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use clippy_utils::diagnostics::span_lint_and_help;
use clippy_utils::ty::is_type_diagnostic_item;
use if_chain::if_chain;
use rustc_ast::ast::LitKind;
use rustc_hir::{Expr, ExprKind};
use rustc_lint::LateContext;
use rustc_span::{source_map::Spanned, symbol::sym, Span};
use super::CASE_SENSITIVE_FILE_EXTENSION_COMPARISONS;
pub(super) fn check<'tcx>(
cx: &LateContext<'tcx>,
expr: &'tcx Expr<'_>,
call_span: Span,
recv: &'tcx Expr<'_>,
arg: &'tcx Expr<'_>,
) {
if_chain! {
if let Some(method_id) = cx.typeck_results().type_dependent_def_id(expr.hir_id);
if let Some(impl_id) = cx.tcx.impl_of_method(method_id);
if cx.tcx.type_of(impl_id).is_str();
if let ExprKind::Lit(Spanned { node: LitKind::Str(ext_literal, ..), ..}) = arg.kind;
if (2..=6).contains(&ext_literal.as_str().len());
let ext_str = ext_literal.as_str();
if ext_str.starts_with('.');
if ext_str.chars().skip(1).all(|c| c.is_uppercase() || c.is_ascii_digit())
|| ext_str.chars().skip(1).all(|c| c.is_lowercase() || c.is_ascii_digit());
let recv_ty = cx.typeck_results().expr_ty(recv).peel_refs();
if recv_ty.is_str() || is_type_diagnostic_item(cx, recv_ty, sym::String);
then {
span_lint_and_help(
cx,
CASE_SENSITIVE_FILE_EXTENSION_COMPARISONS,
call_span,
"case-sensitive file extension comparison",
None,
"consider using a case-insensitive comparison instead",
);
}
}
}
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