Add tests for if let

Author: lilyball

src/test/run-pass/if-let.rs

@@ -0,0 +1,67 @@
+// Copyright 2014 The Rust Project Developers. See the COPYRIGHT
+// file at the top-level directory of this distribution and at
+// http://rust-lang.org/COPYRIGHT.
+//
+// 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.
+
+pub fn main() {
+    let x = Some(3i);
+    if let Some(y) = x {
+        assert_eq!(y, 3i);
+    } else {
+        fail!("if-let failed");
+    }
+    let mut worked = false;
+    if let Some(_) = x {
+        worked = true;
+    }
+    assert!(worked);
+    let clause: uint;
+    if let None = Some("test") {
+        clause = 1;
+    } else if 4u > 5 {
+        clause = 2;
+    } else if let Ok(()) = Err::<(),&'static str>("test") {
+        clause = 3;
+    } else {
+        clause = 4;
+    }
+    assert_eq!(clause, 4u);
+
+    if 3i > 4 {
+        fail!("bad math");
+    } else if let 1 = 2i {
+        fail!("bad pattern match");
+    }
+
+    enum Foo {
+        One,
+        Two(uint),
+        Three(String, int)
+    }
+
+    let foo = Three("three".to_string(), 42i);
+    if let One = foo {
+        fail!("bad pattern match");
+    } else if let Two(_x) = foo {
+        fail!("bad pattern match");
+    } else if let Three(s, _) = foo {
+        assert_eq!(s.as_slice(), "three");
+    } else {
+        fail!("bad else");
+    }
+
+    if false {
+        fail!("wat");
+    } else if let a@Two(_) = Two(42u) {
+        if let Two(b) = a {
+            assert_eq!(b, 42u);
+        } else {
+            fail!("fail in nested if-let");
+        }
+    }
+}