Auto merge of #76964 - RalfJung:rollup-ybn06fs, r=RalfJung

Rollup of 15 pull requests

Successful merges:

 - #76722 (Test and fix Send and Sync traits of BTreeMap artefacts)
 - #76766 (Extract some intrinsics out of rustc_codegen_llvm)
 - #76800 (Don't generate bootstrap usage unless it's needed)
 - #76809 (simplfy condition in ItemLowerer::with_trait_impl_ref())
 - #76815 (Fix wording in mir doc)
 - #76818 (Don't compile regex at every function call.)
 - #76821 (Remove redundant nightly features)
 - #76823 (black_box: silence unused_mut warning when building with cfg(miri))
 - #76825 (use `array_windows` instead of `windows` in the compiler)
 - #76827 (fix array_windows docs)
 - #76828 (use strip_prefix over starts_with and manual slicing based on pattern length (clippy::manual_strip))
 - #76840 (Move to intra doc links in core/src/future)
 - #76845 (Use intra docs links in core::{ascii, option, str, pattern, hash::map})
 - #76853 (Use intra-doc links in library/core/src/task/wake.rs)
 - #76871 (support panic=abort in Miri)

Failed merges:

r? `@ghost`

compiler/rustc_mir/src/borrow_check/diagnostics/move_errors.rs

@@ -492,8 +492,8 @@ impl<'a, 'tcx> MirBorrowckCtxt<'a, 'tcx> {
             {
                 if let Ok(pat_snippet) = self.infcx.tcx.sess.source_map().span_to_snippet(pat_span)
                 {
-                    if pat_snippet.starts_with('&') {
-                        let pat_snippet = pat_snippet[1..].trim_start();
+                    if let Some(stripped) = pat_snippet.strip_prefix('&') {
+                        let pat_snippet = stripped.trim_start();
                         let (suggestion, to_remove) = if pat_snippet.starts_with("mut")
                             && pat_snippet["mut".len()..].starts_with(rustc_lexer::is_whitespace)
                         {

compiler/rustc_mir/src/borrow_check/diagnostics/mutability_errors.rs

@@ -631,9 +631,8 @@ fn suggest_ampmut<'tcx>(
                 let lt_name = &src[1..ws_pos];
                 let ty = &src[ws_pos..];
                 return (assignment_rhs_span, format!("&{} mut {}", lt_name, ty));
-            } else if src.starts_with('&') {
-                let borrowed_expr = &src[1..];
-                return (assignment_rhs_span, format!("&mut {}", borrowed_expr));
+            } else if let Some(stripped) = src.strip_prefix('&') {
+                return (assignment_rhs_span, format!("&mut {}", stripped));
             }
         }
     }

compiler/rustc_mir/src/dataflow/framework/graphviz.rs

@@ -1,6 +1,7 @@
 //! A helpful diagram for debugging dataflow problems.
 
 use std::borrow::Cow;
+use std::lazy::SyncOnceCell;
 use std::{io, ops, str};
 
 use regex::Regex;
@@ -570,6 +571,13 @@ where
     }
 }
 
+macro_rules! regex {
+    ($re:literal $(,)?) => {{
+        static RE: SyncOnceCell<regex::Regex> = SyncOnceCell::new();
+        RE.get_or_init(|| Regex::new($re).unwrap())
+    }};
+}
+
 fn diff_pretty<T, C>(new: T, old: T, ctxt: &C) -> String
 where
     T: DebugWithContext<C>,
@@ -578,7 +586,7 @@ where
         return String::new();
     }
 
-    let re = Regex::new("\t?\u{001f}([+-])").unwrap();
+    let re = regex!("\t?\u{001f}([+-])");
 
     let raw_diff = format!("{:#?}", DebugDiffWithAdapter { new, old, ctxt });
 

compiler/rustc_mir/src/lib.rs

@@ -6,6 +6,7 @@ Rust MIR: a lowered representation of Rust.
 
 #![feature(nll)]
 #![feature(in_band_lifetimes)]
+#![feature(array_windows)]
 #![feature(bindings_after_at)]
 #![feature(bool_to_option)]
 #![feature(box_patterns)]
@@ -14,20 +15,18 @@ Rust MIR: a lowered representation of Rust.
 #![feature(const_panic)]
 #![feature(crate_visibility_modifier)]
 #![feature(decl_macro)]
-#![feature(drain_filter)]
 #![feature(exact_size_is_empty)]
 #![feature(exhaustive_patterns)]
-#![feature(iter_order_by)]
 #![feature(never_type)]
 #![feature(min_specialization)]
 #![feature(trusted_len)]
 #![feature(try_blocks)]
-#![feature(associated_type_bounds)]
 #![feature(associated_type_defaults)]
 #![feature(stmt_expr_attributes)]
 #![feature(trait_alias)]
 #![feature(option_expect_none)]
 #![feature(or_patterns)]
+#![feature(once_cell)]
 #![recursion_limit = "256"]
 
 #[macro_use]

compiler/rustc_mir/src/monomorphize/partitioning/mod.rs

@@ -277,14 +277,8 @@ where
 
     symbols.sort_by_key(|sym| sym.1);
 
-    for pair in symbols.windows(2) {
-        let sym1 = &pair[0].1;
-        let sym2 = &pair[1].1;
-
+    for &[(mono_item1, ref sym1), (mono_item2, ref sym2)] in symbols.array_windows() {
         if sym1 == sym2 {
-            let mono_item1 = pair[0].0;
-            let mono_item2 = pair[1].0;
-
             let span1 = mono_item1.local_span(tcx);
             let span2 = mono_item2.local_span(tcx);