Type check type level references

10 files changed, 96 insertions, 12 deletions

diff --git a/src/main/java/org/shedlang/compiler/ast/typed/TypedTypeLevelExpressionNode.java b/src/main/java/org/shedlang/compiler/ast/typed/TypedTypeLevelExpressionNode.java
new file mode 100644
index 00000000..4b10483d
--- /dev/null
+++ b/src/main/java/org/shedlang/compiler/ast/typed/TypedTypeLevelExpressionNode.java
@@ -0,0 +1,7 @@
+package org.shedlang.compiler.ast.typed;
+
+import org.shedlang.compiler.types.TypeLevelValue;
+
+public interface TypedTypeLevelExpressionNode extends TypedNode {
+    TypeLevelValue value();
+}
diff --git a/src/main/java/org/shedlang/compiler/ast/typed/TypedTypeLevelReferenceNode.java b/src/main/java/org/shedlang/compiler/ast/typed/TypedTypeLevelReferenceNode.java
new file mode 100644
index 00000000..009d0b8b
--- /dev/null
+++ b/src/main/java/org/shedlang/compiler/ast/typed/TypedTypeLevelReferenceNode.java
@@ -0,0 +1,11 @@
+package org.shedlang.compiler.ast.typed;
+
+import org.shedlang.compiler.sources.Source;
+import org.shedlang.compiler.types.TypeLevelValue;
+
+public record TypedTypeLevelReferenceNode(
+    String name,
+    TypeLevelValue value,
+    Source source
+) implements TypedTypeLevelExpressionNode {
+}
diff --git a/src/main/java/org/shedlang/compiler/typechecker/TypeChecker.java b/src/main/java/org/shedlang/compiler/typechecker/TypeChecker.java
index f707dac0..f2af9769 100644
--- a/src/main/java/org/shedlang/compiler/typechecker/TypeChecker.java
+++ b/src/main/java/org/shedlang/compiler/typechecker/TypeChecker.java
@@ -2,10 +2,12 @@ package org.shedlang.compiler.typechecker;
 
 import org.shedlang.compiler.ast.typed.*;
 import org.shedlang.compiler.ast.untyped.*;
+import org.shedlang.compiler.sources.Source;
 import org.shedlang.compiler.typechecker.errors.*;
 import org.shedlang.compiler.typechecker.typesets.TypeSets;
 import org.shedlang.compiler.types.FunctionType;
 import org.shedlang.compiler.types.Type;
+import org.shedlang.compiler.types.TypeLevelValueType;
 
 import java.util.HashSet;
 
@@ -27,6 +29,16 @@ public class TypeChecker {
         return subType.equals(superType);
     }
 
+    private static Type lookupVariable(String name, Source source, TypeCheckerContext context) {
+        var type = context.environment(name);
+
+        if (type.isEmpty()) {
+            throw new UnknownVariableError(name, source);
+        }
+
+        return type.get();
+    }
+
     private static TypedArgsNode typeCheckArgs(
         UntypedArgsNode args,
         TypeCheckerContext context,
@@ -171,25 +183,48 @@ public class TypeChecker {
         UntypedReferenceNode untyped,
         TypeCheckerContext context
     ) {
-        var type = context.environment(untyped.name());
-
-        if (type.isEmpty()) {
-            throw new UnknownVariableError(untyped.name(), untyped.source());
-        }
+        var type = lookupVariable(untyped.name(), untyped.source(), context);
 
         return new TypedReferenceNode(
             untyped.name(),
-            type.get(),
+            type,
             untyped.source()
         );
     }
 
     private static TypedStringLiteralNode typeCheckStringLiteral(
-        UntypedStringLiteralNode untype
+        UntypedStringLiteralNode untyped
     ) {
         return new TypedStringLiteralNode(
-            untype.value(),
-            untype.source()
+            untyped.value(),
+            untyped.source()
+        );
+    }
+
+    static TypedTypeLevelExpressionNode typeCheckTypeLevelExpression(
+        UntypedTypeLevelExpressionNode untyped,
+        TypeCheckerContext context
+    ) {
+        return switch (untyped) {
+            case UntypedTypeLevelReferenceNode reference ->
+                typeCheckTypeLevelReference(reference, context);
+        };
+    }
+
+    private static TypedTypeLevelExpressionNode typeCheckTypeLevelReference(
+        UntypedTypeLevelReferenceNode untyped,
+        TypeCheckerContext context
+    ) {
+        var type = lookupVariable(untyped.name(), untyped.source(), context);
+
+        if (!(type instanceof TypeLevelValueType typeLevelValueType)) {
+            throw new UnexpectedTypeError(TypeSets.TYPE_LEVEL_VALUE, type, untyped.source());
+        }
+
+        return new TypedTypeLevelReferenceNode(
+            untyped.name(),
+            typeLevelValueType.value(),
+            untyped.source()
         );
     }
 }
diff --git a/src/main/java/org/shedlang/compiler/typechecker/typesets/TypeSet.java b/src/main/java/org/shedlang/compiler/typechecker/typesets/TypeSet.java
index 79cb0433..01899978 100644
--- a/src/main/java/org/shedlang/compiler/typechecker/typesets/TypeSet.java
+++ b/src/main/java/org/shedlang/compiler/typechecker/typesets/TypeSet.java
@@ -1,5 +1,5 @@
 package org.shedlang.compiler.typechecker.typesets;
 
-public sealed interface TypeSet permits TypeSetFunction, TypeSetType {
+public sealed interface TypeSet permits TypeSetFunction, TypeSetType, TypeSetTypeLevelValue {
     String describe();
 }
diff --git a/src/main/java/org/shedlang/compiler/typechecker/typesets/TypeSetTypeLevelValue.java b/src/main/java/org/shedlang/compiler/typechecker/typesets/TypeSetTypeLevelValue.java
new file mode 100644
index 00000000..791ec37a
--- /dev/null
+++ b/src/main/java/org/shedlang/compiler/typechecker/typesets/TypeSetTypeLevelValue.java
@@ -0,0 +1,13 @@
+package org.shedlang.compiler.typechecker.typesets;
+
+public final class TypeSetTypeLevelValue implements TypeSet {
+    private TypeSetTypeLevelValue() {
+    }
+
+    static final TypeSetTypeLevelValue INSTANCE = new TypeSetTypeLevelValue();
+
+    @Override
+    public String describe() {
+        return "type-level value";
+    }
+}
diff --git a/src/main/java/org/shedlang/compiler/typechecker/typesets/TypeSets.java b/src/main/java/org/shedlang/compiler/typechecker/typesets/TypeSets.java
index b783a5ef..6bb13f7a 100644
--- a/src/main/java/org/shedlang/compiler/typechecker/typesets/TypeSets.java
+++ b/src/main/java/org/shedlang/compiler/typechecker/typesets/TypeSets.java
@@ -7,6 +7,7 @@ public class TypeSets {
     }
 
     public static final TypeSet FUNCTION = TypeSetFunction.INSTANCE;
+    public static final TypeSet TYPE_LEVEL_VALUE = TypeSetTypeLevelValue.INSTANCE;
 
     public static TypeSet type(Type type) {
         return new TypeSetType(type);
diff --git a/src/main/java/org/shedlang/compiler/types/Type.java b/src/main/java/org/shedlang/compiler/types/Type.java
index 5077776c..fdefb86f 100644
--- a/src/main/java/org/shedlang/compiler/types/Type.java
+++ b/src/main/java/org/shedlang/compiler/types/Type.java
@@ -1,5 +1,5 @@
 package org.shedlang.compiler.types;
 
-public sealed interface Type permits BoolType, FunctionType, IntType, StringType, UnitType {
-    String describe();
+public sealed interface Type extends TypeLevelValue
+    permits BoolType, FunctionType, IntType, StringType, TypeLevelValueType, UnitType {
 }
diff --git a/src/main/java/org/shedlang/compiler/types/TypeLevelValue.java b/src/main/java/org/shedlang/compiler/types/TypeLevelValue.java
new file mode 100644
index 00000000..3eaddb7f
--- /dev/null
+++ b/src/main/java/org/shedlang/compiler/types/TypeLevelValue.java
@@ -0,0 +1,5 @@
+package org.shedlang.compiler.types;
+
+public sealed interface TypeLevelValue permits Type {
+    String describe();
+}
diff --git a/src/main/java/org/shedlang/compiler/types/TypeLevelValueType.java b/src/main/java/org/shedlang/compiler/types/TypeLevelValueType.java
new file mode 100644
index 00000000..ee47af68
--- /dev/null
+++ b/src/main/java/org/shedlang/compiler/types/TypeLevelValueType.java
@@ -0,0 +1,8 @@
+package org.shedlang.compiler.types;
+
+public record TypeLevelValueType(TypeLevelValue value) implements Type {
+    @Override
+    public String describe() {
+        return "TypeLevelValue[" + value.describe() + "]";
+    }
+}
diff --git a/src/main/java/org/shedlang/compiler/types/Types.java b/src/main/java/org/shedlang/compiler/types/Types.java
index 9655d2bb..cb734272 100644
--- a/src/main/java/org/shedlang/compiler/types/Types.java
+++ b/src/main/java/org/shedlang/compiler/types/Types.java
@@ -8,4 +8,8 @@ public class Types {
     public static final Type INT = IntType.INSTANCE;
     public static final Type STRING = StringType.INSTANCE;
     public static final Type UNIT = UnitType.INSTANCE;
+
+    public static Type metaType(Type type) {
+        return new TypeLevelValueType(type);
+    }
 }