c++: remove use_default_args parm of coerce_template_parms

It looks like the parameter use_default_args introduced in r110693 is
effectively unused ever since r7-5536-g3c75aaa3d884ef removed the last
(and probably only) 'coerce_template_parms (..., true, false)' call, so
this patch gets rid of it.

In passing, I noticed we currently define wrapper overloads of
coerce_template_parms that effectively default complain and
require_all_args, but it seems cleaner to specify default arguments
for the main overload instead.  And I suppose we should also give
c_innermost_t_p the same defaults.

However, I'm not sure about defaulting complain to tf_none since it's
contrary to how we default every other complain parameter to either
tf_error or tf_warning_or_error (for sake of non-SFINAE callers), so
this tf_none default seems surprising.  And since just three callers
(all in constraint.cc) use this complain=tf_none default, and just one
caller (determine_specialization) passes complain=tf_warning_or_error,
it seems best to just not default complain here.

Bootstrapped and regtested on x86_64-pc-linux-gnu, does this look OK for
trunk?

gcc/cp/ChangeLog:

	* constraint.cc (resolve_function_concept_overload): Explicitly
	pass tf_none to coerce_template_parms.
	(resolve_concept_check): Likewise.
	(normalize_concept_check): Likewise.
	* cp-tree.h (coerce_template_parms): Declare the main overload
	and default its last parameter to true.  Remove other overloads.
	* pt.cc (determine_specialization): Adjust calls to
	coerce_template_parms and coerce_innermost_template_parms after
	removing their last parameter.
	(coerce_template_args_for_ttp): Likewise.
	(coerce_ttp_args_for_tta): Likewise.
	(coerce_template_template_parms): Likewise.
	(coerce_template_parms): Remove use_default_args parameter.
	Remove wrapper overloads.  No longer static.
	(coerce_innermost_template_parms): Remove use_default_args
	parameter.
	(lookup_template_class): As with determine_specialization.
	(finish_template_variable): Likewise.
	(tsubst_decl): Likewise.
	(instantiate_alias_template): Likewise.
	(fn_type_unification): Likewise.
	(resolve_overloaded_unification): Likewise.
	(resolve_nondeduced_context): Likewise.
	(get_partial_spec_bindings): Likewise.
---
 gcc/cp/constraint.cc |   6 +--
 gcc/cp/cp-tree.h     |   4 +-
 gcc/cp/pt.cc         | 107 +++++++++++--------------------------------
 3 files changed, 32 insertions(+), 85 deletions(-)

On 10/24/22 12:27, Patrick Palka wrote:
> It looks like the parameter use_default_args introduced in r110693 is
> effectively unused ever since r7-5536-g3c75aaa3d884ef removed the last
> (and probably only) 'coerce_template_parms (..., true, false)' call, so
> this patch gets rid of it.
> 
> In passing, I noticed we currently define wrapper overloads of
> coerce_template_parms that effectively default complain and
> require_all_args, but it seems cleaner to specify default arguments
> for the main overload instead.  And I suppose we should also give
> c_innermost_t_p the same defaults.
> 
> However, I'm not sure about defaulting complain to tf_none since it's
> contrary to how we default every other complain parameter to either
> tf_error or tf_warning_or_error (for sake of non-SFINAE callers), so
> this tf_none default seems surprising.  And since just three callers
> (all in constraint.cc) use this complain=tf_none default, and just one
> caller (determine_specialization) passes complain=tf_warning_or_error,
> it seems best to just not default complain here.

Agreed, it's probably better in general not to default complain, that's 
a source of SFINAE bugs.

> Bootstrapped and regtested on x86_64-pc-linux-gnu, does this look OK for
> trunk?

OK.

> gcc/cp/ChangeLog:
> 
> 	* constraint.cc (resolve_function_concept_overload): Explicitly
> 	pass tf_none to coerce_template_parms.
> 	(resolve_concept_check): Likewise.
> 	(normalize_concept_check): Likewise.
> 	* cp-tree.h (coerce_template_parms): Declare the main overload
> 	and default its last parameter to true.  Remove other overloads.
> 	* pt.cc (determine_specialization): Adjust calls to
> 	coerce_template_parms and coerce_innermost_template_parms after
> 	removing their last parameter.
> 	(coerce_template_args_for_ttp): Likewise.
> 	(coerce_ttp_args_for_tta): Likewise.
> 	(coerce_template_template_parms): Likewise.
> 	(coerce_template_parms): Remove use_default_args parameter.
> 	Remove wrapper overloads.  No longer static.
> 	(coerce_innermost_template_parms): Remove use_default_args
> 	parameter.
> 	(lookup_template_class): As with determine_specialization.
> 	(finish_template_variable): Likewise.
> 	(tsubst_decl): Likewise.
> 	(instantiate_alias_template): Likewise.
> 	(fn_type_unification): Likewise.
> 	(resolve_overloaded_unification): Likewise.
> 	(resolve_nondeduced_context): Likewise.
> 	(get_partial_spec_bindings): Likewise.
> ---
>   gcc/cp/constraint.cc |   6 +--
>   gcc/cp/cp-tree.h     |   4 +-
>   gcc/cp/pt.cc         | 107 +++++++++++--------------------------------
>   3 files changed, 32 insertions(+), 85 deletions(-)
> 
> diff --git a/gcc/cp/constraint.cc b/gcc/cp/constraint.cc
> index 74898ca1a23..5e6a3bcf059 100644
> --- a/gcc/cp/constraint.cc
> +++ b/gcc/cp/constraint.cc
> @@ -323,7 +323,7 @@ resolve_function_concept_overload (tree ovl, tree args)
>         /* Remember the candidate if we can deduce a substitution.  */
>         ++processing_template_decl;
>         tree parms = TREE_VALUE (DECL_TEMPLATE_PARMS (tmpl));
> -      if (tree subst = coerce_template_parms (parms, args, tmpl))
> +      if (tree subst = coerce_template_parms (parms, args, tmpl, tf_none))
>           {
>             if (subst == error_mark_node)
>               ++nerrs;
> @@ -404,7 +404,7 @@ resolve_concept_check (tree check)
>     tree args = TREE_OPERAND (id, 1);
>     tree parms = INNERMOST_TEMPLATE_PARMS (DECL_TEMPLATE_PARMS (tmpl));
>     ++processing_template_decl;
> -  tree result = coerce_template_parms (parms, args, tmpl);
> +  tree result = coerce_template_parms (parms, args, tmpl, tf_none);
>     --processing_template_decl;
>     if (result == error_mark_node)
>       return error_mark_node;
> @@ -726,7 +726,7 @@ normalize_concept_check (tree check, tree args, norm_info info)
>     /* Turn on template processing; coercing non-type template arguments
>        will automatically assume they're non-dependent.  */
>     ++processing_template_decl;
> -  tree subst = coerce_template_parms (parms, targs, tmpl);
> +  tree subst = coerce_template_parms (parms, targs, tmpl, tf_none);
>     --processing_template_decl;
>     if (subst == error_mark_node)
>       return error_mark_node;
> diff --git a/gcc/cp/cp-tree.h b/gcc/cp/cp-tree.h
> index 60a25101049..b210943ab25 100644
> --- a/gcc/cp/cp-tree.h
> +++ b/gcc/cp/cp-tree.h
> @@ -7459,8 +7459,8 @@ extern tree get_function_template_decl		(const_tree);
>   extern tree resolve_nondeduced_context		(tree, tsubst_flags_t);
>   extern tree resolve_nondeduced_context_or_error	(tree, tsubst_flags_t);
>   extern hashval_t iterative_hash_template_arg	(tree arg, hashval_t val);
> -extern tree coerce_template_parms               (tree, tree, tree);
> -extern tree coerce_template_parms               (tree, tree, tree, tsubst_flags_t);
> +extern tree coerce_template_parms		(tree, tree, tree, tsubst_flags_t,
> +						 bool = true);
>   extern tree canonicalize_type_argument		(tree, tsubst_flags_t);
>   extern void register_local_specialization       (tree, tree);
>   extern tree retrieve_local_specialization       (tree);
> diff --git a/gcc/cp/pt.cc b/gcc/cp/pt.cc
> index 1289aabec75..9882ee6d9ce 100644
> --- a/gcc/cp/pt.cc
> +++ b/gcc/cp/pt.cc
> @@ -148,10 +148,8 @@ static void add_pending_template (tree);
>   static tree reopen_tinst_level (struct tinst_level *);
>   static tree tsubst_initializer_list (tree, tree);
>   static tree get_partial_spec_bindings (tree, tree, tree);
> -static tree coerce_template_parms (tree, tree, tree, tsubst_flags_t,
> -				   bool, bool);
>   static tree coerce_innermost_template_parms (tree, tree, tree, tsubst_flags_t,
> -					      bool, bool);
> +					     bool = true);
>   static void tsubst_enum	(tree, tree, tree);
>   static bool check_instantiated_args (tree, tree, tsubst_flags_t);
>   static int check_non_deducible_conversion (tree, tree, unification_kind_t, int,
> @@ -2172,8 +2170,7 @@ determine_specialization (tree template_id,
>       {
>         tree parms = INNERMOST_TEMPLATE_PARMS (DECL_TEMPLATE_PARMS (fns));
>         targs = coerce_template_parms (parms, explicit_targs, fns,
> -				     tf_warning_or_error,
> -				     /*req_all*/true, /*use_defarg*/true);
> +				     tf_warning_or_error);
>         if (targs != error_mark_node
>   	  && constraints_satisfied_p (fns, targs))
>           templates = tree_cons (targs, fns, templates);
> @@ -7833,10 +7830,7 @@ coerce_template_args_for_ttp (tree templ, tree arglist,
>       arglist = add_to_template_args (outer, arglist);
>   
>     tree parmlist = DECL_INNERMOST_TEMPLATE_PARMS (templ);
> -  return coerce_template_parms (parmlist, arglist, templ,
> -				complain,
> -				/*require_all_args=*/true,
> -				/*use_default_args=*/true);
> +  return coerce_template_parms (parmlist, arglist, templ, complain);
>   }
>   
>   /* A cache of template template parameters with match-all default
> @@ -7910,9 +7904,7 @@ coerce_ttp_args_for_tta (tree& arg, tree pargs, tsubst_flags_t complain)
>       {
>         tree aparms
>   	= INNERMOST_TEMPLATE_PARMS (DECL_TEMPLATE_PARMS (arg_tmpl));
> -      pargs = coerce_template_parms (aparms, pargs, arg_tmpl, complain,
> -				       /*require_all*/true,
> -				       /*use_default*/true);
> +      pargs = coerce_template_parms (aparms, pargs, arg_tmpl, complain);
>       }
>     --processing_template_decl;
>     return pargs;
> @@ -8079,8 +8071,7 @@ coerce_template_template_parms (tree parm_parms_full,
>   	  pargs = add_to_template_args (outer_args, pargs);
>   	}
>   
> -      pargs = coerce_template_parms (arg_parms, pargs, NULL_TREE, tf_none,
> -				     /*require_all*/true, /*use_default*/true);
> +      pargs = coerce_template_parms (arg_parms, pargs, NULL_TREE, tf_none);
>         if (pargs != error_mark_node)
>   	{
>   	  tree targs = make_tree_vec (nargs);
> @@ -8840,19 +8831,16 @@ pack_expansion_args_count (tree args)
>      warning messages are issued under control of COMPLAIN.
>   
>      If REQUIRE_ALL_ARGS is false, argument deduction will be performed
> -   for arguments not specified in ARGS.  Otherwise, if
> -   USE_DEFAULT_ARGS is true, default arguments will be used to fill in
> -   unspecified arguments.  If REQUIRE_ALL_ARGS is true, but
> -   USE_DEFAULT_ARGS is false, then all arguments must be specified in
> -   ARGS.  */
> +   for arguments not specified in ARGS.  If REQUIRE_ALL_ARGS is true,
> +   arguments not specified in ARGS must have default arguments with
> +   which we'll fill in ARGS.  */
>   
> -static tree
> +tree
>   coerce_template_parms (tree parms,
>   		       tree args,
>   		       tree in_decl,
>   		       tsubst_flags_t complain,
> -		       bool require_all_args,
> -		       bool use_default_args)
> +		       bool require_all_args /* = true */)
>   {
>     int nparms, nargs, parm_idx, arg_idx, lost = 0;
>     tree orig_inner_args;
> @@ -8913,9 +8901,8 @@ coerce_template_parms (tree parms,
>         || (nargs < nparms - variadic_p
>   	  && require_all_args
>   	  && !variadic_args_p
> -	  && (!use_default_args
> -	      || (TREE_VEC_ELT (parms, nargs) != error_mark_node
> -                  && !TREE_PURPOSE (TREE_VEC_ELT (parms, nargs))))))
> +	  && (TREE_VEC_ELT (parms, nargs) != error_mark_node
> +	      && !TREE_PURPOSE (TREE_VEC_ELT (parms, nargs)))))
>       {
>       bad_nargs:
>         if (complain & tf_error)
> @@ -9183,30 +9170,6 @@ coerce_template_parms (tree parms,
>     return new_inner_args;
>   }
>   
> -/* Convert all template arguments to their appropriate types, and
> -   return a vector containing the innermost resulting template
> -   arguments.  If any error occurs, return error_mark_node. Error and
> -   warning messages are not issued.
> -
> -   Note that no function argument deduction is performed, and default
> -   arguments are used to fill in unspecified arguments. */
> -tree
> -coerce_template_parms (tree parms, tree args, tree in_decl)
> -{
> -  return coerce_template_parms (parms, args, in_decl, tf_none, true, true);
> -}
> -
> -/* Convert all template arguments to their appropriate type, and
> -   instantiate default arguments as needed. This returns a vector
> -   containing the innermost resulting template arguments, or
> -   error_mark_node if unsuccessful.  */
> -tree
> -coerce_template_parms (tree parms, tree args, tree in_decl,
> -                       tsubst_flags_t complain)
> -{
> -  return coerce_template_parms (parms, args, in_decl, complain, true, true);
> -}
> -
>   /* Like coerce_template_parms.  If PARMS represents all template
>      parameters levels, this function returns a vector of vectors
>      representing all the resulting argument levels.  Note that in this
> @@ -9219,11 +9182,10 @@ coerce_template_parms (tree parms, tree args, tree in_decl,
>   
>   static tree
>   coerce_innermost_template_parms (tree parms,
> -				  tree args,
> -				  tree in_decl,
> -				  tsubst_flags_t complain,
> -				  bool require_all_args,
> -				  bool use_default_args)
> +				 tree args,
> +				 tree in_decl,
> +				 tsubst_flags_t complain,
> +				 bool require_all_args /* = true */)
>   {
>     int parms_depth = TMPL_PARMS_DEPTH (parms);
>     int args_depth = TMPL_ARGS_DEPTH (args);
> @@ -9243,8 +9205,7 @@ coerce_innermost_template_parms (tree parms,
>   	  if (cur_depth == args_depth)
>   	    l = coerce_template_parms (TREE_VALUE (level),
>   				       args, in_decl, complain,
> -				       require_all_args,
> -				       use_default_args);
> +				       require_all_args);
>   	  else
>   	    l = TMPL_ARGS_LEVEL (args, cur_depth);
>   
> @@ -9257,8 +9218,7 @@ coerce_innermost_template_parms (tree parms,
>     else
>       coerced_args = coerce_template_parms (INNERMOST_TEMPLATE_PARMS (parms),
>   					  args, in_decl, complain,
> -					  require_all_args,
> -					  use_default_args);
> +					  require_all_args);
>     return coerced_args;
>   }
>   
> @@ -9953,9 +9913,7 @@ lookup_template_class (tree d1, tree arglist, tree in_decl, tree context,
>   	 actually tsubst'd into the definition to create the
>   	 instantiation.  */
>         arglist = coerce_innermost_template_parms (parmlist, arglist, gen_tmpl,
> -						 complain,
> -						 /*require_all_args=*/true,
> -						 /*use_default_args=*/true);
> +						 complain);
>   
>         if (arglist == error_mark_node)
>   	/* We were unable to bind the arguments.  */
> @@ -10371,9 +10329,7 @@ finish_template_variable (tree var, tsubst_flags_t complain)
>     tree arglist = TREE_OPERAND (var, 1);
>   
>     tree parms = DECL_TEMPLATE_PARMS (templ);
> -  arglist = coerce_innermost_template_parms (parms, arglist, templ, complain,
> -					     /*req_all*/true,
> -					     /*use_default*/true);
> +  arglist = coerce_innermost_template_parms (parms, arglist, templ, complain);
>     if (arglist == error_mark_node)
>       return error_mark_node;
>   
> @@ -15022,8 +14978,7 @@ tsubst_decl (tree t, tree args, tsubst_flags_t complain)
>   		     the template.  */
>   		  argvec = (coerce_innermost_template_parms
>   			    (DECL_TEMPLATE_PARMS (gen_tmpl),
> -			     argvec, t, complain,
> -			     /*all*/true, /*defarg*/true));
> +			     argvec, t, complain));
>   		if (argvec == error_mark_node)
>   		  RETURN (error_mark_node);
>   		hash = spec_hasher::hash (gen_tmpl, argvec);
> @@ -21956,11 +21911,8 @@ instantiate_alias_template (tree tmpl, tree args, tsubst_flags_t complain)
>     if (tmpl == error_mark_node || args == error_mark_node)
>       return error_mark_node;
>   
> -  args =
> -    coerce_innermost_template_parms (DECL_TEMPLATE_PARMS (tmpl),
> -				     args, tmpl, complain,
> -				     /*require_all_args=*/true,
> -				     /*use_default_args=*/true);
> +  args = coerce_innermost_template_parms (DECL_TEMPLATE_PARMS (tmpl),
> +					  args, tmpl, complain);
>   
>     /* FIXME check for satisfaction in check_instantiated_args.  */
>     if (flag_concepts
> @@ -22210,8 +22162,7 @@ fn_type_unification (tree fn,
>         explicit_targs
>   	= (coerce_template_parms (tparms, explicit_targs, fn,
>   				  complain|tf_partial,
> -				  /*require_all_args=*/false,
> -				  /*use_default_args=*/false));
> +				  /*require_all_args=*/false));
>         if (explicit_targs == error_mark_node)
>   	goto fail;
>   
> @@ -23304,9 +23255,7 @@ resolve_overloaded_unification (tree tparms,
>   	    continue;
>   
>   	  subargs = coerce_template_parms (DECL_INNERMOST_TEMPLATE_PARMS (fn),
> -					   expl_subargs, NULL_TREE, tf_none,
> -					   /*require_all_args=*/true,
> -					   /*use_default_args=*/true);
> +					   expl_subargs, NULL_TREE, tf_none);
>   	  if (subargs != error_mark_node
>   	      && !any_dependent_template_arguments_p (subargs))
>   	    {
> @@ -23450,9 +23399,7 @@ resolve_nondeduced_context (tree orig_expr, tsubst_flags_t complain)
>   	    continue;
>   
>   	  subargs = coerce_template_parms (DECL_INNERMOST_TEMPLATE_PARMS (fn),
> -					   expl_subargs, NULL_TREE, tf_none,
> -					   /*require_all_args=*/true,
> -					   /*use_default_args=*/true);
> +					   expl_subargs, NULL_TREE, tf_none);
>   	  if (subargs != error_mark_node
>   	      && !any_dependent_template_arguments_p (subargs))
>   	    {
> @@ -25581,7 +25528,7 @@ get_partial_spec_bindings (tree tmpl, tree spec_tmpl, tree args)
>     if (spec_args != error_mark_node)
>       spec_args = coerce_template_parms (DECL_INNERMOST_TEMPLATE_PARMS (tmpl),
>   				       INNERMOST_TEMPLATE_ARGS (spec_args),
> -				       tmpl, tf_none, false, false);
> +				       tmpl, tf_none, false);
>   
>     pop_tinst_level ();
>