//! lint on if expressions with an else if, but without a final else branch use rustc::lint::*; use syntax::ast::*; use utils::{in_external_macro, span_lint_and_sugg}; /// **What it does:** Checks for usage of if expressions with an `else if` branch, /// but without a final `else` branch. /// /// **Why is this bad?** Some coding guidelines require this (e.g. MISRA-C:2004 Rule 14.10). /// /// **Known problems:** None. /// /// **Example:** /// ```rust /// if x.is_positive() { /// a(); /// } else if x.is_negative() { /// b(); /// } /// ``` /// /// Could be written: /// /// ```rust /// if x.is_positive() { /// a(); /// } else if x.is_negative() { /// b(); /// } else { /// // we don't care about zero /// } /// ``` declare_clippy_lint! { pub ELSE_IF_WITHOUT_ELSE, restriction, "if expression with an `else if`, but without a final `else` branch" } #[derive(Copy, Clone)] pub struct ElseIfWithoutElse; impl LintPass for ElseIfWithoutElse { fn get_lints(&self) -> LintArray { lint_array!(ELSE_IF_WITHOUT_ELSE) } } impl EarlyLintPass for ElseIfWithoutElse { fn check_expr(&mut self, cx: &EarlyContext, mut item: &Expr) { if in_external_macro(cx, item.span) { return; } while let ExprKind::If(_, _, Some(ref els)) = item.node { if let ExprKind::If(_, _, None) = els.node { span_lint_and_sugg( cx, ELSE_IF_WITHOUT_ELSE, els.span, "if expression with an `else if`, but without a final `else`", "add an `else` block here", "".to_string() ); } item = els; } } }