clippy_lints/src/double_parens.rs

   1 use crate::utils::{in_macro_or_desugar, span_lint};
   2 use rustc::lint::{EarlyContext, EarlyLintPass, LintArray, LintPass};
   3 use rustc::{declare_lint_pass, declare_tool_lint};
   4 use syntax::ast::*;
   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     /// ((0))
  17     /// foo((0))
  18     /// ((1, 2))
  19     /// ```
  20     pub DOUBLE_PARENS,
  21     complexity,
  22     "Warn on unnecessary double parentheses"
  23 }
  24
  25 declare_lint_pass!(DoubleParens => [DOUBLE_PARENS]);
  26
  27 impl EarlyLintPass for DoubleParens {
  28     fn check_expr(&mut self, cx: &EarlyContext<'_>, expr: &Expr) {
  29         if in_macro_or_desugar(expr.span) {
  30             return;
  31         }
  32
  33         match expr.node {
  34             ExprKind::Paren(ref in_paren) => match in_paren.node {
  35                 ExprKind::Paren(_) | ExprKind::Tup(_) => {
  36                     span_lint(
  37                         cx,
  38                         DOUBLE_PARENS,
  39                         expr.span,
  40                         "Consider removing unnecessary double parentheses",
  41                     );
  42                 },
  43                 _ => {},
  44             },
  45             ExprKind::Call(_, ref params) => {
  46                 if params.len() == 1 {
  47                     let param = &params[0];
  48                     if let ExprKind::Paren(_) = param.node {
  49                         span_lint(
  50                             cx,
  51                             DOUBLE_PARENS,
  52                             param.span,
  53                             "Consider removing unnecessary double parentheses",
  54                         );
  55                     }
  56                 }
  57             },
  58             ExprKind::MethodCall(_, ref params) => {
  59                 if params.len() == 2 {
  60                     let param = &params[1];
  61                     if let ExprKind::Paren(_) = param.node {
  62                         span_lint(
  63                             cx,
  64                             DOUBLE_PARENS,
  65                             param.span,
  66                             "Consider removing unnecessary double parentheses",
  67                         );
  68                     }
  69                 }
  70             },
  71             _ => {},
  72         }
  73     }
  74 }