From 776fcb476f229030cb5d34f4b948603f05c01a79 Mon Sep 17 00:00:00 2001
From: Michael Williamson <mike@zwobble.org>
Date: Fri, 24 Apr 2026 12:43:29 +0100
Subject: Type check type level reference

---
 .../hobgoblin/compiler/ast/untyped/UntypedArb.java | 12 ++++
 .../typechecker/TypeCheckerContextArb.java         | 10 +++
 .../TypeCheckerTypeLevelReferenceTests.java        | 75 ++++++++++++++++++++++
 3 files changed, 97 insertions(+)
 create mode 100644 src/test/java/org/zwobble/hobgoblin/compiler/ast/untyped/UntypedArb.java
 create mode 100644 src/test/java/org/zwobble/hobgoblin/compiler/typechecker/TypeCheckerContextArb.java
 create mode 100644 src/test/java/org/zwobble/hobgoblin/compiler/typechecker/TypeCheckerTypeLevelReferenceTests.java

(limited to 'src/test/java/org/zwobble')

diff --git a/src/test/java/org/zwobble/hobgoblin/compiler/ast/untyped/UntypedArb.java b/src/test/java/org/zwobble/hobgoblin/compiler/ast/untyped/UntypedArb.java
new file mode 100644
index 0000000..5a011d7
--- /dev/null
+++ b/src/test/java/org/zwobble/hobgoblin/compiler/ast/untyped/UntypedArb.java
@@ -0,0 +1,12 @@
+package org.zwobble.hobgoblin.compiler.ast.untyped;
+
+import org.zwobble.hobgoblin.compiler.sources.NullSource;
+
+public class UntypedArb {
+    private UntypedArb() {
+    }
+
+    public static UntypedTypeLevelReferenceNode typeLevelReference(String name) {
+        return new UntypedTypeLevelReferenceNode(name, NullSource.INSTANCE);
+    }
+}
diff --git a/src/test/java/org/zwobble/hobgoblin/compiler/typechecker/TypeCheckerContextArb.java b/src/test/java/org/zwobble/hobgoblin/compiler/typechecker/TypeCheckerContextArb.java
new file mode 100644
index 0000000..98d8064
--- /dev/null
+++ b/src/test/java/org/zwobble/hobgoblin/compiler/typechecker/TypeCheckerContextArb.java
@@ -0,0 +1,10 @@
+package org.zwobble.hobgoblin.compiler.typechecker;
+
+public class TypeCheckerContextArb {
+    private TypeCheckerContextArb() {
+    }
+
+    public static TypeCheckerContext context() {
+        return new TypeCheckerContext();
+    }
+}
diff --git a/src/test/java/org/zwobble/hobgoblin/compiler/typechecker/TypeCheckerTypeLevelReferenceTests.java b/src/test/java/org/zwobble/hobgoblin/compiler/typechecker/TypeCheckerTypeLevelReferenceTests.java
new file mode 100644
index 0000000..82704fc
--- /dev/null
+++ b/src/test/java/org/zwobble/hobgoblin/compiler/typechecker/TypeCheckerTypeLevelReferenceTests.java
@@ -0,0 +1,75 @@
+package org.zwobble.hobgoblin.compiler.typechecker;
+
+import org.junit.jupiter.api.Test;
+import org.zwobble.hobgoblin.compiler.ast.typed.TypedTypeLevelReferenceNode;
+import org.zwobble.hobgoblin.compiler.ast.untyped.UntypedArb;
+import org.zwobble.hobgoblin.compiler.types.ScalarType;
+import org.zwobble.hobgoblin.compiler.types.TypeLevelValueType;
+import org.zwobble.hobgoblin.compiler.types.TypeSet;
+
+import static org.junit.jupiter.api.Assertions.assertThrows;
+import static org.zwobble.precisely.AssertThat.assertThat;
+import static org.zwobble.precisely.Matchers.*;
+
+public class TypeCheckerTypeLevelReferenceTests {
+    @Test
+    public void whenNameIsUnrecognisedThenErrorIsThrown() {
+        var untyped = UntypedArb.typeLevelReference("X");
+        var context = TypeCheckerContextArb.context();
+
+        var error = assertThrows(
+            UndeclaredVariableError.class,
+            () -> TypeChecker.typeCheckTypeLevelExpression(untyped, context)
+        );
+
+        assertThat(error.variableName(), equalTo("X"));
+    }
+
+    @Test
+    public void whenNameIsUndefinedThenErrorIsThrown() {
+        var untyped = UntypedArb.typeLevelReference("X");
+        var context = TypeCheckerContextArb.context();
+        context.declare("X");
+
+        var error = assertThrows(
+            UndefinedVariableError.class,
+            () -> TypeChecker.typeCheckTypeLevelExpression(untyped, context)
+        );
+
+        assertThat(error.variableName(), equalTo("X"));
+    }
+
+    @Test
+    public void whenVariableIsNotTypeLevelValueThenErrorIsThrown() {
+        var untyped = UntypedArb.typeLevelReference("X");
+        var context = TypeCheckerContextArb.context();
+        context.declare("X");
+        var scalarType = new ScalarType("Int");
+        context.define("X", scalarType);
+
+        var error = assertThrows(
+            UnexpectedTypeError.class,
+            () -> TypeChecker.typeCheckTypeLevelExpression(untyped, context)
+        );
+
+        assertThat(error.expected(), equalTo(new TypeSet.MetaType()));
+        assertThat(error.actual(), equalTo(scalarType));
+    }
+
+    @Test
+    public void whenNameIsMetaTypeThenValueIsType() {
+        var untyped = UntypedArb.typeLevelReference("X");
+        var context = TypeCheckerContextArb.context();
+        context.declare("X");
+        var scalarType = new ScalarType("Int");
+        context.define("X", new TypeLevelValueType(scalarType));
+
+        var typed = TypeChecker.typeCheckTypeLevelExpression(untyped, context);
+
+        assertThat(typed, instanceOf(
+            TypedTypeLevelReferenceNode.class,
+            has("name", TypedTypeLevelReferenceNode::name, equalTo("X")),
+            has("value", TypedTypeLevelReferenceNode::value, equalTo(scalarType))
+        ));
+    }
+}
-- 
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