1 files changed, 75 insertions, 0 deletions
diff --git a/src/tools/clippy/clippy_lints/src/matches/match_bool.rs b/src/tools/clippy/clippy_lints/src/matches/match_bool.rs
new file mode 100644
index 000000000..1c216e135
--- /dev/null
+++ b/src/tools/clippy/clippy_lints/src/matches/match_bool.rs
@@ -0,0 +1,75 @@
+use clippy_utils::diagnostics::span_lint_and_then;
+use clippy_utils::is_unit_expr;
+use clippy_utils::source::{expr_block, snippet};
+use clippy_utils::sugg::Sugg;
+use rustc_ast::LitKind;
+use rustc_errors::Applicability;
+use rustc_hir::{Arm, Expr, ExprKind, PatKind};
+use rustc_lint::LateContext;
+use rustc_middle::ty;
+
+use super::MATCH_BOOL;
+
+pub(crate) fn check(cx: &LateContext<'_>, ex: &Expr<'_>, arms: &[Arm<'_>], expr: &Expr<'_>) {
+    // Type of expression is `bool`.
+    if *cx.typeck_results().expr_ty(ex).kind() == ty::Bool {
+        span_lint_and_then(
+            cx,
+            MATCH_BOOL,
+            expr.span,
+            "you seem to be trying to match on a boolean expression",
+            move |diag| {
+                if arms.len() == 2 {
+                    // no guards
+                    let exprs = if let PatKind::Lit(arm_bool) = arms[0].pat.kind {
+                        if let ExprKind::Lit(ref lit) = arm_bool.kind {
+                            match lit.node {
+                                LitKind::Bool(true) => Some((arms[0].body, arms[1].body)),
+                                LitKind::Bool(false) => Some((arms[1].body, arms[0].body)),
+                                _ => None,
+                            }
+                        } else {
+                            None
+                        }
+                    } else {
+                        None
+                    };
+
+                    if let Some((true_expr, false_expr)) = exprs {
+                        let sugg = match (is_unit_expr(true_expr), is_unit_expr(false_expr)) {
+                            (false, false) => Some(format!(
+                                "if {} {} else {}",
+                                snippet(cx, ex.span, "b"),
+                                expr_block(cx, true_expr, None, "..", Some(expr.span)),
+                                expr_block(cx, false_expr, None, "..", Some(expr.span))
+                            )),
+                            (false, true) => Some(format!(
+                                "if {} {}",
+                                snippet(cx, ex.span, "b"),
+                                expr_block(cx, true_expr, None, "..", Some(expr.span))
+                            )),
+                            (true, false) => {
+                                let test = Sugg::hir(cx, ex, "..");
+                                Some(format!(
+                                    "if {} {}",
+                                    !test,
+                                    expr_block(cx, false_expr, None, "..", Some(expr.span))
+                                ))
+                            },
+                            (true, true) => None,
+                        };
+
+                        if let Some(sugg) = sugg {
+                            diag.span_suggestion(
+                                expr.span,
+                                "consider using an `if`/`else` expression",
+                                sugg,
+                                Applicability::HasPlaceholders,
+                            );
+                        }
+                    }
+                }
+            },
+        );
+    }
+}