When Lifetimes Liberate: A Type System for Arenas with Higher-Order Reachability Tracking
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arXiv
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| Auteurs principaux: | , , , |
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| Format: | Preprint |
| Publié: |
2025
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| _version_ | 1866910080545325056 |
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| author | He, Siyuan Jia, Songlin Bao, Yuyan Rompf, Tiark |
| author_facet | He, Siyuan Jia, Songlin Bao, Yuyan Rompf, Tiark |
| contents | Static resource management in languages remains challenging due to tensions among control, expressiveness, and flexibility. Region-based systems [Grossman et al . 2002; Tofte et al. 2001] offer bulk deallocation via lexically scoped regions, where all allocations follow a stack discipline. However, both regions and their resources are second-class, and neither can escape its scope nor be freely returned. Ownership and linear type systems, exemplified by Rust [Clarke et al. 2013], offer non-lexical lifetimes and robust static guarantees, but rely on invariants that limit higher-order patterns and expressive sharing.
In this work, we propose a new type system that unifies these strengths. Our system treats all heap-allocated resources as first-class values, while allowing programmers to control lifetime and granularity through three allocation modes: (1) fresh allocation for individual, non-lexical references; (2) subsequent coallocation grouping resources collectively within shadow arenas; and (3) scoped allocation with lexically bounded lifetimes following stack discipline. Regardless of mode, all resources share a uniform type and have no distinction for generic abstractions, preserving the higher-order parametric nature of the language.
Obtaining static safety in higher-order languages with flexible sharing is nontrivial. We address this by extending reachability types [Wei et al. 2024] to collectively track first-class resources, and by adopting flow-insensitive deallocation reasoning for selective stack discipline. These mechanisms yield Aq<: and {A}q<: atop, both formalized and proven type safe and memory safe in Rocq. |
| format | Preprint |
| id |
arxiv_https___arxiv_org_abs_2509_04253 |
| institution | arXiv |
| publishDate | 2025 |
| record_format | arxiv |
| spellingShingle | When Lifetimes Liberate: A Type System for Arenas with Higher-Order Reachability Tracking He, Siyuan Jia, Songlin Bao, Yuyan Rompf, Tiark Programming Languages Static resource management in languages remains challenging due to tensions among control, expressiveness, and flexibility. Region-based systems [Grossman et al . 2002; Tofte et al. 2001] offer bulk deallocation via lexically scoped regions, where all allocations follow a stack discipline. However, both regions and their resources are second-class, and neither can escape its scope nor be freely returned. Ownership and linear type systems, exemplified by Rust [Clarke et al. 2013], offer non-lexical lifetimes and robust static guarantees, but rely on invariants that limit higher-order patterns and expressive sharing. In this work, we propose a new type system that unifies these strengths. Our system treats all heap-allocated resources as first-class values, while allowing programmers to control lifetime and granularity through three allocation modes: (1) fresh allocation for individual, non-lexical references; (2) subsequent coallocation grouping resources collectively within shadow arenas; and (3) scoped allocation with lexically bounded lifetimes following stack discipline. Regardless of mode, all resources share a uniform type and have no distinction for generic abstractions, preserving the higher-order parametric nature of the language. Obtaining static safety in higher-order languages with flexible sharing is nontrivial. We address this by extending reachability types [Wei et al. 2024] to collectively track first-class resources, and by adopting flow-insensitive deallocation reasoning for selective stack discipline. These mechanisms yield Aq<: and {A}q<: atop, both formalized and proven type safe and memory safe in Rocq. |
| title | When Lifetimes Liberate: A Type System for Arenas with Higher-Order Reachability Tracking |
| topic | Programming Languages |
| url | https://arxiv.org/abs/2509.04253 |