Use lint pass macros

Fixes #3917.

clippy_lints/src/vec.rs

@@ -4,7 +4,7 @@ use if_chain::if_chain;
 use rustc::hir::*;
 use rustc::lint::{LateContext, LateLintPass, LintArray, LintPass};
 use rustc::ty::{self, Ty};
-use rustc::{declare_tool_lint, lint_array};
+use rustc::{declare_lint_pass, declare_tool_lint};
 use rustc_errors::Applicability;
 use syntax::source_map::Span;
 
@@ -25,20 +25,9 @@ declare_clippy_lint! {
     "useless `vec!`"
 }
 
-#[derive(Copy, Clone, Debug)]
-pub struct Pass;
+declare_lint_pass!(UselessVec => [USELESS_VEC]);
 
-impl LintPass for Pass {
-    fn get_lints(&self) -> LintArray {
-        lint_array!(USELESS_VEC)
-    }
-
-    fn name(&self) -> &'static str {
-        "UselessVec"
-    }
-}
-
-impl<'a, 'tcx> LateLintPass<'a, 'tcx> for Pass {
+impl<'a, 'tcx> LateLintPass<'a, 'tcx> for UselessVec {
     fn check_expr(&mut self, cx: &LateContext<'a, 'tcx>, expr: &'tcx Expr) {
         // search for `&vec![_]` expressions where the adjusted type is `&[_]`
         if_chain! {