Added FORCED_RETURN lint.

tests/ui/forced_return.rs

@@ -0,0 +1,55 @@
+// Copyright 2014-2018 The Rust Project Developers. See the COPYRIGHT
+// file at the top-level directory of this distribution.
+//
+// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
+// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
+// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
+// option. This file may not be copied, modified, or distributed
+// except according to those terms.
+
+
+
+
+
+#![warn(clippy::forced_return)]
+
+fn test_end_of_fn() -> bool {
+    if true {
+        // no error!
+        return true;
+    }
+    true
+}
+
+#[allow(clippy::needless_bool)]
+fn test_if_block() -> bool {
+    if true {
+        true
+    } else {
+        false
+    }
+}
+
+#[allow(clippy::match_bool)]
+fn test_match(x: bool) -> bool {
+    match x {
+        true => false,
+        false => {
+            true
+        }
+    }
+}
+
+fn test_closure() {
+    let _ = || {
+        true
+    };
+    let _ = || true;
+}
+
+fn main() {
+    let _ = test_end_of_fn();
+    let _ = test_if_block();
+    let _ = test_match(true);
+    test_closure();
+}

tests/ui/forced_return.stderr

@@ -0,0 +1,46 @@
+error: missing return statement
+  --> $DIR/forced_return.rs:21:5
+   |
+21 |     true
+   |     ^^^^ help: add `return` as shown: `return true`
+   |
+   = note: `-D clippy::forced-return` implied by `-D warnings`
+
+error: missing return statement
+  --> $DIR/forced_return.rs:27:9
+   |
+27 |         true
+   |         ^^^^ help: add `return` as shown: `return true`
+
+error: missing return statement
+  --> $DIR/forced_return.rs:29:9
+   |
+29 |         false
+   |         ^^^^^ help: add `return` as shown: `return false`
+
+error: missing return statement
+  --> $DIR/forced_return.rs:36:17
+   |
+36 |         true => false,
+   |                 ^^^^^ help: add `return` as shown: `return false`
+
+error: missing return statement
+  --> $DIR/forced_return.rs:38:13
+   |
+38 |             true
+   |             ^^^^ help: add `return` as shown: `return true`
+
+error: missing return statement
+  --> $DIR/forced_return.rs:45:9
+   |
+45 |         true
+   |         ^^^^ help: add `return` as shown: `return true`
+
+error: missing return statement
+  --> $DIR/forced_return.rs:47:16
+   |
+47 |     let _ = || true;
+   |                ^^^^ help: add `return` as shown: `return true`
+
+error: aborting due to 7 previous errors
+