84 lines
3.2 KiB
Rust
84 lines
3.2 KiB
Rust
use crate::consts::{constant_context, Constant};
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use crate::utils::{in_macro, is_type_diagnostic_item, snippet, span_lint_and_sugg};
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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:** 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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/// **Why is this bad?** For example, `String.repeat(1)` is equivalent to `.clone()`. If cloning the string is the intention behind this, `clone()` should be used.
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///
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/// **Known problems:** None.
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///
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/// **Example:**
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///
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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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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 let Some(Constant::Int(1)) = constant_context(cx, cx.typeck_results()).expr(&count);
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if !in_macro(receiver.span);
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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_type) {
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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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