feat(edit): add retain to Array, Table and InlineTable

[marcospb19]

Solves #311.

[marcospb19]

@epage I tried adding it to TableLike, but the generic for FnMut(...) -> bool made a compilation error, object safety requires that I don't put a generic in the retain method, I believe I could try with &dyn or &mut dyn, not sure if it works tho.

[marcospb19]

@epage I applied all changes and force-pushed accordingly.

Can I take the opportunity to ask two side-questions?

1. Do you prefer me to mark as resolved, or leave it to the reviewer to resolve?
2. Is force pushing in this context bad?

(Trying to learn how to behave in OSS without annoying anyone)

[epage]

This one should be using as_table

[marcospb19]

Applied

-    /// In other words, remove all values for which `keep(&value)` returns `false`.
+    /// In other words, remove all tables for which `keep(&table)` returns `false`.
     ///
     /// This method operates in place, visiting each element exactly once in the
     /// original order, and preserves the order of the retained elements.
     pub fn retain<F>(&mut self, mut keep: F)
     where
-        F: FnMut(&Value) -> bool,
+        F: FnMut(&Table) -> bool,
     {
         self.values
-            .retain(|item| item.as_value().map(&mut keep).unwrap_or(false));
+            .retain(|item| item.as_table().map(&mut keep).unwrap_or(false));

[epage]

This one should be dealing with Item, not Value

[marcospb19]

Applied

-    /// In other words, remove all pairs `(key, value)` for which
-    /// `keep(&key, &mut value)` returns `false`.
+    /// In other words, remove all pairs `(key, item)` for which
+    /// `keep(&key, &mut item)` returns `false`.
     ///
     /// The elements are visited in iteration order.
     pub fn retain<F>(&mut self, mut keep: F)
     where
-        F: FnMut(&str, &mut Value) -> bool,
+        F: FnMut(&str, &mut Item) -> bool,
     {
-        self.items.retain(|key, item| {
-            item.value
-                .as_value_mut()
-                .map(|value| keep(key, value))
-                .unwrap_or(false)
-        });
+        self.items
+            .retain(|key, key_value| keep(key, &mut key_value.value));

This got a bit weird .retain(|key, key_value| ... key_value.value), because this Table maps key -> key_value.

[epage]

1. Do you prefer me to mark as resolved, or leave it to the reviewer to resolve?

If its obvious, go ahead. If its not, its nice to leave it open so we can both better track whether a change actually resolved it.

2. Is force pushing in this context bad?

I very much appreciate force-pushes

[epage]

Thanks!