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### 2982. Making `size_type` consistent in associative container deduction guides

Section: 22.5.6.1 [unord.set.overview], 22.5.7.1 [unord.multiset.overview] Status: C++20 Submitter: Mike Spertus Opened: 2017-06-16 Last modified: 2021-02-25

Priority: 2

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Discussion:

Due to an incompletely implemented change in Kona, some of the size_type deduction guides say something like:

> A `size_type` parameter type in an `unordered_set` deduction guide refers to the `size_type` member type of the primary `unordered_set` template

while others say

> A `size_type` parameter type in an `unordered_map` deduction guide refers to the `size_type` member type of the type deduced by the deduction guide.

Clearly they should both be the same. My recollection is that the intent of the committee was to change them all to be the latter. Note, however, that this issue may be mooted if the suggestions in the upcoming P0433R3 paper are adopted as a DR in Toronto.

[2017-07 Toronto Monday issue prioritization]

Priority 2; Mike is preparing an updated paper — currently named P0433R3.

[2016-07, Toronto Saturday afternoon issues processing]

Status to Ready; Marshall to check with Mike about his paper

Proposed resolution:

This wording is relative to N4659.

1. Edit 22.5.6.1 [unord.set.overview] as indicated:

   > -4- A `size_type` parameter type in an `unordered_set` deduction guide refers to the `size_type` member type of the primary `unordered_set` template type deduced by the deduction guide.

2. Edit 22.5.7.1 [unord.multiset.overview] as indicated:

   > -4- A `size_type` parameter type in an `unordered_multiset` deduction guide refers to the `size_type` member type of the primary `unordered_multiset` template type deduced by the deduction guide.