don't store self in values

Author: MasonProtter

src/variables.jl

@@ -197,7 +197,9 @@ function _varmap_to_vars(varmap::Dict, varlist; defaults = Dict(), check = false
     for var in varlist
         var = unwrap(var)
         val = unwrap(fixpoint_sub(var, varmap; operator = Symbolics.Operator))
-        values[var] = val
+        if !isequal(val, var)
+            values[var] = val
+        end
     end
     missingvars = setdiff(varlist, collect(keys(values)))
     check && (isempty(missingvars) || throw(MissingVariablesError(missingvars)))