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;
4 use rustc::declare_lint_pass;
6 use rustc::lint::{LateContext, LateLintPass, LintArray, LintPass};
7 use rustc::ty::{self, Ty};
8 use rustc_errors::Applicability;
9 use rustc_session::declare_tool_lint;
10 use syntax::source_map::Span;
12 declare_clippy_lint! {
13 /// **What it does:** Checks for usage of `&vec![..]` when using `&[..]` would
16 /// **Why is this bad?** This is less efficient.
18 /// **Known problems:** None.
29 declare_lint_pass!(UselessVec => [USELESS_VEC]);
31 impl<'a, 'tcx> LateLintPass<'a, 'tcx> for UselessVec {
32 fn check_expr(&mut self, cx: &LateContext<'a, 'tcx>, expr: &'tcx Expr) {
33 // search for `&vec![_]` expressions where the adjusted type is `&[_]`
35 if let ty::Ref(_, ty, _) = cx.tables.expr_ty_adjusted(expr).kind;
36 if let ty::Slice(..) = ty.kind;
37 if let ExprKind::AddrOf(BorrowKind::Ref, _, ref addressee) = expr.kind;
38 if let Some(vec_args) = higher::vec_macro(cx, addressee);
40 check_vec_macro(cx, &vec_args, expr.span);
44 // search for `for _ in vec![…]`
46 if let Some((_, arg, _)) = higher::for_loop(expr);
47 if let Some(vec_args) = higher::vec_macro(cx, arg);
48 if is_copy(cx, vec_type(cx.tables.expr_ty_adjusted(arg)));
50 // report the error around the `vec!` not inside `<std macros>:`
58 check_vec_macro(cx, &vec_args, span);
64 fn check_vec_macro<'a, 'tcx>(cx: &LateContext<'a, 'tcx>, vec_args: &higher::VecArgs<'tcx>, span: Span) {
65 let mut applicability = Applicability::MachineApplicable;
66 let snippet = match *vec_args {
67 higher::VecArgs::Repeat(elem, len) => {
68 if constant(cx, cx.tables, len).is_some() {
71 snippet_with_applicability(cx, elem.span, "elem", &mut applicability),
72 snippet_with_applicability(cx, len.span, "len", &mut applicability)
78 higher::VecArgs::Vec(args) => {
79 if let Some(last) = args.iter().last() {
80 let span = args[0].span.to(last.span);
82 format!("&[{}]", snippet_with_applicability(cx, span, "..", &mut applicability))
93 "useless use of `vec!`",
94 "you can use a slice directly",
100 /// Returns the item type of the vector (i.e., the `T` in `Vec<T>`).
101 fn vec_type(ty: Ty<'_>) -> Ty<'_> {
102 if let ty::Adt(_, substs) = ty.kind {
105 panic!("The type of `vec!` is a not a struct?");