--- title: [RFC] [Discussion] Bound-Erased Generic Types | daily.dev description: 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,... canonical: https://daily.dev/posts/rfc-discussion-bound-erased-generic-types-386xnyaux twitter:card: summary_large_image twitter:site: @dailydotdev og:type: website og:site_name: daily.dev og:title: [RFC] [Discussion] Bound-Erased Generic Types | daily.dev og:description: 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,... og:url: https://daily.dev/posts/rfc-discussion-bound-erased-generic-types-386xnyaux og:image: https://api.daily.dev/og/posts/386XnYAux.png og:image:alt: [RFC] [Discussion] Bound-Erased Generic Types og:image:width: 1200 og:image:height: 630 og:locale: en --- > ## Documentation Index > Fetch the complete documentation index at: https://daily.dev/llms.txt > Use this file to discover all available pages before exploring further. # [RFC] [Discussion] Bound-Erased Generic Types **[externals.io](https://daily.dev/sources/externals)** · 308 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 (only triggered when using turbofish syntax), diamond inheritance checks, turbofish syntax (::< >) vs alternatives, and +/- variance markers vs in/out keywords. The RFC author clarifies that arity validation is opt-in via turbofish, making library adoption non-breaking, and that the design is intentionally extensible toward reified runtime generics in the future. ## Full article daily.dev links to this article rather than hosting it. 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