fix: support "Unsupported" type of fields in "@@index"

packages/schema/src/language-server/validator/expression-validator.ts

@@ -59,10 +59,6 @@ export default class ExpressionValidator implements AstValidator<Expression> {
             }
         }
 
-        if (expr.$resolvedType?.decl === 'Unsupported') {
-            accept('error', 'Field of "Unsupported" type cannot be used in expressions', { node: expr });
-        }
-
         // extra validations by expression type
         switch (expr.$type) {
             case 'BinaryExpr':

packages/schema/tests/schema/validation/datamodel-validation.test.ts

@@ -75,7 +75,7 @@ describe('Data Model Validation Tests', () => {
                 @@allow('all', a == 'a')
             }
         `)
-        ).toMatchObject(errorLike('Field of "Unsupported" type cannot be used in expressions'));
+        ).toMatchObject(errorLike('incompatible operand types'));
     });
 
     it('Using `this` in collection predicate', async () => {

tests/regression/tests/issue-1870.test.ts

@@ -0,0 +1,15 @@
+import { loadModel, loadSchema } from '@zenstackhq/testtools';
+
+describe('issue 1870', () => {
+    it('regression', async () => {
+        await loadModel(
+            `
+        model Polygon {
+            id      Int      @id @default(autoincrement())
+            geometry    Unsupported("geometry(MultiPolygon, 4326)")
+            @@index([geometry], name: "parcel_polygon_idx", type: Gist)
+        }
+            `
+        );
+    });
+});