cleanup: Remove useless [T].iter().last()

Author: estebank

compiler/rustc_ast_passes/src/ast_validation.rs

@@ -1741,7 +1741,7 @@ fn deny_equality_constraints(
                         .map(|segment| segment.ident.name)
                         .zip(poly.trait_ref.path.segments.iter().map(|segment| segment.ident.name))
                         .all(|(a, b)| a == b)
-                        && let Some(potential_assoc) = full_path.segments.iter().last()
+                        && let Some(potential_assoc) = full_path.segments.last()
                     {
                         suggest(poly, potential_assoc, predicate);
                     }

compiler/rustc_macros/src/diagnostics/utils.rs

@@ -146,7 +146,7 @@ impl<'ty> FieldInnerTy<'ty> {
             };
 
             let path = &ty_path.path;
-            let ty = path.segments.iter().last().unwrap();
+            let ty = path.segments.last().unwrap();
             let syn::PathArguments::AngleBracketed(bracketed) = &ty.arguments else {
                 panic!("expected bracketed generic arguments");
             };