add if_expressions.rs example file

Author: cormacrelf

examples/if_expressions.rs

@@ -0,0 +1,50 @@
+fn f(n: i32) {
+    // ()-typed
+    if n == 2 {
+    }
+    if n == 1 {
+    } else if n == 2 {
+        return;
+    } else {
+    }
+    // ()-typed (if let)
+    if let 1 = n {
+    } else if let 2 = n {
+        return;
+    } else if n == 2 {
+        return;
+    } else {
+    }
+    // simple if/else expression
+    let y = if x == 5 { 5 } else { 10 };
+    let z = Some(5);
+    // if expression with an else if branch
+    let y = if z.is_some() {
+        30
+    } else if z.is_none() {
+        99
+    } else {
+        0
+    };
+    // if expression with an else if let branch
+    let y = if z.is_some() {
+        30
+    } else if let None = y {
+        99
+    } else {
+        0
+    };
+    // if let expression with both kinds of else if
+    let y = if let Some(3) = y {
+        30
+    } else if let Some(4) = y {
+    } else if y == Some(10) {
+        100
+    } else {
+        0
+    };
+    // if and else-if with let-else chain
+    if let Some(3) = y && let None = z {
+    } else if let None = y && let Some(_) = z {
+    }
+}