rust-clippy/clippy_lints/src/ranges.rs

99 lines
3.7 KiB
Rust
Raw Normal View History

use rustc::lint::*;
use rustc::hir::*;
use syntax::codemap::Spanned;
use utils::{is_integer_literal, match_type, paths, snippet, span_lint};
use utils::higher;
/// **What it does:** Checks for iterating over ranges with a `.step_by(0)`,
/// which never terminates.
///
/// **Why is this bad?** This very much looks like an oversight, since with
/// `loop { .. }` there is an obvious better way to endlessly loop.
///
/// **Known problems:** None.
///
2016-07-15 22:25:44 +00:00
/// **Example:**
/// ```rust
/// for x in (5..5).step_by(0) { .. }
/// ```
declare_lint! {
pub RANGE_STEP_BY_ZERO,
Warn,
"using `Range::step_by(0)`, which produces an infinite iterator"
}
/// **What it does:** Checks for zipping a collection with the range of `0.._.len()`.
///
/// **Why is this bad?** The code is better expressed with `.enumerate()`.
///
/// **Known problems:** None.
///
2016-07-15 22:25:44 +00:00
/// **Example:**
/// ```rust
/// x.iter().zip(0..x.len())
/// ```
declare_lint! {
pub RANGE_ZIP_WITH_LEN,
Warn,
"zipping iterator with a range when `enumerate()` would do"
}
#[derive(Copy,Clone)]
pub struct StepByZero;
impl LintPass for StepByZero {
fn get_lints(&self) -> LintArray {
lint_array!(RANGE_STEP_BY_ZERO, RANGE_ZIP_WITH_LEN)
}
}
impl<'a, 'tcx> LateLintPass<'a, 'tcx> for StepByZero {
fn check_expr(&mut self, cx: &LateContext<'a, 'tcx>, expr: &'tcx Expr) {
2016-01-04 04:26:12 +00:00
if let ExprMethodCall(Spanned { node: ref name, .. }, _, ref args) = expr.node {
let name = &*name.as_str();
// Range with step_by(0).
2016-12-20 17:21:30 +00:00
if name == "step_by" && args.len() == 2 && has_step_by(cx, &args[0]) && is_integer_literal(&args[1], 0) {
2016-03-26 00:49:45 +00:00
span_lint(cx,
RANGE_STEP_BY_ZERO,
expr.span,
"Range::step_by(0) produces an infinite iterator. Consider using `std::iter::repeat()` \
instead");
} else if name == "zip" && args.len() == 2 {
let iter = &args[0].node;
let zip_arg = &args[1];
2016-06-06 00:09:19 +00:00
if_let_chain! {[
// .iter() call
let ExprMethodCall( Spanned { node: ref iter_name, .. }, _, ref iter_args ) = *iter,
&*iter_name.as_str() == "iter",
2016-06-06 00:09:19 +00:00
// range expression in .zip() call: 0..x.len()
let Some(higher::Range { start: Some(ref start), end: Some(ref end), .. }) = higher::range(zip_arg),
2016-06-06 00:09:19 +00:00
is_integer_literal(start, 0),
// .len() call
let ExprMethodCall(Spanned { node: ref len_name, .. }, _, ref len_args) = end.node,
&*len_name.as_str() == "len" && len_args.len() == 1,
2016-06-06 00:09:19 +00:00
// .iter() and .len() called on same Path
let ExprPath(QPath::Resolved(_, ref iter_path)) = iter_args[0].node,
let ExprPath(QPath::Resolved(_, ref len_path)) = len_args[0].node,
2016-12-02 16:38:31 +00:00
iter_path.segments == len_path.segments
2016-06-06 00:09:19 +00:00
], {
2016-12-02 16:38:31 +00:00
span_lint(cx,
RANGE_ZIP_WITH_LEN,
expr.span,
&format!("It is more idiomatic to use {}.iter().enumerate()",
snippet(cx, iter_args[0].span, "_")));
2016-06-06 00:09:19 +00:00
}}
}
}
}
}
fn has_step_by(cx: &LateContext, expr: &Expr) -> bool {
// No need for walk_ptrs_ty here because step_by moves self, so it
// can't be called on a borrowed range.
2017-01-13 16:04:56 +00:00
let ty = cx.tables.expr_ty(expr);
// Note: `RangeTo`, `RangeToInclusive` and `RangeFull` don't have step_by
2016-12-20 17:21:30 +00:00
match_type(cx, ty, &paths::RANGE) || match_type(cx, ty, &paths::RANGE_FROM) ||
match_type(cx, ty, &paths::RANGE_INCLUSIVE)
}