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Why is the ctor of optional<T&> explicit?

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#99 6 comments 0 reactions 0 assignees View on GitHub

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Assessment

Difficulty
5/5
Estimated time
Over a week
Newbie friendliness
25/100
Issue type
Feature
Clarity
Mostly clear
Activity status
Stale
Tech stack
cpp

Research direction

Start by locating the constructor template <class U> explicit optional(const optional<U&>& rhs) in Boost.Optional and review why the conversion is explicit. The issue's desired outcome is to determine whether optional<T&> can convert implicitly when the underlying pointer types allow it, including non-const-reference to const-reference conversion.

Written by the indexing model from the issue text.

Description

I mean the ctor template <class U> explicit optional(const optional<U&>& rhs). It doesn't seem to have much sense - optional<T&> is logically a reference and it seems reasonable to allow it to be converted implicitly if the underlying pointer types allow this.
With the current implementation the usage of optional references can be cumbersome, because even the non-const-ref to const-ref conversion has to be explicit.

Dominant language
C++
Stars
60
Forks
75
PR merge metrics
No merged PRs in 30d

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  4. Open a pull request that references the issue number.

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