69 lines
1.8 KiB
Rust
69 lines
1.8 KiB
Rust
use clippy_utils::diagnostics::span_lint;
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use rustc_ast::ast::{Expr, ExprKind};
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use rustc_lint::{EarlyContext, EarlyLintPass};
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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 unnecessary double parentheses.
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///
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/// ### Why is this bad?
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/// This makes code harder to read and might indicate a
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/// mistake.
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///
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/// ### Example
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/// ```no_run
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/// fn simple_double_parens() -> i32 {
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/// ((0))
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/// }
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///
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/// # fn foo(bar: usize) {}
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/// foo((0));
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/// ```
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///
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/// Use instead:
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/// ```no_run
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/// fn simple_no_parens() -> i32 {
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/// 0
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/// }
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///
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/// # fn foo(bar: usize) {}
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/// foo(0);
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/// ```
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#[clippy::version = "pre 1.29.0"]
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pub DOUBLE_PARENS,
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complexity,
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"Warn on unnecessary double parentheses"
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}
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declare_lint_pass!(DoubleParens => [DOUBLE_PARENS]);
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impl EarlyLintPass for DoubleParens {
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fn check_expr(&mut self, cx: &EarlyContext<'_>, expr: &Expr) {
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let span = match &expr.kind {
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ExprKind::Paren(in_paren) if matches!(in_paren.kind, ExprKind::Paren(_) | ExprKind::Tup(_)) => expr.span,
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ExprKind::Call(_, params)
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if let [param] = &**params
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&& let ExprKind::Paren(_) = param.kind =>
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{
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param.span
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},
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ExprKind::MethodCall(call)
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if let [arg] = &*call.args
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&& let ExprKind::Paren(_) = arg.kind =>
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{
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arg.span
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},
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_ => return,
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};
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if !expr.span.from_expansion() {
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span_lint(
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cx,
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DOUBLE_PARENS,
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span,
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"consider removing unnecessary double parentheses",
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);
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}
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}
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}
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