| use super::utils::{get_arg_name, match_var, remove_blocks, snippet_with_applicability, span_lint_and_sugg}; |
| use if_chain::if_chain; |
| use rustc::hir::*; |
| use rustc::lint::{LateContext, LateLintPass, LintArray, LintPass}; |
| use rustc::{declare_lint_pass, declare_tool_lint}; |
| use rustc_errors::Applicability; |
| |
| declare_clippy_lint! { |
| /// **What it does:** Checks for matches being used to destructure a single-variant enum |
| /// or tuple struct where a `let` will suffice. |
| /// |
| /// **Why is this bad?** Just readability – `let` doesn't nest, whereas a `match` does. |
| /// |
| /// **Known problems:** None. |
| /// |
| /// **Example:** |
| /// ```rust |
| /// enum Wrapper { |
| /// Data(i32), |
| /// } |
| /// |
| /// let wrapper = Wrapper::Data(42); |
| /// |
| /// let data = match wrapper { |
| /// Wrapper::Data(i) => i, |
| /// }; |
| /// ``` |
| /// |
| /// The correct use would be: |
| /// ```rust |
| /// enum Wrapper { |
| /// Data(i32), |
| /// } |
| /// |
| /// let wrapper = Wrapper::Data(42); |
| /// let Wrapper::Data(data) = wrapper; |
| /// ``` |
| pub INFALLIBLE_DESTRUCTURING_MATCH, |
| style, |
| "a match statement with a single infallible arm instead of a `let`" |
| } |
| |
| declare_lint_pass!(InfallibleDestructingMatch => [INFALLIBLE_DESTRUCTURING_MATCH]); |
| |
| impl<'a, 'tcx> LateLintPass<'a, 'tcx> for InfallibleDestructingMatch { |
| fn check_local(&mut self, cx: &LateContext<'a, 'tcx>, local: &'tcx Local) { |
| if_chain! { |
| if let Some(ref expr) = local.init; |
| if let ExprKind::Match(ref target, ref arms, MatchSource::Normal) = expr.kind; |
| if arms.len() == 1 && arms[0].guard.is_none(); |
| if let PatKind::TupleStruct(QPath::Resolved(None, ref variant_name), ref args, _) = arms[0].pat.kind; |
| if args.len() == 1; |
| if let Some(arg) = get_arg_name(&args[0]); |
| let body = remove_blocks(&arms[0].body); |
| if match_var(body, arg); |
| |
| then { |
| let mut applicability = Applicability::MachineApplicable; |
| span_lint_and_sugg( |
| cx, |
| INFALLIBLE_DESTRUCTURING_MATCH, |
| local.span, |
| "you seem to be trying to use match to destructure a single infallible pattern. \ |
| Consider using `let`", |
| "try this", |
| format!( |
| "let {}({}) = {};", |
| snippet_with_applicability(cx, variant_name.span, "..", &mut applicability), |
| snippet_with_applicability(cx, local.pat.span, "..", &mut applicability), |
| snippet_with_applicability(cx, target.span, "..", &mut applicability), |
| ), |
| applicability, |
| ); |
| } |
| } |
| } |
| } |