8 Statements [stmt.stmt]

8.7 Jump statements [stmt.jump]

8.7.5 The co_return statement [stmt.return.coroutine]

A co_return statement transfers control to the caller or resumer of a coroutine ([dcl.fct.def.coroutine]).
A coroutine shall not enclose a return statement ([stmt.return]).
[Note 1: 
For this determination, it is irrelevant whether the return statement is enclosed by a discarded statement ([stmt.if]).
— end note]
The expr-or-braced-init-list of a co_return statement is called its operand.
Let p be an lvalue naming the coroutine promise object ([dcl.fct.def.coroutine]).
A co_return statement is equivalent to:
{ S; goto final-suspend; }
where final-suspend is the exposition-only label defined in [dcl.fct.def.coroutine] and S is defined as follows:
If a search for the name return_void in the scope of the promise type finds any declarations, flowing off the end of a coroutine's function-body is equivalent to a co_return with no operand; otherwise flowing off the end of a coroutine's function-body results in undefined behavior.