Rollup merge of rust-lang#99557 - pierwill:patch-6, r=tmiasko

Edit `rustc_index::vec::IndexVec::pick3_mut` docs

Clarify when this method will panic.

Part of rust-lang#93792.

compiler/rustc_index/src/vec.rs

@@ -234,7 +234,9 @@ impl<I: Idx, T> IndexVec<I, T> {
  self.raw.get_mut(index.index())
  }
 
- /// Returns mutable references to two distinct elements, a and b. Panics if a == b.
+ /// Returns mutable references to two distinct elements, `a` and `b`.
+ ///
+ /// Panics if `a == b`.
  #[inline]
  pub fn pick2_mut(&mut self, a: I, b: I) -> (&mut T, &mut T) {
  let (ai, bi) = (a.index(), b.index());
@@ -249,7 +251,9 @@ impl<I: Idx, T> IndexVec<I, T> {
  }
  }
 
- /// Returns mutable references to three distinct elements or panics otherwise.
+ /// Returns mutable references to three distinct elements.
+ ///
+ /// Panics if the elements are not distinct.
  #[inline]
  pub fn pick3_mut(&mut self, a: I, b: I, c: I) -> (&mut T, &mut T, &mut T) {
  let (ai, bi, ci) = (a.index(), b.index(), c.index());