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### 2052. Mixup between `mapped_type` and `value_type` for associative containers

Section: 24.2.7 [associative.reqmts] Status: Resolved Submitter: Marc Glisse Opened: 2011-05-04 Last modified: 2016-01-28

Priority: 2

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Discussion:

(this is basically reopening the first part of issue 2006, as discussed in the thread starting at c++std-lib-30698 )

Section 24.2.7 [associative.reqmts]

In Table 102, several uses of `T` (which means `mapped_type` here) should be `value_type` instead. This is almost editorial. For instance:

>     a_uniq.emplace(args)

> Requires: `T` shall be `EmplaceConstructible` into `X` from args.

> Effects: Inserts a `T` object `t` constructed with `std::forward<Args>(args)...` if and only if there is no element in the container with key equivalent to the key of `t`. The `bool` component of the returned pair is true if and only if the insertion takes place, and the iterator component of the pair points to the element with key equivalent to the key of `t`.

[ 2011 Bloomington ]

Not even an exhaustive list of problem locations. No reason to doubt issue.

Pablo agrees to provide wording.

[ 2011-09-04 Pablo Halpern provides improved wording ]

[2014-02-15 post-Issaquah session : move to Resolved]

AJM to replace this note with a 'Resolved By...' after tracking down the exact sequence of events, but clearly resolved in C++14 DIS.

Proposed resolution:

In both section 24.2.7 [associative.reqmts] Table 102 and 24.2.8 [unord.req], Table 103, make the following text replacements:

Original text, in FDIS | Replacement text
`T` is CopyInsertable into `X` and `CopyAssignable`. | `value_type` is `CopyInsertable` into `X`, `key_type` is `CopyAssignable`, and `mapped_type` is `CopyAssignable` (for containers having a `mapped_type`)
`T` is `CopyInsertable` | `value_type` is CopyInsertable
`T` shall be `CopyInsertable` | `value_type` shall be CopyInsertable
`T` shall be `MoveInsertable` | `value_type` shall be MoveInsertable
`T` shall be `EmplaceConstructible` | `value_type` shall be EmplaceConstructible
`T` object | `value_type` object

[ Notes to the editor: The above are carefully selected phrases that can be used for global search-and-replace within the specified sections without accidentally making changes to correct uses `T`. ]