Function checkTypeParameters

test/fixtures/snapshot/typescript.js:83956–83981

* Check each type parameter and check that type parameters have no duplicate type parameter declarations

(typeParameterDeclarations)

         * Check each type parameter and check that type parameters have no duplicate type parameter declarations
         */
        function checkTypeParameters(typeParameterDeclarations) {
            var seenDefault = false;
            if (typeParameterDeclarations) {
                for (var i = 0; i < typeParameterDeclarations.length; i++) {
                    var node = typeParameterDeclarations[i];
                    checkTypeParameter(node);
                    addLazyDiagnostic(createCheckTypeParameterDiagnostic(node, i));
                }
            }
            function createCheckTypeParameterDiagnostic(node, i) {
                return function () {
                    if (node.default) {
                        seenDefault = true;
                        checkTypeParametersNotReferenced(node.default, typeParameterDeclarations, i);
                    }
                    else if (seenDefault) {
                        error(node, ts.Diagnostics.Required_type_parameters_may_not_follow_optional_type_parameters);
                    }
                    for (var j = 0; j < i; j++) {
                        if (typeParameterDeclarations[j].symbol === node.symbol) {
                            error(node.name, ts.Diagnostics.Duplicate_identifier_0, ts.declarationNameToString(node.name));
                        }
                    }
                };
            }
        }
        /** Check that type parameter defaults only reference previously declared type parameters */
        function checkTypeParametersNotReferenced(root, typeParameters, index) {
            visit(root);