[c++] describe reasons for function template overload resolution failure

On Fri, May 27, 2011 at 03:14:59PM -0400, Jason Merrill wrote:
> On 05/26/2011 03:04 PM, Nathan Froyd wrote:
> 
> Thanks, this is looking pretty close.  A few more issues, mostly to
> do with wording of the diagnostics:

Thanks for all your feedback during the development of the patch.

> >       converted_args
> >        = (coerce_template_parms (tparms, explicit_targs, NULL_TREE, tf_none,
> >                                  /*require_all_args=*/false,
> >                                  /*use_default_args=*/false));
> >       if (converted_args == error_mark_node)
> >-       return 1;
> >+       {
> >+         /* Run it for diagnostics.  */
> >+         if (explain_p)
> >+           coerce_template_parms (tparms, explicit_targs, NULL_TREE,
> >+                                  tf_warning_or_error,
> >+                                  /*require_all_args=*/false,
> >+                                  /*use_default_args=*/false);
> >+         return 1;
> >+       }
> 
> Instead of calling it twice, pass different tsubst_flags depending
> on explain_p.  And the same for all the other places where you call
> a function again with tf_warning_or_error.

I knew there must have been a better way to do this. =/

I think I've addressed everything in the patch below except for:

> >+  /* FIXME: Should we pass in unification information and then use that
> >+     to elaborate on the error messages below?  */
> 
> Just pass in explain_p = true, and then we shouldn't need the
> "unable to deduce" message here.

I tried this, but for the few examples in the testsuite where it fires,
I thought the error messages were more confusing, so I left this as-is
and removed the FIXME.

Tested as before.

-Nathan

gcc/cp/
	PR c++/45329
	PR c++/48934
        * cp-tree.h (fn_type_unification): Add `bool' parameter.
        * pt.c (enum template_base_result): Define.
	(unify_success, unify_unknown): Define.
	(unify_parameter_deduction_failure): Define.
        (unify_invalid, unify_cv_qual_mismatch, unify_type_mismatch): Define.
        (unify_parameter_pack_mismatch): Define.
        (unify_parameter_pack_inconsistent): Define.
        (unify_ptrmem_cst_mismatch, unify_vla_arg): Define.
        (unify_expression_unequal, unify_inconsistency): Define.
	(unify_method_type_error, unify_arity): Likewise.
        (unify_too_many_parameters, unify_too_few_parameters): Define.
        (unify_arg_conversion, unify_no_common_base): Define.
        (unify_illformed_ptrmem_cst_expr): Define.
	(unify_substitution_failure): Define.
	(unify_inconsistent_template_template_parameters): Define.
	(unify_template_deduction_failure): Define.
	(unify_template_parameter_mismatch): Define.
	(unify_template_argument_mismatch): Define.
	(unify_overload_resolution_failure): Define.
	(comp_template_args_with_info): New function, split out from...
	(comp_template_args): ...here.  Call it.
	(deduction_tsubst_fntype): Add `complain' parameter'.  Pass it
	to tsubst.
        (unify): Add `explain_p' parameter.  Pass to all relevant calls.
	Call above status functions when appropriate.
        (resolve_overloaded_unification, try_one_overload): Likewise.
        (type_unification, type_unification_real): Likewise.
        (unify_pack_expansion): Likewise.
        (get_template_base, try_class_unification): Likewise.
        (get_bindings, more_specialized_fn): Pass false to unification
	calls.
        (get_class_bindings, do_auto_deduction): Likewise.
        (convert_nontype_argument): Likewise.
	(fn_type_unification): Likewise.  Pass tf_warning_or_error if
	explain_p.
	(get_template_base): Add `explain_p' parameter and pass it to
	try_class_unification.  Return an enum template_base_result.
        * class.c (resolve_address_of_overloaded_function): Pass false to
	fn_type_unification.
        * call.c (enum rejection_reason_code): Add new codes.
        (struct rejection_reason): Add template_unification field.
	Add template_instantiation field.
        (template_unification_rejection): Define.
        (template_instantiation_rejection): Define.
        (invalid_copy_with_fn_template_rejection): Define.
        (add_template_candidate): Pass false to unify.
        Provide more rejection reasons when possible.
        (print_template_unification_rejection): Define.
        (print_arity_rejection): Define, split out from...
        (print_z_candidate): ...here.  Add cases for new rejection
	reasons.

gcc/testsuite/
	PR c++/45329
	PR c++/48934
	* g++.dg/cpp0x/lambda/lambda-ice2.C: Adjust.
	* g++.dg/cpp0x/nullptr15.C: Adjust.
	* g++.dg/cpp0x/pr31431-2.C: Adjust.
	* g++.dg/cpp0x/pr31431.C: Adjust.
	* g++.dg/cpp0x/pr31434.C: Adjust.
	* g++.dg/cpp0x/sfinae11.C: Adjust
	* g++.dg/cpp0x/temp_default2.C: Adjust.
	* g++.dg/cpp0x/trailing4.C: Adjust.
	* g++.dg/cpp0x/variadic-ex3.C: Adjust.
	* g++.dg/cpp0x/variadic-ex4.C: Adjust.
	* g++.dg/cpp0x/variadic105.C: Adjust.
	* g++.dg/cpp0x/vt-37737-2.C: Adjust.
	* g++.dg/ext/vla2.C: Adjust.
	* g++.dg/other/ptrmem10.C: Adjust.
	* g++.dg/other/ptrmem11.C: Adjust.
	* g++.dg/overload/unknown1.C: Adjust.
	* g++.dg/template/conv11.C: Adjust.
	* g++.dg/template/dependent-expr5.C: Adjust.
	* g++.dg/template/friend.C: Adjust.
	* g++.dg/template/incomplete2.C: Adjust.
	* g++.dg/template/local4.C: Adjust.
	* g++.dg/template/local6.C: Adjust.
	* g++.dg/template/operator9.C: Adjust.
	* g++.dg/template/ttp25.C: Adjust.
	* g++.dg/template/unify10.C: Adjust.
	* g++.dg/template/unify11.C: Adjust.
	* g++.dg/template/unify6.C: Adjust.
	* g++.dg/template/unify9.C: Adjust.
	* g++.dg/template/varmod1.C: Adjust.
	* g++.old-deja/g++.brendan/crash56.C: Adjust.
	* g++.old-deja/g++.pt/crash28.C: Adjust.
	* g++.old-deja/g++.pt/explicit41.C: Adjust.
	* g++.old-deja/g++.pt/explicit77.C: Adjust.
	* g++.old-deja/g++.pt/expr2.C: Adjust.
	* g++.old-deja/g++.pt/ptrmem6.C: Adjust.
	* g++.old-deja/g++.pt/spec5.C: Adjust.
	* g++.old-deja/g++.pt/spec6.C: Adjust.
	* g++.old-deja/g++.pt/unify4.C: Adjust.
	* g++.old-deja/g++.pt/unify8.C: Adjust.
	* g++.old-deja/g++.robertl/eb98.C: Adjust.
	* g++.dg/overload/template5.C: New testcase.
	* g++.dg/template/overload12.C: New testcase.

[c++] describe reasons for function template overload resolution failure

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