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/matrix.m2

@@ -12,11 +12,11 @@ nottosamering := (X,Y) -> (
      else error("expected ",synonym X," and ",synonym Y," for compatible rings"))
 tosamering = (M,N) -> (
      R := ring M; S := ring N;
-     if instance(R,InexactField) then R = ring R;
-     if instance(S,InexactField) then S = ring S;
+     R' := if instance(R,InexactField) ring R else R;
+     S' := if instance(S,InexactField) then ring S else S;
      if R =!= S then (
-	 if isPromotable(R,S) then (promote(M,S),N)
-	 else if isPromotable(S,R) then (M,promote(N,R))
+	 if isPromotable(R',S) then (promote(M,S),N)
+	 else if isPromotable(S',R) then (M,promote(N,R))
 	 else nottosamering(class M,class N)
 	 )
      else (M,N))

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)