3 files changed, 117 insertions, 10 deletions

diff --git a/crates/stdx/Cargo.toml b/crates/stdx/Cargo.toml
index 8d7a51156..c47e8d0a8 100644
--- a/crates/stdx/Cargo.toml
+++ b/crates/stdx/Cargo.toml
@@ -10,4 +10,9 @@ edition = "2018"
 doctest = false
 
 [dependencies]
+backtrace = { version = "0.3.44", optional = true }
 # Think twice before adding anything here
+
+[features]
+# Uncomment to enable for the whole crate graph
+# default = [ "backtrace" ]
diff --git a/crates/stdx/src/lib.rs b/crates/stdx/src/lib.rs
index 374ed5910..1ff2559bb 100644
--- a/crates/stdx/src/lib.rs
+++ b/crates/stdx/src/lib.rs
@@ -1,9 +1,11 @@
 //! Missing batteries for standard libraries.
-use std::time::Instant;
+use std::{cmp::Ordering, ops, process, time::Instant};
 
 mod macros;
 pub mod panic_context;
 
+pub use crate::macros::{on_assert_failure, set_assert_hook};
+
 #[inline(always)]
 pub fn is_ci() -> bool {
     option_env!("CI").is_some()
@@ -25,6 +27,27 @@ pub fn timeit(label: &'static str) -> impl Drop {
     Guard { label, start: Instant::now() }
 }
 
+/// Prints backtrace to stderr, useful for debugging.
+#[cfg(feature = "backtrace")]
+pub fn print_backtrace() {
+    let bt = backtrace::Backtrace::new();
+    eprintln!("{:?}", bt);
+}
+#[cfg(not(feature = "backtrace"))]
+pub fn print_backtrace() {
+    eprintln!(
+        r#"Enable the backtrace feature.
+Uncomment `default = [ "backtrace" ]` in `crates/stdx/Cargo.toml`.
+"#
+    );
+}
+
+pub fn to_lower_snake_case(s: &str) -> String {
+    to_snake_case(s, char::to_ascii_lowercase)
+}
+pub fn to_upper_snake_case(s: &str) -> String {
+    to_snake_case(s, char::to_ascii_uppercase)
+}
 fn to_snake_case<F: Fn(&char) -> char>(s: &str, change_case: F) -> String {
     let mut buf = String::with_capacity(s.len());
     let mut prev = false;
@@ -43,14 +66,6 @@ fn to_snake_case<F: Fn(&char) -> char>(s: &str, change_case: F) -> String {
     buf
 }
 
-pub fn to_lower_snake_case(s: &str) -> String {
-    to_snake_case(s, char::to_ascii_lowercase)
-}
-
-pub fn to_upper_snake_case(s: &str) -> String {
-    to_snake_case(s, char::to_ascii_uppercase)
-}
-
 pub fn replace(buf: &mut String, from: char, to: &str) {
     if !buf.contains(from) {
         return;
@@ -117,7 +132,12 @@ impl<'a> Iterator for LinesWithEnds<'a> {
     }
 }
 
-// https://github.com/rust-lang/rust/issues/73831
+/// Returns `idx` such that:
+///
+///     ∀ x in slice[..idx]:  pred(x)
+///  && ∀ x in slice[idx..]: !pred(x)
+///
+/// https://github.com/rust-lang/rust/issues/73831
 pub fn partition_point<T, P>(slice: &[T], mut pred: P) -> usize
 where
     P: FnMut(&T) -> bool,
@@ -147,6 +167,36 @@ where
     left
 }
 
+pub fn equal_range_by<T, F>(slice: &[T], mut key: F) -> ops::Range<usize>
+where
+    F: FnMut(&T) -> Ordering,
+{
+    let start = partition_point(slice, |it| key(it) == Ordering::Less);
+    let len = partition_point(&slice[start..], |it| key(it) == Ordering::Equal);
+    start..start + len
+}
+
+pub struct JodChild(pub process::Child);
+
+impl ops::Deref for JodChild {
+    type Target = process::Child;
+    fn deref(&self) -> &process::Child {
+        &self.0
+    }
+}
+
+impl ops::DerefMut for JodChild {
+    fn deref_mut(&mut self) -> &mut process::Child {
+        &mut self.0
+    }
+}
+
+impl Drop for JodChild {
+    fn drop(&mut self) {
+        let _ = self.0.kill();
+    }
+}
+
 #[cfg(test)]
 mod tests {
     use super::*;
diff --git a/crates/stdx/src/macros.rs b/crates/stdx/src/macros.rs
index f5ee3484b..4f5c6100d 100644
--- a/crates/stdx/src/macros.rs
+++ b/crates/stdx/src/macros.rs
@@ -1,4 +1,9 @@
 //! Convenience macros.
+
+use std::{
+    fmt, mem, panic,
+    sync::atomic::{AtomicUsize, Ordering::SeqCst},
+};
 #[macro_export]
 macro_rules! eprintln {
     ($($tt:tt)*) => {{
@@ -44,3 +49,50 @@ macro_rules! impl_from {
         )*
     }
 }
+
+/// A version of `assert!` macro which allows to handle an assertion failure.
+///
+/// In release mode, it returns the condition and logs an error.
+///
+/// ```
+/// if assert_never!(impossible) {
+///     // Heh, this shouldn't have happened, but lets try to soldier on...
+///     return None;
+/// }
+/// ```
+///
+/// Rust analyzer is a long-running process, and crashing really isn't an option.
+///
+/// Shamelessly stolen from: https://www.sqlite.org/assert.html
+#[macro_export]
+macro_rules! assert_never {
+    ($cond:expr) => { $crate::assert_never!($cond, "") };
+    ($cond:expr, $($fmt:tt)*) => {{
+        let value = $cond;
+        if value {
+            $crate::on_assert_failure(
+                format_args!($($fmt)*)
+            );
+        }
+        value
+    }};
+}
+
+type AssertHook = fn(&panic::Location<'_>, fmt::Arguments<'_>);
+static HOOK: AtomicUsize = AtomicUsize::new(0);
+
+pub fn set_assert_hook(hook: AssertHook) {
+    HOOK.store(hook as usize, SeqCst);
+}
+
+#[cold]
+#[track_caller]
+pub fn on_assert_failure(args: fmt::Arguments) {
+    let hook: usize = HOOK.load(SeqCst);
+    if hook == 0 {
+        panic!("\n  assertion failed: {}\n", args);
+    }
+
+    let hook: AssertHook = unsafe { mem::transmute::<usize, AssertHook>(hook) };
+    hook(panic::Location::caller(), args)
+}