---
title: "[RFC] [Discussion] Bound-Erased Generic Types"
url: https://daily.dev/posts/rfc-discussion-bound-erased-generic-types-47kruahki
source_url: https://externals.io/message/131143
type: article
source: "externals.io"
published: 2026-06-04T16:41:25.914Z
updated: 2026-06-04T16:41:53.630Z
tags: ["php"]
reading_time: 276
upvotes: 0
comments: 0
language: en
---

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

**[externals.io](https://daily.dev/sources/externals)** · 276 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, with the pre-erasure form 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 being opt-in via turbofish syntax, diamond inheritance checks, the use of +/- markers for covariance/contravariance, and the turbofish (::< >) syntax for explicit type argument passing. The RFC author clarifies that existing call sites remain unaffected without turbofish, making library adoption non-breaking.

## Full article

daily.dev links to this article rather than hosting it. Read it at the original source: <https://externals.io/message/131143>

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