MMD matching does not match 'scalar' with primitive types

[Austin_Hastings]

When MMD is matching a primitive (int, float, str) argument, it knows about autoboxing and supplies a 1-point manhattan penalty for requiring autoboxing into one of the Scalar types (Integer, Float, etc.)

But MMD does not appear to know about 'scalar' as a superclass of the Scalar types, since it is handing the autoboxing specially. As a result, this code misbehaves:

.sub 'foo' :multi(['scalar'])
	.param pmc x
	say "Scalar!"
.end

.sub 'foo' :multi()
	.param pmc x
	$I0 = isa x, 'scalar'
	print "Scalar? "
	say $I0
.end

.sub 'main' :main
	'foo'(1)
	$P0 = box 1
	'foo'($P0)
.end

While foo(1) is not considered a scalar, foo(box(1)) is, which is confusing. (And wrong, IMO.) I suggest recoding the special-case processing for primitive types in manhattan-distance so autobox is considered a "step" in the MRO below 'scalar' for Scalar types.

That is, the MRO for 'Integer' would be {Integer}->scalar->integer. Alternatively, special-casing the 'scalar' PMC type as an extra builtin would work, but smells like a dead fish.

[whiteknight]

Fixed in r45274. I've added your test case above as proof.