Introduce NativeTypeConstructor for greater safety

7 files changed, 44 insertions, 21 deletions

diff --git a/src/main/java/org/zwobble/hobgoblin/compiler/builtins/NativeTypes.java b/src/main/java/org/zwobble/hobgoblin/compiler/builtins/NativeTypes.java
index 485df8c..f4e499e 100644
--- a/src/main/java/org/zwobble/hobgoblin/compiler/builtins/NativeTypes.java
+++ b/src/main/java/org/zwobble/hobgoblin/compiler/builtins/NativeTypes.java
@@ -13,7 +13,7 @@ public class NativeTypes {
 
     public static final SimpleNativeType BOX_INNER = SimpleNativeType.builtin("Box");
 
-    public static TypeConstructor<SimpleNativeType> BOX = new TypeConstructor<>(
+    public static TypeConstructor<SimpleNativeType> BOX = Types.constructor(
         List.of(new TypeParam("T")),
         BOX_INNER
     );
@@ -24,7 +24,7 @@ public class NativeTypes {
 
     public static final SimpleNativeType LIST_INNER = SimpleNativeType.builtin("List");
 
-    public static TypeConstructor<SimpleNativeType> LIST = new TypeConstructor<>(
+    public static TypeConstructor<SimpleNativeType> LIST = Types.constructor(
         List.of(new TypeParam("T")),
         LIST_INNER
     );
@@ -35,7 +35,7 @@ public class NativeTypes {
 
     public static final SimpleNativeType OPTION_INNER = SimpleNativeType.builtin("Option");
 
-    public static TypeConstructor<SimpleNativeType> OPTION = new TypeConstructor<>(
+    public static TypeConstructor<SimpleNativeType> OPTION = Types.constructor(
         List.of(new TypeParam("T")),
         OPTION_INNER
     );
@@ -46,7 +46,7 @@ public class NativeTypes {
 
     public static final SimpleNativeType SHARED_INNER = SimpleNativeType.builtin("Shared");
 
-    public static TypeConstructor<SimpleNativeType> SHARED = new TypeConstructor<>(
+    public static TypeConstructor<SimpleNativeType> SHARED = Types.constructor(
         List.of(new TypeParam("T")),
         SHARED_INNER
     );
diff --git a/src/main/java/org/zwobble/hobgoblin/compiler/typechecker/TypeChecker.java b/src/main/java/org/zwobble/hobgoblin/compiler/typechecker/TypeChecker.java
index 4b02f60..9429313 100644
--- a/src/main/java/org/zwobble/hobgoblin/compiler/typechecker/TypeChecker.java
+++ b/src/main/java/org/zwobble/hobgoblin/compiler/typechecker/TypeChecker.java
@@ -408,12 +408,9 @@ public class TypeChecker {
             .map(untypedArg -> typeCheckMetaType(untypedArg, context).value())
             .toList();
 
-        var constructedType = switch (receiver.genericType()) {
-            case SimpleNativeType _ -> {
-                @SuppressWarnings("unchecked")
-                var narrowReceiver = (TypeConstructor<SimpleNativeType>) receiver;
-                yield new ConstructedNativeType(narrowReceiver, args);
-            }
+        var constructedType = switch (receiver) {
+            case NativeTypeConstructor nativeTypeConstructor ->
+                new ConstructedNativeType(nativeTypeConstructor, args);
         };
 
         return new TypedConstructedTypeNode(
diff --git a/src/main/java/org/zwobble/hobgoblin/compiler/types/NativeTypeConstructor.java b/src/main/java/org/zwobble/hobgoblin/compiler/types/NativeTypeConstructor.java
new file mode 100644
index 0000000..43e0cfc
--- /dev/null
+++ b/src/main/java/org/zwobble/hobgoblin/compiler/types/NativeTypeConstructor.java
@@ -0,0 +1,9 @@
+package org.zwobble.hobgoblin.compiler.types;
+
+import java.util.List;
+
+public record NativeTypeConstructor(
+    List<TypeParam> params,
+    SimpleNativeType genericType
+) implements TypeConstructor<SimpleNativeType> {
+}
diff --git a/src/main/java/org/zwobble/hobgoblin/compiler/types/TypeConstructor.java b/src/main/java/org/zwobble/hobgoblin/compiler/types/TypeConstructor.java
index 1e412d7..e2726fb 100644
--- a/src/main/java/org/zwobble/hobgoblin/compiler/types/TypeConstructor.java
+++ b/src/main/java/org/zwobble/hobgoblin/compiler/types/TypeConstructor.java
@@ -2,12 +2,11 @@ package org.zwobble.hobgoblin.compiler.types;
 
 import java.util.List;
 
-public record TypeConstructor<T extends ConstructibleType>(
-    List<TypeParam> params,
-    T genericType
-) implements TypeLevelValue {
-    @Override
-    public String describe() {
-        return genericType.describe();
+public sealed interface TypeConstructor<T extends ConstructibleType> extends TypeLevelValue permits NativeTypeConstructor {
+    List<TypeParam> params();
+    T genericType();
+
+    default String describe() {
+        return genericType().describe();
     }
 }
diff --git a/src/main/java/org/zwobble/hobgoblin/compiler/types/Types.java b/src/main/java/org/zwobble/hobgoblin/compiler/types/Types.java
new file mode 100644
index 0000000..6d8fcbb
--- /dev/null
+++ b/src/main/java/org/zwobble/hobgoblin/compiler/types/Types.java
@@ -0,0 +1,18 @@
+package org.zwobble.hobgoblin.compiler.types;
+
+import java.util.List;
+
+public class Types {
+    private Types() {}
+
+    @SuppressWarnings("unchecked")
+    public static <T extends ConstructibleType> TypeConstructor<T> constructor(
+        List<TypeParam> params,
+        T genericType
+    ) {
+        return (TypeConstructor<T>) switch (genericType) {
+            case SimpleNativeType simpleNativeType ->
+                new NativeTypeConstructor(params, simpleNativeType);
+        };
+    }
+}
diff --git a/src/test/java/org/zwobble/hobgoblin/compiler/typechecker/TypeCheckerConstructedTypeTests.java b/src/test/java/org/zwobble/hobgoblin/compiler/typechecker/TypeCheckerConstructedTypeTests.java
index 09c0f8c..c0a7f93 100644
--- a/src/test/java/org/zwobble/hobgoblin/compiler/typechecker/TypeCheckerConstructedTypeTests.java
+++ b/src/test/java/org/zwobble/hobgoblin/compiler/typechecker/TypeCheckerConstructedTypeTests.java
@@ -22,7 +22,7 @@ public class TypeCheckerConstructedTypeTests {
         );
         var context = TypeCheckerContextArb.namespaceContext();
         var listType = SimpleNativeType.builtin("List");
-        var listTypeConstructor = new TypeConstructor<>(List.of(new TypeParam("T")), listType);
+        var listTypeConstructor = Types.constructor(List.of(new TypeParam("T")), listType);
         context.declare("List", new TypeLevelValueType(listTypeConstructor), NullSource.INSTANCE);
         var int32Type = SimpleNativeType.builtin("Int32");
         context.declare("Int32", new TypeLevelValueType(int32Type), NullSource.INSTANCE);
@@ -42,7 +42,7 @@ public class TypeCheckerConstructedTypeTests {
         );
         var context = TypeCheckerContextArb.namespaceContext();
         var listType = SimpleNativeType.builtin("List");
-        var listTypeConstructor = new TypeConstructor<>(List.of(new TypeParam("T")), listType);
+        var listTypeConstructor = Types.constructor(List.of(new TypeParam("T")), listType);
         context.declare("List", new TypeLevelValueType(listTypeConstructor), NullSource.INSTANCE);
 
         var error = assertThrows(
@@ -65,7 +65,7 @@ public class TypeCheckerConstructedTypeTests {
         );
         var context = TypeCheckerContextArb.namespaceContext();
         var listType = SimpleNativeType.builtin("List");
-        var listTypeConstructor = new TypeConstructor<>(List.of(new TypeParam("T")), listType);
+        var listTypeConstructor = Types.constructor(List.of(new TypeParam("T")), listType);
         context.declare("List", new TypeLevelValueType(listTypeConstructor), NullSource.INSTANCE);
 
         var error = assertThrows(
diff --git a/src/test/java/org/zwobble/hobgoblin/compiler/typechecker/TypeCheckerMetaTypeTests.java b/src/test/java/org/zwobble/hobgoblin/compiler/typechecker/TypeCheckerMetaTypeTests.java
index c1b308c..4566b9b 100644
--- a/src/test/java/org/zwobble/hobgoblin/compiler/typechecker/TypeCheckerMetaTypeTests.java
+++ b/src/test/java/org/zwobble/hobgoblin/compiler/typechecker/TypeCheckerMetaTypeTests.java
@@ -35,7 +35,7 @@ public class TypeCheckerMetaTypeTests {
     public void whenVariableIsTypeLevelValueButNotMetaTypeThenErrorIsThrown() {
         var untyped = UntypedArb.typeLevelReference("List");
         var context = TypeCheckerContextArb.namespaceContext();
-        var typeConstructor = new TypeConstructor<>(List.of(new TypeParam("T")), SimpleNativeType.builtin("List"));
+        var typeConstructor = Types.constructor(List.of(new TypeParam("T")), SimpleNativeType.builtin("List"));
         context.declare("List", new TypeLevelValueType(typeConstructor), NullSource.INSTANCE);
 
         var error = assertThrows(