--- /dev/null
+use crate::methods::get_hint_if_single_char_arg;
+use crate::utils::{snippet_with_applicability, span_lint_and_sugg};
+use rustc_errors::Applicability;
+use rustc_hir as hir;
+use rustc_lint::LateContext;
+
+use super::SINGLE_CHAR_ADD_STR;
+
+/// lint for length-1 `str`s as argument for `insert_str`
+pub(super) fn check(cx: &LateContext<'_>, expr: &hir::Expr<'_>, args: &[hir::Expr<'_>]) {
+ let mut applicability = Applicability::MachineApplicable;
+ if let Some(extension_string) = get_hint_if_single_char_arg(cx, &args[2], &mut applicability) {
+ let base_string_snippet =
+ snippet_with_applicability(cx, args[0].span.source_callsite(), "_", &mut applicability);
+ let pos_arg = snippet_with_applicability(cx, args[1].span, "..", &mut applicability);
+ let sugg = format!("{}.insert({}, {})", base_string_snippet, pos_arg, extension_string);
+ span_lint_and_sugg(
+ cx,
+ SINGLE_CHAR_ADD_STR,
+ expr.span,
+ "calling `insert_str()` using a single-character string literal",
+ "consider using `insert` with a character literal",
+ sugg,
+ applicability,
+ );
+ }
+}