clippy_lints/src/methods/manual_repeat_n.rs

use clippy_utils::diagnostics::span_lint_and_sugg;
use clippy_utils::msrvs::{self, Msrv};
use clippy_utils::source::{snippet, snippet_with_context};
use clippy_utils::{expr_use_ctxt, fn_def_id, is_trait_method, std_or_core};
use rustc_errors::Applicability;
use rustc_hir::{Expr, ExprKind};
use rustc_lint::LateContext;
use rustc_span::sym;

use super::MANUAL_REPEAT_N;

pub(super) fn check<'tcx>(
    cx: &LateContext<'tcx>,
    expr: &'tcx Expr<'tcx>,
    repeat_expr: &Expr<'_>,
    take_arg: &Expr<'_>,
    msrv: Msrv,
) {
    if !expr.span.from_expansion()
        && is_trait_method(cx, expr, sym::Iterator)
        && let ExprKind::Call(_, [repeat_arg]) = repeat_expr.kind
        && let Some(def_id) = fn_def_id(cx, repeat_expr)
        && cx.tcx.is_diagnostic_item(sym::iter_repeat, def_id)
        && !expr_use_ctxt(cx, expr).is_ty_unified
        && let Some(std_or_core) = std_or_core(cx)
        && msrv.meets(cx, msrvs::REPEAT_N)
    {
        let mut app = Applicability::MachineApplicable;
        span_lint_and_sugg(
            cx,
            MANUAL_REPEAT_N,
            expr.span,
            "this `repeat().take()` can be written more concisely",
            "consider using `repeat_n()` instead",
            format!(
                "{std_or_core}::iter::repeat_n({}, {})",
                snippet_with_context(cx, repeat_arg.span, expr.span.ctxt(), "..", &mut app).0,
                snippet(cx, take_arg.span, "..")
            ),
            app,
        );
    }
}