$idx and $len do not survive through an explicit context setting, which will work perfectly with my injected-context architecture.
You can use $idx and $len as your explicit context, but as scalar values I do not think there is a way to access them anyway.
Exists and Not-Exists
=====================
Looks like you can exlicitly set a context with exists and not-exists tags too. This works out well in the parser because I am using the same code for those blocks.
Partials
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Explicitly setting a context in a partial also works. The explicit context takes priority over the parameters in the partial tag.
This works for both regular named partials and quoted partials.
While normally parameters are injected 1 level above the current context, if both parameters and explicit are set, they are injected below the current context. So if the context tree was `1->2->3`, with just parameters you'd have `1->2->parameters->3` but with an explicit context you have `1->2->3->parameters->explicit`.
Explicitly setting a context in a helper works too.
Blocks and Inline Partials
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Explicitly setting a context on an inline partial does not work, but it does not error out either, so I need to add support for this in the parser.
Explicitly setting a context on a block does work.
References
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Explicitly setting a context does not work on a reference, but it has revealed that invalid dust is rendered verbatim. I'm going to leave that commented out until I can address that in a later branch.
