AssociationMap loses definition

Bug introduced in 10.0.0 and fixed in 10.1.0.

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I’m facing a strange behavior of AssociationMap.

With a fresh Kernel session:

In[1]:= Definition@AssociationMap
Out[1]= Attributes[AssociationMap] = {Protected, ReadProtected}

After loading a package I’m developing, running some test against this package I sometimes end up with:

In[113]:= Definition@AssociationMap
Out[113]= Null

and AssociationMap no more evaluate anything.

I didn’t ovveride intentionally AssociationMap, and, because it is Protected, I suppose I cannot have ovverride accidentally.

Any help is appreciated.

UPDATE

After a lot of research I found the problem is related with the following minimal code.

Timing@<||>

AssociationMap[f, {a, b, c}]

The problem appear when putting the two expression in two different cells evaluating the two cells sequentially in a fresh Mathematica session. The problem doesn’t appear if:

1. the two expression are evaluated at once, using “Evaluate Notebook” or putting the code in a single cell;
2. or one suppress the Timing@;
3. or one add another AssociationMap cell before the two and evaluate this new cell before the two others.

All tests done with Mathematica v10.0.1.0 under non-Admin account of Windows v8.1 x64.

UPDATE 2

Wolfram Research confirmed this is a bug:

Hi Andrea, Thanks a lot for sending us the feedback. This is indeed a
serious issue and I’ve filed an incidence report on that. I’ve added
your information to the report to make sure that you will be informed
for any updates on this topic. Many thanks again. Regards,

[…] Wolfram Technology Engineer
Wolfram Research, Inc.

Needs["GeneralUtilities`"]