1 use clippy_utils::diagnostics::span_lint_and_sugg;
2 use clippy_utils::ty::is_type_diagnostic_item;
3 use rustc_ast::ast::LitKind;
4 use rustc_errors::Applicability;
5 use rustc_hir::intravisit::{walk_expr, Visitor};
6 use rustc_hir::{Arm, Expr, ExprKind, MatchSource, PatKind};
7 use rustc_lint::{LateContext, LateLintPass};
8 use rustc_middle::lint::in_external_macro;
10 use rustc_session::{declare_lint_pass, declare_tool_lint};
11 use rustc_span::symbol::Symbol;
12 use rustc_span::{sym, Span};
14 declare_clippy_lint! {
16 /// Checks for `match` expressions modifying the case of a string with non-compliant arms
18 /// ### Why is this bad?
19 /// The arm is unreachable, which is likely a mistake
23 /// # let text = "Foo";
25 /// match &*text.to_ascii_lowercase() {
33 /// # let text = "Foo";
35 /// match &*text.to_ascii_lowercase() {
41 #[clippy::version = "1.58.0"]
42 pub MATCH_STR_CASE_MISMATCH,
44 "creation of a case altering match expression with non-compliant arms"
47 declare_lint_pass!(MatchStrCaseMismatch => [MATCH_STR_CASE_MISMATCH]);
57 impl<'tcx> LateLintPass<'tcx> for MatchStrCaseMismatch {
58 fn check_expr(&mut self, cx: &LateContext<'tcx>, expr: &'tcx Expr<'_>) {
60 if !in_external_macro(cx.tcx.sess, expr.span);
61 if let ExprKind::Match(match_expr, arms, MatchSource::Normal) = expr.kind;
62 if let ty::Ref(_, ty, _) = cx.typeck_results().expr_ty(match_expr).kind();
63 if let ty::Str = ty.kind();
65 let mut visitor = MatchExprVisitor {
70 visitor.visit_expr(match_expr);
72 if let Some(case_method) = visitor.case_method {
73 if let Some((bad_case_span, bad_case_sym)) = verify_case(&case_method, arms) {
74 lint(cx, &case_method, bad_case_span, bad_case_sym.as_str());
82 struct MatchExprVisitor<'a, 'tcx> {
83 cx: &'a LateContext<'tcx>,
84 case_method: Option<CaseMethod>,
87 impl<'a, 'tcx> Visitor<'tcx> for MatchExprVisitor<'a, 'tcx> {
88 fn visit_expr(&mut self, ex: &'tcx Expr<'_>) {
90 ExprKind::MethodCall(segment, _, [receiver], _) if self.case_altered(segment.ident.as_str(), receiver) => {
92 _ => walk_expr(self, ex),
97 impl<'a, 'tcx> MatchExprVisitor<'a, 'tcx> {
98 fn case_altered(&mut self, segment_ident: &str, receiver: &Expr<'_>) -> bool {
99 if let Some(case_method) = get_case_method(segment_ident) {
100 let ty = self.cx.typeck_results().expr_ty(receiver).peel_refs();
102 if is_type_diagnostic_item(self.cx, ty, sym::String) || ty.kind() == &ty::Str {
103 self.case_method = Some(case_method);
112 fn get_case_method(segment_ident_str: &str) -> Option<CaseMethod> {
113 match segment_ident_str {
114 "to_lowercase" => Some(CaseMethod::LowerCase),
115 "to_ascii_lowercase" => Some(CaseMethod::AsciiLowerCase),
116 "to_uppercase" => Some(CaseMethod::UpperCase),
117 "to_ascii_uppercase" => Some(CaseMethod::AsciiUppercase),
122 fn verify_case<'a>(case_method: &'a CaseMethod, arms: &'a [Arm<'_>]) -> Option<(Span, Symbol)> {
123 let case_check = match case_method {
124 CaseMethod::LowerCase => |input: &str| -> bool { input.chars().all(|c| c.to_lowercase().next() == Some(c)) },
125 CaseMethod::AsciiLowerCase => |input: &str| -> bool { !input.chars().any(|c| c.is_ascii_uppercase()) },
126 CaseMethod::UpperCase => |input: &str| -> bool { input.chars().all(|c| c.to_uppercase().next() == Some(c)) },
127 CaseMethod::AsciiUppercase => |input: &str| -> bool { !input.chars().any(|c| c.is_ascii_lowercase()) },
132 if let PatKind::Lit(Expr {
133 kind: ExprKind::Lit(lit),
136 if let LitKind::Str(symbol, _) = lit.node;
137 let input = symbol.as_str();
138 if !case_check(input);
140 return Some((lit.span, symbol));
148 fn lint(cx: &LateContext<'_>, case_method: &CaseMethod, bad_case_span: Span, bad_case_str: &str) {
149 let (method_str, suggestion) = match case_method {
150 CaseMethod::LowerCase => ("to_lowercase", bad_case_str.to_lowercase()),
151 CaseMethod::AsciiLowerCase => ("to_ascii_lowercase", bad_case_str.to_ascii_lowercase()),
152 CaseMethod::UpperCase => ("to_uppercase", bad_case_str.to_uppercase()),
153 CaseMethod::AsciiUppercase => ("to_ascii_uppercase", bad_case_str.to_ascii_uppercase()),
158 MATCH_STR_CASE_MISMATCH,
160 "this `match` arm has a differing case than its expression",
161 &*format!("consider changing the case of this arm to respect `{}`", method_str),
162 format!("\"{}\"", suggestion),
163 Applicability::MachineApplicable,