1 use crate::consts::constant;
2 use crate::utils::{higher, is_copy, snippet_with_applicability, span_lint_and_sugg};
3 use if_chain::if_chain;
5 use rustc::lint::{LateContext, LateLintPass, LintArray, LintPass};
6 use rustc::ty::{self, Ty};
7 use rustc::{declare_tool_lint, lint_array};
8 use rustc_errors::Applicability;
9 use syntax::source_map::Span;
11 /// **What it does:** Checks for usage of `&vec![..]` when using `&[..]` would
14 /// **Why is this bad?** This is less efficient.
16 /// **Known problems:** None.
22 declare_clippy_lint! {
28 #[derive(Copy, Clone, Debug)]
31 impl LintPass for Pass {
32 fn get_lints(&self) -> LintArray {
33 lint_array!(USELESS_VEC)
37 impl<'a, 'tcx> LateLintPass<'a, 'tcx> for Pass {
38 fn check_expr(&mut self, cx: &LateContext<'a, 'tcx>, expr: &'tcx Expr) {
39 // search for `&vec![_]` expressions where the adjusted type is `&[_]`
41 if let ty::Ref(_, ty, _) = cx.tables.expr_ty_adjusted(expr).sty;
42 if let ty::Slice(..) = ty.sty;
43 if let ExprKind::AddrOf(_, ref addressee) = expr.node;
44 if let Some(vec_args) = higher::vec_macro(cx, addressee);
46 check_vec_macro(cx, &vec_args, expr.span);
50 // search for `for _ in vec![…]`
52 if let Some((_, arg, _)) = higher::for_loop(expr);
53 if let Some(vec_args) = higher::vec_macro(cx, arg);
54 if is_copy(cx, vec_type(cx.tables.expr_ty_adjusted(arg)));
56 // report the error around the `vec!` not inside `<std macros>:`
61 .map(|info| info.call_site)
62 .expect("unable to get call_site");
63 check_vec_macro(cx, &vec_args, span);
69 fn check_vec_macro<'a, 'tcx>(cx: &LateContext<'a, 'tcx>, vec_args: &higher::VecArgs<'tcx>, span: Span) {
70 let mut applicability = Applicability::MachineApplicable;
71 let snippet = match *vec_args {
72 higher::VecArgs::Repeat(elem, len) => {
73 if constant(cx, cx.tables, len).is_some() {
76 snippet_with_applicability(cx, elem.span, "elem", &mut applicability),
77 snippet_with_applicability(cx, len.span, "len", &mut applicability)
83 higher::VecArgs::Vec(args) => {
84 if let Some(last) = args.iter().last() {
85 let span = args[0].span.to(last.span);
87 format!("&[{}]", snippet_with_applicability(cx, span, "..", &mut applicability))
98 "useless use of `vec!`",
99 "you can use a slice directly",
105 /// Return the item type of the vector (ie. the `T` in `Vec<T>`).
106 fn vec_type(ty: Ty<'_>) -> Ty<'_> {
107 if let ty::Adt(_, substs) = ty.sty {
110 panic!("The type of `vec!` is a not a struct?");