Fix metadata prop

`-(-x)` will simplify back to `x` and setting metadata on the simplified result
is illegal.

src/types.jl

@@ -553,16 +553,23 @@ function basicsymbolic(f, args, stype, metadata)
         T = _promote_symtype(f, args)
     end
     if T <: LiteralReal
-        Term{T}(f, args, metadata=metadata)
-    elseif T <: Number && (f in (+, *) || (f in (/, ^) && length(args) == 2)) && all(x->symtype(x) <: Number, args)
-        res = f(args...)
-        if res isa Symbolic
-            @set! res.metadata = metadata
+        @goto FALLBACK
+    elseif all(x->symtype(x) <: Number, args)
+        if f === (+)
+            Add(T, makeadd(1, 0, args...)...; metadata=metadata)
+        elseif f == (*)
+            Mul(T, makemul(1, args...)...; metadata=metadata)
+        elseif f == (/)
+            @assert length(args) == 2
+            Div{T}(args...; metadata=metadata)
+        elseif f == (^) && length(args) == 2
+            Pow{T}(makepow(args...)...; metadata=metadata)
+        else
+            @goto FALLBACK
         end
-        return res
-    else
-        Term{T}(f, args, metadata=metadata)
     end
+    @label FALLBACK
+    Term{T}(f, args, metadata=metadata)
 end
 
 ###