More type checking

src/typechecker.ts

@@ -127,6 +127,23 @@ function infer(expr: AST, env: TypeEnv, subst: Subst): TypeAST | null {
             return null;
         }
 
+        case 'record-update': {
+            const recType = infer(expr.record, env, subst);
+            if (!recType) return null;
+            const resolved = applySubst(recType, subst);
+            if (resolved.kind !== 'type-record') return null;
+
+            for (const [key, value] of Object.entries(expr.updates)) {
+                const field = resolved.fields.find(f => f.name === key);
+                if (field) {
+                    const err = check(value, field.type, env, subst);
+                    if (err) warn(err, value);
+                }
+            }
+
+            return resolved;
+        }
+
         case 'apply': {
             const funcType = infer(expr.func, env, subst);
             if (!funcType) return null;