[perl #131488] [BUG] .map as return value of sunk Promise doesn't get sunk

[via RT]

# New Ticket Created by  Zoffix Znet 
# Please include the string:  [perl #131488]
# in the subject line of all future correspondence about this issue. 
# <URL: https://rt.perl.org/Ticket/Display.html?id=131488 >


Normally, if you sink a .map, it gets eagerly evaluated:

    <Zoffix__> m: <a b c>.map: &say
    <camelia> rakudo-moar ef9872: OUTPUT: «a␤b␤c␤»
    <Zoffix__> m: for ^1 { <a b c>.map: &say; $ = 42 }
    <camelia> rakudo-moar ef9872: OUTPUT: «a␤b␤c␤»

However, this doesn't happen when the map is the last value of
a sunk Promise:

    <Zoffix__> m: start { <a b c>.map: &say }; sleep 2;
    <camelia> rakudo-moar ef9872: ( no output )

Workarounds:

    <Zoffix__> m: start { @ = <a b c>.map: &say }; sleep 2;
    <camelia> rakudo-moar ef9872: OUTPUT: «a␤b␤c␤»
    <Zoffix__> m: start { <a b c>.map: &say; 42 }; sleep 2;
    <camelia> rakudo-moar ef9872: OUTPUT: «a␤b␤c␤»
    <Zoffix__> m: await start { <a b c>.map: &say; 42 }
    <camelia> rakudo-moar ef9872: OUTPUT: «a␤b␤c␤»
    <Zoffix__> m: @ =  start { <a b c>.map: &say; 42 }; sleep 2
    <camelia> rakudo-moar ef9872: OUTPUT: «a␤b␤c␤»