4 files changed, 36 insertions, 2 deletions
diff --git a/src/main/java/org/shedlang/compiler/typechecker/TypeChecker.java b/src/main/java/org/shedlang/compiler/typechecker/TypeChecker.java
index e89bdd61..fee93041 100644
--- a/src/main/java/org/shedlang/compiler/typechecker/TypeChecker.java
+++ b/src/main/java/org/shedlang/compiler/typechecker/TypeChecker.java
@@ -2,6 +2,9 @@ package org.shedlang.compiler.typechecker;
 
 import org.shedlang.compiler.ast.typed.*;
 import org.shedlang.compiler.ast.untyped.*;
+import org.shedlang.compiler.typechecker.errors.UnexpectedTypeError;
+import org.shedlang.compiler.typechecker.errors.UnknownVariableError;
+import org.shedlang.compiler.typechecker.errors.WrongNumberOfPositionalArgs;
 import org.shedlang.compiler.typechecker.typesets.TypeSets;
 import org.shedlang.compiler.types.FunctionType;
 import org.shedlang.compiler.types.Type;
@@ -29,6 +32,14 @@ public class TypeChecker {
         TypeCheckerContext context,
         FunctionType receiverType
     ) {
+        if (args.positional().size() != receiverType.positionalParams().size()) {
+            throw new WrongNumberOfPositionalArgs(
+                receiverType.positionalParams().size(),
+                args.positional().size(),
+                args.source()
+            );
+        }
+
         var typedPositionalArgs = args.positional().stream()
             .map(arg -> typeCheckExpression(arg, context))
             .toList();
diff --git a/src/main/java/org/shedlang/compiler/typechecker/UnexpectedTypeError.java b/src/main/java/org/shedlang/compiler/typechecker/errors/UnexpectedTypeError.java
index 51cc6652..02355f2a 100644
--- a/src/main/java/org/shedlang/compiler/typechecker/UnexpectedTypeError.java
+++ b/src/main/java/org/shedlang/compiler/typechecker/errors/UnexpectedTypeError.java
@@ -1,4 +1,4 @@
-package org.shedlang.compiler.typechecker;
+package org.shedlang.compiler.typechecker.errors;
 
 import org.shedlang.compiler.errors.SourceError;
 import org.shedlang.compiler.sources.Source;
diff --git a/src/main/java/org/shedlang/compiler/typechecker/UnknownVariableError.java b/src/main/java/org/shedlang/compiler/typechecker/errors/UnknownVariableError.java
index 91ab3fae..bc85c18c 100644
--- a/src/main/java/org/shedlang/compiler/typechecker/UnknownVariableError.java
+++ b/src/main/java/org/shedlang/compiler/typechecker/errors/UnknownVariableError.java
@@ -1,4 +1,4 @@
-package org.shedlang.compiler.typechecker;
+package org.shedlang.compiler.typechecker.errors;
 
 import org.shedlang.compiler.errors.SourceError;
 import org.shedlang.compiler.sources.Source;
diff --git a/src/main/java/org/shedlang/compiler/typechecker/errors/WrongNumberOfPositionalArgs.java b/src/main/java/org/shedlang/compiler/typechecker/errors/WrongNumberOfPositionalArgs.java
new file mode 100644
index 00000000..723c3f7d
--- /dev/null
+++ b/src/main/java/org/shedlang/compiler/typechecker/errors/WrongNumberOfPositionalArgs.java
@@ -0,0 +1,23 @@
+package org.shedlang.compiler.typechecker.errors;
+
+import org.shedlang.compiler.errors.SourceError;
+import org.shedlang.compiler.sources.Source;
+
+public class WrongNumberOfPositionalArgs extends SourceError {
+    private final int expected;
+    private final int actual;
+
+    public WrongNumberOfPositionalArgs(int expected, int actual, Source source) {
+        super("Expected " + expected + " positional arguments but got " + actual, source);
+        this.expected = expected;
+        this.actual = actual;
+    }
+
+    public int expected() {
+        return expected;
+    }
+
+    public int actual() {
+        return actual;
+    }
+}