---
title: "[RFC] [Discussion] Bound-Erased Generic Types"
url: https://daily.dev/posts/rfc-discussion-bound-erased-generic-types-3ib9wz8nm
source_url: https://externals.io/message/131185
type: article
source: "externals.io"
published: 2026-06-09T13:28:22.861Z
updated: 2026-06-09T13:28:53.076Z
tags: ["php"]
reading_time: 302
upvotes: 0
comments: 0
language: en
---

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# [RFC] [Discussion] Bound-Erased Generic Types

**[externals.io](https://daily.dev/sources/externals)** · 302 min read · 0 upvotes · 0 comments

## Summary

A PHP internals mailing list discussion about a proposed RFC for bound-erased generic types in PHP. The RFC proposes adding generic type parameters to classes, interfaces, traits, functions, methods, closures, and arrow functions, with bounds, defaults, and variance markers. Type parameters erase to their bound at runtime, while the pre-erasure form is preserved for Reflection and static analyzers. Key discussion points include: ordering restrictions for mutually-recursive type bounds, intersection type restrictions with unbounded type parameters, arity validation behavior (opt-in via turbofish syntax), diamond inheritance checks, the turbofish `::< >` syntax choice, and `+`/`-` variance markers. The RFC author clarifies that arity validation is opt-in at call sites using turbofish, existing code remains unaffected, and the design is intentionally extensible toward reified runtime generics in the future.

## Full article

daily.dev links to this article rather than hosting it. Read it at the original source: <https://externals.io/message/131185>

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---

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