| //! Lint on if expressions with an else if, but without a final else branch. |
| |
| use rustc::lint::in_external_macro; |
| use rustc_ast::ast::{Expr, ExprKind}; |
| use rustc_lint::{EarlyContext, EarlyLintPass, LintContext}; |
| use rustc_session::{declare_lint_pass, declare_tool_lint}; |
| |
| use crate::utils::span_lint_and_help; |
| |
| declare_clippy_lint! { |
| /// **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 |
| /// # fn a() {} |
| /// # fn b() {} |
| /// # let x: i32 = 1; |
| /// if x.is_positive() { |
| /// a(); |
| /// } else if x.is_negative() { |
| /// b(); |
| /// } |
| /// ``` |
| /// |
| /// Could be written: |
| /// |
| /// ```rust |
| /// # fn a() {} |
| /// # fn b() {} |
| /// # let x: i32 = 1; |
| /// if x.is_positive() { |
| /// a(); |
| /// } else if x.is_negative() { |
| /// b(); |
| /// } else { |
| /// // We don't care about zero. |
| /// } |
| /// ``` |
| pub ELSE_IF_WITHOUT_ELSE, |
| restriction, |
| "`if` expression with an `else if`, but without a final `else` branch" |
| } |
| |
| declare_lint_pass!(ElseIfWithoutElse => [ELSE_IF_WITHOUT_ELSE]); |
| |
| impl EarlyLintPass for ElseIfWithoutElse { |
| fn check_expr(&mut self, cx: &EarlyContext<'_>, mut item: &Expr) { |
| if in_external_macro(cx.sess(), item.span) { |
| return; |
| } |
| |
| while let ExprKind::If(_, _, Some(ref els)) = item.kind { |
| if let ExprKind::If(_, _, None) = els.kind { |
| span_lint_and_help( |
| cx, |
| ELSE_IF_WITHOUT_ELSE, |
| els.span, |
| "`if` expression with an `else if`, but without a final `else`", |
| "add an `else` block here", |
| ); |
| } |
| |
| item = els; |
| } |
| } |
| } |