81 lines
2.5 KiB
Rust
81 lines
2.5 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_ast::ast::{BinOpKind, Expr, ExprKind, UnOp};
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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, declare_tool_lint};
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use crate::utils::span_lint_and_help;
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declare_clippy_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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/// # let v: Vec<usize> = vec![];
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/// # fn a() {}
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/// # fn b() {}
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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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/// # let v: Vec<usize> = vec![];
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/// # fn a() {}
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/// # fn b() {}
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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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pub IF_NOT_ELSE,
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pedantic,
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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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declare_lint_pass!(IfNotElse => [IF_NOT_ELSE]);
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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.sess(), 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.kind {
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if let ExprKind::Block(..) = els.kind {
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match cond.kind {
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ExprKind::Unary(UnOp::Not, _) => {
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span_lint_and_help(
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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_lint_and_help(
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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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