Re: [PATCH 2/1] c++: rename tsubst_copy_and_build and tsubst_expr

[Jason Merrill <jason@redhat.com>]

On 10/4/23 15:23, Patrick Palka wrote:
> Bootstrapped and regtested on x86_64-pc-linux-gnu, does this look OK for
> trunk?

OK.

> -- >8 --
> 
> After the previous patch, we currently have two tsubst entry points
> for expression trees: tsubst_copy_and_build and tsubst_expr.  But the
> latter is just a superset of the former that also handles statement
> trees.  We could merge the two entry points so that we just have
> tsubst_expr, but it seems natural to distinguish statement trees from
> expression trees and to maintain a separate entry point for them.
> 
> To that end, this this patch renames tsubst_copy_and_build to
> tsubst_expr, and renames the current tsubst_expr to tsubst_stmt, which
> continues to be a superset of the former (since sometimes expression
> trees appear in statement contexts, e.g. a branch of an IF_STMT could be
> NOP_EXPR).  Making tsubst_stmt disjoint from tsubst_expr is left as
> future work (if deemed desirable).
> 
> This patch in turn renames suitable existing uses of tsubst_expr (that
> expect to take statement trees) to use tsubst_stmt.  Thus untouched
> tsubst_expr calls are implicitly strengthened to expect only expression
> trees after this patch.  And since I'm not familiar with the
> tsubst_omp_* routines this patch renames all tsubst_expr uses there to
> tsubst_stmt to ensure no unintended functional change in that area.
> This patch also moves the handling of CO_YIELD_EXPR and CO_AWAIT_EXPR
> from tsubst_stmt to tsubst_expr since they're expression trees.
> 
> gcc/cp/ChangeLog:
> 
> 	* cp-lang.cc (objcp_tsubst_copy_and_build): Rename to ...
> 	(objcp_tsubst_expr): ... this.
> 	* cp-objcp-common.h (objcp_tsubst_copy_and_build): Rename to ...
> 	(objcp_tsubst_expr): ... this.
> 	* cp-tree.h (tsubst_copy_and_build): Remove declaration.
> 	* init.cc (maybe_instantiate_nsdmi_init): Use tsubst_expr
> 	instead of tsubst_copy_and_build.
> 	* pt.cc (expand_integer_pack): Likewise.
> 	(instantiate_non_dependent_expr_internal): Likewise.
> 	(instantiate_class_template): Use tsubst_stmt instead of
> 	tsubst_expr for STATIC_ASSERT.
> 	(tsubst_function_decl): Adjust tsubst_copy_and_build uses.
> 	(tsubst_arg_types): Likewise.
> 	(tsubst_exception_specification): Likewise.
> 	(tsubst_tree_list): Likewise.
> 	(tsubst): Likewise.
> 	(tsubst_name): Likewise.
> 	(tsubst_omp_clause_decl): Use tsubst_stmt instead of tsubst_expr.
> 	(tsubst_omp_clauses): Likewise.
> 	(tsubst_copy_asm_operands): Adjust tsubst_copy_and_build use.
> 	(tsubst_omp_for_iterator): Use tsubst_stmt instead of tsubst_expr.
> 	(tsubst_expr): Rename to ...
> 	(tsubst_stmt): ... this.
> 	<case CO_YIELD_EXPR, CO_AWAIT_EXPR>: Move to tsubst_expr.
> 	(tsubst_omp_udr): Use tsubst_stmt instead of tsubst_expr.
> 	(tsubst_non_call_postfix_expression): Adjust tsubst_copy_and_build
> 	use.
> 	(tsubst_lambda_expr): Likewise.  Use tsubst_stmt instead of
> 	tsubst_expr for the body of a lambda.
> 	(tsubst_copy_and_build_call_args): Rename to ...
> 	(tsubst_call_args): ... this.  Adjust tsubst_copy_and_build use.
> 	(tsubst_copy_and_build): Rename to tsubst_expr.  Adjust
> 	tsubst_copy_and_build and tsubst_copy_and_build_call_args use.
> 	<case TRANSACTION_EXPR>: Use tsubst_stmt instead of tsubst_expr.
> 	(maybe_instantiate_noexcept): Adjust tsubst_copy_and_build use.
> 	(instantiate_body): Use tsubst_stmt instead of tsubst_expr for
> 	substituting the function body.
> 	(tsubst_initializer_list): Adjust tsubst_copy_and_build use.
> 
> gcc/objcp/ChangeLog:
> 
> 	* objcp-lang.cc (objcp_tsubst_copy_and_build): Rename to ...
> 	(objcp_tsubst_expr): ... this.  Adjust tsubst_copy_and_build
> 	uses.
> ---
>   gcc/cp/cp-lang.cc        |   6 +-
>   gcc/cp/cp-objcp-common.h |   2 +-
>   gcc/cp/cp-tree.h         |   1 -
>   gcc/cp/init.cc           |   3 +-
>   gcc/cp/pt.cc             | 177 +++++++++++++++++----------------------
>   gcc/objcp/objcp-lang.cc  |   5 +-
>   6 files changed, 85 insertions(+), 109 deletions(-)
> 
> diff --git a/gcc/cp/cp-lang.cc b/gcc/cp/cp-lang.cc
> index 2f541460c4a..f2ed83de4fb 100644
> --- a/gcc/cp/cp-lang.cc
> +++ b/gcc/cp/cp-lang.cc
> @@ -113,10 +113,8 @@ struct lang_hooks lang_hooks = LANG_HOOKS_INITIALIZER;
>   /* The following function does something real, but only in Objective-C++.  */
>   
>   tree
> -objcp_tsubst_copy_and_build (tree /*t*/,
> -			     tree /*args*/,
> -			     tsubst_flags_t /*complain*/,
> -			     tree /*in_decl*/)
> +objcp_tsubst_expr (tree /*t*/, tree /*args*/, tsubst_flags_t /*complain*/,
> +		   tree /*in_decl*/)
>   {
>     return NULL_TREE;
>   }
> diff --git a/gcc/cp/cp-objcp-common.h b/gcc/cp/cp-objcp-common.h
> index 80893aa1752..1408301a300 100644
> --- a/gcc/cp/cp-objcp-common.h
> +++ b/gcc/cp/cp-objcp-common.h
> @@ -24,7 +24,7 @@ along with GCC; see the file COPYING3.  If not see
>   /* In cp/objcp-common.c, cp/cp-lang.cc and objcp/objcp-lang.cc.  */
>   
>   extern tree cp_get_debug_type (const_tree);
> -extern tree objcp_tsubst_copy_and_build (tree, tree, tsubst_flags_t, tree);
> +extern tree objcp_tsubst_expr (tree, tree, tsubst_flags_t, tree);
>   
>   extern int cp_decl_dwarf_attribute (const_tree, int);
>   extern int cp_type_dwarf_attribute (const_tree, int);
> diff --git a/gcc/cp/cp-tree.h b/gcc/cp/cp-tree.h
> index 919eab34803..4b463f12c0c 100644
> --- a/gcc/cp/cp-tree.h
> +++ b/gcc/cp/cp-tree.h
> @@ -7458,7 +7458,6 @@ extern void instantiate_pending_templates	(int);
>   extern tree tsubst_default_argument		(tree, int, tree, tree,
>   						 tsubst_flags_t);
>   extern tree tsubst (tree, tree, tsubst_flags_t, tree);
> -extern tree tsubst_copy_and_build		(tree, tree, tsubst_flags_t, tree);
>   extern tree tsubst_expr                         (tree, tree, tsubst_flags_t, tree);
>   extern tree tsubst_pack_expansion		(tree, tree, tsubst_flags_t, tree);
>   extern tree tsubst_argument_pack		(tree, tree, tsubst_flags_t, tree);
> diff --git a/gcc/cp/init.cc b/gcc/cp/init.cc
> index d1bae3b155f..d48bb16c7c5 100644
> --- a/gcc/cp/init.cc
> +++ b/gcc/cp/init.cc
> @@ -621,8 +621,7 @@ maybe_instantiate_nsdmi_init (tree member, tsubst_flags_t complain)
>   	  start_lambda_scope (member);
>   
>   	  /* Do deferred instantiation of the NSDMI.  */
> -	  init = tsubst_copy_and_build (init, DECL_TI_ARGS (member),
> -					complain, member);
> +	  init = tsubst_expr (init, DECL_TI_ARGS (member), complain, member);
>   	  init = digest_nsdmi_init (member, init, complain);
>   
>   	  finish_lambda_scope ();
> diff --git a/gcc/cp/pt.cc b/gcc/cp/pt.cc
> index e801a224d1b..837e81eea83 100644
> --- a/gcc/cp/pt.cc
> +++ b/gcc/cp/pt.cc
> @@ -204,6 +204,7 @@ static void copy_default_args_to_explicit_spec (tree);
>   static bool invalid_nontype_parm_type_p (tree, tsubst_flags_t);
>   static bool dependent_template_arg_p (tree);
>   static bool dependent_type_p_r (tree);
> +static tree tsubst_stmt (tree, tree, tsubst_flags_t, tree);
>   static tree tsubst_decl (tree, tree, tsubst_flags_t, bool = true);
>   static tree tsubst_scope (tree, tree, tsubst_flags_t, tree);
>   static tree tsubst_name (tree, tree, tsubst_flags_t, tree);
> @@ -3763,7 +3764,7 @@ expand_integer_pack (tree call, tree args, tsubst_flags_t complain,
>   		     tree in_decl)
>   {
>     tree ohi = CALL_EXPR_ARG (call, 0);
> -  tree hi = tsubst_copy_and_build (ohi, args, complain, in_decl);
> +  tree hi = tsubst_expr (ohi, args, complain, in_decl);
>   
>     if (instantiation_dependent_expression_p (hi))
>       {
> @@ -3771,7 +3772,7 @@ expand_integer_pack (tree call, tree args, tsubst_flags_t complain,
>   	{
>   	  /* Work around maybe_convert_nontype_argument not doing this for
>   	     dependent arguments.  Don't use IMPLICIT_CONV_EXPR_NONTYPE_ARG
> -	     because that will make tsubst_copy_and_build ignore it.  */
> +	     because that will make tsubst_expr ignore it.  */
>   	  tree type = tsubst (TREE_TYPE (ohi), args, complain, in_decl);
>   	  if (!TREE_TYPE (hi) || !same_type_p (type, TREE_TYPE (hi)))
>   	    hi = build1 (IMPLICIT_CONV_EXPR, type, hi);
> @@ -6423,10 +6424,7 @@ redeclare_class_template (tree type, tree parms, tree cons)
>   tree
>   instantiate_non_dependent_expr_internal (tree expr, tsubst_flags_t complain)
>   {
> -  return tsubst_copy_and_build (expr,
> -				/*args=*/NULL_TREE,
> -				complain,
> -				/*in_decl=*/NULL_TREE);
> +  return tsubst_expr (expr, /*args=*/NULL_TREE, complain, /*in_decl=*/NULL_TREE);
>   }
>   
>   /* Instantiate the non-dependent expression EXPR.  */
> @@ -12367,7 +12365,7 @@ instantiate_class_template (tree type)
>   	    {
>   	      /* Build new TYPE_FIELDS.  */
>                 if (TREE_CODE (t) == STATIC_ASSERT)
> -		tsubst_expr (t, args, tf_warning_or_error, NULL_TREE);
> +		tsubst_stmt (t, args, tf_warning_or_error, NULL_TREE);
>   	      else if (TREE_CODE (t) != CONST_DECL)
>   		{
>   		  tree r;
> @@ -14455,7 +14453,7 @@ tsubst_function_decl (tree t, tree args, tsubst_flags_t complain,
>     if (DECL_HAS_DEPENDENT_EXPLICIT_SPEC_P (t))
>       {
>         tree spec = lookup_explicit_specifier (t);
> -      spec = tsubst_copy_and_build (spec, args, complain, in_decl);
> +      spec = tsubst_expr (spec, args, complain, in_decl);
>         spec = build_explicit_specifier (spec, complain);
>         if (spec == error_mark_node)
>   	return error_mark_node;
> @@ -15584,7 +15582,7 @@ tsubst_arg_types (tree arg_types,
>     if (lambda_fn_in_template_p (in_decl)
>         || (in_decl && TREE_CODE (in_decl) == FUNCTION_DECL
>   	  && DECL_LOCAL_DECL_P (in_decl)))
> -    default_arg = tsubst_copy_and_build (default_arg, args, complain, in_decl);
> +    default_arg = tsubst_expr (default_arg, args, complain, in_decl);
>   
>     tree remaining_arg_types = tsubst_arg_types (TREE_CHAIN (arg_types),
>   					       args, end, complain, in_decl);
> @@ -15765,7 +15763,7 @@ tsubst_exception_specification (tree fntype,
>   					   args);
>   	      expr = DEFERRED_NOEXCEPT_PATTERN (expr);
>   	    }
> -	  new_specs = tsubst_copy_and_build (expr, args, complain, in_decl);
> +	  new_specs = tsubst_expr (expr, args, complain, in_decl);
>   	}
>         new_specs = build_noexcept_spec (new_specs, complain);
>         /* We've instantiated a template before a noexcept-specifier
> @@ -15862,7 +15860,7 @@ tsubst_tree_list (tree t, tree args, tsubst_flags_t complain, tree in_decl)
>     else if (TYPE_P (purpose))
>       purpose = tsubst (purpose, args, complain, in_decl);
>     else
> -    purpose = tsubst_copy_and_build (purpose, args, complain, in_decl);
> +    purpose = tsubst_expr (purpose, args, complain, in_decl);
>     if (purpose == error_mark_node || purposevec == error_mark_node)
>       return error_mark_node;
>   
> @@ -15879,7 +15877,7 @@ tsubst_tree_list (tree t, tree args, tsubst_flags_t complain, tree in_decl)
>     else if (TYPE_P (value))
>       value = tsubst (value, args, complain, in_decl);
>     else
> -    value = tsubst_copy_and_build (value, args, complain, in_decl);
> +    value = tsubst_expr (value, args, complain, in_decl);
>     if (value == error_mark_node || valuevec == error_mark_node)
>       return error_mark_node;
>   
> @@ -15891,7 +15889,7 @@ tsubst_tree_list (tree t, tree args, tsubst_flags_t complain, tree in_decl)
>     else if (TYPE_P (chain))
>       chain = tsubst (chain, args, complain, in_decl);
>     else
> -    chain = tsubst_copy_and_build (chain, args, complain, in_decl);
> +    chain = tsubst_expr (chain, args, complain, in_decl);
>     if (chain == error_mark_node)
>       return error_mark_node;
>   
> @@ -16104,7 +16102,7 @@ tsubst (tree t, tree args, tsubst_flags_t complain, tree in_decl)
>         if (template_placeholder_p (t))
>   	{
>   	  tree tmpl = CLASS_PLACEHOLDER_TEMPLATE (t);
> -	  tmpl = tsubst_copy_and_build (tmpl, args, complain, in_decl);
> +	  tmpl = tsubst_expr (tmpl, args, complain, in_decl);
>   	  if (TREE_CODE (tmpl) == TEMPLATE_TEMPLATE_PARM)
>   	    tmpl = TEMPLATE_TEMPLATE_PARM_TEMPLATE_DECL (tmpl);
>   
> @@ -16696,8 +16694,8 @@ tsubst (tree t, tree args, tsubst_flags_t complain, tree in_decl)
>   	++cp_unevaluated_operand;
>   	++c_inhibit_evaluation_warnings;
>   
> -	type = tsubst_copy_and_build (DECLTYPE_TYPE_EXPR (t), args,
> -				      complain|tf_decltype, in_decl);
> +	type = tsubst_expr (DECLTYPE_TYPE_EXPR (t), args,
> +			    complain|tf_decltype, in_decl);
>   
>   	--cp_unevaluated_operand;
>   	--c_inhibit_evaluation_warnings;
> @@ -16732,7 +16730,7 @@ tsubst (tree t, tree args, tsubst_flags_t complain, tree in_decl)
>   	if (TYPE_P (type1))
>   	  type1 = tsubst (type1, args, complain, in_decl);
>   	else
> -	  type1 = tsubst_copy_and_build (type1, args, complain, in_decl);
> +	  type1 = tsubst_expr (type1, args, complain, in_decl);
>   	tree type2 = tsubst (TRAIT_TYPE_TYPE2 (t), args, complain, in_decl);
>   	type = finish_trait_type (TRAIT_TYPE_KIND (t), type1, type2, complain);
>   	return cp_build_qualified_type (type,
> @@ -16782,7 +16780,7 @@ tsubst_scope (tree t, tree args, tsubst_flags_t complain, tree in_decl)
>   static tree
>   tsubst_name (tree t, tree args, tsubst_flags_t complain, tree in_decl)
>   {
> -  return tsubst_copy_and_build (t, args, complain | tf_no_name_lookup, in_decl);
> +  return tsubst_expr (t, args, complain | tf_no_name_lookup, in_decl);
>   }
>   
>   /* OLDFNS is a lookup set of member functions from some class template, and
> @@ -17312,11 +17310,11 @@ tsubst_omp_clause_decl (tree decl, tree args, tsubst_flags_t complain,
>   	      DECL_CONTEXT (TREE_VEC_ELT (*tp, 0)) = current_function_decl;
>   	      pushdecl (TREE_VEC_ELT (*tp, 0));
>   	      TREE_VEC_ELT (*tp, 1)
> -		= tsubst_expr (TREE_VEC_ELT (it, 1), args, complain, in_decl);
> +		= tsubst_stmt (TREE_VEC_ELT (it, 1), args, complain, in_decl);
>   	      TREE_VEC_ELT (*tp, 2)
> -		= tsubst_expr (TREE_VEC_ELT (it, 2), args, complain, in_decl);
> +		= tsubst_stmt (TREE_VEC_ELT (it, 2), args, complain, in_decl);
>   	      TREE_VEC_ELT (*tp, 3)
> -		= tsubst_expr (TREE_VEC_ELT (it, 3), args, complain, in_decl);
> +		= tsubst_stmt (TREE_VEC_ELT (it, 3), args, complain, in_decl);
>   	      TREE_CHAIN (*tp) = NULL_TREE;
>   	      tp = &TREE_CHAIN (*tp);
>   	    }
> @@ -17338,8 +17336,8 @@ tsubst_omp_clause_decl (tree decl, tree args, tsubst_flags_t complain,
>     if (TREE_CODE (decl) == TREE_LIST)
>       {
>         tree low_bound
> -	= tsubst_expr (TREE_PURPOSE (decl), args, complain, in_decl);
> -      tree length = tsubst_expr (TREE_VALUE (decl), args, complain, in_decl);
> +	= tsubst_stmt (TREE_PURPOSE (decl), args, complain, in_decl);
> +      tree length = tsubst_stmt (TREE_VALUE (decl), args, complain, in_decl);
>         tree chain = tsubst_omp_clause_decl (TREE_CHAIN (decl), args, complain,
>   					   in_decl, NULL);
>         if (TREE_PURPOSE (decl) == low_bound
> @@ -17351,7 +17349,7 @@ tsubst_omp_clause_decl (tree decl, tree args, tsubst_flags_t complain,
>   	= OMP_CLAUSE_DOACROSS_SINK_NEGATIVE (decl);
>         return ret;
>       }
> -  tree ret = tsubst_expr (decl, args, complain, in_decl);
> +  tree ret = tsubst_stmt (decl, args, complain, in_decl);
>     /* Undo convert_from_reference tsubst_expr could have called.  */
>     if (decl
>         && REFERENCE_REF_P (ret)
> @@ -17382,7 +17380,7 @@ tsubst_omp_clauses (tree clauses, enum c_omp_region_type ort,
>   	  if (OMP_CLAUSE_LASTPRIVATE_STMT (oc))
>   	    {
>   	      OMP_CLAUSE_LASTPRIVATE_STMT (nc) = push_stmt_list ();
> -	      tsubst_expr (OMP_CLAUSE_LASTPRIVATE_STMT (oc), args,
> +	      tsubst_stmt (OMP_CLAUSE_LASTPRIVATE_STMT (oc), args,
>   			   complain, in_decl);
>   	      OMP_CLAUSE_LASTPRIVATE_STMT (nc)
>   		= pop_stmt_list (OMP_CLAUSE_LASTPRIVATE_STMT (nc));
> @@ -17415,7 +17413,7 @@ tsubst_omp_clauses (tree clauses, enum c_omp_region_type ort,
>   	case OMP_CLAUSE_NUM_TEAMS:
>   	  if (OMP_CLAUSE_NUM_TEAMS_LOWER_EXPR (oc))
>   	    OMP_CLAUSE_NUM_TEAMS_LOWER_EXPR (nc)
> -	      = tsubst_expr (OMP_CLAUSE_NUM_TEAMS_LOWER_EXPR (oc), args,
> +	      = tsubst_stmt (OMP_CLAUSE_NUM_TEAMS_LOWER_EXPR (oc), args,
>   			     complain, in_decl);
>   	  /* FALLTHRU */
>   	case OMP_CLAUSE_TILE:
> @@ -17444,7 +17442,7 @@ tsubst_omp_clauses (tree clauses, enum c_omp_region_type ort,
>   	case OMP_CLAUSE_WAIT:
>   	case OMP_CLAUSE_DETACH:
>   	  OMP_CLAUSE_OPERAND (nc, 0)
> -	    = tsubst_expr (OMP_CLAUSE_OPERAND (oc, 0), args, complain, in_decl);
> +	    = tsubst_stmt (OMP_CLAUSE_OPERAND (oc, 0), args, complain, in_decl);
>   	  break;
>   	case OMP_CLAUSE_REDUCTION:
>   	case OMP_CLAUSE_IN_REDUCTION:
> @@ -17474,16 +17472,16 @@ tsubst_omp_clauses (tree clauses, enum c_omp_region_type ort,
>   	    = tsubst_omp_clause_decl (OMP_CLAUSE_DECL (oc), args, complain,
>   				      in_decl, NULL);
>   	  OMP_CLAUSE_OPERAND (nc, 1)
> -	    = tsubst_expr (OMP_CLAUSE_OPERAND (oc, 1), args, complain, in_decl);
> +	    = tsubst_stmt (OMP_CLAUSE_OPERAND (oc, 1), args, complain, in_decl);
>   	  break;
>   	case OMP_CLAUSE_ALLOCATE:
>   	  OMP_CLAUSE_DECL (nc)
>   	    = tsubst_omp_clause_decl (OMP_CLAUSE_DECL (oc), args, complain,
>   				      in_decl, NULL);
>   	  OMP_CLAUSE_OPERAND (nc, 1)
> -	    = tsubst_expr (OMP_CLAUSE_OPERAND (oc, 1), args, complain, in_decl);
> +	    = tsubst_stmt (OMP_CLAUSE_OPERAND (oc, 1), args, complain, in_decl);
>   	  OMP_CLAUSE_OPERAND (nc, 2)
> -	    = tsubst_expr (OMP_CLAUSE_OPERAND (oc, 2), args, complain, in_decl);
> +	    = tsubst_stmt (OMP_CLAUSE_OPERAND (oc, 2), args, complain, in_decl);
>   	  break;
>   	case OMP_CLAUSE_LINEAR:
>   	  OMP_CLAUSE_DECL (nc)
> @@ -17500,7 +17498,7 @@ tsubst_omp_clauses (tree clauses, enum c_omp_region_type ort,
>   					complain, in_decl, NULL);
>   	  else
>   	    OMP_CLAUSE_LINEAR_STEP (nc)
> -	      = tsubst_expr (OMP_CLAUSE_LINEAR_STEP (oc), args,
> +	      = tsubst_stmt (OMP_CLAUSE_LINEAR_STEP (oc), args,
>   			     complain, in_decl);
>   	  break;
>   	case OMP_CLAUSE_NOWAIT:
> @@ -17612,7 +17610,7 @@ tsubst_omp_clauses (tree clauses, enum c_omp_region_type ort,
>     return new_clauses;
>   }
>   
> -/* Like tsubst_copy_and_build, but unshare TREE_LIST nodes.  */
> +/* Like tsubst_expr, but unshare TREE_LIST nodes.  */
>   
>   static tree
>   tsubst_copy_asm_operands (tree t, tree args, tsubst_flags_t complain,
> @@ -17626,7 +17624,7 @@ tsubst_copy_asm_operands (tree t, tree args, tsubst_flags_t complain,
>       return t;
>   
>     if (TREE_CODE (t) != TREE_LIST)
> -    return tsubst_copy_and_build (t, args, complain, in_decl);
> +    return tsubst_expr (t, args, complain, in_decl);
>   
>     if (t == void_list_node)
>       return t;
> @@ -17670,7 +17668,7 @@ tsubst_omp_for_iterator (tree t, int i, tree declv, tree &orig_declv,
>   			 tree args, tsubst_flags_t complain, tree in_decl)
>   {
>   #define RECUR(NODE)				\
> -  tsubst_expr ((NODE), args, complain, in_decl)
> +  tsubst_stmt ((NODE), args, complain, in_decl)
>     tree decl, init, cond = NULL_TREE, incr = NULL_TREE;
>     bool ret = false;
>   
> @@ -18153,15 +18151,14 @@ dependent_operand_p (tree t)
>     return r;
>   }
>   
> -/* Like tsubst_copy for expressions, etc. but also does semantic
> -   processing.  */
> +/* A superset of tsubst_expr that also handles statement trees.  */
>   
> -tree
> -tsubst_expr (tree t, tree args, tsubst_flags_t complain, tree in_decl)
> +static tree
> +tsubst_stmt (tree t, tree args, tsubst_flags_t complain, tree in_decl)
>   {
>   #define RETURN(EXP) do { r = (EXP); goto out; } while(0)
>   #define RECUR(NODE)				\
> -  tsubst_expr ((NODE), args, complain, in_decl)
> +  tsubst_stmt ((NODE), args, complain, in_decl)
>   
>     tree stmt, tmp;
>     tree r;
> @@ -18198,16 +18195,6 @@ tsubst_expr (tree t, tree args, tsubst_flags_t complain, tree in_decl)
>         finish_co_return_stmt (input_location, RECUR (TREE_OPERAND (t, 0)));
>         break;
>   
> -    case CO_YIELD_EXPR:
> -      stmt = finish_co_yield_expr (input_location,
> -				   RECUR (TREE_OPERAND (t, 0)));
> -      RETURN (stmt);
> -
> -    case CO_AWAIT_EXPR:
> -      stmt = finish_co_await_expr (input_location,
> -				   RECUR (TREE_OPERAND (t, 0)));
> -      RETURN (stmt);
> -
>       case EXPR_STMT:
>         tmp = RECUR (EXPR_STMT_EXPR (t));
>         if (EXPR_STMT_STMT_EXPR_RESULT (t))
> @@ -19228,7 +19215,7 @@ tsubst_expr (tree t, tree args, tsubst_flags_t complain, tree in_decl)
>       default:
>         gcc_assert (!STATEMENT_CODE_P (TREE_CODE (t)));
>   
> -      RETURN (tsubst_copy_and_build (t, args, complain, in_decl));
> +      RETURN (tsubst_expr (t, args, complain, in_decl));
>       }
>   
>     RETURN (NULL_TREE);
> @@ -19275,7 +19262,7 @@ tsubst_omp_udr (tree t, tree args, tsubst_flags_t complain, tree in_decl)
>         DECL_CONTEXT (omp_in) = current_function_decl;
>         keep_next_level (true);
>         tree block = begin_omp_structured_block ();
> -      tsubst_expr (stmts[2], args, complain, in_decl);
> +      tsubst_stmt (stmts[2], args, complain, in_decl);
>         block = finish_omp_structured_block (block);
>         block = maybe_cleanup_point_expr_void (block);
>         add_decl_expr (omp_out);
> @@ -19295,7 +19282,7 @@ tsubst_omp_udr (tree t, tree args, tsubst_flags_t complain, tree in_decl)
>         DECL_CONTEXT (omp_orig) = current_function_decl;
>         keep_next_level (true);
>         tree block = begin_omp_structured_block ();
> -      tsubst_expr (stmts[5], args, complain, in_decl);
> +      tsubst_stmt (stmts[5], args, complain, in_decl);
>         block = finish_omp_structured_block (block);
>         block = maybe_cleanup_point_expr_void (block);
>         cp_walk_tree (&block, cp_remove_omp_priv_cleanup_stmt, omp_priv, NULL);
> @@ -19319,7 +19306,7 @@ tsubst_non_call_postfix_expression (tree t, tree args,
>       t = tsubst_qualified_id (t, args, complain, in_decl,
>   			     /*done=*/false, /*address_p=*/false);
>     else
> -    t = tsubst_copy_and_build (t, args, complain, in_decl);
> +    t = tsubst_expr (t, args, complain, in_decl);
>   
>     return t;
>   }
> @@ -19392,7 +19379,7 @@ tsubst_lambda_expr (tree t, tree args, tsubst_flags_t complain, tree in_decl)
>         if (PACK_EXPANSION_P (init))
>   	init = tsubst_pack_expansion (init, args, complain, in_decl);
>         else
> -	init = tsubst_copy_and_build (init, args, complain, in_decl);
> +	init = tsubst_expr (init, args, complain, in_decl);
>   
>         if (init == error_mark_node)
>   	return error_mark_node;
> @@ -19572,7 +19559,7 @@ tsubst_lambda_expr (tree t, tree args, tsubst_flags_t complain, tree in_decl)
>   	   need another to confuse NRV (91217).  */
>   	saved = BIND_EXPR_BODY (saved);
>   
> -      tsubst_expr (saved, args, complain, r);
> +      tsubst_stmt (saved, args, complain, r);
>   
>         finish_lambda_function (body);
>   
> @@ -19657,12 +19644,11 @@ maybe_fold_fn_template_args (tree fn, tsubst_flags_t complain)
>     return fold_targs_r (targs, complain);
>   }
>   
> -/* Helper function for tsubst_copy_and_build CALL_EXPR and ARRAY_REF
> -   handling.  */
> +/* Helper function for tsubst_expr CALL_EXPR and ARRAY_REF handling.  */
>   
>   static void
> -tsubst_copy_and_build_call_args (tree t, tree args, tsubst_flags_t complain,
> -				 tree in_decl, releasing_vec &call_args)
> +tsubst_call_args (tree t, tree args, tsubst_flags_t complain,
> +		  tree in_decl, releasing_vec &call_args)
>   {
>     unsigned int nargs = call_expr_nargs (t);
>     for (unsigned int i = 0; i < nargs; ++i)
> @@ -19670,8 +19656,7 @@ tsubst_copy_and_build_call_args (tree t, tree args, tsubst_flags_t complain,
>         tree arg = CALL_EXPR_ARG (t, i);
>   
>         if (!PACK_EXPANSION_P (arg))
> -	vec_safe_push (call_args,
> -		       tsubst_copy_and_build (arg, args, complain, in_decl));
> +	vec_safe_push (call_args, tsubst_expr (arg, args, complain, in_decl));
>         else
>   	{
>   	  /* Expand the pack expansion and push each entry onto CALL_ARGS.  */
> @@ -19700,14 +19685,11 @@ tsubst_copy_and_build_call_args (tree t, tree args, tsubst_flags_t complain,
>      analysis.  */
>   
>   tree
> -tsubst_copy_and_build (tree t,
> -		       tree args,
> -		       tsubst_flags_t complain,
> -		       tree in_decl)
> +tsubst_expr (tree t, tree args, tsubst_flags_t complain, tree in_decl)
>   {
>   #define RETURN(EXP) do { retval = (EXP); goto out; } while(0)
>   #define RECUR(NODE)						\
> -  tsubst_copy_and_build (NODE, args, complain, in_decl)
> +  tsubst_expr (NODE, args, complain, in_decl)
>   
>     tree retval, op1;
>     location_t save_loc;
> @@ -19792,7 +19774,7 @@ tsubst_copy_and_build (tree t,
>   	if (no_name_lookup_flag)
>   	  templ = tsubst_name (templ, args, complain, in_decl);
>   	else
> -	  templ = tsubst_copy_and_build (templ, args, complain, in_decl);
> +	  templ = tsubst_expr (templ, args, complain, in_decl);
>   
>   	if (targs)
>   	  targs = tsubst_template_args (targs, args, complain, in_decl);
> @@ -20140,8 +20122,7 @@ tsubst_copy_and_build (tree t,
>   	{
>   	  tree c = TREE_OPERAND (t, 1);
>   	  releasing_vec index_exp_list;
> -	  tsubst_copy_and_build_call_args (c, args, complain, in_decl,
> -					   index_exp_list);
> +	  tsubst_call_args (c, args, complain, in_decl, index_exp_list);
>   
>   	  tree r;
>   	  if (vec_safe_length (index_exp_list) == 1
> @@ -20243,7 +20224,7 @@ tsubst_copy_and_build (tree t,
>   	    if (TYPE_P (op1))
>   	      op1 = tsubst (op1, args, complain, in_decl);
>   	    else
> -	      op1 = tsubst_copy_and_build (op1, args, complain, in_decl);
> +	      op1 = tsubst_expr (op1, args, complain, in_decl);
>   	    --cp_unevaluated_operand;
>   	    --c_inhibit_evaluation_warnings;
>   	  }
> @@ -20280,7 +20261,7 @@ tsubst_copy_and_build (tree t,
>   	op1 = TREE_OPERAND (t, 0);
>   	++cp_unevaluated_operand;
>   	++c_inhibit_evaluation_warnings;
> -	op1 = tsubst_copy_and_build (op1, args, complain, in_decl);
> +	op1 = tsubst_expr (op1, args, complain, in_decl);
>   	--cp_unevaluated_operand;
>   	--c_inhibit_evaluation_warnings;
>   	RETURN (objc_build_encode_expr (op1));
> @@ -20291,7 +20272,7 @@ tsubst_copy_and_build (tree t,
>         ++cp_unevaluated_operand;
>         ++c_inhibit_evaluation_warnings;
>         ++cp_noexcept_operand;
> -      op1 = tsubst_copy_and_build (op1, args, complain, in_decl);
> +      op1 = tsubst_expr (op1, args, complain, in_decl);
>         --cp_unevaluated_operand;
>         --c_inhibit_evaluation_warnings;
>         --cp_noexcept_operand;
> @@ -20399,8 +20380,8 @@ tsubst_copy_and_build (tree t,
>   
>       case COMPOUND_EXPR:
>         {
> -	tree op0 = tsubst_copy_and_build (TREE_OPERAND (t, 0), args,
> -					  complain & ~tf_decltype, in_decl);
> +	tree op0 = tsubst_expr (TREE_OPERAND (t, 0), args,
> +				complain & ~tf_decltype, in_decl);
>   	RETURN (build_x_compound_expr (EXPR_LOCATION (t),
>   				       op0,
>   				       RECUR (TREE_OPERAND (t, 1)),
> @@ -20460,7 +20441,7 @@ tsubst_copy_and_build (tree t,
>   		     || (TREE_CODE (function) == TEMPLATE_ID_EXPR
>   			 && identifier_p (TREE_OPERAND (function, 0)))))
>   	  {
> -	    /* Do nothing; calling tsubst_copy_and_build on an identifier
> +	    /* Do nothing; calling tsubst_expr on an identifier
>   	       would incorrectly perform unqualified lookup again.
>   
>   	       Note that we can also have an IDENTIFIER_NODE if the earlier
> @@ -20497,7 +20478,7 @@ tsubst_copy_and_build (tree t,
>   		 augmenting the overload set via ADL, so during this initial
>   		 substitution we disable mark_used by setting tf_conv (68942).  */
>   	      subcomplain |= tf_conv;
> -	    function = tsubst_copy_and_build (function, args, subcomplain, in_decl);
> +	    function = tsubst_expr (function, args, subcomplain, in_decl);
>   
>   	    if (BASELINK_P (function))
>   	      qualified_p = true;
> @@ -20505,8 +20486,7 @@ tsubst_copy_and_build (tree t,
>   
>   	nargs = call_expr_nargs (t);
>   	releasing_vec call_args;
> -	tsubst_copy_and_build_call_args (t, args, complain, in_decl,
> -					 call_args);
> +	tsubst_call_args (t, args, complain, in_decl, call_args);
>   
>   	/* Stripped-down processing for a call in a thunk.  Specifically, in
>   	   the thunk template for a generic lambda.  */
> @@ -20598,8 +20578,7 @@ tsubst_copy_and_build (tree t,
>   		/* For backwards compatibility and good diagnostics, try
>   		   the unqualified lookup again if we aren't in SFINAE
>   		   context.  */
> -		tree unq = tsubst_copy_and_build (function, args,
> -						  complain, in_decl);
> +		tree unq = tsubst_expr (function, args, complain, in_decl);
>   		if (unq == error_mark_node)
>   		  RETURN (error_mark_node);
>   
> @@ -21390,8 +21369,13 @@ tsubst_copy_and_build (tree t,
>   	 to the containing function, inlined copy or so.  */
>         RETURN (t);
>   
> +    case CO_YIELD_EXPR:
> +      RETURN (finish_co_yield_expr (input_location,
> +				    RECUR (TREE_OPERAND (t, 0))));
> +
>       case CO_AWAIT_EXPR:
> -      RETURN (tsubst_expr (t, args, complain, in_decl));
> +      RETURN (finish_co_await_expr (input_location,
> +				    RECUR (TREE_OPERAND (t, 0))));
>   
>       case VA_ARG_EXPR:
>         {
> @@ -21403,8 +21387,7 @@ tsubst_copy_and_build (tree t,
>       case OFFSETOF_EXPR:
>         {
>   	tree object_ptr
> -	  = tsubst_copy_and_build (TREE_OPERAND (t, 1), args,
> -				   complain, in_decl);
> +	  = tsubst_expr (TREE_OPERAND (t, 1), args, complain, in_decl);
>   	RETURN (finish_offsetof (object_ptr,
>   				 RECUR (TREE_OPERAND (t, 0)),
>   				 EXPR_LOCATION (t)));
> @@ -21420,7 +21403,7 @@ tsubst_copy_and_build (tree t,
>   	if (TYPE_P (type1))
>   	  type1 = tsubst (type1, args, complain, in_decl);
>   	else
> -	  type1 = tsubst_copy_and_build (type1, args, complain, in_decl);
> +	  type1 = tsubst_expr (type1, args, complain, in_decl);
>   	tree type2 = tsubst (TRAIT_EXPR_TYPE2 (t), args,
>   			     complain, in_decl);
>   	RETURN (finish_trait_expr (TRAIT_EXPR_LOCATION (t),
> @@ -21433,7 +21416,7 @@ tsubst_copy_and_build (tree t,
>   	tree stmt_expr = begin_stmt_expr ();
>   
>   	cur_stmt_expr = stmt_expr;
> -	tsubst_expr (STMT_EXPR_STMT (t), args, complain, in_decl);
> +	tsubst_stmt (STMT_EXPR_STMT (t), args, complain, in_decl);
>   	stmt_expr = finish_stmt_expr (stmt_expr, false);
>   	cur_stmt_expr = old_stmt_expr;
>   
> @@ -21460,7 +21443,8 @@ tsubst_copy_and_build (tree t,
>         }
>   
>       case TRANSACTION_EXPR:
> -      RETURN (tsubst_expr (t, args, complain, in_decl));
> +      gcc_checking_assert (!TRANSACTION_EXPR_IS_STMT (t));
> +      RETURN (tsubst_stmt (t, args, complain, in_decl));
>   
>       case PAREN_EXPR:
>         if (REF_PARENTHESIZED_P (t))
> @@ -21541,12 +21525,9 @@ tsubst_copy_and_build (tree t,
>   
>       default:
>         /* Handle Objective-C++ constructs, if appropriate.  */
> -      {
> -	tree subst
> -	  = objcp_tsubst_copy_and_build (t, args, complain, in_decl);
> -	if (subst)
> -	  RETURN (subst);
> -      }
> +      if (tree subst = objcp_tsubst_expr (t, args, complain, in_decl))
> +	RETURN (subst);
> +
>         /* We shouldn't get here, but keep going if !flag_checking.  */
>         if (flag_checking)
>   	gcc_unreachable ();
> @@ -26582,9 +26563,9 @@ maybe_instantiate_noexcept (tree fn, tsubst_flags_t complain)
>   	    ++processing_template_decl;
>   
>   	  /* Do deferred instantiation of the noexcept-specifier.  */
> -	  noex = tsubst_copy_and_build (DEFERRED_NOEXCEPT_PATTERN (noex),
> -					DEFERRED_NOEXCEPT_ARGS (noex),
> -					tf_warning_or_error, fn);
> +	  noex = tsubst_expr (DEFERRED_NOEXCEPT_PATTERN (noex),
> +			      DEFERRED_NOEXCEPT_ARGS (noex),
> +			      tf_warning_or_error, fn);
>   
>   	  /* Build up the noexcept-specification.  */
>   	  spec = build_noexcept_spec (noex, tf_warning_or_error);
> @@ -26758,7 +26739,7 @@ instantiate_body (tree pattern, tree args, tree d, bool nested_p)
>   			tf_warning_or_error, d);
>         else
>   	{
> -	  tsubst_expr (DECL_SAVED_TREE (code_pattern), args,
> +	  tsubst_stmt (DECL_SAVED_TREE (code_pattern), args,
>   		       tf_warning_or_error, DECL_TI_TEMPLATE (d));
>   
>   	  /* Set the current input_location to the end of the function
> @@ -27278,8 +27259,8 @@ tsubst_initializer_list (tree t, tree argvec)
>   		decl = tsubst (TREE_PURPOSE (t), argvec,
>   			       tf_warning_or_error, NULL_TREE);
>   	      else
> -		decl = tsubst_copy_and_build (TREE_PURPOSE (t), argvec,
> -					      tf_warning_or_error, NULL_TREE);
> +		decl = tsubst_expr (TREE_PURPOSE (t), argvec,
> +				    tf_warning_or_error, NULL_TREE);
>   
>                 decl = expand_member_init (decl);
>                 if (decl && !DECL_P (decl))
> diff --git a/gcc/objcp/objcp-lang.cc b/gcc/objcp/objcp-lang.cc
> index 9887209b9c8..5b04cd66290 100644
> --- a/gcc/objcp/objcp-lang.cc
> +++ b/gcc/objcp/objcp-lang.cc
> @@ -50,11 +50,10 @@ struct lang_hooks lang_hooks = LANG_HOOKS_INITIALIZER;
>      there should be very few (if any) routines below.  */
>   
>   tree
> -objcp_tsubst_copy_and_build (tree t, tree args, tsubst_flags_t complain,
> -			     tree in_decl)
> +objcp_tsubst_expr (tree t, tree args, tsubst_flags_t complain, tree in_decl)
>   {
>   #define RECURSE(NODE)							\
> -  tsubst_copy_and_build (NODE, args, complain, in_decl)
> +  tsubst_expr (NODE, args, complain, in_decl)
>   
>     /* The following two can only occur in Objective-C++.  */
>