"constructor must be a structure" for Rune?

[Ethan Gardener <eekee57@fastmail.fm>]

I want to put a literal rune string into a program to test a new function, but get this error:

6c -FTVw test.c
test.c:65 constructor must be a structure
mk: 6c -FTVw test.c  : exit status=rc 1676: 6c 1678: error

test.c lines 64 & 65:
		dcrunestring(fg, Pt(50,350), 
			(Rune){0x2308, 0x2190, 0x2395, 0x2192, 0x230a});

in /amd64/include/u.h:
typedef	uint		Rune;

What am I doing wrong?  Am I doing anything wrong?  Is there a way to pass a literal array like that when a pointer to an array is called for?  I know I can do it by assigning to a variable first, perhaps I should just do that.  It's normally my policy to use temporary variables when lines get long, but strong typing makes it a bit more of a fuss.