Require when cases to be structs

5 files changed, 25 insertions, 4 deletions

diff --git a/src/main/java/org/shedlang/compiler/ast/typed/TypedWhenCaseNode.java b/src/main/java/org/shedlang/compiler/ast/typed/TypedWhenCaseNode.java
index b50003ba..eb614cfc 100644
--- a/src/main/java/org/shedlang/compiler/ast/typed/TypedWhenCaseNode.java
+++ b/src/main/java/org/shedlang/compiler/ast/typed/TypedWhenCaseNode.java
@@ -1,10 +1,10 @@
 package org.shedlang.compiler.ast.typed;
 
 import org.shedlang.compiler.sources.Source;
-import org.shedlang.compiler.types.Type;
+import org.shedlang.compiler.types.StructType;
 
 public record TypedWhenCaseNode(
-    TypedTypeLevelExpressionNode<Type> caseType,
+    TypedTypeLevelExpressionNode<StructType> caseType,
     TypedBlockNode body,
     Source source
 ) implements TypedNode {
diff --git a/src/main/java/org/shedlang/compiler/typechecker/TypeChecker.java b/src/main/java/org/shedlang/compiler/typechecker/TypeChecker.java
index 4cb52e54..e429d246 100644
--- a/src/main/java/org/shedlang/compiler/typechecker/TypeChecker.java
+++ b/src/main/java/org/shedlang/compiler/typechecker/TypeChecker.java
@@ -1214,7 +1214,7 @@ public class TypeChecker {
         TypeCheckerContext context
     ) {
         var typedCaseType = typeCheckTypeLevelExpression(
-            TypeSets.META_TYPE,
+            TypeSets.STRUCT_META_TYPE,
             untyped.caseType(),
             context
         );
diff --git a/src/main/java/org/shedlang/compiler/typechecker/typesets/TypeSetStructMetaType.java b/src/main/java/org/shedlang/compiler/typechecker/typesets/TypeSetStructMetaType.java
new file mode 100644
index 00000000..b6db14cc
--- /dev/null
+++ b/src/main/java/org/shedlang/compiler/typechecker/typesets/TypeSetStructMetaType.java
@@ -0,0 +1,20 @@
+package org.shedlang.compiler.typechecker.typesets;
+
+import org.shedlang.compiler.types.StructType;
+
+public final class TypeSetStructMetaType implements TypeSetTypeLevelValue<StructType> {
+    private TypeSetStructMetaType() {
+    }
+
+    static final TypeSetStructMetaType INSTANCE = new TypeSetStructMetaType();
+
+    @Override
+    public String describe() {
+        return "struct metatype";
+    }
+
+    @Override
+    public Class<StructType> valueClass() {
+        return StructType.class;
+    }
+}
diff --git a/src/main/java/org/shedlang/compiler/typechecker/typesets/TypeSetTypeLevelValue.java b/src/main/java/org/shedlang/compiler/typechecker/typesets/TypeSetTypeLevelValue.java
index 4007eb2c..b9e66762 100644
--- a/src/main/java/org/shedlang/compiler/typechecker/typesets/TypeSetTypeLevelValue.java
+++ b/src/main/java/org/shedlang/compiler/typechecker/typesets/TypeSetTypeLevelValue.java
@@ -2,6 +2,6 @@ package org.shedlang.compiler.typechecker.typesets;
 
 import org.shedlang.compiler.types.TypeLevelValue;
 
-public sealed interface TypeSetTypeLevelValue<T extends TypeLevelValue> extends TypeSet permits TypeSetEffect, TypeSetMetaType {
+public sealed interface TypeSetTypeLevelValue<T extends TypeLevelValue> extends TypeSet permits TypeSetEffect, TypeSetMetaType, TypeSetStructMetaType {
     Class<T> valueClass();
 }
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 6b6d2d69..b6a0ad3a 100644
--- a/src/main/java/org/shedlang/compiler/typechecker/typesets/TypeSets.java
+++ b/src/main/java/org/shedlang/compiler/typechecker/typesets/TypeSets.java
@@ -9,6 +9,7 @@ public class TypeSets {
     public static final TypeSetEffect EFFECT = TypeSetEffect.INSTANCE;
     public static final TypeSet FUNCTION = TypeSetFunction.INSTANCE;
     public static final TypeSetMetaType META_TYPE = TypeSetMetaType.INSTANCE;
+    public static final TypeSetStructMetaType STRUCT_META_TYPE = TypeSetStructMetaType.INSTANCE;
     public static final TypeSetTuple TUPLE = TypeSetTuple.INSTANCE;
 
     public static TypeSet type(Type type) {