Add continue statement (#822)

Note that documentation is still required.

test/language/continue/closure_in_for.wren

@@ -0,0 +1,9 @@
+var f
+for (i in [1, 2, 3]) {
+  var j = 4
+  f = Fn.new { System.print(i + j) }
+  continue
+}
+
+f.call()
+// expect: 7

test/language/continue/closure_in_while.wren

@@ -0,0 +1,9 @@
+var f
+while (f == null) {
+  var i = "i"
+  f = Fn.new { System.print(i) }
+  continue
+}
+
+f.call()
+// expect: i

test/language/continue/exit_local_scopes.wren

@@ -0,0 +1,20 @@
+for (i in 0..5) {
+  {
+    var a = "a"
+    {
+      var b = "b"
+      {
+        var c = "c"
+        if (i == 1) continue
+      }
+    }
+  }
+  
+  System.print(i)
+}
+
+// expect: 0
+// expect: 2
+// expect: 3
+// expect: 4
+// expect: 5

test/language/continue/in_for_loop.wren

@@ -0,0 +1,12 @@
+for (i in [1, 2, 3, 4, 5]) {
+  System.print(i)
+  if (i > 2) continue
+  System.print(i)
+}
+// expect: 1
+// expect: 1
+// expect: 2
+// expect: 2
+// expect: 3
+// expect: 4
+// expect: 5

test/language/continue/in_function_in_loop.wren

@@ -0,0 +1,7 @@
+var done = false
+while (!done) {
+  Fn.new {
+    continue // expect error
+  }
+  done = true
+}

test/language/continue/in_method_in_loop.wren

@@ -0,0 +1,9 @@
+var done = false
+while (!done) {
+  class Foo {
+    method {
+      continue // expect error
+    }
+  }
+  done = true
+}

test/language/continue/in_while_loop.wren

@@ -0,0 +1,12 @@
+var i = 0
+while (true) {
+  i = i + 1
+  System.print(i)
+  if (i <= 2) continue
+  System.print(i)
+  break
+}
+// expect: 1
+// expect: 2
+// expect: 3
+// expect: 3

test/language/continue/nested_for_loop.wren

@@ -0,0 +1,17 @@
+for (i in 0..2) {
+  System.print("outer %(i)")
+  if (i == 1) continue
+
+  for (j in 0..2) {
+    if (j == 1) continue
+    System.print("inner %(j)")
+  }
+}
+
+// expect: outer 0
+// expect: inner 0
+// expect: inner 2
+// expect: outer 1
+// expect: outer 2
+// expect: inner 0
+// expect: inner 2

test/language/continue/nested_while_loop.wren

@@ -0,0 +1,23 @@
+var i = 0
+while (i <= 2) {
+  i = i + 1
+
+  System.print("outer %(i)")
+  if (i == 2) continue
+
+  var j = 0
+  while (j <= 2) {
+    j = j + 1
+  
+	if(j == 2) continue
+    System.print("inner %(j)")
+  }
+}
+
+// expect: outer 1
+// expect: inner 1
+// expect: inner 3
+// expect: outer 2
+// expect: outer 3
+// expect: inner 1
+// expect: inner 3

test/language/continue/outside_loop.wren

@@ -0,0 +1 @@
+continue // expect error