clippy_lints/src/matches/match_bool.rs

   1 use clippy_utils::diagnostics::span_lint_and_then;
   2 use clippy_utils::is_unit_expr;
   3 use clippy_utils::source::{expr_block, snippet};
   4 use clippy_utils::sugg::Sugg;
   5 use rustc_ast::LitKind;
   6 use rustc_errors::Applicability;
   7 use rustc_hir::{Arm, Expr, ExprKind, PatKind};
   8 use rustc_lint::LateContext;
   9 use rustc_middle::ty;
  10
  11 use super::MATCH_BOOL;
  12
  13 pub(crate) fn check(cx: &LateContext<'_>, ex: &Expr<'_>, arms: &[Arm<'_>], expr: &Expr<'_>) {
  14     // Type of expression is `bool`.
  15     if *cx.typeck_results().expr_ty(ex).kind() == ty::Bool {
  16         span_lint_and_then(
  17             cx,
  18             MATCH_BOOL,
  19             expr.span,
  20             "you seem to be trying to match on a boolean expression",
  21             move |diag| {
  22                 if arms.len() == 2 {
  23                     // no guards
  24                     let exprs = if let PatKind::Lit(arm_bool) = arms[0].pat.kind {
  25                         if let ExprKind::Lit(ref lit) = arm_bool.kind {
  26                             match lit.node {
  27                                 LitKind::Bool(true) => Some((&*arms[0].body, &*arms[1].body)),
  28                                 LitKind::Bool(false) => Some((&*arms[1].body, &*arms[0].body)),
  29                                 _ => None,
  30                             }
  31                         } else {
  32                             None
  33                         }
  34                     } else {
  35                         None
  36                     };
  37
  38                     if let Some((true_expr, false_expr)) = exprs {
  39                         let sugg = match (is_unit_expr(true_expr), is_unit_expr(false_expr)) {
  40                             (false, false) => Some(format!(
  41                                 "if {} {} else {}",
  42                                 snippet(cx, ex.span, "b"),
  43                                 expr_block(cx, true_expr, None, "..", Some(expr.span)),
  44                                 expr_block(cx, false_expr, None, "..", Some(expr.span))
  45                             )),
  46                             (false, true) => Some(format!(
  47                                 "if {} {}",
  48                                 snippet(cx, ex.span, "b"),
  49                                 expr_block(cx, true_expr, None, "..", Some(expr.span))
  50                             )),
  51                             (true, false) => {
  52                                 let test = Sugg::hir(cx, ex, "..");
  53                                 Some(format!(
  54                                     "if {} {}",
  55                                     !test,
  56                                     expr_block(cx, false_expr, None, "..", Some(expr.span))
  57                                 ))
  58                             },
  59                             (true, true) => None,
  60                         };
  61
  62                         if let Some(sugg) = sugg {
  63                             diag.span_suggestion(
  64                                 expr.span,
  65                                 "consider using an `if`/`else` expression",
  66                                 sugg,
  67                                 Applicability::HasPlaceholders,
  68                             );
  69                         }
  70                     }
  71                 }
  72             },
  73         );
  74     }
  75 }