Serialization of psyir tree

[schreiberx]

A serialization/deepcopy of a psyir tree is currently not possible.
Using copy.deepcopy on certain files leads, e.g., to this error message:

  File "[...]/src/psyclone/psyir/nodes/node.py", line 162, in _check_is_orphan
    raise GenerationError(
psyclone.errors.GenerationError: Generation Error: Item 'Reference' can't be added as child of 'Assignment' because it is not an orphan. It already has a 'Assignment' as a parent.

Allowing for this would have several advantages, e.g.,

• The PsyIR can be cached to persistent storage and read back if required
• The PsyIR could be deep-copied to work independently on it.

[arporter]

A deep copy of the tree is possible and in fact is performed by the Fortran backend prior to code generation (because it has to 'flatten' the nested symbol tables). node.copy() does this.

[schreiberx]

Thanks for the clarification - I wasn't aware of this. Then it's just about the "pickle" problem.