Use cases for Try

As we move towards stabilising trait Try I'm trying to collate real-world, actually-implemented, examples.

Anyone who knows of such cases, or has a concrete use case they would like to see, please drop a reply in this thread. For general discussion of Try please start a new thread.

So far, the ones I know about fall into a few categories^[1]:

Sidecars

Effectively drop-in replacements for the primary try-types with additional "magic" baked into the Try:

• InterpResult in the compiler: adds a guard to ensure correct handling
• Traced<T> in tracing_result: stores tracing events & emits them when the wrapped type is propagated or unwraped
• TracedResult in traced_result: stores call site information each time ? is used to propagate
• DiagnosticResult in proc_macro2_diagnostic: stores compiler diagnostic messages & emits them when the wrapped type is propagated or unwraped

Ergonomics

• Context in thread_safely: allows for remote cancellation of a thread via cx.cancelled()?

Orphan rule avoidance

• exit_safely: create custom return types for main which respond to ? and implement Termination with defined exit codes

Generic over Try

• Iterator::try_xxx in std::iter, Box::try_map in std::boxed, etc.: versions of well-known methods which apply fallible functions
• Extract & Transform in try_v2: bring .unwrap(), .map(), and_then(), etc. to custom try-types

Background

• Goal: Stabilize the Try trait · Issue #654 · rust-lang/goals
• RFC: 3058-try-trait-v2 - The Rust RFC Book

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1. Disclaimer: many of these are my own publications ↩︎

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