TypeConverter.converter_for() was changed to accept a TypeInfo object instead of a concrete types or their string aliases as part of #4711 that added support for specifying types as strings like 'list[int]' and 'int | float'. It would have been strange if TypeConnverter would handle parsing such strings in addition to doing actual conversion. Instead of that, we moved all logic related to parsing and validating types to the TypeInfo class that was earlier used only by Libdoc. Now responsibilities are clear and TypeConverter only needs to care about actual type conversion.

The TypeConverter isn't part of the public API, but it's nevertheless bad that the change breaks Browser and apparently also the RobotCode plugin. Because conversion functionality clearly is used also externally, the real fix is exposing it as a public, stable API. I think it's best to do it via the TypeInfo class that already has a convert method and can be used like this:

>>> from robot.running import TypeInfo
>>> info = TypeInfo.from_type_hint(int)
>>> info.convert('42')
42
>>> info = TypeInfo.from_type_hint('int | float')
>>> info.convert('3.14')

Making this a public API basically requires the following:

• Expose TypeInfo via robot.api.
• Go trough its public methods to see is there anything to be changed before making it public (easier now than afterwards).
• Add docstrings.
• Add unit tests for the exposed functionality.
• Mention TypeInfo.convert in the User Guide.

We could also consider changing TypeConverter.converter_for so that it would handle plain types as earlier. Due to cyclic module dependencies that would be a bit annoying, though, and there seem to be some other changes to TypeConverter that would also need to be reverted or worked around. I'm not sure is that worth the effort, because affected libraries and tools should nevertheless switch to the public API at some point.

TypeInfo has now been exposed via robot.api, its documentation has been enhanced, and some bugs with it fixed. Commit 383d432 contains tests that can be used as examples how the API works also in a bit more advanced cases.

Changing TypeConverter so that it would be compatible with RF < 7 would be somewhat big task and would also require changing some of its functions so that they wouldn't be as convenient to use internally as nowadays. Now that we have the public API available, I don't consider that worth the effort. We we can return to that later if needed, but now I consider this issue done.