Negative Drop impls, Drop auto-trait and ImplicitDrop

[steffahn]

@tema2

Next, there is wanting of some linear type support in rust

There’s previous discussion on the topic. One of the most recent probably

Pre-RFC: Leave auto-trait for reliable destruction

EDIT: Proposal Updated - See Updates Summary of updates here: I'm leaving the rest of this post as it is for posterity, so please see the update. TL;DR Define a new auto-trait Leave, which means that the type can be implicitly destroyed when it goes out of scope. Users can declare must-destroy types by through impl !Leave for Foo {}, which are statically guaranteed to be destroyed before their lifetime's upper bound is reached. This super-charges the RAII pattern, which opens up static, z…

which includes links to more topics, too.

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@tema2

The Drop is implicitly implemented for all types in Rust.

That’s not quite accurate. The trait Drop itself is always explicit when it’s implemented. But types without Drop implementations can have so-called “drop glue”, which can (somewhat) be tested with mem::needs_drop. The situation as it currently stands also means that T: Drop bounds in (generic) Rust code are always useless.