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Optionally add type names to `TypeId`s. This feature is intended to provide expensive but thorough help for developers who have an unexpected `TypeId` value and need to determine what type it actually is. It causes `impl Debug for TypeId` to print the type name in addition to the opaque ID hash, and in order to do so, adds a name field to `TypeId`. The cost of this is the increased size of `TypeId` and the need to store type names in the binary; therefore, it is an optional feature. It does not expose any new public API, only change the `Debug` implementation. It may be enabled via `cargo -Zbuild-std -Zbuild-std-features=debug_typeid`. (Note that `-Zbuild-std-features` disables default features which you may wish to reenable in addition; see <https://doc.rust-lang.org/cargo/reference/unstable.html#build-std-features>.) Example usage and output: ``` fn main() { use std::any::{Any, TypeId}; dbg!(TypeId::of::<usize>(), drop::<usize>.type_id()); } ``` ``` TypeId::of::<usize>() = TypeId(0x763d199bccd319899208909ed1a860c6 = usize) drop::<usize>.type_id() = TypeId(0xe6a34bd13f8c92dd47806da07b8cca9a = core::mem::drop<usize>) ``` Also added feature declarations for the existing `debug_refcell` feature so it is usable from the `rust.std-features` option of `config.toml`. Related issues: * #68379 * #61533 |
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