Rename `IndexVec::last` → `last_index`

As I've been trying to replace a `Vec` with an `IndexVec`, having `last` exist on both but returning very different types makes the transition a bit awkward -- the errors are later, where you get things like "there's no `ty` method on `mir::Field`" rather than a more localized error like "hey, there's no `last` on `IndexVec`".

So I propose renaming `last` to `last_index` to help distinguish `Vec::last`, which returns an element, and `IndexVec::last_index`, which returns an index.

(Similarly, `Iterator::last` also returns an element, not an index.)

1 files changed, 2 insertions, 2 deletions

diff --git a/compiler/rustc_const_eval/src/transform/promote_consts.rs b/compiler/rustc_const_eval/src/transform/promote_consts.rs
index 648a86d32fc..40c848de2be 100644
--- a/compiler/rustc_const_eval/src/transform/promote_consts.rs
+++ b/compiler/rustc_const_eval/src/transform/promote_consts.rs
@@ -707,7 +707,7 @@ impl<'a, 'tcx> Promoter<'a, 'tcx> {
     }
 
     fn assign(&mut self, dest: Local, rvalue: Rvalue<'tcx>, span: Span) {
-        let last = self.promoted.basic_blocks.last().unwrap();
+        let last = self.promoted.basic_blocks.last_index().unwrap();
         let data = &mut self.promoted[last];
         data.statements.push(Statement {
             source_info: SourceInfo::outermost(span),
@@ -800,7 +800,7 @@ impl<'a, 'tcx> Promoter<'a, 'tcx> {
                         self.visit_operand(arg, loc);
                     }
 
-                    let last = self.promoted.basic_blocks.last().unwrap();
+                    let last = self.promoted.basic_blocks.last_index().unwrap();
                     let new_target = self.new_block();
 
                     *self.promoted[last].terminator_mut() = Terminator {