revert, splitting off params-related changes

src/dsl.jl

@@ -348,12 +348,6 @@ function make_reaction_system(ex::Expr; name = :(gensym(:ReactionSystem)))
         variables)))
     species_extracted, parameters_extracted = extract_species_and_parameters!(reactions, declared_syms)
 
-    # Checks that all the symbols in the equation are declared. 
-    eq_syms = extract_syms_eq(equations, union(declared_syms, species_extracted, parameters_extracted))
-    if !isempty(eq_syms)
-        error("Symbols in equations must be explicitly defined using @variable, @species, or @parameter within the @reaction_network input.")
-    end
-
     species = vcat(species_declared, species_extracted)
     parameters = vcat(parameters_declared, parameters_extracted)
 
@@ -534,16 +528,6 @@ function extract_species_and_parameters!(reactions, excluded_syms)
     collect(species), collect(parameters)
 end
 
-# Find undeclared symbols in the RHS of the equations. 
-function extract_syms_eq(equations, excluded_syms)
-    syms = OrderedSet{Union{Symbol, Expr}}()
-    for eq in equations
-        add_syms_from_expr!(syms, eq.args[3], excluded_syms)
-    end
-
-    collect(syms)
-end
-
 # Function called by extract_species_and_parameters!, recursively loops through an
 # expression and find symbols (adding them to the push_symbols vector).
 function add_syms_from_expr!(push_symbols::AbstractSet, rateex::ExprValues, excluded_syms)

test/dsl/dsl_options.jl

@@ -166,10 +166,6 @@ let
     @species A(t)
     @test isequal(equations(rn)[1], D(A) ~ 2*A*t)
 
-    # Tests that error is declared. 
-    @test_throws LoadError @eval @reaction_network begin
-        @equations D(A) ~ hill(A, v, K, n)
-    end
 
     # Test Catalyst function
     rn2 = @reaction_network begin