src/tools/clippy/clippy_lints/src/methods/case_sensitive_file_extension_comparisons.rs

   1 use clippy_utils::diagnostics::span_lint_and_help;
   2 use clippy_utils::ty::is_type_lang_item;
   3 use if_chain::if_chain;
   4 use rustc_ast::ast::LitKind;
   5 use rustc_hir::{Expr, ExprKind, LangItem};
   6 use rustc_lint::LateContext;
   7 use rustc_span::{source_map::Spanned, Span};
   8
   9 use super::CASE_SENSITIVE_FILE_EXTENSION_COMPARISONS;
  10
  11 pub(super) fn check<'tcx>(
  12     cx: &LateContext<'tcx>,
  13     expr: &'tcx Expr<'_>,
  14     call_span: Span,
  15     recv: &'tcx Expr<'_>,
  16     arg: &'tcx Expr<'_>,
  17 ) {
  18     if_chain! {
  19         if let Some(method_id) = cx.typeck_results().type_dependent_def_id(expr.hir_id);
  20         if let Some(impl_id) = cx.tcx.impl_of_method(method_id);
  21         if cx.tcx.type_of(impl_id).is_str();
  22         if let ExprKind::Lit(Spanned { node: LitKind::Str(ext_literal, ..), ..}) = arg.kind;
  23         if (2..=6).contains(&ext_literal.as_str().len());
  24         let ext_str = ext_literal.as_str();
  25         if ext_str.starts_with('.');
  26         if ext_str.chars().skip(1).all(|c| c.is_uppercase() || c.is_ascii_digit())
  27             || ext_str.chars().skip(1).all(|c| c.is_lowercase() || c.is_ascii_digit());
  28         let recv_ty = cx.typeck_results().expr_ty(recv).peel_refs();
  29         if recv_ty.is_str() || is_type_lang_item(cx, recv_ty, LangItem::String);
  30         then {
  31             span_lint_and_help(
  32                 cx,
  33                 CASE_SENSITIVE_FILE_EXTENSION_COMPARISONS,
  34                 call_span,
  35                 "case-sensitive file extension comparison",
  36                 None,
  37                 "consider using a case-insensitive comparison instead",
  38             );
  39         }
  40     }
  41 }