80 lines
2.1 KiB
Rust
80 lines
2.1 KiB
Rust
//! lint on if branches that could be swapped so no `!` operation is necessary
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//! on the condition
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use rustc::lint::*;
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use syntax::ast::*;
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use utils::{in_external_macro, span_help_and_lint};
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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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/// 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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/// 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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declare_lint! {
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pub IF_NOT_ELSE,
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Allow,
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"`if` branches that could be swapped so no negation operation is necessary on the condition"
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}
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pub struct IfNotElse;
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impl LintPass for IfNotElse {
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fn get_lints(&self) -> LintArray {
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lint_array!(IF_NOT_ELSE)
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}
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}
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impl EarlyLintPass for IfNotElse {
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fn check_expr(&mut self, cx: &EarlyContext, 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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if let ExprKind::If(ref cond, _, Some(ref els)) = item.node {
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if let ExprKind::Block(..) = els.node {
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match cond.node {
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ExprKind::Unary(UnOp::Not, _) => {
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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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},
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ExprKind::Binary(ref kind, _, _) if kind.node == BinOpKind::Ne => {
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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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},
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_ => (),
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}
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}
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}
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}
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}
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