[C++ PATCH] Partially fix designated-initializer-list handling in overload resolution (PR c++/71446)

[Jason Merrill]

On 3/1/19 1:53 PM, Jakub Jelinek wrote:
> Hi!
> 
> http://eel.is/c++draft/dcl.init.list#3.1 says that for designated
> initializers only aggregate conversion should be performed,
> while our current code would happily try std::initializer_list
> initialization, or (as extension) complex initialization, or scalar
> initialization if there is { .foobarbaz = 1 }.
> 
> Unfortunately, e.g. reshape_init seems to add ce->index values, so checking
> whether ce->index is NULL for all elements of the CONSTRUCTOR doesn't seem
> to work.
> 
> This patch instead remembers in a bit on the CONSTRUCTOR whether there
> were any user designators.  Bootstrapped/regtested on x86_64-linux and
> i686-linux, ok for trunk?

OK, thanks.

> Note, this is just a partial fix for the PR, for the second part (making
> struct S { void *a; int b; };
> void foo (S);
> ... foo ({.b = 1}) work), I'm afraid I don't really understand what the C++
> standard wants to say in http://eel.is/c++draft/over.ics.list#2 and what
> build_aggr_conv should do, such that the cpp2a/desig{4,6}.C testcases taken
> from the standard as well as the desig11.C in the earlier version of the
> patch (would need to be renamed to desig12.C) can pass.

It seems to me that for designated initializers, we should make sure 
that all the designators match fields, and otherwise check 
convertibility like build_aggr_conv already does.

Jason