mirror of
https://github.com/rust-lang/rust-clippy
synced 2024-12-23 19:43:20 +00:00
165 lines
5.6 KiB
Rust
165 lines
5.6 KiB
Rust
use clippy_utils::diagnostics::span_lint_and_sugg;
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use clippy_utils::ty::is_type_diagnostic_item;
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use rustc_ast::ast::LitKind;
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use rustc_errors::Applicability;
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use rustc_hir::intravisit::{walk_expr, Visitor};
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use rustc_hir::{Arm, Expr, ExprKind, MatchSource, PatKind};
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use rustc_lint::{LateContext, LateLintPass};
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use rustc_middle::lint::in_external_macro;
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use rustc_middle::ty;
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use rustc_session::{declare_lint_pass, declare_tool_lint};
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use rustc_span::symbol::Symbol;
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use rustc_span::{sym, Span};
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declare_clippy_lint! {
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/// ### What it does
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/// Checks for `match` expressions modifying the case of a string with non-compliant arms
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///
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/// ### Why is this bad?
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/// The arm is unreachable, which is likely a mistake
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///
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/// ### Example
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/// ```rust
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/// # let text = "Foo";
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///
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/// match &*text.to_ascii_lowercase() {
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/// "foo" => {},
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/// "Bar" => {},
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/// _ => {},
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/// }
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/// ```
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/// Use instead:
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/// ```rust
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/// # let text = "Foo";
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///
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/// match &*text.to_ascii_lowercase() {
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/// "foo" => {},
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/// "bar" => {},
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/// _ => {},
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/// }
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/// ```
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#[clippy::version = "1.58.0"]
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pub MATCH_STR_CASE_MISMATCH,
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correctness,
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"creation of a case altering match expression with non-compliant arms"
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}
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declare_lint_pass!(MatchStrCaseMismatch => [MATCH_STR_CASE_MISMATCH]);
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#[derive(Debug)]
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enum CaseMethod {
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LowerCase,
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AsciiLowerCase,
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UpperCase,
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AsciiUppercase,
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}
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impl<'tcx> LateLintPass<'tcx> for MatchStrCaseMismatch {
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fn check_expr(&mut self, cx: &LateContext<'tcx>, expr: &'tcx Expr<'_>) {
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if_chain! {
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if !in_external_macro(cx.tcx.sess, expr.span);
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if let ExprKind::Match(match_expr, arms, MatchSource::Normal) = expr.kind;
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if let ty::Ref(_, ty, _) = cx.typeck_results().expr_ty(match_expr).kind();
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if let ty::Str = ty.kind();
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then {
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let mut visitor = MatchExprVisitor {
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cx,
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case_method: None,
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};
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visitor.visit_expr(match_expr);
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if let Some(case_method) = visitor.case_method {
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if let Some((bad_case_span, bad_case_sym)) = verify_case(&case_method, arms) {
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lint(cx, &case_method, bad_case_span, bad_case_sym.as_str());
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}
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}
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}
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}
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}
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}
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struct MatchExprVisitor<'a, 'tcx> {
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cx: &'a LateContext<'tcx>,
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case_method: Option<CaseMethod>,
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}
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impl<'a, 'tcx> Visitor<'tcx> for MatchExprVisitor<'a, 'tcx> {
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fn visit_expr(&mut self, ex: &'tcx Expr<'_>) {
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match ex.kind {
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ExprKind::MethodCall(segment, _, [receiver], _) if self.case_altered(segment.ident.as_str(), receiver) => {
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},
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_ => walk_expr(self, ex),
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}
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}
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}
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impl<'a, 'tcx> MatchExprVisitor<'a, 'tcx> {
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fn case_altered(&mut self, segment_ident: &str, receiver: &Expr<'_>) -> bool {
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if let Some(case_method) = get_case_method(segment_ident) {
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let ty = self.cx.typeck_results().expr_ty(receiver).peel_refs();
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if is_type_diagnostic_item(self.cx, ty, sym::String) || ty.kind() == &ty::Str {
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self.case_method = Some(case_method);
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return true;
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}
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}
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false
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}
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}
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fn get_case_method(segment_ident_str: &str) -> Option<CaseMethod> {
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match segment_ident_str {
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"to_lowercase" => Some(CaseMethod::LowerCase),
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"to_ascii_lowercase" => Some(CaseMethod::AsciiLowerCase),
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"to_uppercase" => Some(CaseMethod::UpperCase),
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"to_ascii_uppercase" => Some(CaseMethod::AsciiUppercase),
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_ => None,
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}
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}
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fn verify_case<'a>(case_method: &'a CaseMethod, arms: &'a [Arm<'_>]) -> Option<(Span, Symbol)> {
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let case_check = match case_method {
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CaseMethod::LowerCase => |input: &str| -> bool { input.chars().all(|c| c.to_lowercase().next() == Some(c)) },
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CaseMethod::AsciiLowerCase => |input: &str| -> bool { !input.chars().any(|c| c.is_ascii_uppercase()) },
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CaseMethod::UpperCase => |input: &str| -> bool { input.chars().all(|c| c.to_uppercase().next() == Some(c)) },
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CaseMethod::AsciiUppercase => |input: &str| -> bool { !input.chars().any(|c| c.is_ascii_lowercase()) },
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};
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for arm in arms {
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if_chain! {
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if let PatKind::Lit(Expr {
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kind: ExprKind::Lit(lit),
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..
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}) = arm.pat.kind;
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if let LitKind::Str(symbol, _) = lit.node;
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let input = symbol.as_str();
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if !case_check(input);
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then {
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return Some((lit.span, symbol));
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}
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}
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}
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None
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}
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fn lint(cx: &LateContext<'_>, case_method: &CaseMethod, bad_case_span: Span, bad_case_str: &str) {
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let (method_str, suggestion) = match case_method {
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CaseMethod::LowerCase => ("to_lowercase", bad_case_str.to_lowercase()),
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CaseMethod::AsciiLowerCase => ("to_ascii_lowercase", bad_case_str.to_ascii_lowercase()),
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CaseMethod::UpperCase => ("to_uppercase", bad_case_str.to_uppercase()),
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CaseMethod::AsciiUppercase => ("to_ascii_uppercase", bad_case_str.to_ascii_uppercase()),
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};
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span_lint_and_sugg(
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cx,
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MATCH_STR_CASE_MISMATCH,
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bad_case_span,
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"this `match` arm has a differing case than its expression",
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&*format!("consider changing the case of this arm to respect `{}`", method_str),
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format!("\"{}\"", suggestion),
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Applicability::MachineApplicable,
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);
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}
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