Summary

Model.validate() is typed to resolve to void, but at runtime it returns the casted-and-validated copy of the input object.

In lib/model.js, Model.validate() does obj = this.castObject(obj) and ends with return obj;. The JSDoc on the implementation already documents this:

@return {Promise<object>} casted and validated copy of \obj` if validation succeeded`

However, the TypeScript declarations in types/models.d.ts typed every overload as Promise<void>, so consumers cannot use the resolved value:

const validated = await MyModel.validate({ a: 'string' });
validated.a; // ts(2339): Property 'a' does not exist on type 'void'.

This PR changes the return type to Promise<TRawDocType>, mirroring the adjacent castObject(...): TRawDocType declaration (validate() returns exactly what castObject() produced). The existing Model['~standard'].validate() adapter already assumes validate resolves to the data (it wraps the result as { value }), and its type test asserts result.value is the raw doc type — consistent with this change.

Fixes #16338

Examples

Added type tests in test/types/models.test.ts (modelValidateReturnsCastedObject):

const validated = await User.validate({ name: 'Val', age: 42 });
expect(validated).type.toBe<IUser>();
expect(validated.name).type.toBe<string>();
expect(validated.age).type.toBe<number>();

These fail before the fix (Property 'age' does not exist on type 'void') and pass after. Full npm run test:types suite passes (39 files, 978 assertions), eslint clean.