Merge #478

478: WIP: implement cancelation via unwinding r=matklad a=matklad

This uses https://github.com/salsa-rs/salsa/pull/107 to implement cancellation.

Now we can get rid of `Cancelable` wrapper from everywhere except the top-level analyzer library. 



Co-authored-by: Aleksey Kladov <[email protected]>

3 files changed, 32 insertions, 7 deletions

diff --git a/crates/ra_db/src/cancellation.rs b/crates/ra_db/src/cancellation.rs
index 8d38eebfb..32a268553 100644
--- a/crates/ra_db/src/cancellation.rs
+++ b/crates/ra_db/src/cancellation.rs
@@ -27,6 +27,12 @@ impl Canceled {
     pub(crate) fn new() -> Canceled {
         Canceled { _private: () }
     }
+
+    pub fn throw() -> ! {
+        // We use resume and not panic here to avoid running the panic
+        // hook (that is, to avoid collecting and printing backtrace).
+        std::panic::resume_unwind(Box::new(Canceled::new()))
+    }
 }
 
 impl std::fmt::Display for Canceled {
diff --git a/crates/ra_db/src/lib.rs b/crates/ra_db/src/lib.rs
index fb8ea2496..20e712afe 100644
--- a/crates/ra_db/src/lib.rs
+++ b/crates/ra_db/src/lib.rs
@@ -5,6 +5,8 @@ mod input;
 mod loc2id;
 pub mod mock;
 
+use std::panic;
+
 use ra_syntax::{TextUnit, TextRange, SourceFile, TreePtr};
 
 pub use crate::{
@@ -18,13 +20,21 @@ pub use crate::{
     loc2id::LocationIntener,
 };
 
-pub trait BaseDatabase: salsa::Database {
+pub trait BaseDatabase: salsa::Database + panic::RefUnwindSafe {
     fn check_canceled(&self) -> Cancelable<()> {
-        if self.salsa_runtime().is_current_revision_canceled() {
-            Err(Canceled::new())
-        } else {
-            Ok(())
-        }
+        self.salsa_runtime()
+            .if_current_revision_is_canceled(Canceled::throw);
+        Ok(())
+    }
+
+    fn catch_canceled<F: FnOnce(&Self) -> T + panic::UnwindSafe, T>(
+        &self,
+        f: F,
+    ) -> Result<T, Canceled> {
+        panic::catch_unwind(|| f(self)).map_err(|err| match err.downcast::<Canceled>() {
+            Ok(canceled) => *canceled,
+            Err(payload) => panic::resume_unwind(payload),
+        })
     }
 }
 
diff --git a/crates/ra_db/src/loc2id.rs b/crates/ra_db/src/loc2id.rs
index 254c52629..359cd893d 100644
--- a/crates/ra_db/src/loc2id.rs
+++ b/crates/ra_db/src/loc2id.rs
@@ -1,4 +1,4 @@
-use std::hash::Hash;
+use std::{panic, hash::Hash};
 
 use parking_lot::Mutex;
 use rustc_hash::FxHashMap;
@@ -70,6 +70,15 @@ where
     map: Mutex<Loc2IdMap<LOC, ID>>,
 }
 
+impl<LOC, ID> panic::RefUnwindSafe for LocationIntener<LOC, ID>
+where
+    ID: ArenaId + Clone,
+    LOC: Clone + Eq + Hash,
+    ID: panic::RefUnwindSafe,
+    LOC: panic::RefUnwindSafe,
+{
+}
+
 impl<LOC, ID> Default for LocationIntener<LOC, ID>
 where
     ID: ArenaId + Clone,