Adding Equality Operators to Templates

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+- Start Date: 2019-12-08
+- Relevant Team(s): (fill this in with the [team(s)](README.md#relevant-teams) to which this RFC applies)
+- RFC PR: https://github.com/emberjs/rfcs/pull/560
+- Tracking: (leave this empty)
+
+# Adding Equality Operators to Templates
+
+## Summary
+
+Add new built-in template `{{eq}}` and `{{neq}}` helpers to perform basic equality operations in templates, similar to those included in `ember-truth-helpers`.
+
+This RFC is a subset of the changes proposed in #388.
+
+## Motivation
+
+It is a very common need in any sufficiently complex Ember app to perform some equality operations and often the most convenient place to do it is right in the templates.
+Because of that, [ember-truth-helpers](https://github.com/jmurphyau/ember-truth-helpers) is one of the most installed addons out there, either directly by apps or indirectly by
+other addons that those apps consume.
+
+The fact that `ember-truth-helpers` is so popular is a good signal that this it is filling a perceived gap in Ember's functionality.
+
+A second reason is that it might help make Ember more approachable to newcomers that have some experience in other frameworks.
+Most if not all web frameworks have some way of comparing values in the templates and it's surprising that Ember requires an third party package to perform
+even the most basic operations.
+
+
+## Detailed design
+
+Add `{{eq}}` and `{{neq}}` helpers.
+
+#### `{{eq}}`
+Binary operation. Throws an error if not called with exactly two arguments.
+Equivalent of <arg1> === <arg2>
+This is identical to the `eq` helper in `ember-truth-helpers`
+
+#### `{{neq}}`
+Binary operation. Throws an error if not called with exactly two arguments.
+Equivalent of <arg1> !== <arg2>
+This is identical to the `not-eq` helper in `ember-truth-helpers`, except for the name.
+
+This RFC intentionally leaves the implementation details unspecified, those could be implemented in Glimmer VM or
+in a higher level in Ember itself.
+
+## How we teach this
+
+The introduction of these helpers does not impact the current mental model for Ember applications.
+
+In addition to API and Guides documentation with illustrative examples of usage of the various helpers.
+
+## Drawbacks
+
+Adding new helpers increases the surface area of the framework and the code the core team commits to support long term.
+
+## Alternatives
+
+One alternative path is don't do anything and let users continue to define their own helpers (or install `ember-truth-helpers`).
+
+## Unresolved questions
+
+- If an app already use `ember-truth-helpers`, the `{{eq}}` helper will conflict with the one proposed here. How do we
+  update `ember-truth-helpers` to make sure the helper of the same name doesn't collide with the built-in one?
+- The inequality helper proposed in this RFC is `{{neq}}` while the one in ember-truth-helpers is `{{not-eq}}`. It is
+  worth considering the benefits that keeping the same name might have in helping apps and addon migrate to the built-in helper.