+use crate::consts::{constant, Constant};
use if_chain::if_chain;
-use rustc::hir::*;
-use rustc::lint::{LateContext, LateLintPass, LintArray, LintPass};
-use rustc::{declare_lint_pass, declare_tool_lint};
+use rustc_ast::ast::RangeLimits;
use rustc_errors::Applicability;
-use syntax::ast::RangeLimits;
-use syntax::source_map::Spanned;
+use rustc_hir::{BinOpKind, Expr, ExprKind, QPath};
+use rustc_lint::{LateContext, LateLintPass};
+use rustc_middle::ty;
+use rustc_session::{declare_lint_pass, declare_tool_lint};
+use rustc_span::source_map::Spanned;
+use std::cmp::Ordering;
use crate::utils::sugg::Sugg;
-use crate::utils::{get_trait_def_id, higher, implements_trait, SpanlessEq};
-use crate::utils::{is_integer_literal, paths, snippet, snippet_opt, span_lint, span_lint_and_then};
-
-declare_clippy_lint! {
- /// **What it does:** Checks for calling `.step_by(0)` on iterators,
- /// 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.
- ///
- /// **Example:**
- /// ```ignore
- /// for x in (5..5).step_by(0) {
- /// ..
- /// }
- /// ```
- pub ITERATOR_STEP_BY_ZERO,
- correctness,
- "using `Iterator::step_by(0)`, which produces an infinite iterator"
-}
+use crate::utils::{get_parent_expr, is_integer_const, snippet, snippet_opt, span_lint, span_lint_and_then};
+use crate::utils::{higher, SpanlessEq};
declare_clippy_lint! {
/// **What it does:** Checks for zipping a collection with the range of
/// and ends with a closing one.
/// I.e., `let _ = (f()+1)..(f()+1)` results in `let _ = ((f()+1)..=f())`.
///
+ /// Also in many cases, inclusive ranges are still slower to run than
+ /// exclusive ranges, because they essentially add an extra branch that
+ /// LLVM may fail to hoist out of the loop.
+ ///
/// **Example:**
/// ```rust,ignore
/// for x..(y+1) { .. }
/// for x..=y { .. }
/// ```
pub RANGE_PLUS_ONE,
- complexity,
+ pedantic,
"`x..(y+1)` reads better as `x..=y`"
}
"`x..=(y-1)` reads better as `x..y`"
}
+declare_clippy_lint! {
+ /// **What it does:** Checks for range expressions `x..y` where both `x` and `y`
+ /// are constant and `x` is greater or equal to `y`.
+ ///
+ /// **Why is this bad?** Empty ranges yield no values so iterating them is a no-op.
+ /// Moreover, trying to use a reversed range to index a slice will panic at run-time.
+ ///
+ /// **Known problems:** None.
+ ///
+ /// **Example:**
+ ///
+ /// ```rust,no_run
+ /// fn main() {
+ /// (10..=0).for_each(|x| println!("{}", x));
+ ///
+ /// let arr = [1, 2, 3, 4, 5];
+ /// let sub = &arr[3..1];
+ /// }
+ /// ```
+ /// Use instead:
+ /// ```rust
+ /// fn main() {
+ /// (0..=10).rev().for_each(|x| println!("{}", x));
+ ///
+ /// let arr = [1, 2, 3, 4, 5];
+ /// let sub = &arr[1..3];
+ /// }
+ /// ```
+ pub REVERSED_EMPTY_RANGES,
+ correctness,
+ "reversing the limits of range expressions, resulting in empty ranges"
+}
+
declare_lint_pass!(Ranges => [
- ITERATOR_STEP_BY_ZERO,
RANGE_ZIP_WITH_LEN,
RANGE_PLUS_ONE,
- RANGE_MINUS_ONE
+ RANGE_MINUS_ONE,
+ REVERSED_EMPTY_RANGES,
]);
impl<'a, 'tcx> LateLintPass<'a, 'tcx> for Ranges {
- fn check_expr(&mut self, cx: &LateContext<'a, 'tcx>, expr: &'tcx Expr) {
- if let ExprKind::MethodCall(ref path, _, ref args) = expr.node {
+ fn check_expr(&mut self, cx: &LateContext<'a, 'tcx>, expr: &'tcx Expr<'_>) {
+ if let ExprKind::MethodCall(ref path, _, ref args) = expr.kind {
let name = path.ident.as_str();
-
- // Range with step_by(0).
- if name == "step_by" && args.len() == 2 && has_step_by(cx, &args[0]) {
- use crate::consts::{constant, Constant};
- if let Some((Constant::Int(0), _)) = constant(cx, cx.tables, &args[1]) {
- span_lint(
- cx,
- ITERATOR_STEP_BY_ZERO,
- expr.span,
- "Iterator::step_by(0) will panic at runtime",
- );
- }
- } else if name == "zip" && args.len() == 2 {
- let iter = &args[0].node;
+ if name == "zip" && args.len() == 2 {
+ let iter = &args[0].kind;
let zip_arg = &args[1];
if_chain! {
// `.iter()` call
if iter_path.ident.name == sym!(iter);
// range expression in `.zip()` call: `0..x.len()`
if let Some(higher::Range { start: Some(start), end: Some(end), .. }) = higher::range(cx, zip_arg);
- if is_integer_literal(start, 0);
+ if is_integer_const(cx, start, 0);
// `.len()` call
- if let ExprKind::MethodCall(ref len_path, _, ref len_args) = end.node;
+ if let ExprKind::MethodCall(ref len_path, _, ref len_args) = end.kind;
if len_path.ident.name == sym!(len) && len_args.len() == 1;
// `.iter()` and `.len()` called on same `Path`
- if let ExprKind::Path(QPath::Resolved(_, ref iter_path)) = iter_args[0].node;
- if let ExprKind::Path(QPath::Resolved(_, ref len_path)) = len_args[0].node;
+ if let ExprKind::Path(QPath::Resolved(_, ref iter_path)) = iter_args[0].kind;
+ if let ExprKind::Path(QPath::Resolved(_, ref len_path)) = len_args[0].kind;
if SpanlessEq::new(cx).eq_path_segments(&iter_path.segments, &len_path.segments);
then {
span_lint(cx,
RANGE_ZIP_WITH_LEN,
expr.span,
- &format!("It is more idiomatic to use {}.iter().enumerate()",
+ &format!("It is more idiomatic to use `{}.iter().enumerate()`",
snippet(cx, iter_args[0].span, "_")));
}
}
check_exclusive_range_plus_one(cx, expr);
check_inclusive_range_minus_one(cx, expr);
+ check_reversed_empty_range(cx, expr);
}
}
// exclusive range plus one: `x..(y+1)`
-fn check_exclusive_range_plus_one(cx: &LateContext<'_, '_>, expr: &Expr) {
+fn check_exclusive_range_plus_one(cx: &LateContext<'_, '_>, expr: &Expr<'_>) {
if_chain! {
if let Some(higher::Range {
start,
end: Some(end),
limits: RangeLimits::HalfOpen
}) = higher::range(cx, expr);
- if let Some(y) = y_plus_one(end);
+ if let Some(y) = y_plus_one(cx, end);
then {
let span = if expr.span.from_expansion() {
expr.span
RANGE_PLUS_ONE,
span,
"an inclusive range would be more readable",
- |db| {
+ |diag| {
let start = start.map_or(String::new(), |x| Sugg::hir(cx, x, "x").to_string());
let end = Sugg::hir(cx, y, "y");
if let Some(is_wrapped) = &snippet_opt(cx, span) {
if is_wrapped.starts_with('(') && is_wrapped.ends_with(')') {
- db.span_suggestion(
+ diag.span_suggestion(
span,
"use",
format!("({}..={})", start, end),
Applicability::MaybeIncorrect,
);
} else {
- db.span_suggestion(
+ diag.span_suggestion(
span,
"use",
format!("{}..={}", start, end),
}
// inclusive range minus one: `x..=(y-1)`
-fn check_inclusive_range_minus_one(cx: &LateContext<'_, '_>, expr: &Expr) {
+fn check_inclusive_range_minus_one(cx: &LateContext<'_, '_>, expr: &Expr<'_>) {
if_chain! {
if let Some(higher::Range { start, end: Some(end), limits: RangeLimits::Closed }) = higher::range(cx, expr);
- if let Some(y) = y_minus_one(end);
+ if let Some(y) = y_minus_one(cx, end);
then {
span_lint_and_then(
cx,
RANGE_MINUS_ONE,
expr.span,
"an exclusive range would be more readable",
- |db| {
+ |diag| {
let start = start.map_or(String::new(), |x| Sugg::hir(cx, x, "x").to_string());
let end = Sugg::hir(cx, y, "y");
- db.span_suggestion(
+ diag.span_suggestion(
expr.span,
"use",
format!("{}..{}", start, end),
}
}
-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.
- let ty = cx.tables.expr_ty_adjusted(expr);
+fn check_reversed_empty_range(cx: &LateContext<'_, '_>, expr: &Expr<'_>) {
+ fn inside_indexing_expr<'a>(cx: &'a LateContext<'_, '_>, expr: &Expr<'_>) -> Option<&'a Expr<'a>> {
+ match get_parent_expr(cx, expr) {
+ parent_expr @ Some(Expr {
+ kind: ExprKind::Index(..),
+ ..
+ }) => parent_expr,
+ _ => None,
+ }
+ }
+
+ fn is_empty_range(limits: RangeLimits, ordering: Ordering) -> bool {
+ match limits {
+ RangeLimits::HalfOpen => ordering != Ordering::Less,
+ RangeLimits::Closed => ordering == Ordering::Greater,
+ }
+ }
+
+ if_chain! {
+ if let Some(higher::Range { start: Some(start), end: Some(end), limits }) = higher::range(cx, expr);
+ let ty = cx.tables.expr_ty(start);
+ if let ty::Int(_) | ty::Uint(_) = ty.kind;
+ if let Some((start_idx, _)) = constant(cx, cx.tables, start);
+ if let Some((end_idx, _)) = constant(cx, cx.tables, end);
+ if let Some(ordering) = Constant::partial_cmp(cx.tcx, ty, &start_idx, &end_idx);
+ if is_empty_range(limits, ordering);
+ then {
+ if let Some(parent_expr) = inside_indexing_expr(cx, expr) {
+ let (reason, outcome) = if ordering == Ordering::Equal {
+ ("empty", "always yield an empty slice")
+ } else {
+ ("reversed", "panic at run-time")
+ };
+
+ span_lint_and_then(
+ cx,
+ REVERSED_EMPTY_RANGES,
+ expr.span,
+ &format!("this range is {} and using it to index a slice will {}", reason, outcome),
+ |diag| {
+ if_chain! {
+ if ordering == Ordering::Equal;
+ if let ty::Slice(slice_ty) = cx.tables.expr_ty(parent_expr).kind;
+ then {
+ diag.span_suggestion(
+ parent_expr.span,
+ "if you want an empty slice, use",
+ format!("[] as &[{}]", slice_ty),
+ Applicability::MaybeIncorrect
+ );
+ }
+ }
+ }
+ );
+ } else {
+ span_lint_and_then(
+ cx,
+ REVERSED_EMPTY_RANGES,
+ expr.span,
+ "this range is empty so it will yield no values",
+ |diag| {
+ if ordering != Ordering::Equal {
+ let start_snippet = snippet(cx, start.span, "_");
+ let end_snippet = snippet(cx, end.span, "_");
+ let dots = match limits {
+ RangeLimits::HalfOpen => "..",
+ RangeLimits::Closed => "..="
+ };
- get_trait_def_id(cx, &paths::ITERATOR).map_or(false, |iterator_trait| implements_trait(cx, ty, iterator_trait, &[]))
+ diag.span_suggestion(
+ expr.span,
+ "consider using the following if you are attempting to iterate over this \
+ range in reverse",
+ format!("({}{}{}).rev()", end_snippet, dots, start_snippet),
+ Applicability::MaybeIncorrect,
+ );
+ }
+ },
+ );
+ }
+ }
+ }
}
-fn y_plus_one(expr: &Expr) -> Option<&Expr> {
- match expr.node {
+fn y_plus_one<'t>(cx: &LateContext<'_, '_>, expr: &'t Expr<'_>) -> Option<&'t Expr<'t>> {
+ match expr.kind {
ExprKind::Binary(
Spanned {
node: BinOpKind::Add, ..
ref lhs,
ref rhs,
) => {
- if is_integer_literal(lhs, 1) {
+ if is_integer_const(cx, lhs, 1) {
Some(rhs)
- } else if is_integer_literal(rhs, 1) {
+ } else if is_integer_const(cx, rhs, 1) {
Some(lhs)
} else {
None
}
}
-fn y_minus_one(expr: &Expr) -> Option<&Expr> {
- match expr.node {
+fn y_minus_one<'t>(cx: &LateContext<'_, '_>, expr: &'t Expr<'_>) -> Option<&'t Expr<'t>> {
+ match expr.kind {
ExprKind::Binary(
Spanned {
node: BinOpKind::Sub, ..
},
ref lhs,
ref rhs,
- ) if is_integer_literal(rhs, 1) => Some(lhs),
+ ) if is_integer_const(cx, rhs, 1) => Some(lhs),
_ => None,
}
}
projects / rust.git / blobdiff