review feedback: no reason to clone just to make a singleton slice.

Author: pnkfelix

src/librustc_mir/build/block.rs

@@ -16,6 +16,8 @@ use rustc::mir::*;
 use rustc::hir;
 use syntax_pos::Span;
 
+use std::slice;
+
 impl<'a, 'gcx, 'tcx> Builder<'a, 'gcx, 'tcx> {
     pub fn ast_block(&mut self,
                      destination: &Place<'tcx>,
@@ -126,7 +128,7 @@ impl<'a, 'gcx, 'tcx> Builder<'a, 'gcx, 'tcx> {
                             None,
                             remainder_span,
                             lint_level,
-                            &[pattern.clone()],
+                            slice::from_ref(&pattern),
                             ArmHasGuard(false),
                             Some((None, initializer_span)),
                         );
@@ -139,7 +141,7 @@ impl<'a, 'gcx, 'tcx> Builder<'a, 'gcx, 'tcx> {
                             }));
                     } else {
                         scope = this.declare_bindings(
-                            None, remainder_span, lint_level, &[pattern.clone()],
+                            None, remainder_span, lint_level, slice::from_ref(&pattern),
                             ArmHasGuard(false), None);
 
                         // FIXME(#47184): We currently only insert `UserAssertTy` statements for