@Override
        public String pathVariable(PathMappingType type) {
            switch (type) {
                case PARAMETERIZED:
                    if (parentFieldPath != null) {
                        return parentFieldPath;
                    } else {
                        return 'p' + StringUtil.toString(pathVarIndex);
                    }
                case REGEX:
                    // A group name for regex must start with a letter and contain only letters, digits.
                    // parentFieldPath may contain non-alphanumeric characters, so we prepend 'p' to the index.
                    return 'p' + StringUtil.toString(pathVarIndex);
                case GLOB:
                    return StringUtil.toString(pathVarIndex);
            }
            // Should not reach here.
            throw new Error();
        }
Returns whether the specified {@link PathMappingType} is supported by
this {@link PathSegment}.
grpc/src/main/java/com/linecorp/armeria/server/grpc/HttpJsonTranscodingPathParser.java