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rust-clippy/clippy_lints/src/double_parens.rs
2016-12-28 12:03:49 -08:00

62 lines
1.9 KiB
Rust

use syntax::ast::*;
use rustc::lint::{EarlyContext, LintContext, LintArray, LintPass, EarlyLintPass};
/// **What it does:** Checks for unnecessary double parentheses.
///
/// **Why is this bad?** This makes code harder to read and might indicate a
/// mistake.
///
/// **Known problems:** None.
///
/// **Example:**
/// ```rust
/// ((0))
/// foo((0))
/// ((1, 2))
/// ```
declare_lint! {
pub DOUBLE_PARENS, Warn,
"Warn on unnecessary double parentheses"
}
#[derive(Copy, Clone)]
pub struct DoubleParens;
impl LintPass for DoubleParens {
fn get_lints(&self) -> LintArray {
lint_array!(DOUBLE_PARENS)
}
}
impl EarlyLintPass for DoubleParens {
fn check_expr(&mut self, cx: &EarlyContext, expr: &Expr) {
match expr.node {
ExprKind::Paren(ref in_paren) => {
match in_paren.node {
ExprKind::Paren(_) |
ExprKind::Tup(_) => {
cx.span_lint(DOUBLE_PARENS, expr.span, "Consider removing unnecessary double parentheses");
},
_ => {},
}
},
ExprKind::Call(_, ref params) => {
if params.len() == 1 {
let param = &params[0];
if let ExprKind::Paren(_) = param.node {
cx.span_lint(DOUBLE_PARENS, param.span, "Consider removing unnecessary double parentheses");
}
}
},
ExprKind::MethodCall(_, _, ref params) => {
if params.len() == 2 {
let param = &params[1];
if let ExprKind::Paren(_) = param.node {
cx.span_lint(DOUBLE_PARENS, param.span, "Consider removing unnecessary double parentheses");
}
}
},
_ => {},
}
}
}