71 lines
1.9 KiB
Rust
71 lines
1.9 KiB
Rust
//! Lint on if expressions with an else if, but without a final else branch.
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use clippy_utils::diagnostics::span_lint_and_help;
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use rustc_ast::ast::{Expr, ExprKind};
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use rustc_lint::{EarlyContext, EarlyLintPass, LintContext};
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use rustc_middle::lint::in_external_macro;
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use rustc_session::declare_lint_pass;
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declare_clippy_lint! {
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/// ### What it does
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/// 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?
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/// Some coding guidelines require this (e.g., MISRA-C:2004 Rule 14.10).
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///
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/// ### Example
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/// ```no_run
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/// # fn a() {}
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/// # fn b() {}
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/// # let x: i32 = 1;
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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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/// Use instead:
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///
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/// ```no_run
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/// # fn a() {}
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/// # fn b() {}
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/// # let x: i32 = 1;
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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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#[clippy::version = "pre 1.29.0"]
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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"
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}
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declare_lint_pass!(ElseIfWithoutElse => [ELSE_IF_WITHOUT_ELSE]);
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impl EarlyLintPass for ElseIfWithoutElse {
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fn check_expr(&mut self, cx: &EarlyContext<'_>, item: &Expr) {
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if in_external_macro(cx.sess(), item.span) {
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return;
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}
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if let ExprKind::If(_, _, Some(ref els)) = item.kind
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&& let ExprKind::If(_, _, None) = els.kind
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{
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span_lint_and_help(
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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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None,
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"add an `else` block here",
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);
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}
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}
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}
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