238 lines
8.1 KiB
Rust
238 lines
8.1 KiB
Rust
use if_chain::if_chain;
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use rustc_ast::ast::RangeLimits;
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use rustc_errors::Applicability;
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use rustc_hir::{BinOpKind, Expr, ExprKind, QPath};
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use rustc_lint::{LateContext, LateLintPass};
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use rustc_session::{declare_lint_pass, declare_tool_lint};
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use rustc_span::source_map::Spanned;
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use crate::utils::sugg::Sugg;
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use crate::utils::{higher, SpanlessEq};
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use crate::utils::{is_integer_const, snippet, snippet_opt, span_lint, span_lint_and_then};
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declare_clippy_lint! {
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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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/// # let x = vec![1];
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/// x.iter().zip(0..x.len());
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/// ```
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/// Could be written as
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/// ```rust
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/// # let x = vec![1];
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/// x.iter().enumerate();
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/// ```
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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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declare_clippy_lint! {
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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:** Will add unnecessary pair of parentheses when the
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/// expression is not wrapped in a pair but starts with a opening parenthesis
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/// and ends with a closing one.
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/// I.e., `let _ = (f()+1)..(f()+1)` results in `let _ = ((f()+1)..=f())`.
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///
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/// Also in many cases, inclusive ranges are still slower to run than
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/// exclusive ranges, because they essentially add an extra branch that
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/// LLVM may fail to hoist out of the loop.
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///
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/// **Example:**
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/// ```rust,ignore
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/// for x..(y+1) { .. }
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/// ```
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/// Could be written as
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/// ```rust,ignore
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/// for x..=y { .. }
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/// ```
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pub RANGE_PLUS_ONE,
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pedantic,
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"`x..(y+1)` reads better as `x..=y`"
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}
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declare_clippy_lint! {
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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,ignore
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/// for x..=(y-1) { .. }
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/// ```
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/// Could be written as
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/// ```rust,ignore
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/// for x..y { .. }
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/// ```
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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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declare_lint_pass!(Ranges => [
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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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impl<'a, 'tcx> LateLintPass<'a, 'tcx> for Ranges {
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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.kind {
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let name = path.ident.as_str();
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if name == "zip" && args.len() == 2 {
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let iter = &args[0].kind;
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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 == sym!(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_const(cx, start, 0);
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// `.len()` call
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if let ExprKind::MethodCall(ref len_path, _, ref len_args) = end.kind;
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if len_path.ident.name == sym!(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].kind;
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if let ExprKind::Path(QPath::Resolved(_, ref len_path)) = len_args[0].kind;
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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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check_exclusive_range_plus_one(cx, expr);
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check_inclusive_range_minus_one(cx, expr);
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}
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}
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// exclusive range plus one: `x..(y+1)`
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fn check_exclusive_range_plus_one(cx: &LateContext<'_, '_>, expr: &Expr<'_>) {
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if_chain! {
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if let Some(higher::Range {
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start,
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end: Some(end),
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limits: RangeLimits::HalfOpen
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}) = higher::range(cx, expr);
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if let Some(y) = y_plus_one(cx, end);
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then {
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let span = if expr.span.from_expansion() {
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expr.span
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.ctxt()
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.outer_expn_data()
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.call_site
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} else {
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expr.span
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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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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(String::new(), |x| Sugg::hir(cx, x, "x").to_string());
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let end = Sugg::hir(cx, y, "y");
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if let Some(is_wrapped) = &snippet_opt(cx, span) {
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if is_wrapped.starts_with('(') && is_wrapped.ends_with(')') {
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db.span_suggestion(
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span,
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"use",
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format!("({}..={})", start, end),
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Applicability::MaybeIncorrect,
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);
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} else {
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db.span_suggestion(
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span,
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"use",
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format!("{}..={}", start, end),
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Applicability::MachineApplicable, // snippet
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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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}
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}
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// inclusive range minus one: `x..=(y-1)`
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fn check_inclusive_range_minus_one(cx: &LateContext<'_, '_>, expr: &Expr<'_>) {
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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(cx, 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(String::new(), |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(
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expr.span,
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"use",
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format!("{}..{}", start, end),
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Applicability::MachineApplicable, // snippet
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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 y_plus_one<'t>(cx: &LateContext<'_, '_>, expr: &'t Expr<'_>) -> Option<&'t Expr<'t>> {
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match expr.kind {
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ExprKind::Binary(
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Spanned {
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node: BinOpKind::Add, ..
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},
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ref lhs,
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ref rhs,
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) => {
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if is_integer_const(cx, lhs, 1) {
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Some(rhs)
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} else if is_integer_const(cx, 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<'t>(cx: &LateContext<'_, '_>, expr: &'t Expr<'_>) -> Option<&'t Expr<'t>> {
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match expr.kind {
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ExprKind::Binary(
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Spanned {
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node: BinOpKind::Sub, ..
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},
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ref lhs,
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ref rhs,
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) if is_integer_const(cx, rhs, 1) => Some(lhs),
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_ => None,
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}
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}
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