c++: Fix error recovery when redeclaring enum in different module [PR99573]

Message ID 65c981eb.050a0220.8c171.ba05@mx.google.com
State New
Headers
Series c++: Fix error recovery when redeclaring enum in different module [PR99573] |

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Commit Message

Nathaniel Shead Feb. 12, 2024, 2:26 a.m. UTC
  Bootstrapped and regtested on x86_64-pc-linux-gnu, OK for trunk?

-- >8 --

This ensures that with modules enabled, redeclaring an enum in the wrong
module or with the wrong underlying type no longer ICEs.

The patch also rearranges the order of the checks a little because I
think it's probably more important to note that you can't redeclare the
enum all before complaining about mismatched underlying types etc.

As a drive by this patch also adds some missing diagnostic groups, and
rewords the module redeclaration error message to more closely match the
wording used in other places this check is done.

	PR c++/99573

gcc/cp/ChangeLog:

	* decl.cc (start_enum): Reorder check for redeclaring in module.
	Add missing auto_diagnostic_groups.

gcc/testsuite/ChangeLog:

	* g++.dg/modules/enum-12.C: New test.

Signed-off-by: Nathaniel Shead <nathanieloshead@gmail.com>
---
 gcc/cp/decl.cc                         | 31 +++++++++++++++-----------
 gcc/testsuite/g++.dg/modules/enum-12.C | 10 +++++++++
 2 files changed, 28 insertions(+), 13 deletions(-)
 create mode 100644 gcc/testsuite/g++.dg/modules/enum-12.C
  

Comments

Jason Merrill Feb. 13, 2024, 11:12 p.m. UTC | #1
On 2/11/24 21:26, Nathaniel Shead wrote:
> Bootstrapped and regtested on x86_64-pc-linux-gnu, OK for trunk?
> 
> -- >8 --
> 
> This ensures that with modules enabled, redeclaring an enum in the wrong
> module or with the wrong underlying type no longer ICEs.
> 
> The patch also rearranges the order of the checks a little because I
> think it's probably more important to note that you can't redeclare the
> enum all before complaining about mismatched underlying types etc.
> 
> As a drive by this patch also adds some missing diagnostic groups, and
> rewords the module redeclaration error message to more closely match the
> wording used in other places this check is done.
> 
> 	PR c++/99573
> 
> gcc/cp/ChangeLog:
> 
> 	* decl.cc (start_enum): Reorder check for redeclaring in module.
> 	Add missing auto_diagnostic_groups.
> 
> gcc/testsuite/ChangeLog:
> 
> 	* g++.dg/modules/enum-12.C: New test.
> 
> Signed-off-by: Nathaniel Shead <nathanieloshead@gmail.com>
> ---
>   gcc/cp/decl.cc                         | 31 +++++++++++++++-----------
>   gcc/testsuite/g++.dg/modules/enum-12.C | 10 +++++++++
>   2 files changed, 28 insertions(+), 13 deletions(-)
>   create mode 100644 gcc/testsuite/g++.dg/modules/enum-12.C
> 
> diff --git a/gcc/cp/decl.cc b/gcc/cp/decl.cc
> index 3e41fd4fa31..f982b5f88de 100644
> --- a/gcc/cp/decl.cc
> +++ b/gcc/cp/decl.cc
> @@ -16951,12 +16951,28 @@ start_enum (tree name, tree enumtype, tree underlying_type,
>   				     /*tag_scope=*/TAG_how::CURRENT_ONLY,
>   				     /*template_header_p=*/false);
>   
> +  /* Attempt to set the declaring module.  */
> +  if (modules_p () && enumtype && TREE_CODE (enumtype) == ENUMERAL_TYPE)
> +    {
> +      tree decl = TYPE_NAME (enumtype);
> +      if (!module_may_redeclare (decl))
> +	{
> +	  auto_diagnostic_group d;
> +	  error ("cannot declare %qD in different module", decl);
> +	  inform (DECL_SOURCE_LOCATION (decl), "previously declared here");
> +	  enumtype = error_mark_node;
> +	}
> +      else
> +	set_instantiating_module (decl);
> +    }
> +
>     /* In case of a template_decl, the only check that should be deferred
>        to instantiation time is the comparison of underlying types.  */
>     if (enumtype && TREE_CODE (enumtype) == ENUMERAL_TYPE)
>       {

How about moving the module checks here, instead of a few lines higher, 
where you need to duplicate the ENUMERAL_TYPE condition?

>         if (scoped_enum_p != SCOPED_ENUM_P (enumtype))
>   	{
> +	  auto_diagnostic_group d;
>   	  error_at (input_location, "scoped/unscoped mismatch "
>   		    "in enum %q#T", enumtype);
>   	  inform (DECL_SOURCE_LOCATION (TYPE_MAIN_DECL (enumtype)),
> @@ -16965,6 +16981,7 @@ start_enum (tree name, tree enumtype, tree underlying_type,
>   	}
>         else if (ENUM_FIXED_UNDERLYING_TYPE_P (enumtype) != !! underlying_type)
>   	{
> +	  auto_diagnostic_group d;
>   	  error_at (input_location, "underlying type mismatch "
>   		    "in enum %q#T", enumtype);
>   	  inform (DECL_SOURCE_LOCATION (TYPE_MAIN_DECL (enumtype)),
> @@ -16975,25 +16992,13 @@ start_enum (tree name, tree enumtype, tree underlying_type,
>   	       && !same_type_p (underlying_type,
>   				ENUM_UNDERLYING_TYPE (enumtype)))
>   	{
> +	  auto_diagnostic_group d;
>   	  error_at (input_location, "different underlying type "
>   		    "in enum %q#T", enumtype);
>   	  inform (DECL_SOURCE_LOCATION (TYPE_MAIN_DECL (enumtype)),
>   		  "previous definition here");
>   	  underlying_type = NULL_TREE;
>   	}
> -
> -      if (modules_p ())
> -	{
> -	  if (!module_may_redeclare (TYPE_NAME (enumtype)))
> -	    {
> -	      error ("cannot define %qD in different module",
> -		     TYPE_NAME (enumtype));
> -	      inform (DECL_SOURCE_LOCATION (TYPE_NAME (enumtype)),
> -		      "declared here");
> -	      enumtype = error_mark_node;
> -	    }
> -	  set_instantiating_module (TYPE_NAME (enumtype));
> -	}
>       }
>   
>     if (!enumtype || TREE_CODE (enumtype) != ENUMERAL_TYPE
> diff --git a/gcc/testsuite/g++.dg/modules/enum-12.C b/gcc/testsuite/g++.dg/modules/enum-12.C
> new file mode 100644
> index 00000000000..57eeb85d92a
> --- /dev/null
> +++ b/gcc/testsuite/g++.dg/modules/enum-12.C
> @@ -0,0 +1,10 @@
> +// PR c++/99573
> +// { dg-additional-options "-fmodules-ts" }
> +// { dg-module-cmi !foo }
> +
> +export module foo;
> +namespace std {
> +  enum class align_val_t : decltype(sizeof(int)) {};  // { dg-error "different module" }
> +}
> +
> +// { dg-prune-output "not writing module" }
  
Nathaniel Shead Feb. 13, 2024, 11:20 p.m. UTC | #2
On Tue, Feb 13, 2024 at 06:12:51PM -0500, Jason Merrill wrote:
> On 2/11/24 21:26, Nathaniel Shead wrote:
> > Bootstrapped and regtested on x86_64-pc-linux-gnu, OK for trunk?
> > 
> > -- >8 --
> > 
> > This ensures that with modules enabled, redeclaring an enum in the wrong
> > module or with the wrong underlying type no longer ICEs.
> > 
> > The patch also rearranges the order of the checks a little because I
> > think it's probably more important to note that you can't redeclare the
> > enum all before complaining about mismatched underlying types etc.
> > 
> > As a drive by this patch also adds some missing diagnostic groups, and
> > rewords the module redeclaration error message to more closely match the
> > wording used in other places this check is done.
> > 
> > 	PR c++/99573
> > 
> > gcc/cp/ChangeLog:
> > 
> > 	* decl.cc (start_enum): Reorder check for redeclaring in module.
> > 	Add missing auto_diagnostic_groups.
> > 
> > gcc/testsuite/ChangeLog:
> > 
> > 	* g++.dg/modules/enum-12.C: New test.
> > 
> > Signed-off-by: Nathaniel Shead <nathanieloshead@gmail.com>
> > ---
> >   gcc/cp/decl.cc                         | 31 +++++++++++++++-----------
> >   gcc/testsuite/g++.dg/modules/enum-12.C | 10 +++++++++
> >   2 files changed, 28 insertions(+), 13 deletions(-)
> >   create mode 100644 gcc/testsuite/g++.dg/modules/enum-12.C
> > 
> > diff --git a/gcc/cp/decl.cc b/gcc/cp/decl.cc
> > index 3e41fd4fa31..f982b5f88de 100644
> > --- a/gcc/cp/decl.cc
> > +++ b/gcc/cp/decl.cc
> > @@ -16951,12 +16951,28 @@ start_enum (tree name, tree enumtype, tree underlying_type,
> >   				     /*tag_scope=*/TAG_how::CURRENT_ONLY,
> >   				     /*template_header_p=*/false);
> > +  /* Attempt to set the declaring module.  */
> > +  if (modules_p () && enumtype && TREE_CODE (enumtype) == ENUMERAL_TYPE)
> > +    {
> > +      tree decl = TYPE_NAME (enumtype);
> > +      if (!module_may_redeclare (decl))
> > +	{
> > +	  auto_diagnostic_group d;
> > +	  error ("cannot declare %qD in different module", decl);
> > +	  inform (DECL_SOURCE_LOCATION (decl), "previously declared here");
> > +	  enumtype = error_mark_node;
> > +	}
> > +      else
> > +	set_instantiating_module (decl);
> > +    }
> > +
> >     /* In case of a template_decl, the only check that should be deferred
> >        to instantiation time is the comparison of underlying types.  */
> >     if (enumtype && TREE_CODE (enumtype) == ENUMERAL_TYPE)
> >       {
> 
> How about moving the module checks here, instead of a few lines higher,
> where you need to duplicate the ENUMERAL_TYPE condition?

So like this?

-- >8 --

This ensures that with modules enabled, redeclaring an enum in the wrong
module or with the wrong underlying type no longer ICEs.

The patch also rearranges the order of the checks a little because I
think it's probably more important to note that you can't redeclare the
enum all before complaining about mismatched underlying types etc.

As a drive by this patch also adds some missing diagnostic groups, and
rewords the module redeclaration error message to more closely match the
wording used in other places this check is done.

	PR c++/99573

gcc/cp/ChangeLog:

	* decl.cc (start_enum): Reorder check for redeclaring in module.
	Add missing auto_diagnostic_groups.

gcc/testsuite/ChangeLog:

	* g++.dg/modules/enum-12.C: New test.

Signed-off-by: Nathaniel Shead <nathanieloshead@gmail.com>
---
 gcc/cp/decl.cc                         | 35 +++++++++++++++-----------
 gcc/testsuite/g++.dg/modules/enum-12.C | 10 ++++++++
 2 files changed, 31 insertions(+), 14 deletions(-)
 create mode 100644 gcc/testsuite/g++.dg/modules/enum-12.C

diff --git a/gcc/cp/decl.cc b/gcc/cp/decl.cc
index 3e41fd4fa31..d19d09adde4 100644
--- a/gcc/cp/decl.cc
+++ b/gcc/cp/decl.cc
@@ -16955,8 +16955,26 @@ start_enum (tree name, tree enumtype, tree underlying_type,
      to instantiation time is the comparison of underlying types.  */
   if (enumtype && TREE_CODE (enumtype) == ENUMERAL_TYPE)
     {
-      if (scoped_enum_p != SCOPED_ENUM_P (enumtype))
+      /* Attempt to set the declaring module.  */
+      if (modules_p ())
 	{
+	  tree decl = TYPE_NAME (enumtype);
+	  if (!module_may_redeclare (decl))
+	    {
+	      auto_diagnostic_group d;
+	      error ("cannot declare %qD in different module", decl);
+	      inform (DECL_SOURCE_LOCATION (decl), "previously declared here");
+	      enumtype = error_mark_node;
+	    }
+	  else
+	    set_instantiating_module (decl);
+	}
+
+      if (enumtype == error_mark_node)
+	;
+      else if (scoped_enum_p != SCOPED_ENUM_P (enumtype))
+	{
+	  auto_diagnostic_group d;
 	  error_at (input_location, "scoped/unscoped mismatch "
 		    "in enum %q#T", enumtype);
 	  inform (DECL_SOURCE_LOCATION (TYPE_MAIN_DECL (enumtype)),
@@ -16965,6 +16983,7 @@ start_enum (tree name, tree enumtype, tree underlying_type,
 	}
       else if (ENUM_FIXED_UNDERLYING_TYPE_P (enumtype) != !! underlying_type)
 	{
+	  auto_diagnostic_group d;
 	  error_at (input_location, "underlying type mismatch "
 		    "in enum %q#T", enumtype);
 	  inform (DECL_SOURCE_LOCATION (TYPE_MAIN_DECL (enumtype)),
@@ -16975,25 +16994,13 @@ start_enum (tree name, tree enumtype, tree underlying_type,
 	       && !same_type_p (underlying_type,
 				ENUM_UNDERLYING_TYPE (enumtype)))
 	{
+	  auto_diagnostic_group d;
 	  error_at (input_location, "different underlying type "
 		    "in enum %q#T", enumtype);
 	  inform (DECL_SOURCE_LOCATION (TYPE_MAIN_DECL (enumtype)),
 		  "previous definition here");
 	  underlying_type = NULL_TREE;
 	}
-
-      if (modules_p ())
-	{
-	  if (!module_may_redeclare (TYPE_NAME (enumtype)))
-	    {
-	      error ("cannot define %qD in different module",
-		     TYPE_NAME (enumtype));
-	      inform (DECL_SOURCE_LOCATION (TYPE_NAME (enumtype)),
-		      "declared here");
-	      enumtype = error_mark_node;
-	    }
-	  set_instantiating_module (TYPE_NAME (enumtype));
-	}
     }
 
   if (!enumtype || TREE_CODE (enumtype) != ENUMERAL_TYPE
diff --git a/gcc/testsuite/g++.dg/modules/enum-12.C b/gcc/testsuite/g++.dg/modules/enum-12.C
new file mode 100644
index 00000000000..57eeb85d92a
--- /dev/null
+++ b/gcc/testsuite/g++.dg/modules/enum-12.C
@@ -0,0 +1,10 @@
+// PR c++/99573
+// { dg-additional-options "-fmodules-ts" }
+// { dg-module-cmi !foo }
+
+export module foo;
+namespace std {
+  enum class align_val_t : decltype(sizeof(int)) {};  // { dg-error "different module" }
+}
+
+// { dg-prune-output "not writing module" }
  
Jason Merrill Feb. 14, 2024, 2:45 a.m. UTC | #3
On 2/13/24 18:20, Nathaniel Shead wrote:
> On Tue, Feb 13, 2024 at 06:12:51PM -0500, Jason Merrill wrote:
>> On 2/11/24 21:26, Nathaniel Shead wrote:
>>> Bootstrapped and regtested on x86_64-pc-linux-gnu, OK for trunk?
>>>
>>> -- >8 --
>>>
>>> This ensures that with modules enabled, redeclaring an enum in the wrong
>>> module or with the wrong underlying type no longer ICEs.
>>>
>>> The patch also rearranges the order of the checks a little because I
>>> think it's probably more important to note that you can't redeclare the
>>> enum all before complaining about mismatched underlying types etc.
>>>
>>> As a drive by this patch also adds some missing diagnostic groups, and
>>> rewords the module redeclaration error message to more closely match the
>>> wording used in other places this check is done.
>>>
>>> 	PR c++/99573
>>>
>>> gcc/cp/ChangeLog:
>>>
>>> 	* decl.cc (start_enum): Reorder check for redeclaring in module.
>>> 	Add missing auto_diagnostic_groups.
>>>
>>> gcc/testsuite/ChangeLog:
>>>
>>> 	* g++.dg/modules/enum-12.C: New test.
>>>
>>> Signed-off-by: Nathaniel Shead <nathanieloshead@gmail.com>
>>> ---
>>>    gcc/cp/decl.cc                         | 31 +++++++++++++++-----------
>>>    gcc/testsuite/g++.dg/modules/enum-12.C | 10 +++++++++
>>>    2 files changed, 28 insertions(+), 13 deletions(-)
>>>    create mode 100644 gcc/testsuite/g++.dg/modules/enum-12.C
>>>
>>> diff --git a/gcc/cp/decl.cc b/gcc/cp/decl.cc
>>> index 3e41fd4fa31..f982b5f88de 100644
>>> --- a/gcc/cp/decl.cc
>>> +++ b/gcc/cp/decl.cc
>>> @@ -16951,12 +16951,28 @@ start_enum (tree name, tree enumtype, tree underlying_type,
>>>    				     /*tag_scope=*/TAG_how::CURRENT_ONLY,
>>>    				     /*template_header_p=*/false);
>>> +  /* Attempt to set the declaring module.  */
>>> +  if (modules_p () && enumtype && TREE_CODE (enumtype) == ENUMERAL_TYPE)
>>> +    {
>>> +      tree decl = TYPE_NAME (enumtype);
>>> +      if (!module_may_redeclare (decl))
>>> +	{
>>> +	  auto_diagnostic_group d;
>>> +	  error ("cannot declare %qD in different module", decl);
>>> +	  inform (DECL_SOURCE_LOCATION (decl), "previously declared here");
>>> +	  enumtype = error_mark_node;
>>> +	}
>>> +      else
>>> +	set_instantiating_module (decl);
>>> +    }
>>> +
>>>      /* In case of a template_decl, the only check that should be deferred
>>>         to instantiation time is the comparison of underlying types.  */
>>>      if (enumtype && TREE_CODE (enumtype) == ENUMERAL_TYPE)
>>>        {
>>
>> How about moving the module checks here, instead of a few lines higher,
>> where you need to duplicate the ENUMERAL_TYPE condition?
> 
> So like this?

OK.

> -- >8 --
> 
> This ensures that with modules enabled, redeclaring an enum in the wrong
> module or with the wrong underlying type no longer ICEs.
> 
> The patch also rearranges the order of the checks a little because I
> think it's probably more important to note that you can't redeclare the
> enum all before complaining about mismatched underlying types etc.
> 
> As a drive by this patch also adds some missing diagnostic groups, and
> rewords the module redeclaration error message to more closely match the
> wording used in other places this check is done.
> 
> 	PR c++/99573
> 
> gcc/cp/ChangeLog:
> 
> 	* decl.cc (start_enum): Reorder check for redeclaring in module.
> 	Add missing auto_diagnostic_groups.
> 
> gcc/testsuite/ChangeLog:
> 
> 	* g++.dg/modules/enum-12.C: New test.
> 
> Signed-off-by: Nathaniel Shead <nathanieloshead@gmail.com>
> ---
>   gcc/cp/decl.cc                         | 35 +++++++++++++++-----------
>   gcc/testsuite/g++.dg/modules/enum-12.C | 10 ++++++++
>   2 files changed, 31 insertions(+), 14 deletions(-)
>   create mode 100644 gcc/testsuite/g++.dg/modules/enum-12.C
> 
> diff --git a/gcc/cp/decl.cc b/gcc/cp/decl.cc
> index 3e41fd4fa31..d19d09adde4 100644
> --- a/gcc/cp/decl.cc
> +++ b/gcc/cp/decl.cc
> @@ -16955,8 +16955,26 @@ start_enum (tree name, tree enumtype, tree underlying_type,
>        to instantiation time is the comparison of underlying types.  */
>     if (enumtype && TREE_CODE (enumtype) == ENUMERAL_TYPE)
>       {
> -      if (scoped_enum_p != SCOPED_ENUM_P (enumtype))
> +      /* Attempt to set the declaring module.  */
> +      if (modules_p ())
>   	{
> +	  tree decl = TYPE_NAME (enumtype);
> +	  if (!module_may_redeclare (decl))
> +	    {
> +	      auto_diagnostic_group d;
> +	      error ("cannot declare %qD in different module", decl);
> +	      inform (DECL_SOURCE_LOCATION (decl), "previously declared here");
> +	      enumtype = error_mark_node;
> +	    }
> +	  else
> +	    set_instantiating_module (decl);
> +	}
> +
> +      if (enumtype == error_mark_node)
> +	;
> +      else if (scoped_enum_p != SCOPED_ENUM_P (enumtype))
> +	{
> +	  auto_diagnostic_group d;
>   	  error_at (input_location, "scoped/unscoped mismatch "
>   		    "in enum %q#T", enumtype);
>   	  inform (DECL_SOURCE_LOCATION (TYPE_MAIN_DECL (enumtype)),
> @@ -16965,6 +16983,7 @@ start_enum (tree name, tree enumtype, tree underlying_type,
>   	}
>         else if (ENUM_FIXED_UNDERLYING_TYPE_P (enumtype) != !! underlying_type)
>   	{
> +	  auto_diagnostic_group d;
>   	  error_at (input_location, "underlying type mismatch "
>   		    "in enum %q#T", enumtype);
>   	  inform (DECL_SOURCE_LOCATION (TYPE_MAIN_DECL (enumtype)),
> @@ -16975,25 +16994,13 @@ start_enum (tree name, tree enumtype, tree underlying_type,
>   	       && !same_type_p (underlying_type,
>   				ENUM_UNDERLYING_TYPE (enumtype)))
>   	{
> +	  auto_diagnostic_group d;
>   	  error_at (input_location, "different underlying type "
>   		    "in enum %q#T", enumtype);
>   	  inform (DECL_SOURCE_LOCATION (TYPE_MAIN_DECL (enumtype)),
>   		  "previous definition here");
>   	  underlying_type = NULL_TREE;
>   	}
> -
> -      if (modules_p ())
> -	{
> -	  if (!module_may_redeclare (TYPE_NAME (enumtype)))
> -	    {
> -	      error ("cannot define %qD in different module",
> -		     TYPE_NAME (enumtype));
> -	      inform (DECL_SOURCE_LOCATION (TYPE_NAME (enumtype)),
> -		      "declared here");
> -	      enumtype = error_mark_node;
> -	    }
> -	  set_instantiating_module (TYPE_NAME (enumtype));
> -	}
>       }
>   
>     if (!enumtype || TREE_CODE (enumtype) != ENUMERAL_TYPE
> diff --git a/gcc/testsuite/g++.dg/modules/enum-12.C b/gcc/testsuite/g++.dg/modules/enum-12.C
> new file mode 100644
> index 00000000000..57eeb85d92a
> --- /dev/null
> +++ b/gcc/testsuite/g++.dg/modules/enum-12.C
> @@ -0,0 +1,10 @@
> +// PR c++/99573
> +// { dg-additional-options "-fmodules-ts" }
> +// { dg-module-cmi !foo }
> +
> +export module foo;
> +namespace std {
> +  enum class align_val_t : decltype(sizeof(int)) {};  // { dg-error "different module" }
> +}
> +
> +// { dg-prune-output "not writing module" }
  

Patch

diff --git a/gcc/cp/decl.cc b/gcc/cp/decl.cc
index 3e41fd4fa31..f982b5f88de 100644
--- a/gcc/cp/decl.cc
+++ b/gcc/cp/decl.cc
@@ -16951,12 +16951,28 @@  start_enum (tree name, tree enumtype, tree underlying_type,
 				     /*tag_scope=*/TAG_how::CURRENT_ONLY,
 				     /*template_header_p=*/false);
 
+  /* Attempt to set the declaring module.  */
+  if (modules_p () && enumtype && TREE_CODE (enumtype) == ENUMERAL_TYPE)
+    {
+      tree decl = TYPE_NAME (enumtype);
+      if (!module_may_redeclare (decl))
+	{
+	  auto_diagnostic_group d;
+	  error ("cannot declare %qD in different module", decl);
+	  inform (DECL_SOURCE_LOCATION (decl), "previously declared here");
+	  enumtype = error_mark_node;
+	}
+      else
+	set_instantiating_module (decl);
+    }
+
   /* In case of a template_decl, the only check that should be deferred
      to instantiation time is the comparison of underlying types.  */
   if (enumtype && TREE_CODE (enumtype) == ENUMERAL_TYPE)
     {
       if (scoped_enum_p != SCOPED_ENUM_P (enumtype))
 	{
+	  auto_diagnostic_group d;
 	  error_at (input_location, "scoped/unscoped mismatch "
 		    "in enum %q#T", enumtype);
 	  inform (DECL_SOURCE_LOCATION (TYPE_MAIN_DECL (enumtype)),
@@ -16965,6 +16981,7 @@  start_enum (tree name, tree enumtype, tree underlying_type,
 	}
       else if (ENUM_FIXED_UNDERLYING_TYPE_P (enumtype) != !! underlying_type)
 	{
+	  auto_diagnostic_group d;
 	  error_at (input_location, "underlying type mismatch "
 		    "in enum %q#T", enumtype);
 	  inform (DECL_SOURCE_LOCATION (TYPE_MAIN_DECL (enumtype)),
@@ -16975,25 +16992,13 @@  start_enum (tree name, tree enumtype, tree underlying_type,
 	       && !same_type_p (underlying_type,
 				ENUM_UNDERLYING_TYPE (enumtype)))
 	{
+	  auto_diagnostic_group d;
 	  error_at (input_location, "different underlying type "
 		    "in enum %q#T", enumtype);
 	  inform (DECL_SOURCE_LOCATION (TYPE_MAIN_DECL (enumtype)),
 		  "previous definition here");
 	  underlying_type = NULL_TREE;
 	}
-
-      if (modules_p ())
-	{
-	  if (!module_may_redeclare (TYPE_NAME (enumtype)))
-	    {
-	      error ("cannot define %qD in different module",
-		     TYPE_NAME (enumtype));
-	      inform (DECL_SOURCE_LOCATION (TYPE_NAME (enumtype)),
-		      "declared here");
-	      enumtype = error_mark_node;
-	    }
-	  set_instantiating_module (TYPE_NAME (enumtype));
-	}
     }
 
   if (!enumtype || TREE_CODE (enumtype) != ENUMERAL_TYPE
diff --git a/gcc/testsuite/g++.dg/modules/enum-12.C b/gcc/testsuite/g++.dg/modules/enum-12.C
new file mode 100644
index 00000000000..57eeb85d92a
--- /dev/null
+++ b/gcc/testsuite/g++.dg/modules/enum-12.C
@@ -0,0 +1,10 @@ 
+// PR c++/99573
+// { dg-additional-options "-fmodules-ts" }
+// { dg-module-cmi !foo }
+
+export module foo;
+namespace std {
+  enum class align_val_t : decltype(sizeof(int)) {};  // { dg-error "different module" }
+}
+
+// { dg-prune-output "not writing module" }