humpty_dumpty 0.0.1

A plugin to prevent certain types from being dropped, thus making them linear
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Humpty Dumpty

Build Status

The goal of this library is to be able to define types that cannot be implicitly dropped except in controlled situations.

A sketch of the design can be found here. The design does not handle branches, though it can be extended to do so. It's also a bit different from what I finally implemented

The idea is, that for a type that is marked #[drop_protection], only functions annotated with #[allowed_on_protected] can use these, and each local must be dropped with a function marked #[allowed_drop] before its scope finishes.

Current status: Is able to track such types and report on their usage. Maintains a list of what has been dropped properly to detect implicit drops.

Some missing (but planned) functionality:

  • Cannot yet handle conditional drops, i.e. those in branches.
  • Cannot yet handle any bindings other than a let binding
  • Allowed functions cannot yet take &/&mut inputs
  • Cannot yet mark method calls as allowed

To test, run cargo run --example test, or even better rustc examples/test.rs -L target (after building). The latter is better because it will rebuild every time, and we're only interested in build output.