Use `Itertools::all_equal_value()` where applicable

3 files changed, 18 insertions, 22 deletions

diff --git a/compiler/rustc_mir_transform/src/gvn.rs b/compiler/rustc_mir_transform/src/gvn.rs
index 5a13394543b..9da6e034c3b 100644
--- a/compiler/rustc_mir_transform/src/gvn.rs
+++ b/compiler/rustc_mir_transform/src/gvn.rs
@@ -87,6 +87,7 @@
 use std::borrow::Cow;
 
 use either::Either;
+use itertools::Itertools as _;
 use rustc_abi::{self as abi, BackendRepr, FIRST_VARIANT, FieldIdx, Primitive, Size, VariantIdx};
 use rustc_const_eval::const_eval::DummyMachine;
 use rustc_const_eval::interpret::{
@@ -1023,15 +1024,15 @@ impl<'body, 'tcx> VnState<'body, 'tcx> {
             }
         };
 
-        if ty.is_array() && fields.len() > 4 {
-            let first = fields[0];
-            if fields.iter().all(|&v| v == first) {
-                let len = ty::Const::from_target_usize(self.tcx, fields.len().try_into().unwrap());
-                if let Some(op) = self.try_as_operand(first, location) {
-                    *rvalue = Rvalue::Repeat(op, len);
-                }
-                return Some(self.insert(ty, Value::Repeat(first, len)));
+        if ty.is_array()
+            && fields.len() > 4
+            && let Ok(&first) = fields.iter().all_equal_value()
+        {
+            let len = ty::Const::from_target_usize(self.tcx, fields.len().try_into().unwrap());
+            if let Some(op) = self.try_as_operand(first, location) {
+                *rvalue = Rvalue::Repeat(op, len);
             }
+            return Some(self.insert(ty, Value::Repeat(first, len)));
         }
 
         if let Some(value) =
diff --git a/compiler/rustc_mir_transform/src/lint_tail_expr_drop_order.rs b/compiler/rustc_mir_transform/src/lint_tail_expr_drop_order.rs
index 794984d2f3e..61c9bbe3123 100644
--- a/compiler/rustc_mir_transform/src/lint_tail_expr_drop_order.rs
+++ b/compiler/rustc_mir_transform/src/lint_tail_expr_drop_order.rs
@@ -2,6 +2,7 @@ use std::cell::RefCell;
 use std::collections::hash_map;
 use std::rc::Rc;
 
+use itertools::Itertools as _;
 use rustc_data_structures::fx::{FxHashMap, FxHashSet, FxIndexMap};
 use rustc_data_structures::unord::{UnordMap, UnordSet};
 use rustc_errors::Subdiagnostic;
@@ -339,9 +340,9 @@ pub(crate) fn run_lint<'tcx>(tcx: TyCtxt<'tcx>, def_id: LocalDefId, body: &Body<
             // Suppose that all BIDs point into the same local,
             // we can remove the this local from the observed drops,
             // so that we can focus our diagnosis more on the others.
-            if candidates.iter().all(|&(_, place)| candidates[0].1.local == place.local) {
+            if let Ok(local) = candidates.iter().map(|&(_, place)| place.local).all_equal_value() {
                 for path_idx in all_locals_dropped.iter() {
-                    if move_data.move_paths[path_idx].place.local == candidates[0].1.local {
+                    if move_data.move_paths[path_idx].place.local == local {
                         to_exclude.insert(path_idx);
                     }
                 }
diff --git a/compiler/rustc_mir_transform/src/simplify.rs b/compiler/rustc_mir_transform/src/simplify.rs
index 468ef742dfb..75917d23883 100644
--- a/compiler/rustc_mir_transform/src/simplify.rs
+++ b/compiler/rustc_mir_transform/src/simplify.rs
@@ -34,6 +34,7 @@
 //! The normal logic that a program with UB can be changed to do anything does not apply to
 //! pre-"runtime" MIR!
 
+use itertools::Itertools as _;
 use rustc_index::{Idx, IndexSlice, IndexVec};
 use rustc_middle::mir::visit::{MutVisitor, MutatingUseContext, PlaceContext, Visitor};
 use rustc_middle::mir::*;
@@ -288,20 +289,13 @@ impl<'a, 'tcx> CfgSimplifier<'a, 'tcx> {
             return false;
         };
 
-        let first_succ = {
-            if let Some(first_succ) = terminator.successors().next() {
-                if terminator.successors().all(|s| s == first_succ) {
-                    let count = terminator.successors().count();
-                    self.pred_count[first_succ] -= (count - 1) as u32;
-                    first_succ
-                } else {
-                    return false;
-                }
-            } else {
-                return false;
-            }
+        let Ok(first_succ) = terminator.successors().all_equal_value() else {
+            return false;
         };
 
+        let count = terminator.successors().count();
+        self.pred_count[first_succ] -= (count - 1) as u32;
+
         debug!("simplifying branch {:?}", terminator);
         terminator.kind = TerminatorKind::Goto { target: first_succ };
         true