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 declare_clippy_lint! {
12 /// **What it does:** Checks for usage of `&vec![..]` when using `&[..]` would
15 /// **Why is this bad?** This is less efficient.
17 /// **Known problems:** None.
28 #[derive(Copy, Clone, Debug)]
31 impl LintPass for Pass {
32 fn get_lints(&self) -> LintArray {
33 lint_array!(USELESS_VEC)
36 fn name(&self) -> &'static str {
41 impl<'a, 'tcx> LateLintPass<'a, 'tcx> for Pass {
42 fn check_expr(&mut self, cx: &LateContext<'a, 'tcx>, expr: &'tcx Expr) {
43 // search for `&vec![_]` expressions where the adjusted type is `&[_]`
45 if let ty::Ref(_, ty, _) = cx.tables.expr_ty_adjusted(expr).sty;
46 if let ty::Slice(..) = ty.sty;
47 if let ExprKind::AddrOf(_, ref addressee) = expr.node;
48 if let Some(vec_args) = higher::vec_macro(cx, addressee);
50 check_vec_macro(cx, &vec_args, expr.span);
54 // search for `for _ in vec![…]`
56 if let Some((_, arg, _)) = higher::for_loop(expr);
57 if let Some(vec_args) = higher::vec_macro(cx, arg);
58 if is_copy(cx, vec_type(cx.tables.expr_ty_adjusted(arg)));
60 // report the error around the `vec!` not inside `<std macros>:`
65 .map(|info| info.call_site)
66 .expect("unable to get call_site")
70 .map(|info| info.call_site)
71 .expect("unable to get call_site");
72 check_vec_macro(cx, &vec_args, span);
78 fn check_vec_macro<'a, 'tcx>(cx: &LateContext<'a, 'tcx>, vec_args: &higher::VecArgs<'tcx>, span: Span) {
79 let mut applicability = Applicability::MachineApplicable;
80 let snippet = match *vec_args {
81 higher::VecArgs::Repeat(elem, len) => {
82 if constant(cx, cx.tables, len).is_some() {
85 snippet_with_applicability(cx, elem.span, "elem", &mut applicability),
86 snippet_with_applicability(cx, len.span, "len", &mut applicability)
92 higher::VecArgs::Vec(args) => {
93 if let Some(last) = args.iter().last() {
94 let span = args[0].span.to(last.span);
96 format!("&[{}]", snippet_with_applicability(cx, span, "..", &mut applicability))
107 "useless use of `vec!`",
108 "you can use a slice directly",
114 /// Returns the item type of the vector (i.e., the `T` in `Vec<T>`).
115 fn vec_type(ty: Ty<'_>) -> Ty<'_> {
116 if let ty::Adt(_, substs) = ty.sty {
119 panic!("The type of `vec!` is a not a struct?");