rust/clippy_lints/src/else_if_without_else.rs

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//! 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
/// }
/// ```
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declare_clippy_lint! {
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pub ELSE_IF_WITHOUT_ELSE,
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restriction,
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"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;
}
}
}