Fix typo

Author: YingboMa

src/systems/discrete_system/discrete_system.jl

@@ -103,7 +103,8 @@ struct DiscreteSystem <: AbstractTimeDependentSystem
             check_parameters(ps, iv)
         end
         if checks == true || (checks & CheckUnits) > 0
-            all_dimensionless([dvs; ps; iv; ctrls]) || check_units(discreteEqs)
+            u = __get_unit_type(dvs, ps, iv, ctrls)
+            check_units(u, discreteEqs)
         end
         new(tag, discreteEqs, iv, dvs, ps, tspan, var_to_name, ctrls, observed, name,
             systems,

src/systems/pde/pdesystem.jl

@@ -99,7 +99,7 @@ struct PDESystem <: ModelingToolkit.AbstractMultivariateSystem
             name)
         if checks == true || (checks & CheckUnits) > 0
             u = __get_unit_type(dvs, ivs, ps)
-            check_units(u, deqs)
+            check_units(u, eqs)
         end
 
         eqs = eqs isa Vector ? eqs : [eqs]

src/systems/unit_check.jl

@@ -7,7 +7,16 @@ end
 
 check_units(::Nothing, _...) = true
 
-__get_literal_unit(x) = getmetadata(x, VariableUnit, nothing)
+function __get_literal_unit(x)
+    if x isa Pair
+        x = x[1]
+    end
+    if !(x isa Union{Num, Symbolic})
+        return nothing
+    end
+    v = value(x)
+    getmetadata(v, VariableUnit, nothing)
+end
 function __get_scalar_unit_type(v)
     u = __get_literal_unit(v)
     if u isa DQ.AbstractQuantity