Implement main-thread Camino sessions and synchronous CRDT editing

src/capability-language/parser.ts

@@ -316,6 +316,7 @@ const lowerValueType = (state: LoweringState, context: ValueTypeContext | null):
     throw new Error("Missing value type after a successful parse");
   }
   if (
+    context.VARIANT() ||
     context.REF() ||
     context.typeArguments() ||
     (context.identifier() && !context.ATOM_REF() && !context.INTERFACE_REF())
@@ -1658,6 +1659,13 @@ const lowerPackage = (
     const operation = exportContext.packageOperationExport();
     const generic = operation ?? exportContext.packageFunctionExport();
     if (generic?.typeParameters()) {
+      if (generic.preparationClause())
+        loweringIssue(
+          state,
+          generic,
+          "unsupported-generic-preparation",
+          "Creation preparation currently requires a closed export",
+        );
       if (generic.acceptanceClause())
         loweringIssue(
           state,
@@ -1689,6 +1697,19 @@ const lowerPackage = (
   // Resolve after all exports have been declared, so checks can follow bodies.
   for (const source of context.packageExport()) {
     const declaration = source.packageOperationExport() ?? source.packageFunctionExport();
+    const preparation = declaration?.preparationClause();
+    if (declaration && preparation && !declaration.typeParameters()) {
+      const entry = exports.find((entry) => entry.displayName === identifier(declaration.identifier()));
+      const port = entry?.dependencyPorts.find((port) => port.displayName === identifier(preparation.identifier()));
+      if (!entry || port?.requirement.kind !== "creation")
+        loweringIssue(
+          state,
+          preparation,
+          "invalid-creation-preparation",
+          "Preparation must name a creation port of this export",
+        );
+      else entry.preparation = { port: port.id, key: stringValue(preparation.stringLiteral()) };
+    }
     const clause = declaration?.acceptanceClause();
     if (!declaration || !clause || declaration.typeParameters()) continue;
     const entry = exports.find((entry) => entry.displayName === identifier(declaration.identifier()));