types: automatically infer discriminator type

[vkarpov15]

Fix #15535

Summary

Add a discriminator() function override that automatically infers the returned schema type from TypeScript types by combining the schema generics.

Examples

[Copilot]

Pull Request Overview

This PR fixes issue #15535 by implementing automatic type inference for discriminator schemas. The main purpose is to enhance TypeScript support by allowing the discriminator function to automatically combine schema generics and return the properly typed discriminator model.

• Adds a new test case demonstrating proper type inference for discriminator models with parent and child schemas
• Updates TypeScript instantiation limits to accommodate the enhanced type checking complexity
• Upgrades TypeScript version in benchmarks to support the new type inference features

Reviewed Changes

Copilot reviewed 3 out of 6 changed files in this pull request and generated no comments.

File	Description
test/types/discriminator.test.ts	Adds comprehensive test case for automatic discriminator type inference using expectType assertions
scripts/tsc-diagnostics-check.js	Increases maximum TypeScript instantiation limit from 275,000 to 280,000
benchmarks/typescript/simple/package.json	Updates TypeScript dependency from 5.5.x to 5.8.x

Comments suppressed due to low confidence (1)

[vkarpov15]

@hasezoey can you take another look? I did some performance refactoring to reduce and offset the additional instantiations introduced by this PR.

[hasezoey]

Still looks good to me.