Nuitka: Error handling immediately-invoked lambda expression with default parameters

[ajkerrigan]

I was testing Nuitka on a few packages, and ran into an issue with a specific lambda construct. I've been able to reproduce it in multiple Nuitka versions, most recently 0.6.5rc4 built off the develop branch. The minimal example is this statement:

(lambda x='hi': print(x))()

Nuitka handles these similar statements without a problem:

(lambda x: print(x))('hi')
func = (lambda x='hi': print(x))
func()
(lambda: print('hi'))()

So as far as I can tell this issue only arises from lambda expressions which:

1. Provide a default parameter value
2. Are invoked immediately with no arguments

This is admittedly an edge case, and a weird construct to see in Python code. That said, it runs in all Python 2/3 versions I've tested. With Nuitka, it throws this:

Problem with statement at test.py:7:
-> (lambda x='hi': print(x))()

Nuitka:INFO:Interrupted while working on '<Node 'PYTHON_MAIN_MODULE' with {'filename': 'test.py', 'main_added': False, 'mode': 'compiled'}>'.
Traceback (most recent call last):
  File "/Users/akerrigan/code/Nuitka/nuitka/__main__.py", line 184, in <module>
    main()
  File "/Users/akerrigan/code/Nuitka/nuitka/__main__.py", line 177, in main
    MainControl.main()
  File "/Users/akerrigan/code/Nuitka/nuitka/MainControl.py", line 746, in main
    main_module = createNodeTree(filename=filename)
  File "/Users/akerrigan/code/Nuitka/nuitka/MainControl.py", line 141, in createNodeTree
    Optimization.optimize(main_module.getOutputFilename())
  File "/Users/akerrigan/code/Nuitka/nuitka/optimizations/Optimization.py", line 542, in optimize
    makeOptimizationPass(initial_pass=True)
  File "/Users/akerrigan/code/Nuitka/nuitka/optimizations/Optimization.py", line 456, in makeOptimizationPass
    changed = optimizeModule(current_module)
  File "/Users/akerrigan/code/Nuitka/nuitka/optimizations/Optimization.py", line 167, in optimizeModule
    changed = optimizeCompiledPythonModule(module)
  File "/Users/akerrigan/code/Nuitka/nuitka/optimizations/Optimization.py", line 100, in optimizeCompiledPythonModule
    module.computeModule()
  File "/Users/akerrigan/code/Nuitka/nuitka/nodes/ModuleNodes.py", line 489, in computeModule
    trace_collection=self.trace_collection
  File "/Users/akerrigan/code/Nuitka/nuitka/nodes/StatementNodes.py", line 165, in computeStatementsSequence
    new_statement = statement.computeStatementsSequence(trace_collection)
  File "/Users/akerrigan/code/Nuitka/nuitka/nodes/FrameNodes.py", line 182, in computeStatementsSequence
    new_statement = trace_collection.onStatement(statement=statement)
  File "/Users/akerrigan/code/Nuitka/nuitka/optimizations/TraceCollections.py", line 550, in onStatement
    new_statement, change_tags, change_desc = statement.computeStatement(self)
  File "/Users/akerrigan/code/Nuitka/nuitka/nodes/StatementNodes.py", line 229, in computeStatement
    trace_collection.onExpression(expression=self.getExpression())
  File "/Users/akerrigan/code/Nuitka/nuitka/optimizations/TraceCollections.py", line 531, in onExpression
    r = expression.computeExpressionRaw(trace_collection=self)
  File "/Users/akerrigan/code/Nuitka/nuitka/nodes/ExpressionBases.py", line 1005, in computeExpressionRaw
    return self.computeExpression(trace_collection=trace_collection)
  File "/Users/akerrigan/code/Nuitka/nuitka/nodes/CallNodes.py", line 172, in computeExpression
    trace_collection=trace_collection,
  File "/Users/akerrigan/code/Nuitka/nuitka/nodes/FunctionNodes.py", line 708, in computeExpressionCall
    function=self, values=values, source_ref=call_node.getSourceReference()
  File "/Users/akerrigan/code/Nuitka/nuitka/nodes/FunctionNodes.py", line 861, in __init__
    source_ref=source_ref,
  File "/Users/akerrigan/code/Nuitka/nuitka/nodes/ExpressionBases.py", line 974, in __init__
    ChildrenHavingMixin.__init__(self, values=values)
  File "/Users/akerrigan/code/Nuitka/nuitka/nodes/NodeBases.py", line 526, in __init__
    assert None not in value, name
AssertionError: values

python -m nuitka --version output:

0.6.5rc4
Python: 3.7.3 (default, Mar 27 2019, 09:23:32)
Executable: /usr/local/opt/python/bin/python3.7
OS: Darwin
Arch: x86_64

Installation methods: Python 3.7 via homebrew, Nuitka via pip

[kayhayen]

Thanks for your report, this is of course a very valid bug report. As the result of optimization, this ought to be also possibe, but I recall that I disabled some for functions with defaults, which avoids this. I will take care of this to work though. I think defaults ought to be very easy anyway for function inlining, as they can be assigned first, and only then arguments.

[kayhayen]

There is a workaround on factory branch, effectively disable the optimization for cases where default values are used. The whole optimization needs more work there, few cases are currently dealt with only.

[ajkerrigan]

Neat, thank you! Following the effects of the change helps me understand the flow a little better too :).

[kayhayen]

Released as part of 0.6.6, need to check back on this how to make the optimization work generally