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Subject: Re: [boost] [proto] subscript_wrapper and templated operator[]
From: Eric Niebler (eric_at_[hidden])
Date: 2009-01-15 00:35:27

Eric Niebler wrote:
> David Deakins wrote:
>> While using proto with some classes that have a templated operator[]
>> on VC8 and VC9, I have run into a '2 overloads have similar
>> conversions' ambiguity error (C2666). The problem seems to be with
>> subscript_wrapper in detail/decltype.hpp, where neither the templated
>> operator[] from the original class nor the fallback 'any
>> operator[](any)' function in subscript_wrapper have priority. Any
>> thoughts on how to tweak subscript_wrapper so that the 'any
>> operator[](any)' function looks like a worse match than the templated
>> operator[] and thus prevents the ambiguity? I attached a small test
>> case that reproduces the problem. Also, for reference, I am using the
>> proto code from the release branch as of a couple days ago (~12 Jan
>> 2009).
> I can reproduce this error with msvc but not with gcc. I think this may
> be a msvc bug. Sadly, I don't know of a work-around. I'll give the issue
> some thought.
> Thanks for the report.

I've filed this bug with microsoft:

I've also committed a work-around to trunk. If the test results look
good, I should have this merged to release in time for 1.38.


Eric Niebler
BoostPro Computing

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