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_lint_pass, declare_tool_lint};
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 declare_lint_pass!(UselessVec => [USELESS_VEC]);
30 impl<'a, 'tcx> LateLintPass<'a, 'tcx> for UselessVec {
31 fn check_expr(&mut self, cx: &LateContext<'a, 'tcx>, expr: &'tcx Expr) {
32 // search for `&vec![_]` expressions where the adjusted type is `&[_]`
34 if let ty::Ref(_, ty, _) = cx.tables.expr_ty_adjusted(expr).sty;
35 if let ty::Slice(..) = ty.sty;
36 if let ExprKind::AddrOf(_, ref addressee) = expr.node;
37 if let Some(vec_args) = higher::vec_macro(cx, addressee);
39 check_vec_macro(cx, &vec_args, expr.span);
43 // search for `for _ in vec![…]`
45 if let Some((_, arg, _)) = higher::for_loop(expr);
46 if let Some(vec_args) = higher::vec_macro(cx, arg);
47 if is_copy(cx, vec_type(cx.tables.expr_ty_adjusted(arg)));
49 // report the error around the `vec!` not inside `<std macros>:`
54 .map(|info| info.call_site)
55 .expect("unable to get call_site")
59 .map(|info| info.call_site)
60 .expect("unable to get call_site");
61 check_vec_macro(cx, &vec_args, span);
67 fn check_vec_macro<'a, 'tcx>(cx: &LateContext<'a, 'tcx>, vec_args: &higher::VecArgs<'tcx>, span: Span) {
68 let mut applicability = Applicability::MachineApplicable;
69 let snippet = match *vec_args {
70 higher::VecArgs::Repeat(elem, len) => {
71 if constant(cx, cx.tables, len).is_some() {
74 snippet_with_applicability(cx, elem.span, "elem", &mut applicability),
75 snippet_with_applicability(cx, len.span, "len", &mut applicability)
81 higher::VecArgs::Vec(args) => {
82 if let Some(last) = args.iter().last() {
83 let span = args[0].span.to(last.span);
85 format!("&[{}]", snippet_with_applicability(cx, span, "..", &mut applicability))
96 "useless use of `vec!`",
97 "you can use a slice directly",
103 /// Returns the item type of the vector (i.e., the `T` in `Vec<T>`).
104 fn vec_type(ty: Ty<'_>) -> Ty<'_> {
105 if let ty::Adt(_, substs) = ty.sty {
108 panic!("The type of `vec!` is a not a struct?");