Please add an analogue of emplace

[adamemerson]

@Naios

Being able to construct an object rather than having to copy/move one in would be very useful, particularly for objects that may be expensive to construct, or (for unique_function) immovable objects. (After all, if they're on the heap we can still move the pointer.)

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Commit Hash

7cd9537

Expected Behavior

Being able to type something like
fun.emplace<Foo>(something, something)

Actual Behavior

Needing to type fun = Foo(something, something)

Steps to Reproduce

N/A

Your Environment

• OS: Fedora 30
• Compiler and version: GCC 9.2.1
• Standard library (if non default): libstdc++-9.2.1

[Naios]

This sounds like a promising feature.
Probably I will implement it in the future.