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