Only allow positional args before named args

3 files changed, 46 insertions, 4 deletions

diff --git a/src/main/java/org/shedlang/compiler/parser/Parser.java b/src/main/java/org/shedlang/compiler/parser/Parser.java
index 855634e7..74f9a79b 100644
--- a/src/main/java/org/shedlang/compiler/parser/Parser.java
+++ b/src/main/java/org/shedlang/compiler/parser/Parser.java
@@ -52,10 +52,9 @@ public class Parser {
                     named.add(new UntypedNamedArgNode(argName, expression, argSource));
                 } else {
                     var expression = parseTopLevelExpression(tokens);
-                    // TODO:
-//                    if (named.isEmpty()) {
-//                        throw new PositionalArgAfterNamedArgError(tokens.peek());
-//                    }
+                    if (!named.isEmpty()) {
+                        throw new PositionalArgAfterNamedArgError(expression.source());
+                    }
                     positional.add(expression);
                 }
                 return null;
diff --git a/src/main/java/org/shedlang/compiler/parser/PositionalArgAfterNamedArgError.java b/src/main/java/org/shedlang/compiler/parser/PositionalArgAfterNamedArgError.java
new file mode 100644
index 00000000..11a8d177
--- /dev/null
+++ b/src/main/java/org/shedlang/compiler/parser/PositionalArgAfterNamedArgError.java
@@ -0,0 +1,11 @@
+package org.shedlang.compiler.parser;
+
+import org.shedlang.compiler.errors.SourceError;
+import org.shedlang.compiler.sources.Source;
+
+public class PositionalArgAfterNamedArgError extends SourceError {
+    public PositionalArgAfterNamedArgError(Source source) {
+        super("Positional arg cannot follow named arg", source);
+    }
+}
+
diff --git a/src/test/java/org/shedlang/compiler/parser/ParserCallTests.java b/src/test/java/org/shedlang/compiler/parser/ParserCallTests.java
index 1020b430..d75c6643 100644
--- a/src/test/java/org/shedlang/compiler/parser/ParserCallTests.java
+++ b/src/test/java/org/shedlang/compiler/parser/ParserCallTests.java
@@ -2,6 +2,7 @@ package org.shedlang.compiler.parser;
 
 import org.junit.jupiter.api.Test;
 
+import static org.junit.jupiter.api.Assertions.assertThrows;
 import static org.shedlang.compiler.ast.UntypedNodeMatchers.*;
 import static org.shedlang.compiler.parser.ParserTesting.parseString;
 import static org.zwobble.precisely.AssertThat.assertThat;
@@ -121,6 +122,37 @@ public class ParserCallTests {
     }
 
     @Test
+    public void canParseNamedArgumentAfterPositionalArgument() {
+        var source = "f(a, .named = b)";
+
+        var node = parseString(source, Parser::parseTopLevelExpression);
+
+        assertThat(
+            node,
+            isUntypedCallNode()
+                .withArgs(
+                    isUntypedArgsNode()
+                        .withPositional(isSequence(
+                            isUntypedReferenceNode("a")
+                        ))
+                        .withNamed(isSequence(
+                            isUntypedNamedArgNode("named", isUntypedReferenceNode("b"))
+                        ))
+                )
+        );
+    }
+
+    @Test
+    public void cannotParsePositionalArgumentAfterNamedArgument() {
+        var source = "f(.y = false, true)";
+
+        assertThrows(
+            PositionalArgAfterNamedArgError.class,
+            () -> parseString(source, Parser::parseTopLevelExpression)
+        );
+    }
+
+    @Test
     public void argumentListCanHaveTrailingComma() {
         var source = "f(a,)";