Can't call partials stored in LetContext as Call Expressions

[phillipskevin]

This works:

    {{< foo }}
      This is foo
    {{/ foo }}

    <p>{{ scope.templateContext.partials.foo() }}</p>

...and this works:

    {{< foo }}
      This is foo
    {{/ foo }}

    {{ let bar = scope.templateContext.partials.foo }}

    <p>{{ bar "baz" }}</p>

...but this doesn't work:

    {{< foo }}
      This is foo
    {{/ foo }}

    {{ let bar = scope.templateContext.partials.foo }}

    <p>{{ bar() }}</p>

In this case, the partial is called, but not rendered. I'm not sure why.

[justinbmeyer]

Probably because the render function is inside an observable.

[justinbmeyer]

https://github.com/canjs/can-stache/blob/master/expressions/call.js#L75