206 lines
7.2 KiB
Rust
206 lines
7.2 KiB
Rust
use rustc::lint::{LateContext, LateLintPass, LintArray, LintPass};
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use rustc::{declare_lint, lint_array};
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use if_chain::if_chain;
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use rustc::hir::*;
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use syntax::ast::RangeLimits;
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use syntax::source_map::Spanned;
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use crate::utils::{is_integer_literal, paths, snippet, span_lint, span_lint_and_then};
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use crate::utils::{get_trait_def_id, higher, implements_trait, SpanlessEq};
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use crate::utils::sugg::Sugg;
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/// **What it does:** Checks for calling `.step_by(0)` on iterators,
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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_clippy_lint! {
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pub ITERATOR_STEP_BY_ZERO,
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correctness,
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"using `Iterator::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
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/// `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_clippy_lint! {
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pub RANGE_ZIP_WITH_LEN,
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complexity,
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"zipping iterator with a range when `enumerate()` would do"
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}
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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_clippy_lint! {
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pub RANGE_PLUS_ONE,
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complexity,
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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_clippy_lint! {
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pub RANGE_MINUS_ONE,
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complexity,
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"`x..=(y-1)` reads better as `x..y`"
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}
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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!(ITERATOR_STEP_BY_ZERO, RANGE_ZIP_WITH_LEN, RANGE_PLUS_ONE, RANGE_MINUS_ONE)
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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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if let ExprKind::MethodCall(ref path, _, ref args) = expr.node {
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let name = path.ident.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]) {
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use crate::consts::{constant, Constant};
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if let Some((Constant::Int(0), _)) = constant(cx, cx.tables, &args[1]) {
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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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}
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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_chain! {
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// .iter() call
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if let ExprKind::MethodCall(ref iter_path, _, ref iter_args ) = *iter;
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if iter_path.ident.name == "iter";
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// range expression in .zip() call: 0..x.len()
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if let Some(higher::Range { start: Some(start), end: Some(end), .. }) = higher::range(cx, zip_arg);
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if is_integer_literal(start, 0);
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// .len() call
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if let ExprKind::MethodCall(ref len_path, _, ref len_args) = end.node;
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if len_path.ident.name == "len" && len_args.len() == 1;
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// .iter() and .len() called on same Path
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if let ExprKind::Path(QPath::Resolved(_, ref iter_path)) = iter_args[0].node;
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if let ExprKind::Path(QPath::Resolved(_, ref len_path)) = len_args[0].node;
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if SpanlessEq::new(cx).eq_path_segments(&iter_path.segments, &len_path.segments);
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then {
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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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// exclusive range plus one: x..(y+1)
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if_chain! {
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if let Some(higher::Range { start, end: Some(end), limits: RangeLimits::HalfOpen }) = higher::range(cx, expr);
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if let Some(y) = y_plus_one(end);
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then {
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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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}
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// inclusive range minus one: x..=(y-1)
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if_chain! {
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if let Some(higher::Range { start, end: Some(end), limits: RangeLimits::Closed }) = higher::range(cx, expr);
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if let Some(y) = y_minus_one(end);
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then {
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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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}
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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_adjusted(expr);
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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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}
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fn y_plus_one(expr: &Expr) -> Option<&Expr> {
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match expr.node {
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ExprKind::Binary(Spanned { node: BinOpKind::Add, .. }, ref lhs, ref rhs) => 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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_ => 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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ExprKind::Binary(Spanned { node: BinOpKind::Sub, .. }, 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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