Currently, before Mysql 5.7, there was no way to get information from a temporary table (session table) using the information_schema. Now with Mysql 5.7 there is a new table named 'INNODB_TEMP_TABLE_INFO'.
According to documentation: https://mariadb.com/kb/en/mariadb/information-schema-temp_tables_info-table/
There was a table names 'TEMP_TABLES_INFO' which was introduced in 10.2.2 but removed in 10.2.4. I think maybe you're thinking to implement another solution which can cover all the needs.
The example shows how to use 'INNODB_TEMP_TABLE_INFO' but it doesn't exist
BTW that mysql's implementation is very limited, there no way you can query against temporary tables fields using a SELECT statement.
Summary from comments
This is what will be implemented:
1. list session ([#1]) temporary tables in I_S.TABLES with column TABLE_TYPE="TEMPORARY"([#2])
2. by design they will not be listed in I_S.COLUMNS and other I_S tables ([#3]). This MDEV will not implement changes related to the temporary table and I_S.COLUMNS .
3. issue a warning on CREATE if a new temp table shadows non-temp table ([#4]), not vice-versa.
[#1] - No need for connection_id column to list all threads (MDEV-15623 should do that).
[#2] - Standard prescribes "GLOBAL TEMPORARY" or "LOCAL TEMPORARY" but our tables are neither, so let's just use "TEMPORARY".
[#3] - I_S.COLUMNS, I_S.STATISTICS, I_S.TABLE_CONSTRAINTS, I_S.KEY_COLUMN_USAGE, I_S.PARTITIONS, I_S.FILES ( ? ), I_S.CHECK_CONSTRAINTS. Comment.
MariaDB should be also able to show their fields in INFORMATION_SCHEMA.COLUMNS, and any other metadata associated to a normal table. But at least, implementing INFORMATION_SCHEMA.TABLES and INFORMATION_SCHEMA.COLUMNS will help a lot.
[#4] - Based on comment