added interoperability with C++20 ranges

[joaquintides]

Added interoperability with C++20 ranges to all the containers in the library: insert_range (plus insert_range_(or|and)_[c]visit for concurrent containers), std::from_range construction and associated CTAD deduction guides. The boost::unordered::from_range construction tag is provided as an alternative to C++23 std::from_range or when this is not available.

Closes #347.

[cppalliance-bot]

An automated preview of the documentation is available at https://355.unordered.prtest2.cppalliance.org/libs/unordered/doc/html/index.html

If more commits are pushed to the pull request, the docs will rebuild at the same URL.

2026-06-15 11:30:17 UTC

[codecov]

Codecov Report

❌ Patch coverage is 99.56835% with 3 lines in your changes missing coverage. Please review.
✅ Project coverage is 98.28%. Comparing base (b785bb5) to head (fde54f3).

Files with missing lines	Patch %	Lines
test/unordered/deduction_tests.cpp	94.23%	3 Missing ⚠️

Additional details and impacted files

@@             Coverage Diff             @@
##           develop     #355      +/-   ##
===========================================
+ Coverage    98.23%   98.28%   +0.05%     
===========================================
  Files          161      161              
  Lines        22293    22938     +645     
===========================================
+ Hits         21899    22545     +646     
+ Misses         394      393       -1     

Files with missing lines	Coverage Δ
include/boost/unordered/concurrent_flat_map.hpp	100.00% <100.00%> (ø)
include/boost/unordered/concurrent_flat_set.hpp	100.00% <100.00%> (ø)
include/boost/unordered/concurrent_node_map.hpp	99.43% <100.00%> (+0.06%)	⬆️
include/boost/unordered/concurrent_node_set.hpp	99.38% <100.00%> (+0.08%)	⬆️
include/boost/unordered/detail/implementation.hpp	99.23% <100.00%> (+<0.01%)	⬆️
include/boost/unordered/unordered_flat_map.hpp	100.00% <100.00%> (ø)
include/boost/unordered/unordered_flat_set.hpp	100.00% <100.00%> (ø)
include/boost/unordered/unordered_map.hpp	99.70% <100.00%> (+0.02%)	⬆️
include/boost/unordered/unordered_node_map.hpp	99.29% <100.00%> (+0.04%)	⬆️
include/boost/unordered/unordered_node_set.hpp	99.11% <100.00%> (+0.07%)	⬆️
... and 6 more

... and 3 files with indirect coverage changes

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