c++: EH and partially constructed aggr temp [PR66139]

c++: EH and partially constructed aggr temp [PR66139]

Now that PR94041 is fixed, I can return to addressing PR66139, missing
cleanups for partially constructed aggregate temporaries.  My previous
approach of calling split_nonconstant_init in cp_gimplify_init_expr broke
because gimplification is too late to be introducing destructor calls.  So
instead I now call it under cp_fold_function, just before cp_genericize;
doing it from cp_genericize itself ran into trouble with the rewriting of
invisible references.

So now the prediction in cp_gimplify_expr that cp_gimplify_init_expr
might need to replace references to TARGET_EXPR_SLOT within
TARGET_EXPR_INITIAL has come to pass.  constexpr.c already had the simple
search-and-replace tree walk I needed, but it needed to be fixed to actually
replace all occurrences instead of just the first one.

Handling of VEC_INIT_EXPR at gimplify time had similar issues that we worked
around with build_vec_init_elt, so I'm moving that to cp_fold_function as
well.  But it seems that build_vec_init_elt is still useful for setting the
VEC_INIT_EXPR_IS_CONSTEXPR flag, so I'm leaving it alone.

This also fixes 52320, because build_aggr_init of each X from build_vec_init
builds an INIT_EXPR rather than call split_nonconstant_init at that point,
and now that INIT_EXPR gets split later.

	PR c++/66139
	PR c++/52320

gcc/cp/ChangeLog:

	* constexpr.c (replace_decl): Rename from replace_result_decl.
	* cp-tree.h (replace_decl): Declare it.
	* cp-gimplify.c (cp_gimplify_init_expr): Call it.
	(cp_gimplify_expr): Don't handle VEC_INIT_EXPR.
	(cp_genericize_init, cp_genericize_init_expr)
	(cp_genericize_target_expr): New.
	(cp_fold_r): Call them.
	* tree.c (build_array_copy): Add a TARGET_EXPR.
	* typeck2.c (digest_init_r): Look through a TARGET_EXPR.

gcc/testsuite/ChangeLog:

	* g++.dg/cpp0x/initlist116.C: New test.
	* g++.dg/cpp0x/initlist117.C: New test.
	* g++.dg/cpp0x/lambda/lambda-eh.C: New test.
	* g++.dg/eh/aggregate1.C: New test.