mirror of
https://github.com/rust-lang/rust-clippy
synced 2024-12-16 00:02:55 +00:00
103 lines
3 KiB
Rust
103 lines
3 KiB
Rust
use rustc::hir::*;
|
|
use rustc::lint::*;
|
|
use rustc::{declare_lint, lint_array};
|
|
use if_chain::if_chain;
|
|
use rustc::ty::{self, Ty};
|
|
use syntax::codemap::Span;
|
|
use crate::utils::{higher, is_copy, snippet, span_lint_and_sugg};
|
|
use crate::consts::constant;
|
|
|
|
/// **What it does:** Checks for usage of `&vec![..]` when using `&[..]` would
|
|
/// be possible.
|
|
///
|
|
/// **Why is this bad?** This is less efficient.
|
|
///
|
|
/// **Known problems:** None.
|
|
///
|
|
/// **Example:**
|
|
/// ```rust,ignore
|
|
/// foo(&vec![1, 2])
|
|
/// ```
|
|
declare_clippy_lint! {
|
|
pub USELESS_VEC,
|
|
perf,
|
|
"useless `vec!`"
|
|
}
|
|
|
|
#[derive(Copy, Clone, Debug)]
|
|
pub struct Pass;
|
|
|
|
impl LintPass for Pass {
|
|
fn get_lints(&self) -> LintArray {
|
|
lint_array!(USELESS_VEC)
|
|
}
|
|
}
|
|
|
|
impl<'a, 'tcx> LateLintPass<'a, 'tcx> for Pass {
|
|
fn check_expr(&mut self, cx: &LateContext<'a, 'tcx>, expr: &'tcx Expr) {
|
|
// search for `&vec![_]` expressions where the adjusted type is `&[_]`
|
|
if_chain! {
|
|
if let ty::TyRef(_, ty, _) = cx.tables.expr_ty_adjusted(expr).sty;
|
|
if let ty::TySlice(..) = ty.sty;
|
|
if let ExprKind::AddrOf(_, ref addressee) = expr.node;
|
|
if let Some(vec_args) = higher::vec_macro(cx, addressee);
|
|
then {
|
|
check_vec_macro(cx, &vec_args, expr.span);
|
|
}
|
|
}
|
|
|
|
// search for `for _ in vec![…]`
|
|
if_chain! {
|
|
if let Some((_, arg, _)) = higher::for_loop(expr);
|
|
if let Some(vec_args) = higher::vec_macro(cx, arg);
|
|
if is_copy(cx, vec_type(cx.tables.expr_ty_adjusted(arg)));
|
|
then {
|
|
// report the error around the `vec!` not inside `<std macros>:`
|
|
let span = arg.span
|
|
.ctxt()
|
|
.outer()
|
|
.expn_info()
|
|
.map(|info| info.call_site)
|
|
.expect("unable to get call_site");
|
|
check_vec_macro(cx, &vec_args, span);
|
|
}
|
|
}
|
|
}
|
|
}
|
|
|
|
fn check_vec_macro<'a, 'tcx>(cx: &LateContext<'a, 'tcx>, vec_args: &higher::VecArgs<'tcx>, span: Span) {
|
|
let snippet = match *vec_args {
|
|
higher::VecArgs::Repeat(elem, len) => {
|
|
if constant(cx, cx.tables, len).is_some() {
|
|
format!("&[{}; {}]", snippet(cx, elem.span, "elem"), snippet(cx, len.span, "len"))
|
|
} else {
|
|
return;
|
|
}
|
|
},
|
|
higher::VecArgs::Vec(args) => if let Some(last) = args.iter().last() {
|
|
let span = args[0].span.to(last.span);
|
|
|
|
format!("&[{}]", snippet(cx, span, ".."))
|
|
} else {
|
|
"&[]".into()
|
|
},
|
|
};
|
|
|
|
span_lint_and_sugg(
|
|
cx,
|
|
USELESS_VEC,
|
|
span,
|
|
"useless use of `vec!`",
|
|
"you can use a slice directly",
|
|
snippet,
|
|
);
|
|
}
|
|
|
|
/// Return the item type of the vector (ie. the `T` in `Vec<T>`).
|
|
fn vec_type(ty: Ty<'_>) -> Ty<'_> {
|
|
if let ty::TyAdt(_, substs) = ty.sty {
|
|
substs.type_at(0)
|
|
} else {
|
|
panic!("The type of `vec!` is a not a struct?");
|
|
}
|
|
}
|