1 use clippy_utils::diagnostics::span_lint;
2 use rustc_ast::ast::{Expr, ExprKind};
3 use rustc_lint::{EarlyContext, EarlyLintPass};
4 use rustc_session::{declare_lint_pass, declare_tool_lint};
7 /// **What it does:** Checks for unnecessary double parentheses.
9 /// **Why is this bad?** This makes code harder to read and might indicate a
12 /// **Known problems:** None.
17 /// fn simple_double_parens() -> i32 {
22 /// fn simple_no_parens() -> i32 {
28 /// # fn foo(bar: usize) {}
37 "Warn on unnecessary double parentheses"
40 declare_lint_pass!(DoubleParens => [DOUBLE_PARENS]);
42 impl EarlyLintPass for DoubleParens {
43 fn check_expr(&mut self, cx: &EarlyContext<'_>, expr: &Expr) {
44 if expr.span.from_expansion() {
48 let msg: &str = "consider removing unnecessary double parentheses";
51 ExprKind::Paren(ref in_paren) => match in_paren.kind {
52 ExprKind::Paren(_) | ExprKind::Tup(_) => {
53 span_lint(cx, DOUBLE_PARENS, expr.span, &msg);
57 ExprKind::Call(_, ref params) => {
58 if params.len() == 1 {
59 let param = ¶ms[0];
60 if let ExprKind::Paren(_) = param.kind {
61 span_lint(cx, DOUBLE_PARENS, param.span, &msg);
65 ExprKind::MethodCall(_, ref params, _) => {
66 if params.len() == 2 {
67 let param = ¶ms[1];
68 if let ExprKind::Paren(_) = param.kind {
69 span_lint(cx, DOUBLE_PARENS, param.span, &msg);