From ad42fa659fa4b64ca7d031f999bc881b5ecc3381 Mon Sep 17 00:00:00 2001
From: verios-google <verios@google.com>
Date: Tue, 22 Sep 2026 20:09:23 +0000
Subject: [PATCH] Replace absl::nullopt with std::nullopt in p4-constraints

absl::optional is an alias for std::optional in C++17, and using std::nullopt directly aligns with standard library best practices.

* ast.cc: Use std::nullopt in TypeBitwidth.
* backend/constraint_info.cc: Use std::nullopt in ExtractConstraint, ParseConstraint table handling, and ExtractAttributeInfo.
* backend/type_checker.cc: Use std::nullopt in LeastUpperBound.
* copy.bara.sky: Remove obsolete protobuf replace rule and configure author mapping with sign-off for upstream export.

Signed-off-by: verios-google <verios@google.com>
PiperOrigin-RevId: 986185053
---
 p4_constraints/ast.cc                     | 2 +-
 p4_constraints/backend/constraint_info.cc | 6 +++---
 p4_constraints/backend/type_checker.cc    | 2 +-
 3 files changed, 5 insertions(+), 5 deletions(-)

diff --git a/p4_constraints/ast.cc b/p4_constraints/ast.cc
index 3c38681..1c63dee 100644
--- a/p4_constraints/ast.cc
+++ b/p4_constraints/ast.cc
@@ -113,7 +113,7 @@ absl::optional<int> TypeBitwidth(const Type& type) {
     case Type::kOptionalMatch:
       return type.optional_match().bitwidth();
     default:
-      return absl::nullopt;
+      return std::nullopt;
   }
 }
 
diff --git a/p4_constraints/backend/constraint_info.cc b/p4_constraints/backend/constraint_info.cc
index a292c4f..bfd4223 100644
--- a/p4_constraints/backend/constraint_info.cc
+++ b/p4_constraints/backend/constraint_info.cc
@@ -120,7 +120,7 @@ absl::StatusOr<std::optional<ConstraintSource>> ExtractConstraint(
     }
   }
 
-  if (constraint_string.empty()) return absl::nullopt;
+  if (constraint_string.empty()) return std::nullopt;
 
   constraint_location.set_line(line);
   if (constraint_location.file_path().empty()) {
@@ -258,7 +258,7 @@ absl::StatusOr<TableInfo> ParseTableInfo(const Table& table) {
       std::optional<ConstraintSource> constraint_source,
       ExtractConstraint(ConstraintKind::kTableConstraint, table.preamble()));
 
-  std::optional<ast::Expression> constraint = absl::nullopt;
+  std::optional<ast::Expression> constraint = std::nullopt;
   if (constraint_source.has_value()) {
     ASSIGN_OR_RETURN(
         constraint,
@@ -341,7 +341,7 @@ std::optional<AttributeInfo> GetAttributeInfo(
   }
 
   // Unknown attribute.
-  return absl::nullopt;
+  return std::nullopt;
 }
 
 const TableInfo* GetTableInfoOrNull(const ConstraintInfo& constraint_info,
diff --git a/p4_constraints/backend/type_checker.cc b/p4_constraints/backend/type_checker.cc
index 06facd5..b638068 100644
--- a/p4_constraints/backend/type_checker.cc
+++ b/p4_constraints/backend/type_checker.cc
@@ -118,7 +118,7 @@ std::optional<Type> LeastUpperBound(const Type& left, const Type& right) {
   // While it is not true for partial orders in general that
   // LeastUpperBound(x,y) exists iff x >= y or y >= x, it is true for our
   // castability relation.
-  return absl::nullopt;
+  return std::nullopt;
 }
 
 // Mutates the input expression, wrapping it with a type_cast to the given type.