mirror of
https://github.com/rust-lang/rust-clippy
synced 2024-12-23 03:23:33 +00:00
98 lines
3.7 KiB
Rust
98 lines
3.7 KiB
Rust
use rustc::lint::*;
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use rustc::hir::*;
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use syntax::codemap::Spanned;
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use utils::{is_integer_literal, match_type, paths, snippet, span_lint};
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use utils::higher;
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/// **What it does:** Checks for iterating over ranges with a `.step_by(0)`,
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/// which never terminates.
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///
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/// **Why is this bad?** This very much looks like an oversight, since with
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/// `loop { .. }` there is an obvious better way to endlessly loop.
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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
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/// for x in (5..5).step_by(0) { .. }
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/// ```
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declare_lint! {
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pub RANGE_STEP_BY_ZERO,
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Warn,
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"using `Range::step_by(0)`, which produces an infinite iterator"
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}
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/// **What it does:** Checks for zipping a collection with the range of `0.._.len()`.
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///
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/// **Why is this bad?** The code is better expressed with `.enumerate()`.
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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
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/// x.iter().zip(0..x.len())
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/// ```
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declare_lint! {
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pub RANGE_ZIP_WITH_LEN,
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Warn,
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"zipping iterator with a range when `enumerate()` would do"
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}
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#[derive(Copy,Clone)]
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pub struct StepByZero;
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impl LintPass for StepByZero {
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fn get_lints(&self) -> LintArray {
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lint_array!(RANGE_STEP_BY_ZERO, RANGE_ZIP_WITH_LEN)
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}
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}
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impl<'a, 'tcx> LateLintPass<'a, 'tcx> for StepByZero {
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fn check_expr(&mut self, cx: &LateContext<'a, 'tcx>, expr: &'tcx Expr) {
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if let ExprMethodCall(Spanned { node: ref name, .. }, _, ref args) = expr.node {
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let name = name.as_str();
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// Range with step_by(0).
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if name == "step_by" && args.len() == 2 && has_step_by(cx, &args[0]) && is_integer_literal(&args[1], 0) {
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span_lint(cx,
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RANGE_STEP_BY_ZERO,
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expr.span,
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"Range::step_by(0) produces an infinite iterator. Consider using `std::iter::repeat()` \
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instead");
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} else if name == "zip" && args.len() == 2 {
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let iter = &args[0].node;
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let zip_arg = &args[1];
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if_let_chain! {[
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// .iter() call
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let ExprMethodCall( Spanned { node: iter_name, .. }, _, ref iter_args ) = *iter,
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iter_name == "iter",
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// range expression in .zip() call: 0..x.len()
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let Some(higher::Range { start: Some(start), end: Some(end), .. }) = higher::range(zip_arg),
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is_integer_literal(start, 0),
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// .len() call
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let ExprMethodCall(Spanned { node: len_name, .. }, _, ref len_args) = end.node,
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len_name == "len" && len_args.len() == 1,
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// .iter() and .len() called on same Path
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let ExprPath(QPath::Resolved(_, ref iter_path)) = iter_args[0].node,
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let ExprPath(QPath::Resolved(_, ref len_path)) = len_args[0].node,
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iter_path.segments == len_path.segments
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], {
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span_lint(cx,
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RANGE_ZIP_WITH_LEN,
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expr.span,
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&format!("It is more idiomatic to use {}.iter().enumerate()",
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snippet(cx, iter_args[0].span, "_")));
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}}
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}
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}
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}
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}
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fn has_step_by(cx: &LateContext, expr: &Expr) -> bool {
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// No need for walk_ptrs_ty here because step_by moves self, so it
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// can't be called on a borrowed range.
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let ty = cx.tables.expr_ty(expr);
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// Note: `RangeTo`, `RangeToInclusive` and `RangeFull` don't have step_by
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match_type(cx, ty, &paths::RANGE) || match_type(cx, ty, &paths::RANGE_FROM) ||
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match_type(cx, ty, &paths::RANGE_INCLUSIVE)
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}
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