Compiler Panics on Some Slice files without Module Declarations

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The logic used by the slice parser to push and pop scopes assumes there is a module scope present in some cases
(anything with 2 levels of nesting like operations or the new enumerator with associated fields).

If you forget to add a module declaration in files containing these things, the compiler will panic instead of correctly emitting a
"syntax error: module declaration is required".

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This was fixed by b443994.