102 lines
2.9 KiB
Rust
102 lines
2.9 KiB
Rust
use rustc::hir::*;
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use rustc::lint::*;
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use rustc::ty::{self, Ty};
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use syntax::codemap::Span;
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use utils::{higher, is_copy, snippet, span_lint_and_sugg};
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use consts::constant;
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/// **What it does:** Checks for usage of `&vec![..]` when using `&[..]` would
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/// be possible.
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///
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/// **Why is this bad?** This is less efficient.
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///
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/// **Known problems:** None.
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///
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/// **Example:**
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/// ```rust,ignore
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/// foo(&vec![1, 2])
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/// ```
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declare_clippy_lint! {
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pub USELESS_VEC,
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perf,
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"useless `vec!`"
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}
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#[derive(Copy, Clone, Debug)]
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pub struct Pass;
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impl LintPass for Pass {
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fn get_lints(&self) -> LintArray {
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lint_array!(USELESS_VEC)
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}
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}
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impl<'a, 'tcx> LateLintPass<'a, 'tcx> for Pass {
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fn check_expr(&mut self, cx: &LateContext<'a, 'tcx>, expr: &'tcx Expr) {
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// search for `&vec![_]` expressions where the adjusted type is `&[_]`
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if_chain! {
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if let ty::TyRef(_, ty, _) = cx.tables.expr_ty_adjusted(expr).sty;
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if let ty::TySlice(..) = ty.sty;
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if let ExprAddrOf(_, ref addressee) = expr.node;
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if let Some(vec_args) = higher::vec_macro(cx, addressee);
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then {
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check_vec_macro(cx, &vec_args, expr.span);
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}
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}
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// search for `for _ in vec![…]`
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if_chain! {
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if let Some((_, arg, _)) = higher::for_loop(expr);
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if let Some(vec_args) = higher::vec_macro(cx, arg);
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if is_copy(cx, vec_type(cx.tables.expr_ty_adjusted(arg)));
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then {
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// report the error around the `vec!` not inside `<std macros>:`
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let span = arg.span
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.ctxt()
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.outer()
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.expn_info()
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.map(|info| info.call_site)
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.expect("unable to get call_site");
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check_vec_macro(cx, &vec_args, span);
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}
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}
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}
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}
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fn check_vec_macro<'a, 'tcx>(cx: &LateContext<'a, 'tcx>, vec_args: &higher::VecArgs<'tcx>, span: Span) {
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let snippet = match *vec_args {
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higher::VecArgs::Repeat(elem, len) => {
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if constant(cx, cx.tables, len).is_some() {
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format!("&[{}; {}]", snippet(cx, elem.span, "elem"), snippet(cx, len.span, "len"))
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} else {
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return;
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}
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},
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higher::VecArgs::Vec(args) => if let Some(last) = args.iter().last() {
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let span = args[0].span.to(last.span);
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format!("&[{}]", snippet(cx, span, ".."))
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} else {
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"&[]".into()
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},
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};
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span_lint_and_sugg(
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cx,
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USELESS_VEC,
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span,
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"useless use of `vec!`",
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"you can use a slice directly",
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snippet,
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);
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}
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/// Return the item type of the vector (ie. the `T` in `Vec<T>`).
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fn vec_type(ty: Ty) -> Ty {
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if let ty::TyAdt(_, substs) = ty.sty {
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substs.type_at(0)
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} else {
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panic!("The type of `vec!` is a not a struct?");
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}
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}
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