Implement for loop (#374)

* implement for loop execution

* for loop benchmark

* add more for loop tests

* Update boa/src/exec/tests.rs

Co-authored-by: Iban Eguia <razican@protonmail.ch>

boa/benches/exec.rs

@@ -26,30 +26,25 @@ fn symbol_creation(c: &mut Criterion) {
     });
 }
 
-// TODO: implement for loops.
-// static FOR_LOOP: &str = r#"
-// let a = 10;
-// let b = "hello";
-// for (;;) {
-//     a += 5;
+static FOR_LOOP: &str = r#"
+let a = 10;
+let b = "hello";
+for (;a > 100;) {
+    a += 5;
 
-//     if (a < 50) {
-//         b += "world";
-//     }
+    if (a < 50) {
+        b += "world";
+    }
+}
 
-//     if (a > 100) {
-//         break;
-//     }
-// }
-// let c = a;
-// let d = b;
-// "#;
+b
+"#;
 
-// fn for_loop_execution(c: &mut Criterion) {
-//     c.bench_function("For loop (Execution)", move |b| {
-//         b.iter(|| exec(black_box(FOR_LOOP)))
-//     });
-// }
+fn for_loop_execution(c: &mut Criterion) {
+    c.bench_function("For loop (Execution)", move |b| {
+        b.iter(|| exec(black_box(FOR_LOOP)))
+    });
+}
 
 static FIBONACCI: &str = r#"
 let num = 12;
@@ -74,7 +69,7 @@ criterion_group!(
     execution,
     create_realm,
     symbol_creation,
-    // for_loop_execution,
+    for_loop_execution,
     fibonacci
 );
 criterion_main!(execution);

boa/src/exec/mod.rs

@@ -173,6 +173,24 @@ impl Executor for Interpreter {
                 }
                 Ok(result)
             }
+            Node::ForLoop(ref init, ref cond, ref step, ref body) => {
+                if let Some(init) = init {
+                    self.run(init)?;
+                }
+
+                while match cond {
+                    Some(cond) => self.run(cond)?.borrow().is_true(),
+                    None => true,
+                } {
+                    self.run(body)?;
+
+                    if let Some(step) = step {
+                        self.run(step)?;
+                    }
+                }
+
+                Ok(Gc::new(ValueData::Undefined))
+            }
             Node::If(ref cond, ref expr, None) => Ok(if self.run(cond)?.borrow().is_true() {
                 self.run(expr)?
             } else {

boa/src/exec/tests.rs

@@ -304,6 +304,51 @@ fn test_do_while_post_inc() {
     assert_eq!(exec(with_post_incrementors), String::from("11"));
 }
 
+#[test]
+fn test_for_loop() {
+    let simple = r#"
+        const a = ['h', 'e', 'l', 'l', 'o'];
+        let b = '';
+        for (let i = 0; i < a.length; i = i + 1) {
+            b = b + a[i];
+        }
+        b
+        "#;
+    assert_eq!(exec(simple), String::from("hello"));
+
+    let without_init_and_inc_step = r#"
+        let a = 0;
+        let i = 0;
+        for (;i < 10;) {
+            a = a + i;
+            i = i + 1;
+        }
+
+        a
+        "#;
+    assert_eq!(exec(without_init_and_inc_step), String::from("45"));
+
+    let body_should_not_execute_on_false_condition = r#"
+        let a = 0
+        for (;false;) {
+            a = a + 1;
+        }
+
+        a
+        "#;
+    assert_eq!(
+        exec(body_should_not_execute_on_false_condition),
+        String::from("0")
+    );
+
+    let inner_scope = r#"
+        for (let i = 0;false;) {}
+
+        i
+        "#;
+    assert_eq!(exec(inner_scope), String::from("undefined"));
+}
+
 #[test]
 #[ignore]
 fn test_unary_pre() {