Make Zero be a subtype of Number

src/rewrite.jl

@@ -28,7 +28,7 @@ macro rewrite(args...)
     return rewrite_and_return(args[1]; move_factors_into_sums = args[2].args[2])
 end
 
-struct Zero end
+struct Zero <: Number end
 
 # This method is called in various `promote_operation_fallback` methods if one
 # of the arguments is `::Zero`.
@@ -59,13 +59,19 @@ broadcast!!(::typeof(add_mul), ::Zero, x, y) = x * y
 
 # Needed in `@rewrite(1 .+ sum(1 for i in 1:0) * 1^2)`
 Base.:*(z::Zero, ::Any) = z
+Base.:*(z::Zero, ::Number) = z
 Base.:*(::Any, z::Zero) = z
+Base.:*(::Number, z::Zero) = z
 Base.:*(z::Zero, ::Zero) = z
 Base.:+(::Zero, x::Any) = x
+Base.:+(::Zero, x::Number) = x
 Base.:+(x::Any, ::Zero) = x
+Base.:+(x::Number, ::Zero) = x
 Base.:+(z::Zero, ::Zero) = z
 Base.:-(::Zero, x::Any) = -x
+Base.:-(::Zero, x::Number) = -x
 Base.:-(x::Any, ::Zero) = x
+Base.:-(x::Number, ::Zero) = x
 Base.:-(z::Zero, ::Zero) = z
 Base.:-(z::Zero) = z
 Base.:+(z::Zero) = z
@@ -79,6 +85,14 @@ function Base.:/(z::Zero, x::Any)
     end
 end
 
+function Base.:/(z::Zero, x::Number)
+    if iszero(x)
+        throw(DivideError())
+    else
+        return z
+    end
+end
+
 # These methods are used to provide an efficient implementation for the common
 # case like `x^2 * sum(f for i in 1:0)`, which lowers to
 # `_MA.operate!!(*, x^2, _MA.Zero())`. We don't need the method with reversed