55 lines
1.8 KiB
Rust
55 lines
1.8 KiB
Rust
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use clippy_utils::diagnostics::span_lint_and_note;
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use if_chain::if_chain;
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use rustc_hir as hir;
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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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declare_clippy_lint! {
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/// ### What it does
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/// It checks for `str::bytes().count()` and suggests replacing it with
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/// `str::len()`.
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///
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/// ### Why is this bad?
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/// `str::bytes().count()` is longer and may not be as performant as using
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/// `str::len()`.
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///
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/// ### Example
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/// ```rust
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/// "hello".bytes().count();
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/// ```
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/// Use instead:
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/// ```rust
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/// "hello".len();
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/// ```
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#[clippy::version = "1.60.0"]
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pub BYTES_COUNT_TO_LEN,
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complexity,
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"Using bytest().count() when len() performs the same functionality"
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}
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declare_lint_pass!(BytesCountToLen => [BYTES_COUNT_TO_LEN]);
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impl<'tcx> LateLintPass<'tcx> for BytesCountToLen {
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fn check_expr(&mut self, cx: &LateContext<'tcx>, expr: &'tcx hir::Expr<'_>) {
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if_chain! {
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//check for method call called "count"
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if let hir::ExprKind::MethodCall(count_path, count_args, _) = &expr.kind;
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if count_path.ident.name == rustc_span::sym::count;
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if let [bytes_expr] = &**count_args;
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//check for method call called "bytes" that was linked to "count"
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if let hir::ExprKind::MethodCall(bytes_path, _, _) = &bytes_expr.kind;
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if bytes_path.ident.name.as_str() == "bytes";
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then {
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span_lint_and_note(
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cx,
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BYTES_COUNT_TO_LEN,
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expr.span,
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"using long and hard to read `.bytes().count()`",
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None,
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"`.len()` achieves same functionality"
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);
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}
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};
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}
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}
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