escaped newline in macro expansion in command line

[Humm]

(I’m not subscribed to the list.)

Consider the Makefile:
        .POSIX:
        M = word
        all:
                echo ${M:word=a\
                b}

I believe, as the escaped newline is in a command line, the expected 
behavior is to let the macro expand to it, and thus to run the command

        echo a\
        b

with output `ab`.  The actual output is `a b`.

Tested with gmake 4.3 (Alpine Linux) (same with bmake).

--
Humm