fix #3906, prevent promote(CC,RR)

Author: pzinn

M2/Macaulay2/m2/engine.m2

@@ -255,6 +255,7 @@ raw Number := x -> x_((class x).RawRing)
 raw InexactNumber := x -> x_((ring x).RawRing)
 Number _ RawRing := (n,R) -> rawFromNumber(R,n)
 RawRingElement _ RawRing := (x,R) -> rawPromote(R,x)
+raw Constant := raw @@ numeric
 
 RawRingElement == RawRingElement := (x,y) -> x === y
 

M2/Macaulay2/m2/reals.m2

@@ -103,7 +103,9 @@ promote(RawRingElement,RRi') := (x,R) -> new RRi from x
 promote(RawRingElement,CC') := (x,R) -> new CC from x
 promote(RawRingElement,Number) := (x,R) -> new R from x
 promote(RawRingElement,RingElement) := (x,R) -> new R from x
-promote(Number,InexactNumber) := (x,RR) -> promote(x,default RR)
+promote(QQ,RR) :=
+promote(ZZ,RR) := (x,RR) -> promote(x,default RR)
+promote(Number,CC) := (x,CC) -> promote(x,default CC)
 promote(ZZ,RR') := 
 promote(QQ,RR') := 
 promote(RR,RR') := (i,K) -> toRR(K.precision,i)