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Diffstat (limited to 'crates/ra_db/src/cancellation.rs')
-rw-r--r-- | crates/ra_db/src/cancellation.rs | 44 |
1 files changed, 44 insertions, 0 deletions
diff --git a/crates/ra_db/src/cancellation.rs b/crates/ra_db/src/cancellation.rs new file mode 100644 index 000000000..8d38eebfb --- /dev/null +++ b/crates/ra_db/src/cancellation.rs | |||
@@ -0,0 +1,44 @@ | |||
1 | //! Utility types to support cancellation. | ||
2 | //! | ||
3 | //! In a typical IDE use-case, requests and modification happen concurrently, as | ||
4 | //! in the following scenario: | ||
5 | //! | ||
6 | //! * user types a character, | ||
7 | //! * a syntax highlighting process is started | ||
8 | //! * user types next character, while syntax highlighting *is still in | ||
9 | //! progress*. | ||
10 | //! | ||
11 | //! In this situation, we want to react to modification as quickly as possible. | ||
12 | //! At the same time, in-progress results are not very interesting, because they | ||
13 | //! are invalidated by the edit anyway. So, we first cancel all in-flight | ||
14 | //! requests, and then apply modification knowing that it won't interfere with | ||
15 | //! any background processing (this bit is handled by salsa, see the | ||
16 | //! `BaseDatabase::check_canceled` method). | ||
17 | |||
18 | /// An "error" signifing that the operation was canceled. | ||
19 | #[derive(Clone, PartialEq, Eq, Hash)] | ||
20 | pub struct Canceled { | ||
21 | _private: (), | ||
22 | } | ||
23 | |||
24 | pub type Cancelable<T> = Result<T, Canceled>; | ||
25 | |||
26 | impl Canceled { | ||
27 | pub(crate) fn new() -> Canceled { | ||
28 | Canceled { _private: () } | ||
29 | } | ||
30 | } | ||
31 | |||
32 | impl std::fmt::Display for Canceled { | ||
33 | fn fmt(&self, fmt: &mut std::fmt::Formatter<'_>) -> std::fmt::Result { | ||
34 | fmt.write_str("canceled") | ||
35 | } | ||
36 | } | ||
37 | |||
38 | impl std::fmt::Debug for Canceled { | ||
39 | fn fmt(&self, fmt: &mut std::fmt::Formatter<'_>) -> std::fmt::Result { | ||
40 | write!(fmt, "Canceled") | ||
41 | } | ||
42 | } | ||
43 | |||
44 | impl std::error::Error for Canceled {} | ||