Check number of type-level arguments

3 files changed, 65 insertions, 1 deletions

diff --git a/src/main/java/org/shedlang/compiler/typechecker/TypeChecker.java b/src/main/java/org/shedlang/compiler/typechecker/TypeChecker.java
index c51758bb..d9a52038 100644
--- a/src/main/java/org/shedlang/compiler/typechecker/TypeChecker.java
+++ b/src/main/java/org/shedlang/compiler/typechecker/TypeChecker.java
@@ -385,6 +385,7 @@ public class TypeChecker {
                     var typeLevelArgs = typeCheckTypeLevelArgs(
                         untypedTypeLevelArgNodes,
                         typeConstructor.params(),
+                        untyped.source(),
                         contextForReceiver
                     );
                     specificReceiverType = Types.metaType(
@@ -397,6 +398,7 @@ public class TypeChecker {
                     var typeLevelArgs = typeCheckTypeLevelArgs(
                         untypedTypeLevelArgNodes,
                         initialReceiverType.typeLevelParams().get(),
+                        untyped.source(),
                         contextForReceiver
                     );
                     specificReceiverType = initialReceiverType.applyTypeLevelArgs(typeLevelArgs);
@@ -1883,11 +1885,19 @@ public class TypeChecker {
     private static ArrayList<TypeLevelValue> typeCheckTypeLevelArgs(
         List<UntypedTypeLevelExpressionNode> untyped,
         List<TypeLevelParam> typeLevelParams,
+        Source source,
         TypeCheckerContext context
     ) {
+        if (untyped.size() != typeLevelParams.size()) {
+            throw new WrongNumberOfTypeLevelArgsError(
+                typeLevelParams.size(),
+                untyped.size(),
+                source
+            );
+        }
+
         var typeLevelArgs = new ArrayList<TypeLevelValue>();
 
-        // TODO: check length
         // TODO: check arg is appropriate for param
 
         for (var paramIndex = 0; paramIndex < typeLevelParams.size(); paramIndex++) {
diff --git a/src/main/java/org/shedlang/compiler/typechecker/errors/WrongNumberOfTypeLevelArgsError.java b/src/main/java/org/shedlang/compiler/typechecker/errors/WrongNumberOfTypeLevelArgsError.java
new file mode 100644
index 00000000..9af86c37
--- /dev/null
+++ b/src/main/java/org/shedlang/compiler/typechecker/errors/WrongNumberOfTypeLevelArgsError.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 WrongNumberOfTypeLevelArgsError extends SourceError {
+    private final int expected;
+    private final int actual;
+
+    public WrongNumberOfTypeLevelArgsError(int expected, int actual, Source source) {
+        super("Expected " + expected + " type-level arguments but got " + actual, source);
+        this.expected = expected;
+        this.actual = actual;
+    }
+
+    public int expected() {
+        return expected;
+    }
+
+    public int actual() {
+        return actual;
+    }
+}
diff --git a/src/test/java/org/shedlang/compiler/typechecker/TypeCheckerCallTests.java b/src/test/java/org/shedlang/compiler/typechecker/TypeCheckerCallTests.java
index 21a3e718..3027304e 100644
--- a/src/test/java/org/shedlang/compiler/typechecker/TypeCheckerCallTests.java
+++ b/src/test/java/org/shedlang/compiler/typechecker/TypeCheckerCallTests.java
@@ -632,4 +632,35 @@ public class TypeCheckerCallTests {
                 .withHasEffects(true)
         );
     }
+
+    @Test
+    public void whenReceiverIsCalledWithWrongNumberOfTypeLevelArgsThenErrorIsThrown() {
+        var untyped = UntypedCallNode.builder()
+            .withReceiver(Untyped.reference("identity"))
+            .withTypeLevelArgs(List.of(
+                Untyped.typeLevelReference("Int"),
+                Untyped.typeLevelReference("Int")
+            ))
+            .addPositionalArg(Untyped.intLiteral(42))
+            .build();
+        var context = TypeCheckerContext.EMPTY
+            .enterGlobal(P.map(
+                Map.entry(
+                    "identity",
+                    FunctionType.builder()
+                        .withTypeLevelParams(List.of(
+                            TypeParam.forFunction(NamespaceName.of("Example"), "identity", "T")
+                        ))
+                        .addPositionalParam(TypeParam.forFunction(NamespaceName.of("Example"), "identity", "T"))
+                        .withReturnType(TypeParam.forFunction(NamespaceName.of("Example"), "identity", "T"))
+                        .build()
+                ),
+                Map.entry("Int", Types.metaType(Types.INT))
+            ));
+
+        var error = assertThrows(WrongNumberOfTypeLevelArgsError.class, () -> typeCheckExpression(untyped, context));
+
+        assertThat(error.expected(), equalTo(1));
+        assertThat(error.actual(), equalTo(2));
+    }
 }