90 lines
3.5 KiB
Rust
90 lines
3.5 KiB
Rust
use clippy_utils::consts::{constant_context, Constant};
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use clippy_utils::diagnostics::span_lint_and_sugg;
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use clippy_utils::source::snippet;
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use clippy_utils::ty::is_type_diagnostic_item;
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use if_chain::if_chain;
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use rustc_errors::Applicability;
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use rustc_hir::{Expr, ExprKind};
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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::sym;
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declare_clippy_lint! {
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/// ### What it does
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/// Checks for usage of `.repeat(1)` and suggest the following method for each types.
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/// - `.to_string()` for `str`
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/// - `.clone()` for `String`
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/// - `.to_vec()` for `slice`
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///
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/// The lint will evaluate constant expressions and values as arguments of `.repeat(..)` and emit a message if
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/// they are equivalent to `1`. (Related discussion in [rust-clippy#7306](https://github.com/rust-lang/rust-clippy/issues/7306))
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///
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/// ### Why is this bad?
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/// For example, `String.repeat(1)` is equivalent to `.clone()`. If cloning
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/// the string is the intention behind this, `clone()` should be used.
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///
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/// ### Example
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/// ```rust
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/// fn main() {
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/// let x = String::from("hello world").repeat(1);
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/// }
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/// ```
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/// Use instead:
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/// ```rust
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/// fn main() {
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/// let x = String::from("hello world").clone();
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/// }
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/// ```
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#[clippy::version = "1.47.0"]
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pub REPEAT_ONCE,
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complexity,
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"using `.repeat(1)` instead of `String.clone()`, `str.to_string()` or `slice.to_vec()` "
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}
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declare_lint_pass!(RepeatOnce => [REPEAT_ONCE]);
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impl<'tcx> LateLintPass<'tcx> for RepeatOnce {
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fn check_expr(&mut self, cx: &LateContext<'_>, expr: &'tcx Expr<'_>) {
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if_chain! {
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if let ExprKind::MethodCall(path, _, [receiver, count], _) = &expr.kind;
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if path.ident.name == sym!(repeat);
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if constant_context(cx, cx.typeck_results()).expr(count) == Some(Constant::Int(1));
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if !receiver.span.from_expansion();
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then {
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let ty = cx.typeck_results().expr_ty(receiver).peel_refs();
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if ty.is_str() {
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span_lint_and_sugg(
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cx,
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REPEAT_ONCE,
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expr.span,
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"calling `repeat(1)` on str",
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"consider using `.to_string()` instead",
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format!("{}.to_string()", snippet(cx, receiver.span, r#""...""#)),
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Applicability::MachineApplicable,
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);
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} else if ty.builtin_index().is_some() {
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span_lint_and_sugg(
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cx,
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REPEAT_ONCE,
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expr.span,
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"calling `repeat(1)` on slice",
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"consider using `.to_vec()` instead",
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format!("{}.to_vec()", snippet(cx, receiver.span, r#""...""#)),
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Applicability::MachineApplicable,
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);
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} else if is_type_diagnostic_item(cx, ty, sym::String) {
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span_lint_and_sugg(
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cx,
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REPEAT_ONCE,
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expr.span,
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"calling `repeat(1)` on a string literal",
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"consider using `.clone()` instead",
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format!("{}.clone()", snippet(cx, receiver.span, r#""...""#)),
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Applicability::MachineApplicable,
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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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