refactor(jj-lib): remove nightly_shims gunk

Summary: Now that we have Rust 1.71.0 at our fingertips, the `map_first_last`
feature has been stabilized. That means we can get rid of the `jj-lib` build
script and also the `nightly_shims` module.

Signed-off-by: Austin Seipp <aseipp@pobox.com>
Change-Id: Ibb5ce3258818a2de670763fbbaf3c2e7

lib/build.rs

@@ -1,23 +0,0 @@
-// Copyright 2020 The Jujutsu Authors
-//
-// Licensed under the Apache License, Version 2.0 (the "License");
-// you may not use this file except in compliance with the License.
-// You may obtain a copy of the License at
-//
-// https://www.apache.org/licenses/LICENSE-2.0
-//
-// Unless required by applicable law or agreed to in writing, software
-// distributed under the License is distributed on an "AS IS" BASIS,
-// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
-// See the License for the specific language governing permissions and
-// limitations under the License.
-
-fn main() -> std::io::Result<()> {
-    println!("cargo:rerun-if-changed=build.rs");
-
-    if let Some(true) = version_check::supports_feature("map_first_last") {
-        println!("cargo:rustc-cfg=feature=\"map_first_last\"");
-    }
-
-    Ok(())
-}

lib/src/default_index_store.rs

@@ -40,11 +40,6 @@ use crate::file_util::persist_content_addressed_temp_file;
 use crate::index::{
     HexPrefix, Index, IndexStore, IndexWriteError, MutableIndex, PrefixResolution, ReadonlyIndex,
 };
-#[cfg(not(feature = "map_first_last"))]
-// This import is used on Rust 1.61, but not on recent version.
-// TODO: Remove it when our MSRV becomes recent enough.
-#[allow(unused_imports)]
-use crate::nightly_shims::BTreeSetExt;
 use crate::op_store::OperationId;
 use crate::operation::Operation;
 use crate::revset::{ResolvedExpression, Revset, RevsetEvaluationError};

lib/src/default_revset_graph_iterator.rs

@@ -19,7 +19,6 @@ use std::collections::{BTreeMap, HashSet};
 
 use crate::backend::CommitId;
 use crate::default_index_store::{IndexEntry, IndexPosition};
-use crate::nightly_shims::BTreeMapExt;
 use crate::revset::{RevsetGraphEdge, RevsetGraphEdgeType};
 
 /// Given an iterator over some set of revisions, yields the same revisions with
@@ -122,7 +121,7 @@ impl<'revset, 'index> RevsetGraphIterator<'revset, 'index> {
     }
 
     fn next_index_entry(&mut self) -> Option<IndexEntry<'index>> {
-        if let Some(index_entry) = self.look_ahead.pop_last_value() {
+        if let Some(index_entry) = self.look_ahead.last_entry().map(|x| x.remove()) {
             return Some(index_entry);
         }
         self.input_set_iter.next()

lib/src/diff.rs

@@ -22,8 +22,6 @@ use std::slice;
 
 use itertools::Itertools;
 
-use crate::nightly_shims::BTreeMapExt;
-
 pub fn find_line_ranges(text: &[u8]) -> Vec<Range<usize>> {
     let mut ranges = vec![];
     let mut start = 0;
@@ -185,7 +183,7 @@ pub(crate) fn unchanged_ranges(
 
     let max_occurrences = 100;
     let mut left_histogram = Histogram::calculate(left, left_ranges, max_occurrences);
-    if *left_histogram.count_to_words.first_key().unwrap() > max_occurrences {
+    if *left_histogram.count_to_words.keys().next().unwrap() > max_occurrences {
         // If there are very many occurrences of all words, then we just give up.
         return vec![];
     }
@@ -195,7 +193,11 @@ pub(crate) fn unchanged_ranges(
     // the LCS.
     let mut uncommon_shared_words = vec![];
     while !left_histogram.count_to_words.is_empty() && uncommon_shared_words.is_empty() {
-        let left_words = left_histogram.count_to_words.pop_first_value().unwrap();
+        let left_words = left_histogram
+            .count_to_words
+            .first_entry()
+            .map(|x| x.remove())
+            .unwrap();
         for left_word in left_words {
             if right_histogram.word_to_positions.contains_key(left_word) {
                 uncommon_shared_words.push(left_word);

lib/src/lib.rs

@@ -43,7 +43,6 @@ pub mod local_backend;
 pub mod lock;
 pub mod matchers;
 pub mod merge;
-pub mod nightly_shims;
 pub mod op_heads_store;
 pub mod op_store;
 pub mod operation;

lib/src/nightly_shims.rs

@@ -1,109 +0,0 @@
-// Copyright 2023 The Jujutsu Authors
-//
-// Licensed under the Apache License, Version 2.0 (the "License");
-// you may not use this file except in compliance with the License.
-// You may obtain a copy of the License at
-//
-// https://www.apache.org/licenses/LICENSE-2.0
-//
-// Unless required by applicable law or agreed to in writing, software
-// distributed under the License is distributed on an "AS IS" BASIS,
-// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
-// See the License for the specific language governing permissions and
-// limitations under the License.
-
-#![allow(missing_docs)]
-
-#[cfg(feature = "map_first_last")]
-pub trait BTreeMapExt<K, V> {
-    fn first_key(&self) -> Option<&K>;
-    fn last_key(&self) -> Option<&K>;
-    fn pop_first_value(&mut self) -> Option<V>;
-    fn pop_last_value(&mut self) -> Option<V>;
-}
-
-#[cfg(feature = "map_first_last")]
-impl<K: Ord + Clone, V> BTreeMapExt<K, V> for std::collections::BTreeMap<K, V> {
-    fn first_key(&self) -> Option<&K> {
-        self.keys().next()
-    }
-
-    fn last_key(&self) -> Option<&K> {
-        self.keys().next_back()
-    }
-    fn pop_first_value(&mut self) -> Option<V> {
-        self.first_entry().map(|x| x.remove())
-    }
-
-    fn pop_last_value(&mut self) -> Option<V> {
-        self.last_entry().map(|x| x.remove())
-    }
-}
-
-#[cfg(not(feature = "map_first_last"))]
-pub trait BTreeMapExt<K, V> {
-    fn first_key(&self) -> Option<&K>;
-    fn last_key(&self) -> Option<&K>;
-    fn pop_first_key(&mut self) -> Option<K>;
-    fn pop_last_key(&mut self) -> Option<K>;
-    fn pop_first_value(&mut self) -> Option<V>;
-    fn pop_last_value(&mut self) -> Option<V>;
-}
-
-#[cfg(not(feature = "map_first_last"))]
-impl<K: Ord + Clone, V> BTreeMapExt<K, V> for std::collections::BTreeMap<K, V> {
-    fn first_key(&self) -> Option<&K> {
-        self.keys().next()
-    }
-
-    fn last_key(&self) -> Option<&K> {
-        self.keys().next_back()
-    }
-
-    fn pop_first_key(&mut self) -> Option<K> {
-        let key = self.first_key()?;
-        let key = key.clone(); // ownership hack
-        Some(self.remove_entry(&key).unwrap().0)
-    }
-
-    fn pop_last_key(&mut self) -> Option<K> {
-        let key = self.last_key()?;
-        let key = key.clone(); // ownership hack
-        Some(self.remove_entry(&key).unwrap().0)
-    }
-
-    fn pop_first_value(&mut self) -> Option<V> {
-        let key = self.first_key()?;
-        let key = key.clone(); // ownership hack
-        Some(self.remove_entry(&key).unwrap().1)
-    }
-
-    fn pop_last_value(&mut self) -> Option<V> {
-        let key = self.last_key()?;
-        let key = key.clone(); // ownership hack
-        Some(self.remove_entry(&key).unwrap().1)
-    }
-}
-
-#[cfg(feature = "map_first_last")]
-pub trait BTreeSetExt<K> {}
-
-#[cfg(not(feature = "map_first_last"))]
-pub trait BTreeSetExt<K> {
-    fn last(&self) -> Option<&K>;
-    fn pop_last(&mut self) -> Option<K>;
-}
-
-#[cfg(not(feature = "map_first_last"))]
-impl<K: Ord + Clone> BTreeSetExt<K> for std::collections::BTreeSet<K> {
-    fn last(&self) -> Option<&K> {
-        self.iter().next_back()
-    }
-
-    fn pop_last(&mut self) -> Option<K> {
-        #[allow(unstable_name_collisions)]
-        let key = self.last()?;
-        let key = key.clone(); // ownership hack
-        self.take(&key)
-    }
-}