--- /dev/null
+use crate::utils::span_lint_and_help;
+use if_chain::if_chain;
+use rustc_ast::ast::LitKind;
+use rustc_hir::{Expr, ExprKind, PathSegment};
+use rustc_lint::{LateContext, LateLintPass};
+use rustc_middle::ty;
+use rustc_session::{declare_lint_pass, declare_tool_lint};
+use rustc_span::{source_map::Spanned, symbol::sym, Span};
+
+declare_clippy_lint! {
+ /// **What it does:**
+ /// Checks for calls to `ends_with` with possible file extensions
+ /// and suggests to use a case-insensitive approach instead.
+ ///
+ /// **Why is this bad?**
+ /// `ends_with` is case-sensitive and may not detect files with a valid extension.
+ ///
+ /// **Known problems:** None.
+ ///
+ /// **Example:**
+ ///
+ /// ```rust
+ /// fn is_rust_file(filename: &str) -> bool {
+ /// filename.ends_with(".rs")
+ /// }
+ /// ```
+ /// Use instead:
+ /// ```rust
+ /// fn is_rust_file(filename: &str) -> bool {
+ /// filename.rsplit('.').next().map(|ext| ext.eq_ignore_ascii_case("rs")) == Some(true)
+ /// }
+ /// ```
+ pub CASE_SENSITIVE_FILE_EXTENSION_COMPARISONS,
+ pedantic,
+ "Checks for calls to ends_with with case-sensitive file extensions"
+}
+
+declare_lint_pass!(CaseSensitiveFileExtensionComparisons => [CASE_SENSITIVE_FILE_EXTENSION_COMPARISONS]);
+
+fn check_case_sensitive_file_extension_comparison(ctx: &LateContext<'_>, expr: &Expr<'_>) -> Option<Span> {
+ if_chain! {
+ if let ExprKind::MethodCall(PathSegment { ident, .. }, _, [obj, extension, ..], span) = expr.kind;
+ if ident.as_str() == "ends_with";
+ if let ExprKind::Lit(Spanned { node: LitKind::Str(ext_literal, ..), ..}) = extension.kind;
+ if (2..=6).contains(&ext_literal.as_str().len());
+ if ext_literal.as_str().starts_with('.');
+ if ext_literal.as_str().chars().skip(1).all(|c| c.is_uppercase() || c.is_digit(10))
+ || ext_literal.as_str().chars().skip(1).all(|c| c.is_lowercase() || c.is_digit(10));
+ then {
+ let mut ty = ctx.typeck_results().expr_ty(obj);
+ ty = match ty.kind() {
+ ty::Ref(_, ty, ..) => ty,
+ _ => ty
+ };
+
+ match ty.kind() {
+ ty::Str => {
+ return Some(span);
+ },
+ ty::Adt(&ty::AdtDef { did, .. }, _) => {
+ if ctx.tcx.is_diagnostic_item(sym::string_type, did) {
+ return Some(span);
+ }
+ },
+ _ => { return None; }
+ }
+ }
+ }
+ None
+}
+
+impl LateLintPass<'tcx> for CaseSensitiveFileExtensionComparisons {
+ fn check_expr(&mut self, ctx: &LateContext<'tcx>, expr: &'tcx Expr<'tcx>) {
+ if let Some(span) = check_case_sensitive_file_extension_comparison(ctx, expr) {
+ span_lint_and_help(
+ ctx,
+ CASE_SENSITIVE_FILE_EXTENSION_COMPARISONS,
+ span,
+ "case-sensitive file extension comparison",
+ None,
+ "consider using a case-insensitive comparison instead",
+ );
+ }
+ }
+}