Use utils::sugg in MATCH_BOOL

clippy_lints/src/matches.rs

@@ -10,6 +10,7 @@ use syntax::ast::LitKind;
 use syntax::codemap::Span;
 use utils::paths;
 use utils::{match_type, snippet, span_note_and_lint, span_lint_and_then, in_external_macro, expr_block};
+use utils::sugg::Sugg;
 
 /// **What it does:** This lint checks for matches with a single arm where an `if let` will usually suffice.
 ///
@@ -262,8 +263,9 @@ fn check_match_bool(cx: &LateContext, ex: &Expr, arms: &[Arm], expr: &Expr) {
                         Some(format!("if {} {}", snippet(cx, ex.span, "b"), expr_block(cx, true_expr, None, "..")))
                     }
                     (true, false) => {
-                        Some(format!("try\nif !{} {}",
+                        let test = &Sugg::hir(cx, ex, "..");
-                                     snippet(cx, ex.span, "b"),
+                        Some(format!("if {} {}",
+                                     !test,
                                      expr_block(cx, false_expr, None, "..")))
                     }
                     (true, true) => None,

clippy_lints/src/utils/sugg.rs

@@ -123,6 +123,13 @@ impl<'a, 'b> std::ops::Sub<&'b Sugg<'b>> for &'a Sugg<'a> {
     }
 }
 
+impl<'a> std::ops::Not for &'a Sugg<'a> {
+    type Output = Sugg<'static>;
+    fn not(self) -> Sugg<'static> {
+        make_unop("!", self)
+    }
+}
+
 struct ParenHelper<T> {
     paren: bool,
     wrapped: T,
@@ -147,6 +154,15 @@ impl<T: std::fmt::Display> std::fmt::Display for ParenHelper<T> {
     }
 }
 
+/// Build the string for `<op> <expr>` adding parenthesis when necessary.
+///
+/// For convenience, the operator is taken as a string because all unary operators have the same
+/// precedence.
+pub fn make_unop(op: &str, expr: &Sugg) -> Sugg<'static> {
+    let needs_paren = !matches!(*expr, Sugg::NonParen(..));
+    Sugg::MaybeParen(format!("{}{}", op, ParenHelper::new(needs_paren, expr)).into())
+}
+
 /// Build the string for `<lhs> <op> <rhs>` adding parenthesis when necessary.
 ///
 /// Precedence of shift operator relative to other arithmetic operation is often confusing so

tests/compile-fail/matches.rs

@@ -130,7 +130,7 @@ fn match_bool() {
     match test {
     //~^ ERROR you seem to be trying to match on a boolean expression
     //~| HELP try
-    //~^^ SUGGESTION if !test { println!("Noooo!"); };
+    //~| SUGGESTION if !test { println!("Noooo!"); };
         true => (),
         false => { println!("Noooo!"); }
     };
@@ -138,7 +138,16 @@ fn match_bool() {
     match test {
     //~^ ERROR you seem to be trying to match on a boolean expression
     //~| HELP try
-    //~^^ SUGGESTION if !test { println!("Noooo!"); };
+    //~| SUGGESTION if !test { println!("Noooo!"); };
+        false => { println!("Noooo!"); }
+        _ => (),
+    };
+
+    match test && test {
+    //~^ ERROR you seem to be trying to match on a boolean expression
+    //~| HELP try
+    //~| SUGGESTION if !(test && test) { println!("Noooo!"); };
+    //~| ERROR equal expressions as operands
         false => { println!("Noooo!"); }
         _ => (),
     };