Vendor things

third-party/vendor/salsa-2022/src/cancelled.rs

@@ -0,0 +1,57 @@
+use std::{
+    fmt,
+    panic::{self, UnwindSafe},
+};
+
+/// A panic payload indicating that execution of a salsa query was cancelled.
+///
+/// This can occur for a few reasons:
+/// *
+/// *
+/// *
+#[derive(Debug)]
+#[non_exhaustive]
+pub enum Cancelled {
+    /// The query was operating on revision R, but there is a pending write to move to revision R+1.
+    #[non_exhaustive]
+    PendingWrite,
+
+    /// The query was blocked on another thread, and that thread panicked.
+    #[non_exhaustive]
+    PropagatedPanic,
+}
+
+impl Cancelled {
+    pub(crate) fn throw(self) -> ! {
+        // 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(self));
+    }
+
+    /// Runs `f`, and catches any salsa cancellation.
+    pub fn catch<F, T>(f: F) -> Result<T, Cancelled>
+    where
+        F: FnOnce() -> T + UnwindSafe,
+    {
+        match panic::catch_unwind(f) {
+            Ok(t) => Ok(t),
+            Err(payload) => match payload.downcast() {
+                Ok(cancelled) => Err(*cancelled),
+                Err(payload) => panic::resume_unwind(payload),
+            },
+        }
+    }
+}
+
+impl std::fmt::Display for Cancelled {
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+        let why = match self {
+            Cancelled::PendingWrite => "pending write",
+            Cancelled::PropagatedPanic => "propagated panic",
+        };
+        f.write_str("cancelled because of ")?;
+        f.write_str(why)
+    }
+}
+
+impl std::error::Error for Cancelled {}