser/ParserFunctionDefinitionTests.java
@@ -1,7 +1,6 @@
 package org.shedlang.compiler.parser;
 
 import org.junit.jupiter.api.Test;
-import org.shedlang.compiler.parser.errors.PositionalParamAfterNamedParamError;
 import org.shedlang.compiler.tokeniser.UnexpectedTokenException;
 import org.shedlang.compiler.types.Visibility;
 
@@ -24,9 +23,12 @@ public class ParserFunctionDefinitionTests {
             node,
             isUntypedFunctionDefinitionNode()
                 .withName("f")
-                .withParams(isUntypedParamsNode(isSequence(), isSequence()))
-                .withEffect(isOptionalEmpty())
-                .withReturnType(isUntypedTypeLevelReferenceNode("Unit"))
+                .withSignature(
+                    isUntypedFunctionSignatureNode()
+                        .withParams(isUntypedParamsNode(isSequence(), isSequence()))
+                        .withEffect(isOptionalEmpty())
+                        .withReturnType(isUntypedTypeLevelReferenceNode("Unit"))
+                )
                 .withBody(isUntypedBlockNode(isSequence()))
         );
     }
@@ -46,7 +48,7 @@ public class ParserFunctionDefinitionTests {
     }
 
     @Test
-    public void whenFunIsPrefixWithPubThenVisibilityIsPublic() {
+    public void whenFunIsPrefixedWithPubThenVisibilityIsPublic() {
         var source = """
             pub fun f() -> Unit {
             }""";
@@ -60,159 +62,6 @@ public class ParserFunctionDefinitionTests {
     }
 
     @Test
-    public void canParseFunctionWithSinglePositionalParam() {
-        var source = """
-            fun f(a: Int) -> Unit {
-            }""";
-
-        var node = parseString(source, Parser::parseNamespaceStatement);
-
-        assertThat(
-            node,
-            isUntypedFunctionDefinitionNode()
-                .withParams(isUntypedParamsNode(
-                    isSequence(
-                        isUntypedParamNode("a", isUntypedTypeLevelReferenceNode("Int"))
-                    ),
-                    isSequence()
-                ))
-        );
-    }
-
-    @Test
-    public void canParseFunctionWithManyPositionalParams() {
-        var source = """
-            fun f(a: Int, b: String, c: Bool) -> Unit {
-            }""";
-
-        var node = parseString(source, Parser::parseNamespaceStatement);
-
-        assertThat(
-            node,
-            isUntypedFunctionDefinitionNode()
-                .withParams(isUntypedParamsNode(
-                    isSequence(
-                        isUntypedParamNode("a", isUntypedTypeLevelReferenceNode("Int")),
-                        isUntypedParamNode("b", isUntypedTypeLevelReferenceNode("String")),
-                        isUntypedParamNode("c", isUntypedTypeLevelReferenceNode("Bool"))
-                    ),
-                    isSequence()
-                ))
-        );
-    }
-
-    @Test
-    public void canParseFunctionWithSingleNamedParam() {
-        var source = """
-            fun f(.a: Int) -> Unit {
-            }""";
-
-        var node = parseString(source, Parser::parseNamespaceStatement);
-
-        assertThat(
-            node,
-            isUntypedFunctionDefinitionNode()
-                .withParams(isUntypedParamsNode(
-                    isSequence(),
-                    isSequence(
-                        isUntypedParamNode("a", isUntypedTypeLevelReferenceNode("Int"))
-                    )
-                ))
-        );
-    }
-
-    @Test
-    public void canParseFunctionWithManyNamedParams() {
-        var source = """
-            fun f(.a: Int, .b: String, .c: Bool) -> Unit {
-            }""";
-
-        var node = parseString(source, Parser::parseNamespaceStatement);
-
-        assertThat(
-            node,
-            isUntypedFunctionDefinitionNode()
-                .withParams(isUntypedParamsNode(
-                    isSequence(),
-                    isSequence(
-                        isUntypedParamNode("a", isUntypedTypeLevelReferenceNode("Int")),
-                        isUntypedParamNode("b", isUntypedTypeLevelReferenceNode("String")),
-                        isUntypedParamNode("c", isUntypedTypeLevelReferenceNode("Bool"))
-                    )
-                ))
-        );
-    }
-
-    @Test
-    public void canParseNamedParamAfterPositionalParam() {
-        var source = """
-            fun f(a: Int, .b: String) -> Unit {
-            }""";
-
-        var node = parseString(source, Parser::parseNamespaceStatement);
-
-        assertThat(
-            node,
-            isUntypedFunctionDefinitionNode()
-                .withParams(isUntypedParamsNode(
-                    isSequence(
-                        isUntypedParamNode("a", isUntypedTypeLevelReferenceNode("Int"))
-                    ),
-                    isSequence(
-                        isUntypedParamNode("b", isUntypedTypeLevelReferenceNode("String"))
-                    )
-                ))
-        );
-    }
-
-    @Test
-    public void cannotParsePositionalParamAfterNamedParam() {
-        var source = """
-            fun f(.a: Int, b: String) -> Unit {
-            }""";
-
-        assertThrows(
-            PositionalParamAfterNamedParamError.class,
-            () -> parseString(source, Parser::parseNamespaceStatement)
-        );
-    }
-
-    @Test
-    public void paramsCanHaveTrailingComma() {
-        var source = """
-            fun f(a: Int, ) -> Unit {
-            }""";
-
-        var node = parseString(source, Parser::parseNamespaceStatement);
-
-        assertThat(
-            node,
-            isUntypedFunctionDefinitionNode()
-                .withParams(isUntypedParamsNode(
-                    isSequence(
-                        isUntypedParamNode("a", isUntypedTypeLevelReferenceNode("Int"))
-                    ),
-                    isSequence()
-                ))
-        );
-    }
-
-    @Test
-    public void canParseFunctionWithEffect() {
-        var source = """
-            fun f() ! Io -> Unit {
-            }""";
-
-        var node = parseString(source, Parser::parseNamespaceStatement);
-
-        assertThat(
-            node,
-            isUntypedFunctionDefinitionNode()
-                .withEffect(isOptionalOf(isUntypedTypeLevelReferenceNode("Io")))
-        );
-    }
-
-    @Test
     public void canParseFunctionWithBodyWithoutReturn() {
         var source = """
             fun f() -> Unit {
diff --git a/src/test/java/org/shedlang/compiler/parser/ParserFunctionExpressionTests.java b/src/test/java/org/shedlang/compiler/parser/ParserFunctionExpressionTests.java
index d86776be..8b4c72a6 100644
--- a/src/test/java/org/shedlang/compiler/parser/ParserFunctionExpressionTests.java
+++ b/src/test/java/org/shedlang/compiler/parser/ParserFunctionExpressionTests.java
@@ -1,7 +1,6 @@
 package org.shedlang.compiler.parser;
 
 import org.junit.jupiter.api.Test;
-import org.shedlang.compiler.parser.errors.PositionalParamAfterNamedParamError;
 import org.shedlang.compiler.tokeniser.UnexpectedTokenException;
 
 import static org.junit.jupiter.api.Assertions.assertThrows;
@@ -22,167 +21,17 @@ public class ParserFunctionExpressionTests {
         assertThat(
             node,
             isUntypedFunctionExpressionNode()
-                .withParams(isUntypedParamsNode(isSequence(), isSequence()))
-                .withEffect(isOptionalEmpty())
-                .withReturnType(isUntypedTypeLevelReferenceNode("Unit"))
+                .withSignature(
+                    isUntypedFunctionSignatureNode()
+                        .withParams(isUntypedParamsNode(isSequence(), isSequence()))
+                        .withEffect(isOptionalEmpty())
+                        .withReturnType(isUntypedTypeLevelReferenceNode("Unit"))
+                )
                 .withBody(isUntypedBlockNode(isSequence()))
         );
     }
 
     @Test
-    public void canParseFunctionWithSinglePositionalParam() {
-        var source = """
-            fn (a: Int) -> Unit {
-            }""";
-
-        var node = parseString(source, Parser::parseTopLevelExpression);
-
-        assertThat(
-            node,
-            isUntypedFunctionExpressionNode()
-                .withParams(isUntypedParamsNode(
-                    isSequence(
-                        isUntypedParamNode("a", isUntypedTypeLevelReferenceNode("Int"))
-                    ),
-                    isSequence()
-                ))
-        );
-    }
-
-    @Test
-    public void canParseFunctionWithManyPositionalParams() {
-        var source = """
-            fn (a: Int, b: String, c: Bool) -> Unit {
-            }""";
-
-        var node = parseString(source, Parser::parseTopLevelExpression);
-
-        assertThat(
-            node,
-            isUntypedFunctionExpressionNode()
-                .withParams(isUntypedParamsNode(
-                    isSequence(
-                        isUntypedParamNode("a", isUntypedTypeLevelReferenceNode("Int")),
-                        isUntypedParamNode("b", isUntypedTypeLevelReferenceNode("String")),
-                        isUntypedParamNode("c", isUntypedTypeLevelReferenceNode("Bool"))
-                    ),
-                    isSequence()
-                ))
-        );
-    }
-
-    @Test
-    public void canParseFunctionWithSingleNamedParam() {
-        var source = """
-            fn (.a: Int) -> Unit {
-            }""";
-
-        var node = parseString(source, Parser::parseTopLevelExpression);
-
-        assertThat(
-            node,
-            isUntypedFunctionExpressionNode()
-                .withParams(isUntypedParamsNode(
-                    isSequence(),
-                    isSequence(
-                        isUntypedParamNode("a", isUntypedTypeLevelReferenceNode("Int"))
-                    )
-                ))
-        );
-    }
-
-    @Test
-    public void canParseFunctionWithManyNamedParams() {
-        var source = """
-            fn (.a: Int, .b: String, .c: Bool) -> Unit {
-            }""";
-
-        var node = parseString(source, Parser::parseTopLevelExpression);
-
-        assertThat(
-            node,
-            isUntypedFunctionExpressionNode()
-                .withParams(isUntypedParamsNode(
-                    isSequence(),
-                    isSequence(
-                        isUntypedParamNode("a", isUntypedTypeLevelReferenceNode("Int")),
-                        isUntypedParamNode("b", isUntypedTypeLevelReferenceNode("String")),
-                        isUntypedParamNode("c", isUntypedTypeLevelReferenceNode("Bool"))
-                    )
-                ))
-        );
-    }
-
-    @Test
-    public void canParseNamedParamAfterPositionalParam() {
-        var source = """
-            fn (a: Int, .b: String) -> Unit {
-            }""";
-
-        var node = parseString(source, Parser::parseTopLevelExpression);
-
-        assertThat(
-            node,
-            isUntypedFunctionExpressionNode()
-                .withParams(isUntypedParamsNode(
-                    isSequence(
-                        isUntypedParamNode("a", isUntypedTypeLevelReferenceNode("Int"))
-                    ),
-                    isSequence(
-                        isUntypedParamNode("b", isUntypedTypeLevelReferenceNode("String"))
-                    )
-                ))
-        );
-    }
-
-    @Test
-    public void cannotParsePositionalParamAfterNamedParam() {
-        var source = """
-            fn (.a: Int, b: String) -> Unit {
-            }""";
-
-        assertThrows(
-            PositionalParamAfterNamedParamError.class,
-            () -> parseString(source, Parser::parseTopLevelExpression)
-        );
-    }
-
-    @Test
-    public void paramsCanHaveTrailingComma() {
-        var source = """
-            fn (a: Int, ) -> Unit {
-            }""";
-
-        var node = parseString(source, Parser::parseTopLevelExpression);
-
-        assertThat(
-            node,
-            isUntypedFunctionExpressionNode()
-                .withParams(isUntypedParamsNode(
-                    isSequence(
-                        isUntypedParamNode("a", isUntypedTypeLevelReferenceNode("Int"))
-                    ),
-                    isSequence()
-                ))
-        );
-    }
-
-    @Test
-    public void canParseFunctionWithEffect() {
-        var source = """
-            fn () ! Io -> Unit {
-            }""";
-
-        var node = parseString(source, Parser::parseTopLevelExpression);
-
-        assertThat(
-            node,
-            isUntypedFunctionExpressionNode()
-                .withEffect(isOptionalOf(isUntypedTypeLevelReferenceNode("Io")))
-        );
-    }
-
-    @Test
     public void canParseFunctionWithBodyWithoutReturn() {
         var source = """
             fn () -> Unit {
diff --git a/src/test/java/org/shedlang/compiler/parser/ParserFunctionSignatureTests.java b/src/test/java/org/shedlang/compiler/parser/ParserFunctionSignatureTests.java
new file mode 100644
index 00000000..cfb610af
--- /dev/null
+++ b/src/test/java/org/shedlang/compiler/parser/ParserFunctionSignatureTests.java
@@ -0,0 +1,183 @@
+package org.shedlang.compiler.parser;
+
+import org.junit.jupiter.api.Test;
+import org.shedlang.compiler.parser.errors.PositionalParamAfterNamedParamError;
+
+import static org.junit.jupiter.api.Assertions.assertThrows;
+import static org.shedlang.compiler.ast.untyped.UntypedNodeMatchers.*;
+import static org.shedlang.compiler.ast.untyped.UntypedNodeMatchers.isUntypedTypeLevelReferenceNode;
+import static org.shedlang.compiler.parser.ParserTesting.parseString;
+import static org.zwobble.precisely.AssertThat.assertThat;
+import static org.zwobble.precisely.Matchers.*;
+
+public class ParserFunctionSignatureTests {
+    @Test
+    public void canParseEmptyParams() {
+        var source = "() -> Unit";
+
+        var node = parseString(source, Parser::parseFunctionSignature);
+
+        assertThat(
+            node,
+            isUntypedFunctionSignatureNode()
+                .withParams(isUntypedParamsNode(isSequence(), isSequence()))
+        );
+    }
+
+    @Test
+    public void canParseSinglePositionalParam() {
+        var source = "(a: Int) -> Unit";
+
+        var node = parseString(source, Parser::parseFunctionSignature);
+
+        assertThat(
+            node,
+            isUntypedFunctionSignatureNode().withParams(isUntypedParamsNode(
+                isSequence(
+                    isUntypedParamNode("a", isUntypedTypeLevelReferenceNode("Int"))
+                ),
+                isSequence()
+            ))
+        );
+    }
+
+    @Test
+    public void canParseManyPositionalParams() {
+        var source = "(a: Int, b: String, c: Bool) -> Unit";
+
+        var node = parseString(source, Parser::parseFunctionSignature);
+
+        assertThat(
+            node,
+            isUntypedFunctionSignatureNode().withParams(isUntypedParamsNode(
+                isSequence(
+                    isUntypedParamNode("a", isUntypedTypeLevelReferenceNode("Int")),
+                    isUntypedParamNode("b", isUntypedTypeLevelReferenceNode("String")),
+                    isUntypedParamNode("c", isUntypedTypeLevelReferenceNode("Bool"))
+                ),
+                isSequence()
+            ))
+        );
+    }
+
+    @Test
+    public void canParseSingleNamedParam() {
+        var source = "(.a: Int) -> Unit";
+
+        var node = parseString(source, Parser::parseFunctionSignature);
+
+        assertThat(
+            node,
+            isUntypedFunctionSignatureNode().withParams(isUntypedParamsNode(
+                isSequence(),
+                isSequence(
+                    isUntypedParamNode("a", isUntypedTypeLevelReferenceNode("Int"))
+                )
+            ))
+        );
+    }
+
+    @Test
+    public void canParseManyNamedParams() {
+        var source = "(.a: Int, .b: String, .c: Bool) -> Unit";
+
+        var node = parseString(source, Parser::parseFunctionSignature);
+
+        assertThat(
+            node,
+            isUntypedFunctionSignatureNode().withParams(isUntypedParamsNode(
+                isSequence(),
+                isSequence(
+                    isUntypedParamNode("a", isUntypedTypeLevelReferenceNode("Int")),
+                    isUntypedParamNode("b", isUntypedTypeLevelReferenceNode("String")),
+                    isUntypedParamNode("c", isUntypedTypeLevelReferenceNode("Bool"))
+                )
+            ))
+        );
+    }
+
+    @Test
+    public void canParseNamedParamAfterPositionalParam() {
+        var source = "(a: Int, .b: String) -> Unit";
+
+        var node = parseString(source, Parser::parseFunctionSignature);
+
+        assertThat(
+            node,
+            isUntypedFunctionSignatureNode().withParams(isUntypedParamsNode(
+                isSequence(
+                    isUntypedParamNode("a", isUntypedTypeLevelReferenceNode("Int"))
+                ),
+                isSequence(
+                    isUntypedParamNode("b", isUntypedTypeLevelReferenceNode("String"))
+                )
+            ))
+        );
+    }
+
+    @Test
+    public void cannotParsePositionalParamAfterNamedParam() {
+        var source = "(.a: Int, b: String) -> Unit";
+
+        assertThrows(
+            PositionalParamAfterNamedParamError.class,
+            () -> parseString(source, Parser::parseFunctionSignature)
+        );
+    }
+
+    @Test
+    public void paramsCanHaveTrailingComma() {
+        var source = "(a: Int, ) -> Unit";
+
+        var node = parseString(source, Parser::parseFunctionSignature);
+
+        assertThat(
+            node,
+            isUntypedFunctionSignatureNode().withParams(isUntypedParamsNode(
+                isSequence(
+                    isUntypedParamNode("a", isUntypedTypeLevelReferenceNode("Int"))
+                ),
+                isSequence()
+            ))
+        );
+    }
+
+    @Test
+    public void canParseSignatureWithoutEffect() {
+        var source = "() -> Unit";
+
+        var node = parseString(source, Parser::parseFunctionSignature);
+
+        assertThat(
+            node,
+            isUntypedFunctionSignatureNode()
+                .withEffect(isOptionalEmpty())
+        );
+    }
+
+    @Test
+    public void canParseSignatureWithEffect() {
+        var source = "() ! Io -> Unit";
+
+        var node = parseString(source, Parser::parseFunctionSignature);
+
+        assertThat(
+            node,
+            isUntypedFunctionSignatureNode()
+                .withEffect(isOptionalOf(isUntypedTypeLevelReferenceNode("Io")))
+        );
+    }
+
+    @Test
+    public void canParseReturnType() {
+        var source = "() -> Unit";
+
+        var node = parseString(source, Parser::parseFunctionSignature);
+
+        assertThat(
+            node,
+            isUntypedFunctionSignatureNode()
+                .withReturnType(isUntypedTypeLevelReferenceNode("Unit"))
+        );
+    }
+}
diff --git a/src/test/java/org/shedlang/compiler/parser/ParserFunctionTypeTests.java b/src/test/java/org/shedlang/compiler/parser/ParserFunctionTypeTests.java
index 038baef4..76311a97 100644
--- a/src/test/java/org/shedlang/compiler/parser/ParserFunctionTypeTests.java
+++ b/src/test/java/org/shedlang/compiler/parser/ParserFunctionTypeTests.java
@@ -136,18 +136,16 @@ public class ParserFunctionTypeTests {
 
     @Test
     public void paramsCanHaveTrailingComma() {
-        var source = """
-            fun f(a: Int, ) -> Unit {
-            }""";
+        var source = "fn (Int, ) -> Unit";
 
-        var node = parseString(source, Parser::parseNamespaceStatement);
+        var node = parseString(source, Parser::parseTopLevelTypeLevelExpression);
 
         assertThat(
             node,
-            isUntypedFunctionDefinitionNode()
-                .withParams(isUntypedParamsNode(
+            isUntypedFunctionTypeNode()
+                .withParams(isUntypedParamTypesNode(
                     isSequence(
-                        isUntypedParamNode("a", isUntypedTypeLevelReferenceNode("Int"))
+                        isUntypedTypeLevelReferenceNode("Int")
                     ),
                     isSequence()
                 ))