eplace usages of vec![].into_iter with [].into_iter

compiler/rustc_trait_selection/src/traits/error_reporting/mod.rs

@@ -2247,7 +2247,7 @@ pub fn recursive_type_with_infinite_size_error(
             spans
                 .iter()
                 .flat_map(|&span| {
-                    vec![
+                    [
                         (span.shrink_to_lo(), "Box<".to_string()),
                         (span.shrink_to_hi(), ">".to_string()),
                     ]

compiler/rustc_trait_selection/src/traits/error_reporting/suggestions.rs

@@ -1226,7 +1226,7 @@ impl<'a, 'tcx> InferCtxtExt<'tcx> for InferCtxt<'a, 'tcx> {
                     .returns
                     .iter()
                     .flat_map(|expr| {
-                        vec![
+                        [
                             (expr.span.shrink_to_lo(), "Box::new(".to_string()),
                             (expr.span.shrink_to_hi(), ")".to_string()),
                         ]

compiler/rustc_trait_selection/src/traits/select/mod.rs

@@ -1953,7 +1953,7 @@ impl<'cx, 'tcx> SelectionContext<'cx, 'tcx> {
             ty::Generator(_, ref substs, _) => {
                 let ty = self.infcx.shallow_resolve(substs.as_generator().tupled_upvars_ty());
                 let witness = substs.as_generator().witness();
-                t.rebind(vec![ty].into_iter().chain(iter::once(witness)).collect())
+                t.rebind([ty].into_iter().chain(iter::once(witness)).collect())
             }
 
             ty::GeneratorWitness(types) => {