compiler: rename "requires" to "needs"

As of C++20 "requires" is a C++ keyword.

Change-Id: Ie57d19f90c603bb5cc10709b56abe40b97196916
Reviewed-on: https://go-review.googlesource.com/c/gofrontend/+/415754
Reviewed-by: Than McIntosh <thanm@google.com>
Reviewed-by: Cherry Mui <cherryyz@google.com>
diff --git a/go/gogo.cc b/go/gogo.cc
index e13df0d..67b91fa 100644
--- a/go/gogo.cc
+++ b/go/gogo.cc
@@ -5302,16 +5302,16 @@
       Named_object* no = types.front();
       types.pop_front();
 
-      std::vector<const Named_object*> requires;
+      std::vector<const Named_object*> needs;
       std::vector<const Named_object*> declare;
-      if (!no->type_value()->struct_type()->can_write_to_c_header(&requires,
+      if (!no->type_value()->struct_type()->can_write_to_c_header(&needs,
 								  &declare))
 	continue;
 
       bool ok = true;
       for (std::vector<const Named_object*>::const_iterator pr
-	     = requires.begin();
-	   pr != requires.end() && ok;
+	     = needs.begin();
+	   pr != needs.end() && ok;
 	   ++pr)
 	{
 	  for (std::list<Named_object*>::const_iterator pt = types.begin();
@@ -5342,10 +5342,10 @@
 	  if (*pd == no)
 	    continue;
 
-	  std::vector<const Named_object*> drequires;
+	  std::vector<const Named_object*> dneeds;
 	  std::vector<const Named_object*> ddeclare;
 	  if (!(*pd)->type_value()->struct_type()->
-	      can_write_to_c_header(&drequires, &ddeclare))
+	      can_write_to_c_header(&dneeds, &ddeclare))
 	    continue;
 
 	  bool done = false;
diff --git a/go/types.cc b/go/types.cc
index e82be68..4995283 100644
--- a/go/types.cc
+++ b/go/types.cc
@@ -6967,7 +6967,7 @@
 
 bool
 Struct_type::can_write_to_c_header(
-    std::vector<const Named_object*>* requires,
+    std::vector<const Named_object*>* needs,
     std::vector<const Named_object*>* declare) const
 {
   const Struct_field_list* fields = this->fields_;
@@ -6978,7 +6978,7 @@
        p != fields->end();
        ++p)
     {
-      if (!this->can_write_type_to_c_header(p->type(), requires, declare))
+      if (!this->can_write_type_to_c_header(p->type(), needs, declare))
 	return false;
       if (Gogo::message_name(p->field_name()) == "_")
 	sinks++;
@@ -6993,7 +6993,7 @@
 bool
 Struct_type::can_write_type_to_c_header(
     const Type* t,
-    std::vector<const Named_object*>* requires,
+    std::vector<const Named_object*>* needs,
     std::vector<const Named_object*>* declare) const
 {
   t = t->forwarded();
@@ -7027,13 +7027,13 @@
       return true;
 
     case TYPE_STRUCT:
-      return t->struct_type()->can_write_to_c_header(requires, declare);
+      return t->struct_type()->can_write_to_c_header(needs, declare);
 
     case TYPE_ARRAY:
       if (t->is_slice_type())
 	return true;
       return this->can_write_type_to_c_header(t->array_type()->element_type(),
-					      requires, declare);
+					      needs, declare);
 
     case TYPE_NAMED:
       {
@@ -7049,10 +7049,10 @@
 	    // We will accept empty struct fields, but not print them.
 	    if (t->struct_type()->total_field_count() == 0)
 	      return true;
-	    requires->push_back(no);
-	    return t->struct_type()->can_write_to_c_header(requires, declare);
+	    needs->push_back(no);
+	    return t->struct_type()->can_write_to_c_header(needs, declare);
 	  }
-	return this->can_write_type_to_c_header(t->base(), requires, declare);
+	return this->can_write_type_to_c_header(t->base(), needs, declare);
       }
 
     case TYPE_CALL_MULTIPLE_RESULT:
@@ -7150,9 +7150,9 @@
 
     case TYPE_POINTER:
       {
-	std::vector<const Named_object*> requires;
+	std::vector<const Named_object*> needs;
 	std::vector<const Named_object*> declare;
-	if (!this->can_write_type_to_c_header(t->points_to(), &requires,
+	if (!this->can_write_type_to_c_header(t->points_to(), &needs,
 					      &declare))
 	  os << "void*";
 	else