2015-09-18 21:53:04 -05:00
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use rustc::lint::*;
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2016-04-07 10:46:48 -05:00
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use rustc::hir::*;
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2017-10-07 09:56:45 -05:00
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use syntax::ast::RangeLimits;
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use syntax::codemap::Spanned;
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use utils::{is_integer_literal, paths, snippet, span_lint, span_lint_and_then};
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2017-09-05 04:33:04 -05:00
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use utils::{get_trait_def_id, higher, implements_trait};
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2017-10-07 09:56:45 -05:00
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use utils::sugg::Sugg;
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2015-08-15 11:55:25 -05:00
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2017-06-18 08:14:46 -05:00
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/// **What it does:** Checks for calling `.step_by(0)` on iterators,
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2016-08-06 02:55:04 -05:00
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/// which never terminates.
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2015-12-10 18:22:27 -06:00
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///
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2016-08-06 02:55:04 -05:00
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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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2015-12-10 18:22:27 -06:00
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///
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2016-08-06 02:55:04 -05:00
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/// **Known problems:** None.
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2015-12-10 18:22:27 -06:00
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///
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2016-07-15 17:25:44 -05:00
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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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2015-08-15 11:55:25 -05:00
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declare_lint! {
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2017-06-18 08:14:46 -05:00
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pub ITERATOR_STEP_BY_ZERO,
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2016-08-06 03:18:36 -05:00
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Warn,
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"using `Iterator::step_by(0)`, which produces an infinite iterator"
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2015-08-15 11:55:25 -05:00
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}
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2017-06-18 08:14:46 -05:00
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2017-08-09 02:30:56 -05:00
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/// **What it does:** Checks for zipping a collection with the range of
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/// `0.._.len()`.
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2015-12-10 18:22:27 -06:00
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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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2016-08-06 02:55:04 -05:00
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/// **Known problems:** None.
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2015-12-10 18:22:27 -06:00
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///
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2016-07-15 17:25:44 -05:00
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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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2015-11-03 08:42:52 -06:00
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declare_lint! {
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2016-08-06 03:18:36 -05:00
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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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2015-11-03 08:42:52 -06:00
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}
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2015-08-15 11:55:25 -05:00
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2017-10-07 09:56:45 -05:00
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/// **What it does:** Checks for exclusive ranges where 1 is added to the
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/// upper bound, e.g. `x..(y+1)`.
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///
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/// **Why is this bad?** The code is more readable with an inclusive range
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/// like `x..=y`.
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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..(y+1) { .. }
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/// ```
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declare_lint! {
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pub RANGE_PLUS_ONE,
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2017-10-08 05:42:17 -05:00
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Allow,
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2017-10-07 09:56:45 -05:00
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"`x..(y+1)` reads better as `x..=y`"
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}
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/// **What it does:** Checks for inclusive ranges where 1 is subtracted from
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/// the upper bound, e.g. `x..=(y-1)`.
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///
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/// **Why is this bad?** The code is more readable with an exclusive range
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/// like `x..y`.
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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..=(y-1) { .. }
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/// ```
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declare_lint! {
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pub RANGE_MINUS_ONE,
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Warn,
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"`x..=(y-1)` reads better as `x..y`"
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}
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2017-08-09 02:30:56 -05:00
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#[derive(Copy, Clone)]
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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!(
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ITERATOR_STEP_BY_ZERO,
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RANGE_ZIP_WITH_LEN,
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RANGE_PLUS_ONE,
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RANGE_MINUS_ONE
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)
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2015-08-15 11:55:25 -05:00
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}
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2015-09-18 21:53:04 -05:00
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}
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2015-08-15 11:55:25 -05:00
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2017-10-07 09:56:45 -05:00
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impl<'a, 'tcx> LateLintPass<'a, 'tcx> for Pass {
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2016-12-07 06:13:40 -06:00
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fn check_expr(&mut self, cx: &LateContext<'a, 'tcx>, expr: &'tcx Expr) {
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2017-07-10 03:17:40 -05:00
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if let ExprMethodCall(ref path, _, ref args) = expr.node {
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let name = path.name.as_str();
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2016-11-23 14:19:03 -06:00
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2015-11-03 08:42:52 -06:00
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// Range with step_by(0).
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2017-06-18 08:14:46 -05:00
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if name == "step_by" && args.len() == 2 && has_step_by(cx, &args[0]) {
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2017-09-05 04:33:04 -05:00
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use consts::{constant, Constant};
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2017-06-18 08:14:46 -05:00
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use rustc_const_math::ConstInt::Usize;
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if let Some((Constant::Int(Usize(us)), _)) = constant(cx, &args[1]) {
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2017-09-13 08:34:04 -05:00
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if us.as_u64() == 0 {
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2017-08-09 02:30:56 -05:00
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span_lint(
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cx,
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ITERATOR_STEP_BY_ZERO,
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expr.span,
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"Iterator::step_by(0) will panic at runtime",
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);
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2017-06-18 08:14:46 -05:00
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}
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}
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2016-11-23 14:19:03 -06:00
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} else if name == "zip" && args.len() == 2 {
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2015-11-03 08:42:52 -06:00
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let iter = &args[0].node;
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2016-03-07 09:31:38 -06:00
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let zip_arg = &args[1];
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2016-06-05 19:09:19 -05:00
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if_let_chain! {[
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// .iter() call
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let ExprMethodCall(ref iter_path, _, ref iter_args ) = *iter,
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iter_path.name == "iter",
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2016-06-05 19:09:19 -05:00
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// range expression in .zip() call: 0..x.len()
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2017-04-06 09:49:13 -05:00
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let Some(higher::Range { start: Some(start), end: Some(end), .. }) = higher::range(zip_arg),
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2016-06-05 19:09:19 -05:00
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is_integer_literal(start, 0),
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// .len() call
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2017-07-10 03:17:40 -05:00
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let ExprMethodCall(ref len_path, _, ref len_args) = end.node,
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len_path.name == "len" && len_args.len() == 1,
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2016-06-05 19:09:19 -05:00
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// .iter() and .len() called on same Path
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2016-12-01 15:31:56 -06:00
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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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2016-12-02 10:38:31 -06:00
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iter_path.segments == len_path.segments
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2016-06-05 19:09:19 -05:00
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], {
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2016-12-02 10:38:31 -06:00
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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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2016-06-05 19:09:19 -05:00
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}}
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2015-11-03 08:42:52 -06:00
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}
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2015-08-15 11:55:25 -05:00
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}
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2017-10-07 09:56:45 -05:00
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// exclusive range plus one: x..(y+1)
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if_let_chain! {[
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let Some(higher::Range { start, end: Some(end), limits: RangeLimits::HalfOpen }) = higher::range(expr),
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let Some(y) = y_plus_one(end),
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], {
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span_lint_and_then(
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cx,
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RANGE_PLUS_ONE,
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expr.span,
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"an inclusive range would be more readable",
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|db| {
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let start = start.map_or("".to_owned(), |x| Sugg::hir(cx, x, "x").to_string());
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let end = Sugg::hir(cx, y, "y");
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db.span_suggestion(expr.span,
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"use",
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format!("{}..={}", start, end));
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},
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);
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}}
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// inclusive range minus one: x..=(y-1)
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if_let_chain! {[
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let Some(higher::Range { start, end: Some(end), limits: RangeLimits::Closed }) = higher::range(expr),
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let Some(y) = y_minus_one(end),
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], {
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span_lint_and_then(
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cx,
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RANGE_MINUS_ONE,
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expr.span,
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"an exclusive range would be more readable",
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|db| {
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let start = start.map_or("".to_owned(), |x| Sugg::hir(cx, x, "x").to_string());
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let end = Sugg::hir(cx, y, "y");
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db.span_suggestion(expr.span,
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"use",
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format!("{}..{}", start, end));
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},
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);
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}}
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2015-08-15 11:55:25 -05:00
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}
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}
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2016-04-26 06:31:52 -05:00
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fn has_step_by(cx: &LateContext, expr: &Expr) -> bool {
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2015-08-15 11:55:25 -05:00
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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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2017-06-18 08:14:46 -05:00
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let ty = cx.tables.expr_ty_adjusted(expr);
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2016-04-26 06:31:52 -05:00
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2017-06-29 09:07:43 -05:00
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get_trait_def_id(cx, &paths::ITERATOR).map_or(false, |iterator_trait| implements_trait(cx, ty, iterator_trait, &[]))
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2015-08-15 11:55:25 -05:00
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}
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2017-10-07 09:56:45 -05:00
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fn y_plus_one(expr: &Expr) -> Option<&Expr> {
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match expr.node {
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ExprBinary(Spanned { node: BiAdd, .. }, ref lhs, ref rhs) => {
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if is_integer_literal(lhs, 1) {
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Some(rhs)
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} else if is_integer_literal(rhs, 1) {
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Some(lhs)
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} else {
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None
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}
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},
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_ => None,
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}
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}
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fn y_minus_one(expr: &Expr) -> Option<&Expr> {
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match expr.node {
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ExprBinary(Spanned { node: BiSub, .. }, ref lhs, ref rhs) if is_integer_literal(rhs, 1) => Some(lhs),
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_ => None,
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}
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}
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