Change in behavior for implicit params in partials in handlebars 4.5.2

[aschwarte10]

First of all thanks for maintaining this library 👍

We're in the process of upgrading Handlebars.java from 4.5.0 to 4.5.2 and noticed a subtle behavior change around partial context inheritance. We wanted to discuss it and ask whether this is intentional or an unintended side-effect of some 4.5.2 change

We found that implicit params are no longer accessible inside the partial

Minimal abstract reproducing example

  {{! outer template }}
  {{> testParamPage param="hello"}}

  {{! testParamPage }}
  {{> parameters }}              {{! implicit — param should be inherited }}
  {{> parameters param=param}}   {{! explicit — still works in both versions }}

  {{! parameters }}
  {{param}}

In 4.5.0: both calls render hello.
In 4.5.2: the implicit call renders nothing; only the explicit re-binding works.

Potential related change / ticket: #1173

We would like to ask whether this is intended or a side-effect. In our use-case we aim now to make params to partials explicit and avoid issues in the first place

cc @jknack