private static boolean isAssignable()

in src/main/java/org/apache/commons/lang3/reflect/TypeUtils.java [1123:1183]
35 lines of code
15 McCabe index (conditional complexity)

    private static boolean isAssignable(final Type type, final ParameterizedType toParameterizedType, final Map<TypeVariable<?>, Type> typeVarAssigns) {
        if (type == null) {
            return true;
        }

        // only a null type can be assigned to null type which
        // would have cause the previous to return true
        if (toParameterizedType == null) {
            return false;
        }

        // cannot cast an array type to a parameterized type.
        if (type instanceof GenericArrayType) {
            return false;
        }

        // all types are assignable to themselves
        if (toParameterizedType.equals(type)) {
            return true;
        }

        // get the target type's raw type
        final Class<?> toClass = getRawType(toParameterizedType);
        // get the subject type's type arguments including owner type arguments
        // and supertype arguments up to and including the target class.
        final Map<TypeVariable<?>, Type> fromTypeVarAssigns = getTypeArguments(type, toClass, null);

        // null means the two types are not compatible
        if (fromTypeVarAssigns == null) {
            return false;
        }

        // compatible types, but there's no type arguments. this is equivalent
        // to comparing Map< ?, ? > to Map, and raw types are always assignable
        // to parameterized types.
        if (fromTypeVarAssigns.isEmpty()) {
            return true;
        }

        // get the target type's type arguments including owner type arguments
        final Map<TypeVariable<?>, Type> toTypeVarAssigns = getTypeArguments(toParameterizedType, toClass, typeVarAssigns);

        // now to check each type argument
        for (final TypeVariable<?> var : toTypeVarAssigns.keySet()) {
            final Type toTypeArg = unrollVariableAssignments(var, toTypeVarAssigns);
            final Type fromTypeArg = unrollVariableAssignments(var, fromTypeVarAssigns);

            if (toTypeArg == null && fromTypeArg instanceof Class) {
                continue;
            }

            // parameters must either be absent from the subject type, within
            // the bounds of the wildcard type, or be an exact match to the
            // parameters of the target type.
            if (fromTypeArg != null && toTypeArg != null && !toTypeArg.equals(fromTypeArg)
                    && !(toTypeArg instanceof WildcardType && isAssignable(fromTypeArg, toTypeArg, typeVarAssigns))) {
                return false;
            }
        }
        return true;
    }