Fix suggestions for needless_bool

Author: mcarton

clippy_lints/src/needless_bool.rs

@@ -7,6 +7,7 @@ use rustc::hir::*;
 use syntax::ast::LitKind;
 use syntax::codemap::Spanned;
 use utils::{span_lint, span_lint_and_then, snippet, snippet_opt};
+use utils::sugg::Sugg;
 
 /// **What it does:** This lint checks for expressions of the form `if c { true } else { false }` (or vice versa) and suggest using the condition directly.
 ///
@@ -49,11 +50,20 @@ impl LateLintPass for NeedlessBool {
     fn check_expr(&mut self, cx: &LateContext, e: &Expr) {
         use self::Expression::*;
         if let ExprIf(ref pred, ref then_block, Some(ref else_expr)) = e.node {
-            let reduce = |hint: &str, not| {
-                let hint = match snippet_opt(cx, pred.span) {
-                    Some(pred_snip) => format!("`{}{}`", not, pred_snip),
-                    None => hint.into(),
+            let reduce = |ret, not| {
+                let snip = Sugg::hir(cx, pred, "<predicate>");
+                let snip = if not {
+                    !snip
+                } else {
+                    snip
                 };
+
+                let hint = if ret {
+                    format!("return {};", snip)
+                } else {
+                    snip.to_string()
+                };
+
                 span_lint_and_then(cx,
                                    NEEDLESS_BOOL,
                                    e.span,
@@ -77,10 +87,10 @@ impl LateLintPass for NeedlessBool {
                               e.span,
                               "this if-then-else expression will always return false");
                 }
-                (RetBool(true), RetBool(false)) => reduce("its predicate", "return "),
-                (Bool(true), Bool(false)) => reduce("its predicate", ""),
-                (RetBool(false), RetBool(true)) => reduce("`!` and its predicate", "return !"),
-                (Bool(false), Bool(true)) => reduce("`!` and its predicate", "!"),
+                (RetBool(true), RetBool(false)) => reduce(true, false),
+                (Bool(true), Bool(false)) => reduce(false, false),
+                (RetBool(false), RetBool(true)) => reduce(true, true),
+                (Bool(false), Bool(true)) => reduce(false, true),
                 _ => (),
             }
         }

tests/compile-fail/needless_bool.rs

@@ -5,16 +5,21 @@
 #[allow(if_same_then_else)]
 fn main() {
     let x = true;
+    let y = false;
     if x { true } else { true }; //~ERROR this if-then-else expression will always return true
     if x { false } else { false }; //~ERROR this if-then-else expression will always return false
     if x { true } else { false };
     //~^ ERROR this if-then-else expression returns a bool literal
     //~| HELP you can reduce it to
-    //~| SUGGESTION `x`
+    //~| SUGGESTION x
     if x { false } else { true };
     //~^ ERROR this if-then-else expression returns a bool literal
     //~| HELP you can reduce it to
-    //~| SUGGESTION `!x`
+    //~| SUGGESTION !x
+    if x && y { false } else { true };
+    //~^ ERROR this if-then-else expression returns a bool literal
+    //~| HELP you can reduce it to
+    //~| SUGGESTION !(x && y)
     if x { x } else { false }; // would also be questionable, but we don't catch this yet
     bool_ret(x);
     bool_ret2(x);
@@ -39,13 +44,13 @@ fn bool_ret3(x: bool) -> bool {
     if x { return true } else { return false };
     //~^ ERROR this if-then-else expression returns a bool literal
     //~| HELP you can reduce it to
-    //~| SUGGESTION `return x`
+    //~| SUGGESTION return x
 }
 
 #[allow(needless_return)]
 fn bool_ret4(x: bool) -> bool {
     if x { return false } else { return true };
     //~^ ERROR this if-then-else expression returns a bool literal
     //~| HELP you can reduce it to
-    //~| SUGGESTION `return !x`
+    //~| SUGGESTION return !x
 }