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use clippy_utils::diagnostics::span_lint_and_sugg;
use clippy_utils::source::{snippet_with_applicability, str_literal_to_char_literal};
use rustc_ast::BorrowKind;
use rustc_errors::Applicability;
use rustc_hir::{self as hir, ExprKind};
use rustc_lint::LateContext;
use super::SINGLE_CHAR_ADD_STR;
/// lint for length-1 `str`s as argument for `push_str`
pub(super) fn check(cx: &LateContext<'_>, expr: &hir::Expr<'_>, receiver: &hir::Expr<'_>, args: &[hir::Expr<'_>]) {
let mut applicability = Applicability::MachineApplicable;
if let Some(extension_string) = str_literal_to_char_literal(cx, &args[0], &mut applicability, false) {
let base_string_snippet =
snippet_with_applicability(cx, receiver.span.source_callsite(), "..", &mut applicability);
let sugg = format!("{base_string_snippet}.push({extension_string})");
span_lint_and_sugg(
cx,
SINGLE_CHAR_ADD_STR,
expr.span,
"calling `push_str()` using a single-character string literal",
"consider using `push` with a character literal",
sugg,
applicability,
);
}
if let ExprKind::AddrOf(BorrowKind::Ref, _, arg) = &args[0].kind
&& let ExprKind::MethodCall(path_segment, method_arg, [], _) = &arg.kind
&& path_segment.ident.name == rustc_span::sym::to_string
&& (is_ref_char(cx, method_arg) || is_char(cx, method_arg))
{
let base_string_snippet =
snippet_with_applicability(cx, receiver.span.source_callsite(), "..", &mut applicability);
let extension_string =
snippet_with_applicability(cx, method_arg.span.source_callsite(), "..", &mut applicability);
let deref_string = if is_ref_char(cx, method_arg) { "*" } else { "" };
let sugg = format!("{base_string_snippet}.push({deref_string}{extension_string})");
span_lint_and_sugg(
cx,
SINGLE_CHAR_ADD_STR,
expr.span,
"calling `push_str()` using a single-character converted to string",
"consider using `push` without `to_string()`",
sugg,
applicability,
);
}
}
fn is_ref_char(cx: &LateContext<'_>, expr: &hir::Expr<'_>) -> bool {
if cx.typeck_results().expr_ty(expr).is_ref()
&& let rustc_middle::ty::Ref(_, ty, _) = cx.typeck_results().expr_ty(expr).kind()
&& ty.is_char()
{
return true;
}
false
}
fn is_char(cx: &LateContext<'_>, expr: &hir::Expr<'_>) -> bool {
cx.typeck_results().expr_ty(expr).is_char()
}
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