Fix Debug insert_return_type

[François Dumont]

Here is a patch to fix those failures of the latest report:

UNRESOLVED: 23_containers/map/modifiers/extract.cc compilation failed to produce executable
FAIL: 23_containers/set/modifiers/extract.cc (test for excess errors)
UNRESOLVED: 23_containers/set/modifiers/extract.cc compilation failed to produce executable
FAIL: 23_containers/unordered_map/modifiers/extract.cc (test for excess errors)
UNRESOLVED: 23_containers/unordered_map/modifiers/extract.cc compilation failed to produce executable
FAIL: 23_containers/unordered_set/modifiers/extract.cc (test for excess errors)
UNRESOLVED: 23_containers/unordered_set/modifiers/extract.cc compilation failed to produce executable


Tested under Linux x86_64 Debug mode.

Ok to commit ?

Note that I don't understand this in _Rb_tree:

       using insert_return_type = _Node_insert_return<
	conditional_t<is_same_v<_Key, _Val>, const_iterator, iterator>,
	node_type>;

Why the conditional_t part ? In Debug mode it is always using iterator and I don't understand what represent this is_same_v<_Key, _Val> condition.

François

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