Implement main-thread Camino sessions and synchronous CRDT editing

src/capability-language/generic-types.ts

@@ -110,6 +110,7 @@ export class GenericSourceTypes {
       }
       if (type.kind === "list" || type.kind === "optional") return storable(type.value, depth + 1);
       if (type.kind === "record") return Object.values(type.fields).every((field) => storable(field, depth + 1));
+      if (type.kind === "variant") return Object.values(type.cases).every((entry) => storable(entry.value, depth + 1));
       if (type.kind === "alias") {
         const alias = aliases.get(type.definitionId);
         if (!alias || alias.parameters.length !== type.arguments.length) return false;
@@ -301,6 +302,24 @@ export class GenericSourceTypes {
   }
 
   expression(context: ValueTypeContext): ValueTypeExpression {
+    if (context.VARIANT()) {
+      const entries = context.variantCase().map(
+        (entry) =>
+          [
+            entry.identifier().getText(),
+            {
+              id: literal(entry.stringLiteral()),
+              value: this.expression(entry.valueType()),
+            },
+          ] as const,
+      );
+      if (
+        new Set(entries.map(([label]) => label)).size !== entries.length ||
+        new Set(entries.map(([, entry]) => entry.id)).size !== entries.length
+      )
+        throw new GenericTypeError("duplicate-variant-case", "variant", "Variant labels and case IDs must be unique");
+      return { kind: "variant", id: literal(context.stringLiteral()!), cases: Object.fromEntries(entries) };
+    }
     if (context.scalarType())
       return {
         kind: "scalar",