c++: Support lambdas attached to more places in modules [PR111710]

The fix for PR107398 weakened the restrictions that lambdas must belong
to namespace scope. However this was not sufficient: we also need to
allow lambdas attached to FIELD_DECLs, PARM_DECLs, and TYPE_DECLs.

For field decls we key the lambda to its class rather than the field
itself. Otherwise we can run into issues when deduplicating the lambda's
TYPE_DECL, because when loading its context we load the containing field
before we've deduplicated the keyed lambda, causing mismatches; by
keying to the class instead we defer checking keyed declarations until
deduplication has completed.

Additionally, by [basic.link] p15.2 a lambda defined anywhere in a
class-specifier should not be TU-local, which includes base-class
declarations, so ensure that lambdas declared there are keyed
appropriately as well.

Because this now requires 'DECL_MODULE_KEYED_DECLS_P' to be checked on a
fairly large number of different kinds of DECLs, and that in general
it's safe to just get 'false' as a result of a check on an unexpected
DECL type, this patch also removes the tree checking from the accessor.

Finally, to handle deduplicating templated lambda fields, we need to
ensure that we can determine that two lambdas from different field decls
match, so we ensure that we also deduplicate LAMBDA_EXPRs on stream in.

	PR c++/111710

gcc/cp/ChangeLog:

	* cp-tree.h (DECL_MODULE_KEYED_DECLS_P): Remove tree checking.
	(struct lang_decl_base): Update comments and fix whitespace.
	* module.cc (trees_out::lang_decl_bools): Always write
	module_keyed_decls_p flag...
	(trees_in::lang_decl_bools): ...and always read it.
	(trees_out::decl_value): Handle all kinds of keyed decls.
	(trees_in::decl_value): Likewise.
	(trees_in::tree_value): Deduplicate LAMBDA_EXPRs.
	(maybe_key_decl): Also support lambdas attached to fields,
	parameters, and types. Key lambdas attached to fields to their
	class.
	(trees_out::get_merge_kind): Likewise.
	(trees_out::key_mergeable): Likewise.
	(trees_in::key_mergeable): Support keyed decls in a TYPE_DECL
	container.
	* parser.cc (cp_parser_class_head): Start a lambda scope when
	parsing base classes.

gcc/testsuite/ChangeLog:

	* g++.dg/modules/lambda-7.h: New test.
	* g++.dg/modules/lambda-7_a.H: New test.
	* g++.dg/modules/lambda-7_b.C: New test.
	* g++.dg/modules/lambda-7_c.C: New test.

Signed-off-by: Nathaniel Shead <nathanieloshead@gmail.com>
Reviewed-by: Patrick Palka <ppalka@redhat.com>
Reviewed-by: Jason Merrill <jason@redhat.com>

1 files changed, 62 insertions, 39 deletions

diff --git a/gcc/cp/module.cc b/gcc/cp/module.cc
index 106af7b..1b2ba2e 100644
--- a/gcc/cp/module.cc
+++ b/gcc/cp/module.cc
@@ -5664,8 +5664,7 @@ trees_out::lang_decl_bools (tree t)
      want to mark them as in module purview.  */
   WB (lang->u.base.module_purview_p && !header_module_p ());
   WB (lang->u.base.module_attach_p);
-  if (VAR_OR_FUNCTION_DECL_P (t))
-    WB (lang->u.base.module_keyed_decls_p);
+  WB (lang->u.base.module_keyed_decls_p);
   switch (lang->u.base.selector)
     {
     default:
@@ -5738,8 +5737,7 @@ trees_in::lang_decl_bools (tree t)
   RB (lang->u.base.dependent_init_p);
   RB (lang->u.base.module_purview_p);
   RB (lang->u.base.module_attach_p);
-  if (VAR_OR_FUNCTION_DECL_P (t))
-    RB (lang->u.base.module_keyed_decls_p);
+  RB (lang->u.base.module_keyed_decls_p);
   switch (lang->u.base.selector)
     {
     default:
@@ -7871,8 +7869,7 @@ trees_out::decl_value (tree decl, depset *dep)
       install_entity (decl, dep);
     }
 
-  if (VAR_OR_FUNCTION_DECL_P (inner)
-      && DECL_LANG_SPECIFIC (inner)
+  if (DECL_LANG_SPECIFIC (inner)
       && DECL_MODULE_KEYED_DECLS_P (inner)
       && !is_key_order ())
     {
@@ -8172,8 +8169,7 @@ trees_in::decl_value ()
   bool installed = install_entity (existing);
   bool is_new = existing == decl;
 
-  if (VAR_OR_FUNCTION_DECL_P (inner)
-      && DECL_LANG_SPECIFIC (inner)
+  if (DECL_LANG_SPECIFIC (inner)
       && DECL_MODULE_KEYED_DECLS_P (inner))
     {
       /* Read and maybe install the attached entities.  */
@@ -9187,6 +9183,13 @@ trees_in::tree_value ()
       return NULL_TREE;
     }
 
+  if (TREE_CODE (t) == LAMBDA_EXPR
+      && CLASSTYPE_LAMBDA_EXPR (TREE_TYPE (t)))
+    {
+      existing = CLASSTYPE_LAMBDA_EXPR (TREE_TYPE (t));
+      back_refs[~tag] = existing;
+    }
+
   dump (dumper::TREE) && dump ("Read tree:%d %C:%N", tag, TREE_CODE (t), t);
 
   if (TREE_CODE (existing) == INTEGER_CST && !TREE_OVERFLOW (existing))
@@ -10484,12 +10487,17 @@ trees_out::get_merge_kind (tree decl, depset *dep)
 	      if (tree scope
 		  = LAMBDA_EXPR_EXTRA_SCOPE (CLASSTYPE_LAMBDA_EXPR
 					     (TREE_TYPE (decl))))
-		if (TREE_CODE (scope) == VAR_DECL
-		    && DECL_MODULE_KEYED_DECLS_P (scope))
-		  {
-		    mk = MK_keyed;
-		    break;
-		  }
+		{
+		  /* Lambdas attached to fields are keyed to its class.  */
+		  if (TREE_CODE (scope) == FIELD_DECL)
+		    scope = TYPE_NAME (DECL_CONTEXT (scope));
+		  if (DECL_LANG_SPECIFIC (scope)
+		      && DECL_MODULE_KEYED_DECLS_P (scope))
+		    {
+		      mk = MK_keyed;
+		      break;
+		    }
+		}
 
 	    if (RECORD_OR_UNION_TYPE_P (ctx))
 	      {
@@ -10789,7 +10797,13 @@ trees_out::key_mergeable (int tag, merge_kind mk, tree decl, tree inner,
 	    gcc_checking_assert (LAMBDA_TYPE_P (TREE_TYPE (inner)));
 	    tree scope = LAMBDA_EXPR_EXTRA_SCOPE (CLASSTYPE_LAMBDA_EXPR
 						  (TREE_TYPE (inner)));
-	    gcc_checking_assert (TREE_CODE (scope) == VAR_DECL);
+	    gcc_checking_assert (TREE_CODE (scope) == VAR_DECL
+				 || TREE_CODE (scope) == FIELD_DECL
+				 || TREE_CODE (scope) == PARM_DECL
+				 || TREE_CODE (scope) == TYPE_DECL);
+	    /* Lambdas attached to fields are keyed to the class.  */
+	    if (TREE_CODE (scope) == FIELD_DECL)
+	      scope = TYPE_NAME (DECL_CONTEXT (scope));
 	    auto *root = keyed_table->get (scope);
 	    unsigned ix = root->length ();
 	    /* If we don't find it, we'll write a really big number
@@ -11067,6 +11081,26 @@ trees_in::key_mergeable (int tag, merge_kind mk, tree decl, tree inner,
 		}
 	    }
 	}
+      else if (mk == MK_keyed
+	       && DECL_LANG_SPECIFIC (name)
+	       && DECL_MODULE_KEYED_DECLS_P (name))
+	{
+	  gcc_checking_assert (TREE_CODE (container) == NAMESPACE_DECL
+			       || TREE_CODE (container) == TYPE_DECL);
+	  if (auto *set = keyed_table->get (name))
+	    if (key.index < set->length ())
+	      {
+		existing = (*set)[key.index];
+		if (existing)
+		  {
+		    gcc_checking_assert
+		      (DECL_IMPLICIT_TYPEDEF_P (existing));
+		    if (inner != decl)
+		      existing
+			= CLASSTYPE_TI_TEMPLATE (TREE_TYPE (existing));
+		  }
+	      }
+	}
       else
 	switch (TREE_CODE (container))
 	  {
@@ -11074,27 +11108,8 @@ trees_in::key_mergeable (int tag, merge_kind mk, tree decl, tree inner,
 	    gcc_unreachable ();
 
 	  case NAMESPACE_DECL:
-	    if (mk == MK_keyed)
-	      {
-		if (DECL_LANG_SPECIFIC (name)
-		    && VAR_OR_FUNCTION_DECL_P (name)
-		    && DECL_MODULE_KEYED_DECLS_P (name))
-		  if (auto *set = keyed_table->get (name))
-		    if (key.index < set->length ())
-		      {
-			existing = (*set)[key.index];
-			if (existing)
-			  {
-			    gcc_checking_assert
-			      (DECL_IMPLICIT_TYPEDEF_P (existing));
-			    if (inner != decl)
-			      existing
-				= CLASSTYPE_TI_TEMPLATE (TREE_TYPE (existing));
-			  }
-		      }
-	      }
-	    else if (is_attached
-		     && !(state->is_module () || state->is_partition ()))
+	    if (is_attached
+		&& !(state->is_module () || state->is_partition ()))
 	      kind = "unique";
 	    else
 	      {
@@ -18984,11 +18999,19 @@ maybe_key_decl (tree ctx, tree decl)
   if (!modules_p ())
     return;
 
-  // FIXME: For now just deal with lambdas attached to var decls.
-  // This might be sufficient?
-  if (TREE_CODE (ctx) != VAR_DECL)
+  /* We only need to deal with lambdas attached to var, field,
+     parm, or type decls.  */
+  if (TREE_CODE (ctx) != VAR_DECL
+      && TREE_CODE (ctx) != FIELD_DECL
+      && TREE_CODE (ctx) != PARM_DECL
+      && TREE_CODE (ctx) != TYPE_DECL)
     return;
 
+  /* For fields, key it to the containing type to handle deduplication
+     correctly.  */
+  if (TREE_CODE (ctx) == FIELD_DECL)
+    ctx = TYPE_NAME (DECL_CONTEXT (ctx));
+
   if (!keyed_table)
     keyed_table = new keyed_map_t (EXPERIMENT (1, 400));