2017-08-09 07:30:56 +00:00
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//! lint on if branches that could be swapped so no `!` operation is necessary
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//! on the condition
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2016-02-29 08:45:36 +00:00
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2019-12-03 23:16:03 +00:00
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use rustc::declare_lint_pass;
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2018-12-29 15:04:45 +00:00
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use rustc::lint::{in_external_macro, EarlyContext, EarlyLintPass, LintArray, LintContext, LintPass};
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2019-12-03 23:16:03 +00:00
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use rustc_session::declare_tool_lint;
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2018-12-29 15:04:45 +00:00
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use syntax::ast::*;
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2016-02-29 08:45:36 +00:00
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2018-07-24 06:55:38 +00:00
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use crate::utils::span_help_and_lint;
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2016-02-29 08:45:36 +00:00
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2018-03-28 13:24:26 +00:00
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declare_clippy_lint! {
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2019-03-05 16:50:33 +00:00
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/// **What it does:** Checks for usage of `!` or `!=` in an if condition with an
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/// else branch.
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///
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/// **Why is this bad?** Negations reduce the readability of statements.
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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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2019-08-03 16:42:05 +00:00
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/// # let v: Vec<usize> = vec![];
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/// # fn a() {}
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/// # fn b() {}
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2019-03-05 16:50:33 +00:00
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/// if !v.is_empty() {
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/// a()
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/// } else {
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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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2019-08-03 16:42:05 +00:00
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/// # let v: Vec<usize> = vec![];
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/// # fn a() {}
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/// # fn b() {}
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2019-03-05 16:50:33 +00:00
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/// if v.is_empty() {
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/// b()
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/// } else {
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/// a()
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/// }
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/// ```
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2016-08-06 08:18:36 +00:00
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pub IF_NOT_ELSE,
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2018-03-28 13:24:26 +00:00
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pedantic,
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2016-08-06 08:18:36 +00:00
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"`if` branches that could be swapped so no negation operation is necessary on the condition"
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2016-02-29 08:45:36 +00:00
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}
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2019-04-08 20:43:55 +00:00
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declare_lint_pass!(IfNotElse => [IF_NOT_ELSE]);
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2016-02-29 08:45:36 +00:00
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impl EarlyLintPass for IfNotElse {
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2018-07-23 11:01:12 +00:00
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fn check_expr(&mut self, cx: &EarlyContext<'_>, item: &Expr) {
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2018-07-24 06:55:38 +00:00
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if in_external_macro(cx.sess(), item.span) {
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2017-10-27 08:51:43 +00:00
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return;
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}
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2019-09-27 15:16:06 +00:00
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if let ExprKind::If(ref cond, _, Some(ref els)) = item.kind {
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if let ExprKind::Block(..) = els.kind {
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match cond.kind {
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2016-02-29 08:45:36 +00:00
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ExprKind::Unary(UnOp::Not, _) => {
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2017-08-09 07:30:56 +00:00
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span_help_and_lint(
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cx,
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IF_NOT_ELSE,
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item.span,
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"Unnecessary boolean `not` operation",
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"remove the `!` and swap the blocks of the if/else",
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);
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2016-12-20 17:21:30 +00:00
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},
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2016-02-29 08:45:36 +00:00
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ExprKind::Binary(ref kind, _, _) if kind.node == BinOpKind::Ne => {
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2017-08-09 07:30:56 +00:00
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span_help_and_lint(
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cx,
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IF_NOT_ELSE,
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item.span,
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"Unnecessary `!=` operation",
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"change to `==` and swap the blocks of the if/else",
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);
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2016-12-20 17:21:30 +00:00
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},
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2016-04-14 18:14:03 +00:00
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_ => (),
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2016-02-29 08:45:36 +00:00
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}
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}
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}
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}
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}
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