topic "Rules for references to Value internal maps elements";
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[{_}%EN-US 
[s10; Rules for references to ValueArray, ValueMap and Value elements&]
[s0; Value is originally designed as non`-mutable concrete Value 
of different concrete types.&]
[s0; &]
[s0; However, as Value is commonly used to store complex hierarchies 
(using ValueArray/ValueMap), it is in the end very useful to 
be able to reference ValueArray/ValueMap elements directly. Validity 
of such references is restricted by following rule:&]
[s0; &]
[s0; Reference obtained from Value/ValueArray/ValueMap (by Value`::At, 
Value`::GetAdd, ValueArray`::At, ValueMap`::GetAdd and derivative 
methods) are [* only valid until the next operation on originating 
Value `- including just reading it.]&]
[s0; &]
[s0; Examples of invalid code:&]
[s0; &]
[s13; &]
[s13; Value m;&]
[s13; Value`& x `= m(`"key`");&]
[s13; x `= m; // using m as source invalidates x&]
[s13; ....&]
[s13; Value m;&]
[s13; Value`& x `= m(`"key`");&]
[s13; Value`& y `= m(`"key2`"); // Invalidates x&]
[s13; x `= 123; // undefined&]
[s13; ....&]
[s13; Value m;&]
[s13; Value`& x `= m.At(1);&]
[s13; Value m2 `= m; // Invalidates x&]
[s13; x `= `"fail`"; // undefined&]
[s0; ]]