mirror of
https://github.com/rust-lang/rust-analyzer
synced 2024-12-31 23:38:45 +00:00
50 lines
1.9 KiB
Rust
50 lines
1.9 KiB
Rust
//!
|
|
/// Describes how likely a value is to change -- how "durable" it is.
|
|
/// By default, inputs have `Durability::LOW` and interned values have
|
|
/// `Durability::HIGH`. But inputs can be explicitly set with other
|
|
/// durabilities.
|
|
///
|
|
/// We use durabilities to optimize the work of "revalidating" a query
|
|
/// after some input has changed. Ordinarily, in a new revision,
|
|
/// queries have to trace all their inputs back to the base inputs to
|
|
/// determine if any of those inputs have changed. But if we know that
|
|
/// the only changes were to inputs of low durability (the common
|
|
/// case), and we know that the query only used inputs of medium
|
|
/// durability or higher, then we can skip that enumeration.
|
|
///
|
|
/// Typically, one assigns low durabilites to inputs that the user is
|
|
/// frequently editing. Medium or high durabilities are used for
|
|
/// configuration, the source from library crates, or other things
|
|
/// that are unlikely to be edited.
|
|
#[derive(Copy, Clone, Debug, PartialEq, Eq, PartialOrd, Ord)]
|
|
pub struct Durability(u8);
|
|
|
|
impl Durability {
|
|
/// Low durability: things that change frequently.
|
|
///
|
|
/// Example: part of the crate being edited
|
|
pub const LOW: Durability = Durability(0);
|
|
|
|
/// Medium durability: things that change sometimes, but rarely.
|
|
///
|
|
/// Example: a Cargo.toml file
|
|
pub const MEDIUM: Durability = Durability(1);
|
|
|
|
/// High durability: things that are not expected to change under
|
|
/// common usage.
|
|
///
|
|
/// Example: the standard library or something from crates.io
|
|
pub const HIGH: Durability = Durability(2);
|
|
|
|
/// The maximum possible durability; equivalent to HIGH but
|
|
/// "conceptually" distinct (i.e., if we add more durability
|
|
/// levels, this could change).
|
|
pub(crate) const MAX: Durability = Self::HIGH;
|
|
|
|
/// Number of durability levels.
|
|
pub(crate) const LEN: usize = 3;
|
|
|
|
pub(crate) fn index(self) -> usize {
|
|
self.0 as usize
|
|
}
|
|
}
|