clippy_lints/src/double_parens.rs

   1 use crate::utils::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};
   5
   6 declare_clippy_lint! {
   7     /// **What it does:** Checks for unnecessary double parentheses.
   8     ///
   9     /// **Why is this bad?** This makes code harder to read and might indicate a
  10     /// mistake.
  11     ///
  12     /// **Known problems:** None.
  13     ///
  14     /// **Example:**
  15     /// ```rust
  16     /// # fn foo(bar: usize) {}
  17     /// ((0));
  18     /// foo((0));
  19     /// ((1, 2));
  20     /// ```
  21     pub DOUBLE_PARENS,
  22     complexity,
  23     "Warn on unnecessary double parentheses"
  24 }
  25
  26 declare_lint_pass!(DoubleParens => [DOUBLE_PARENS]);
  27
  28 impl EarlyLintPass for DoubleParens {
  29     fn check_expr(&mut self, cx: &EarlyContext<'_>, expr: &Expr) {
  30         if expr.span.from_expansion() {
  31             return;
  32         }
  33
  34         match expr.kind {
  35             ExprKind::Paren(ref in_paren) => match in_paren.kind {
  36                 ExprKind::Paren(_) | ExprKind::Tup(_) => {
  37                     span_lint(
  38                         cx,
  39                         DOUBLE_PARENS,
  40                         expr.span,
  41                         "Consider removing unnecessary double parentheses",
  42                     );
  43                 },
  44                 _ => {},
  45             },
  46             ExprKind::Call(_, ref params) => {
  47                 if params.len() == 1 {
  48                     let param = &params[0];
  49                     if let ExprKind::Paren(_) = param.kind {
  50                         span_lint(
  51                             cx,
  52                             DOUBLE_PARENS,
  53                             param.span,
  54                             "Consider removing unnecessary double parentheses",
  55                         );
  56                     }
  57                 }
  58             },
  59             ExprKind::MethodCall(_, ref params) => {
  60                 if params.len() == 2 {
  61                     let param = &params[1];
  62                     if let ExprKind::Paren(_) = param.kind {
  63                         span_lint(
  64                             cx,
  65                             DOUBLE_PARENS,
  66                             param.span,
  67                             "Consider removing unnecessary double parentheses",
  68                         );
  69                     }
  70                 }
  71             },
  72             _ => {},
  73         }
  74     }
  75 }