c++: some missing-SFINAE fixes

  It looks like we aren't respecting SFINAE for:

  * an invalid/non-constant conditional explicit-specifier
  * a non-constant conditional noexcept-specifier
  * a non-constant argument to __integer_pack

This patch fixes these issues in the usual way, by passing complain
and propagating error_mark_node appropriately.

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

gcc/cp/ChangeLog:

	* decl.cc (build_explicit_specifier): Pass complain to
	cxx_constant_value.
	* except.cc (build_noexcept_spec): Likewise.
	* pt.cc (expand_integer_pack): Likewise.
	(tsubst_function_decl): Propagate error_mark_node returned
	from build_explicit_specifier.

gcc/testsuite/ChangeLog:

	* g++.dg/cpp1z/noexcept-type26.C: New test.
	* g++.dg/cpp2a/explicit19.C: New test.
	* g++.dg/ext/integer-pack6.C: New test.
---
 gcc/cp/decl.cc                               |  2 +-
 gcc/cp/except.cc                             |  2 +-
 gcc/cp/pt.cc                                 |  6 ++++--
 gcc/testsuite/g++.dg/cpp1z/noexcept-type26.C | 12 ++++++++++++
 gcc/testsuite/g++.dg/cpp2a/explicit19.C      | 12 ++++++++++++
 gcc/testsuite/g++.dg/ext/integer-pack6.C     | 13 +++++++++++++
 6 files changed, 43 insertions(+), 4 deletions(-)
 create mode 100644 gcc/testsuite/g++.dg/cpp1z/noexcept-type26.C
 create mode 100644 gcc/testsuite/g++.dg/cpp2a/explicit19.C
 create mode 100644 gcc/testsuite/g++.dg/ext/integer-pack6.C
  

On 9/13/22 07:45, Patrick Palka wrote:
> It looks like we aren't respecting SFINAE for:
> 
>    * an invalid/non-constant conditional explicit-specifier
>    * a non-constant conditional noexcept-specifier
>    * a non-constant argument to __integer_pack
> 
> This patch fixes these issues in the usual way, by passing complain
> and propagating error_mark_node appropriately.
> 
> Bootstrapped and regtested on x86_64-pc-linux-gnu, does this look OK for
> trunk?
> 
> gcc/cp/ChangeLog:
> 
> 	* decl.cc (build_explicit_specifier): Pass complain to
> 	cxx_constant_value.
> 	* except.cc (build_noexcept_spec): Likewise.
> 	* pt.cc (expand_integer_pack): Likewise.
> 	(tsubst_function_decl): Propagate error_mark_node returned
> 	from build_explicit_specifier.
> 
> gcc/testsuite/ChangeLog:
> 
> 	* g++.dg/cpp1z/noexcept-type26.C: New test.
> 	* g++.dg/cpp2a/explicit19.C: New test.
> 	* g++.dg/ext/integer-pack6.C: New test.
> ---
>   gcc/cp/decl.cc                               |  2 +-
>   gcc/cp/except.cc                             |  2 +-
>   gcc/cp/pt.cc                                 |  6 ++++--
>   gcc/testsuite/g++.dg/cpp1z/noexcept-type26.C | 12 ++++++++++++
>   gcc/testsuite/g++.dg/cpp2a/explicit19.C      | 12 ++++++++++++
>   gcc/testsuite/g++.dg/ext/integer-pack6.C     | 13 +++++++++++++
>   6 files changed, 43 insertions(+), 4 deletions(-)
>   create mode 100644 gcc/testsuite/g++.dg/cpp1z/noexcept-type26.C
>   create mode 100644 gcc/testsuite/g++.dg/cpp2a/explicit19.C
>   create mode 100644 gcc/testsuite/g++.dg/ext/integer-pack6.C
> 
> diff --git a/gcc/cp/decl.cc b/gcc/cp/decl.cc
> index 936f1cf0197..5404d7e084c 100644
> --- a/gcc/cp/decl.cc
> +++ b/gcc/cp/decl.cc
> @@ -18557,7 +18557,7 @@ build_explicit_specifier (tree expr, tsubst_flags_t complain)
>   
>     expr = build_converted_constant_bool_expr (expr, complain);
>     expr = instantiate_non_dependent_expr (expr, complain);
> -  expr = cxx_constant_value (expr);
> +  expr = cxx_constant_value (expr, NULL_TREE, complain);

The patch is OK, but perhaps we want another overload that omits the 
object parameter?

>     return expr;
>   }
>   
> diff --git a/gcc/cp/except.cc b/gcc/cp/except.cc
> index 7fdbc747c22..4d7f0ce102d 100644
> --- a/gcc/cp/except.cc
> +++ b/gcc/cp/except.cc
> @@ -1257,7 +1257,7 @@ build_noexcept_spec (tree expr, tsubst_flags_t complain)
>       {
>         expr = build_converted_constant_bool_expr (expr, complain);
>         expr = instantiate_non_dependent_expr (expr, complain);
> -      expr = cxx_constant_value (expr);
> +      expr = cxx_constant_value (expr, NULL_TREE, complain);
>       }
>     if (TREE_CODE (expr) == INTEGER_CST)
>       {
> diff --git a/gcc/cp/pt.cc b/gcc/cp/pt.cc
> index 1c6f4b84612..f16f5ffca20 100644
> --- a/gcc/cp/pt.cc
> +++ b/gcc/cp/pt.cc
> @@ -3869,7 +3869,7 @@ expand_integer_pack (tree call, tree args, tsubst_flags_t complain,
>     else
>       {
>         hi = instantiate_non_dependent_expr (hi, complain);
> -      hi = cxx_constant_value (hi);
> +      hi = cxx_constant_value (hi, NULL_TREE, complain);
>         int len = valid_constant_size_p (hi) ? tree_to_shwi (hi) : -1;
>   
>         /* Calculate the largest value of len that won't make the size of the vec
> @@ -14312,7 +14312,9 @@ tsubst_function_decl (tree t, tree args, tsubst_flags_t complain,
>   				    /*function_p=*/false,
>   				    /*i_c_e_p=*/true);
>         spec = build_explicit_specifier (spec, complain);
> -      if (instantiation_dependent_expression_p (spec))
> +      if (spec == error_mark_node)
> +	return error_mark_node;
> +      else if (instantiation_dependent_expression_p (spec))
>   	store_explicit_specifier (r, spec);
>         else
>   	{
> diff --git a/gcc/testsuite/g++.dg/cpp1z/noexcept-type26.C b/gcc/testsuite/g++.dg/cpp1z/noexcept-type26.C
> new file mode 100644
> index 00000000000..73058395f0a
> --- /dev/null
> +++ b/gcc/testsuite/g++.dg/cpp1z/noexcept-type26.C
> @@ -0,0 +1,12 @@
> +// Verify a non-constant conditional noexcept-specifier of a function type
> +// is a SFINAE error.
> +// { dg-do compile { target c++17 } }
> +
> +template<class T> void f(void() noexcept(T::value)) = delete;
> +template<class T> void f(...);
> +
> +struct B { static bool value; };
> +
> +int main() {
> +  f<B>(nullptr);
> +}
> diff --git a/gcc/testsuite/g++.dg/cpp2a/explicit19.C b/gcc/testsuite/g++.dg/cpp2a/explicit19.C
> new file mode 100644
> index 00000000000..47903813680
> --- /dev/null
> +++ b/gcc/testsuite/g++.dg/cpp2a/explicit19.C
> @@ -0,0 +1,12 @@
> +// Verify a conditional explicit-specifier is a SFINAE context.
> +// { dg-do compile { target c++20 } }
> +
> +struct A {
> +  template<class T> explicit(T::value) A(T) = delete;
> +  A(...);
> +};
> +
> +struct B { static bool value; };
> +
> +A x(0);
> +A y(B{});
> diff --git a/gcc/testsuite/g++.dg/ext/integer-pack6.C b/gcc/testsuite/g++.dg/ext/integer-pack6.C
> new file mode 100644
> index 00000000000..7e16bc44b40
> --- /dev/null
> +++ b/gcc/testsuite/g++.dg/ext/integer-pack6.C
> @@ -0,0 +1,13 @@
> +// Verify a non-constant argument to __integer_pack is a SFINAE error.
> +// { dg-do compile { target c++11 } }
> +
> +template<int...> struct A { };
> +
> +template<class T> auto f(int) -> A<__integer_pack(T::value)...> = delete;
> +template<class T> void f(...);
> +
> +struct B { static int value; };
> +
> +int main() {
> +  f<B>(0);
> +}
  

On Tue, 13 Sep 2022, Jason Merrill wrote:

> On 9/13/22 07:45, Patrick Palka wrote:
> > It looks like we aren't respecting SFINAE for:
> > 
> >    * an invalid/non-constant conditional explicit-specifier
> >    * a non-constant conditional noexcept-specifier
> >    * a non-constant argument to __integer_pack
> > 
> > This patch fixes these issues in the usual way, by passing complain
> > and propagating error_mark_node appropriately.
> > 
> > Bootstrapped and regtested on x86_64-pc-linux-gnu, does this look OK for
> > trunk?
> > 
> > gcc/cp/ChangeLog:
> > 
> > 	* decl.cc (build_explicit_specifier): Pass complain to
> > 	cxx_constant_value.
> > 	* except.cc (build_noexcept_spec): Likewise.
> > 	* pt.cc (expand_integer_pack): Likewise.
> > 	(tsubst_function_decl): Propagate error_mark_node returned
> > 	from build_explicit_specifier.
> > 
> > gcc/testsuite/ChangeLog:
> > 
> > 	* g++.dg/cpp1z/noexcept-type26.C: New test.
> > 	* g++.dg/cpp2a/explicit19.C: New test.
> > 	* g++.dg/ext/integer-pack6.C: New test.
> > ---
> >   gcc/cp/decl.cc                               |  2 +-
> >   gcc/cp/except.cc                             |  2 +-
> >   gcc/cp/pt.cc                                 |  6 ++++--
> >   gcc/testsuite/g++.dg/cpp1z/noexcept-type26.C | 12 ++++++++++++
> >   gcc/testsuite/g++.dg/cpp2a/explicit19.C      | 12 ++++++++++++
> >   gcc/testsuite/g++.dg/ext/integer-pack6.C     | 13 +++++++++++++
> >   6 files changed, 43 insertions(+), 4 deletions(-)
> >   create mode 100644 gcc/testsuite/g++.dg/cpp1z/noexcept-type26.C
> >   create mode 100644 gcc/testsuite/g++.dg/cpp2a/explicit19.C
> >   create mode 100644 gcc/testsuite/g++.dg/ext/integer-pack6.C
> > 
> > diff --git a/gcc/cp/decl.cc b/gcc/cp/decl.cc
> > index 936f1cf0197..5404d7e084c 100644
> > --- a/gcc/cp/decl.cc
> > +++ b/gcc/cp/decl.cc
> > @@ -18557,7 +18557,7 @@ build_explicit_specifier (tree expr, tsubst_flags_t
> > complain)
> >       expr = build_converted_constant_bool_expr (expr, complain);
> >     expr = instantiate_non_dependent_expr (expr, complain);
> > -  expr = cxx_constant_value (expr);
> > +  expr = cxx_constant_value (expr, NULL_TREE, complain);
> 
> The patch is OK, but perhaps we want another overload that omits the object
> parameter?

Thanks -- sounds good, like the following incremental patch?

-- >8 --

Subject: [PATCH] c++: two-parameter version of cxx_constant_value

Since some callers need the complain parameter but not the object
parameter, let's introduce and use an overload of cxx_constant_value
that omits the latter.

gcc/cp/ChangeLog:

	* cp-tree.h (cxx_constant_value): Define two-parameter version
	that omits the object parameter.
	* decl.cc (build_explicit_specifier): Omit NULL_TREE object
	argument to cxx_constant_value.
	* except.cc (build_noexcept_spec): Likewise.
	* pt.cc (expand_integer_pack): Likewise.
	(fold_targs_r): Likewise.
	* semantics.cc (finish_if_stmt_cond): Likewise.
---
 gcc/cp/cp-tree.h    | 2 ++
 gcc/cp/decl.cc      | 2 +-
 gcc/cp/except.cc    | 2 +-
 gcc/cp/pt.cc        | 4 ++--
 gcc/cp/semantics.cc | 2 +-
 5 files changed, 7 insertions(+), 5 deletions(-)

diff --git a/gcc/cp/cp-tree.h b/gcc/cp/cp-tree.h
index 2ba44e80e20..1eb176d4a50 100644
--- a/gcc/cp/cp-tree.h
+++ b/gcc/cp/cp-tree.h
@@ -8414,6 +8414,8 @@ extern bool require_rvalue_constant_expression (tree);
 extern bool require_potential_rvalue_constant_expression (tree);
 extern tree cxx_constant_value			(tree, tree = NULL_TREE,
 						 tsubst_flags_t = tf_error);
+inline tree cxx_constant_value (tree t, tsubst_flags_t complain)
+{ return cxx_constant_value (t, NULL_TREE, complain); }
 extern void cxx_constant_dtor			(tree, tree);
 extern tree cxx_constant_init			(tree, tree = NULL_TREE);
 extern tree maybe_constant_value		(tree, tree = NULL_TREE, bool = false);
diff --git a/gcc/cp/decl.cc b/gcc/cp/decl.cc
index 5404d7e084c..006e9affcba 100644
--- a/gcc/cp/decl.cc
+++ b/gcc/cp/decl.cc
@@ -18557,7 +18557,7 @@ build_explicit_specifier (tree expr, tsubst_flags_t complain)
 
   expr = build_converted_constant_bool_expr (expr, complain);
   expr = instantiate_non_dependent_expr (expr, complain);
-  expr = cxx_constant_value (expr, NULL_TREE, complain);
+  expr = cxx_constant_value (expr, complain);
   return expr;
 }
 
diff --git a/gcc/cp/except.cc b/gcc/cp/except.cc
index 4d7f0ce102d..048612de400 100644
--- a/gcc/cp/except.cc
+++ b/gcc/cp/except.cc
@@ -1257,7 +1257,7 @@ build_noexcept_spec (tree expr, tsubst_flags_t complain)
     {
       expr = build_converted_constant_bool_expr (expr, complain);
       expr = instantiate_non_dependent_expr (expr, complain);
-      expr = cxx_constant_value (expr, NULL_TREE, complain);
+      expr = cxx_constant_value (expr, complain);
     }
   if (TREE_CODE (expr) == INTEGER_CST)
     {
diff --git a/gcc/cp/pt.cc b/gcc/cp/pt.cc
index 074179288b6..db4e808adec 100644
--- a/gcc/cp/pt.cc
+++ b/gcc/cp/pt.cc
@@ -3869,7 +3869,7 @@ expand_integer_pack (tree call, tree args, tsubst_flags_t complain,
   else
     {
       hi = instantiate_non_dependent_expr (hi, complain);
-      hi = cxx_constant_value (hi, NULL_TREE, complain);
+      hi = cxx_constant_value (hi, complain);
       int len = valid_constant_size_p (hi) ? tree_to_shwi (hi) : -1;
 
       /* Calculate the largest value of len that won't make the size of the vec
@@ -20121,7 +20121,7 @@ fold_targs_r (tree targs, tsubst_flags_t complain)
 	       && !glvalue_p (elt)
 	       && !TREE_CONSTANT (elt))
 	{
-	  elt = cxx_constant_value (elt, NULL_TREE, complain);
+	  elt = cxx_constant_value (elt, complain);
 	  if (elt == error_mark_node)
 	    return false;
 	}
diff --git a/gcc/cp/semantics.cc b/gcc/cp/semantics.cc
index 3edefb2fca2..4f189978484 100644
--- a/gcc/cp/semantics.cc
+++ b/gcc/cp/semantics.cc
@@ -1042,7 +1042,7 @@ finish_if_stmt_cond (tree orig_cond, tree if_stmt)
     {
       maybe_warn_for_constant_evaluated (cond, /*constexpr_if=*/true);
       cond = instantiate_non_dependent_expr (cond);
-      cond = cxx_constant_value (cond, NULL_TREE);
+      cond = cxx_constant_value (cond);
     }
   else
     {
  

On 9/13/22 09:46, Patrick Palka wrote:
> On Tue, 13 Sep 2022, Jason Merrill wrote:
> 
>> On 9/13/22 07:45, Patrick Palka wrote:
>>> It looks like we aren't respecting SFINAE for:
>>>
>>>     * an invalid/non-constant conditional explicit-specifier
>>>     * a non-constant conditional noexcept-specifier
>>>     * a non-constant argument to __integer_pack
>>>
>>> This patch fixes these issues in the usual way, by passing complain
>>> and propagating error_mark_node appropriately.
>>>
>>> Bootstrapped and regtested on x86_64-pc-linux-gnu, does this look OK for
>>> trunk?
>>>
>>> gcc/cp/ChangeLog:
>>>
>>> 	* decl.cc (build_explicit_specifier): Pass complain to
>>> 	cxx_constant_value.
>>> 	* except.cc (build_noexcept_spec): Likewise.
>>> 	* pt.cc (expand_integer_pack): Likewise.
>>> 	(tsubst_function_decl): Propagate error_mark_node returned
>>> 	from build_explicit_specifier.
>>>
>>> gcc/testsuite/ChangeLog:
>>>
>>> 	* g++.dg/cpp1z/noexcept-type26.C: New test.
>>> 	* g++.dg/cpp2a/explicit19.C: New test.
>>> 	* g++.dg/ext/integer-pack6.C: New test.
>>> ---
>>>    gcc/cp/decl.cc                               |  2 +-
>>>    gcc/cp/except.cc                             |  2 +-
>>>    gcc/cp/pt.cc                                 |  6 ++++--
>>>    gcc/testsuite/g++.dg/cpp1z/noexcept-type26.C | 12 ++++++++++++
>>>    gcc/testsuite/g++.dg/cpp2a/explicit19.C      | 12 ++++++++++++
>>>    gcc/testsuite/g++.dg/ext/integer-pack6.C     | 13 +++++++++++++
>>>    6 files changed, 43 insertions(+), 4 deletions(-)
>>>    create mode 100644 gcc/testsuite/g++.dg/cpp1z/noexcept-type26.C
>>>    create mode 100644 gcc/testsuite/g++.dg/cpp2a/explicit19.C
>>>    create mode 100644 gcc/testsuite/g++.dg/ext/integer-pack6.C
>>>
>>> diff --git a/gcc/cp/decl.cc b/gcc/cp/decl.cc
>>> index 936f1cf0197..5404d7e084c 100644
>>> --- a/gcc/cp/decl.cc
>>> +++ b/gcc/cp/decl.cc
>>> @@ -18557,7 +18557,7 @@ build_explicit_specifier (tree expr, tsubst_flags_t
>>> complain)
>>>        expr = build_converted_constant_bool_expr (expr, complain);
>>>      expr = instantiate_non_dependent_expr (expr, complain);
>>> -  expr = cxx_constant_value (expr);
>>> +  expr = cxx_constant_value (expr, NULL_TREE, complain);
>>
>> The patch is OK, but perhaps we want another overload that omits the object
>> parameter?
> 
> Thanks -- sounds good, like the following incremental patch?

OK.

> -- >8 --
> 
> Subject: [PATCH] c++: two-parameter version of cxx_constant_value
> 
> Since some callers need the complain parameter but not the object
> parameter, let's introduce and use an overload of cxx_constant_value
> that omits the latter.
> 
> gcc/cp/ChangeLog:
> 
> 	* cp-tree.h (cxx_constant_value): Define two-parameter version
> 	that omits the object parameter.
> 	* decl.cc (build_explicit_specifier): Omit NULL_TREE object
> 	argument to cxx_constant_value.
> 	* except.cc (build_noexcept_spec): Likewise.
> 	* pt.cc (expand_integer_pack): Likewise.
> 	(fold_targs_r): Likewise.
> 	* semantics.cc (finish_if_stmt_cond): Likewise.
> ---
>   gcc/cp/cp-tree.h    | 2 ++
>   gcc/cp/decl.cc      | 2 +-
>   gcc/cp/except.cc    | 2 +-
>   gcc/cp/pt.cc        | 4 ++--
>   gcc/cp/semantics.cc | 2 +-
>   5 files changed, 7 insertions(+), 5 deletions(-)
> 
> diff --git a/gcc/cp/cp-tree.h b/gcc/cp/cp-tree.h
> index 2ba44e80e20..1eb176d4a50 100644
> --- a/gcc/cp/cp-tree.h
> +++ b/gcc/cp/cp-tree.h
> @@ -8414,6 +8414,8 @@ extern bool require_rvalue_constant_expression (tree);
>   extern bool require_potential_rvalue_constant_expression (tree);
>   extern tree cxx_constant_value			(tree, tree = NULL_TREE,
>   						 tsubst_flags_t = tf_error);
> +inline tree cxx_constant_value (tree t, tsubst_flags_t complain)
> +{ return cxx_constant_value (t, NULL_TREE, complain); }
>   extern void cxx_constant_dtor			(tree, tree);
>   extern tree cxx_constant_init			(tree, tree = NULL_TREE);
>   extern tree maybe_constant_value		(tree, tree = NULL_TREE, bool = false);
> diff --git a/gcc/cp/decl.cc b/gcc/cp/decl.cc
> index 5404d7e084c..006e9affcba 100644
> --- a/gcc/cp/decl.cc
> +++ b/gcc/cp/decl.cc
> @@ -18557,7 +18557,7 @@ build_explicit_specifier (tree expr, tsubst_flags_t complain)
>   
>     expr = build_converted_constant_bool_expr (expr, complain);
>     expr = instantiate_non_dependent_expr (expr, complain);
> -  expr = cxx_constant_value (expr, NULL_TREE, complain);
> +  expr = cxx_constant_value (expr, complain);
>     return expr;
>   }
>   
> diff --git a/gcc/cp/except.cc b/gcc/cp/except.cc
> index 4d7f0ce102d..048612de400 100644
> --- a/gcc/cp/except.cc
> +++ b/gcc/cp/except.cc
> @@ -1257,7 +1257,7 @@ build_noexcept_spec (tree expr, tsubst_flags_t complain)
>       {
>         expr = build_converted_constant_bool_expr (expr, complain);
>         expr = instantiate_non_dependent_expr (expr, complain);
> -      expr = cxx_constant_value (expr, NULL_TREE, complain);
> +      expr = cxx_constant_value (expr, complain);
>       }
>     if (TREE_CODE (expr) == INTEGER_CST)
>       {
> diff --git a/gcc/cp/pt.cc b/gcc/cp/pt.cc
> index 074179288b6..db4e808adec 100644
> --- a/gcc/cp/pt.cc
> +++ b/gcc/cp/pt.cc
> @@ -3869,7 +3869,7 @@ expand_integer_pack (tree call, tree args, tsubst_flags_t complain,
>     else
>       {
>         hi = instantiate_non_dependent_expr (hi, complain);
> -      hi = cxx_constant_value (hi, NULL_TREE, complain);
> +      hi = cxx_constant_value (hi, complain);
>         int len = valid_constant_size_p (hi) ? tree_to_shwi (hi) : -1;
>   
>         /* Calculate the largest value of len that won't make the size of the vec
> @@ -20121,7 +20121,7 @@ fold_targs_r (tree targs, tsubst_flags_t complain)
>   	       && !glvalue_p (elt)
>   	       && !TREE_CONSTANT (elt))
>   	{
> -	  elt = cxx_constant_value (elt, NULL_TREE, complain);
> +	  elt = cxx_constant_value (elt, complain);
>   	  if (elt == error_mark_node)
>   	    return false;
>   	}
> diff --git a/gcc/cp/semantics.cc b/gcc/cp/semantics.cc
> index 3edefb2fca2..4f189978484 100644
> --- a/gcc/cp/semantics.cc
> +++ b/gcc/cp/semantics.cc
> @@ -1042,7 +1042,7 @@ finish_if_stmt_cond (tree orig_cond, tree if_stmt)
>       {
>         maybe_warn_for_constant_evaluated (cond, /*constexpr_if=*/true);
>         cond = instantiate_non_dependent_expr (cond);
> -      cond = cxx_constant_value (cond, NULL_TREE);
> +      cond = cxx_constant_value (cond);
>       }
>     else
>       {