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Rollup merge of #109718 - scottmcm:indexvec-last, r=Nilstrieb
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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.)
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Dylan-DPC authored Mar 29, 2023
2 parents 2a4455d + 843c5e3 commit 1415756
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Showing 4 changed files with 5 additions and 5 deletions.
4 changes: 2 additions & 2 deletions compiler/rustc_const_eval/src/transform/promote_consts.rs
Original file line number Diff line number Diff line change
Expand Up @@ -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),
Expand Down Expand Up @@ -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 {
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2 changes: 1 addition & 1 deletion compiler/rustc_index/src/vec.rs
Original file line number Diff line number Diff line change
Expand Up @@ -216,7 +216,7 @@ impl<I: Idx, T> IndexVec<I, T> {
}

#[inline]
pub fn last(&self) -> Option<I> {
pub fn last_index(&self) -> Option<I> {
self.len().checked_sub(1).map(I::new)
}

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2 changes: 1 addition & 1 deletion compiler/rustc_mir_transform/src/coverage/tests.rs
Original file line number Diff line number Diff line change
Expand Up @@ -65,7 +65,7 @@ impl<'tcx> MockBlocks<'tcx> {
}

fn push(&mut self, kind: TerminatorKind<'tcx>) -> BasicBlock {
let next_lo = if let Some(last) = self.blocks.last() {
let next_lo = if let Some(last) = self.blocks.last_index() {
self.blocks[last].terminator().source_info.span.hi()
} else {
BytePos(1)
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Original file line number Diff line number Diff line change
Expand Up @@ -70,7 +70,7 @@ impl<'tcx> SearchGraph<'tcx> {
/// Whether we're currently in a cycle. This should only be used
/// for debug assertions.
pub(super) fn in_cycle(&self) -> bool {
if let Some(stack_depth) = self.stack.last() {
if let Some(stack_depth) = self.stack.last_index() {
// Either the current goal on the stack is the root of a cycle...
if self.stack[stack_depth].has_been_used {
return true;
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