3 files changed, 87 insertions, 22 deletions

diff --git a/crates/stdx/Cargo.toml b/crates/stdx/Cargo.toml
index f9e380c10..4c0b85861 100644
--- a/crates/stdx/Cargo.toml
+++ b/crates/stdx/Cargo.toml
@@ -3,6 +3,7 @@ name = "stdx"
 version = "0.1.0"
 authors = ["rust-analyzer developers"]
 edition = "2018"
+license = "MIT OR Apache-2.0"
 
 [lib]
 doctest = false
diff --git a/crates/stdx/src/lib.rs b/crates/stdx/src/lib.rs
index 08ac6f70f..b65875c96 100644
--- a/crates/stdx/src/lib.rs
+++ b/crates/stdx/src/lib.rs
@@ -1,30 +1,13 @@
 //! Missing batteries for standard libraries.
 use std::{cell::Cell, fmt, time::Instant};
 
+mod macros;
+
 #[inline(always)]
 pub fn is_ci() -> bool {
     option_env!("CI").is_some()
 }
 
-#[macro_export]
-macro_rules! eprintln {
-    ($($tt:tt)*) => {{
-        if $crate::is_ci() {
-            panic!("Forgot to remove debug-print?")
-        }
-        std::eprintln!($($tt)*)
-    }}
-}
-
-/// Appends formatted string to a `String`.
-#[macro_export]
-macro_rules! format_to {
-    ($buf:expr) => ();
-    ($buf:expr, $lit:literal $($arg:tt)*) => {
-        { use ::std::fmt::Write as _; let _ = ::std::write!($buf, $lit $($arg)*); }
-    };
-}
-
 pub trait SepBy: Sized {
     /// Returns an `impl fmt::Display`, which joins elements via a separator.
     fn sep_by<'a>(self, sep: &'a str) -> SepByBuilder<'a, Self>;
@@ -87,6 +70,8 @@ where
         Ok(())
     }
 }
+
+#[must_use]
 pub fn timeit(label: &'static str) -> impl Drop {
     struct Guard {
         label: &'static str,
@@ -124,9 +109,18 @@ pub fn replace(buf: &mut String, from: char, to: &str) {
     *buf = buf.replace(from, to)
 }
 
-pub fn split_delim(haystack: &str, delim: char) -> Option<(&str, &str)> {
-    let idx = haystack.find(delim)?;
-    Some((&haystack[..idx], &haystack[idx + delim.len_utf8()..]))
+// https://github.com/rust-lang/rust/issues/74773
+pub fn split_once(haystack: &str, delim: char) -> Option<(&str, &str)> {
+    let mut split = haystack.splitn(2, delim);
+    let prefix = split.next()?;
+    let suffix = split.next()?;
+    Some((prefix, suffix))
+}
+pub fn rsplit_once(haystack: &str, delim: char) -> Option<(&str, &str)> {
+    let mut split = haystack.rsplitn(2, delim);
+    let suffix = split.next()?;
+    let prefix = split.next()?;
+    Some((prefix, suffix))
 }
 
 pub fn trim_indent(mut text: &str) -> String {
@@ -173,6 +167,36 @@ impl<'a> Iterator for LinesWithEnds<'a> {
     }
 }
 
+// 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,
+{
+    let mut left = 0;
+    let mut right = slice.len();
+
+    while left != right {
+        let mid = left + (right - left) / 2;
+        // SAFETY:
+        // When left < right, left <= mid < right.
+        // Therefore left always increases and right always decreases,
+        // and either of them is selected.
+        // In both cases left <= right is satisfied.
+        // Therefore if left < right in a step,
+        // left <= right is satisfied in the next step.
+        // Therefore as long as left != right, 0 <= left < right <= len is satisfied
+        // and if this case 0 <= mid < len is satisfied too.
+        let value = unsafe { slice.get_unchecked(mid) };
+        if pred(value) {
+            left = mid + 1;
+        } else {
+            right = mid;
+        }
+    }
+
+    left
+}
+
 #[cfg(test)]
 mod tests {
     use super::*;
diff --git a/crates/stdx/src/macros.rs b/crates/stdx/src/macros.rs
new file mode 100644
index 000000000..bf298460f
--- /dev/null
+++ b/crates/stdx/src/macros.rs
@@ -0,0 +1,40 @@
+//! Convenience macros.
+#[macro_export]
+macro_rules! eprintln {
+    ($($tt:tt)*) => {{
+        if $crate::is_ci() {
+            panic!("Forgot to remove debug-print?")
+        }
+        std::eprintln!($($tt)*)
+    }}
+}
+
+/// Appends formatted string to a `String`.
+#[macro_export]
+macro_rules! format_to {
+    ($buf:expr) => ();
+    ($buf:expr, $lit:literal $($arg:tt)*) => {
+        { use ::std::fmt::Write as _; let _ = ::std::write!($buf, $lit $($arg)*); }
+    };
+}
+
+// Generates `From` impls for `Enum E { Foo(Foo), Bar(Bar) }` enums
+#[macro_export]
+macro_rules! impl_from {
+    ($($variant:ident $(($($sub_variant:ident),*))?),* for $enum:ident) => {
+        $(
+            impl From<$variant> for $enum {
+                fn from(it: $variant) -> $enum {
+                    $enum::$variant(it)
+                }
+            }
+            $($(
+                impl From<$sub_variant> for $enum {
+                    fn from(it: $sub_variant) -> $enum {
+                        $enum::$variant($variant::$sub_variant(it))
+                    }
+                }
+            )*)?
+        )*
+    }
+}