From 5cfcace1d301088457fe1f6794f498be6fea5986 Mon Sep 17 00:00:00 2001
From: Dmitri Plotnikov <dplotnikov@google.com>
Date: Thu, 3 Sep 2026 16:30:02 -0700
Subject: [PATCH] Simplify SavePosition/RestorePosition functions

PiperOrigin-RevId: 975984463
---
 parser/internal/lexer.cc              |  2 --
 parser/internal/lexer.h               | 28 ++++++---------------------
 parser/internal/lexer_test.cc         |  3 ++-
 parser/internal/pratt_parser_worker.h |  2 +-
 4 files changed, 9 insertions(+), 26 deletions(-)

diff --git a/parser/internal/lexer.cc b/parser/internal/lexer.cc
index db08b644f..897a63399 100644
--- a/parser/internal/lexer.cc
+++ b/parser/internal/lexer.cc
@@ -163,8 +163,6 @@ std::string_view TokenTypeToString(TokenType type) {
 Token Lexer::Lex() {
   int32_t start = GetPosition();
   if (ABSL_PREDICT_FALSE(position_ >= content_.size())) {
-    at_end_ = true;
-    done_ = true;
     return MakeToken(TokenType::kEnd, start, start);
   }
   char32_t c = content_.at(position_);
diff --git a/parser/internal/lexer.h b/parser/internal/lexer.h
index c35dc08e2..502be627a 100644
--- a/parser/internal/lexer.h
+++ b/parser/internal/lexer.h
@@ -140,13 +140,6 @@ class Lexer final {
                                         std::numeric_limits<int32_t>::max()));
   }
 
-  struct Position final {
-    int32_t position = 0;
-    bool at_end = false;
-    bool done = false;
-    LexerError error;
-  };
-
   Lexer(const Lexer&) = delete;
   Lexer(Lexer&&) = delete;
   Lexer& operator=(const Lexer&) = delete;
@@ -165,15 +158,13 @@ class Lexer final {
 
   [[nodiscard]] int32_t GetPosition() const { return position_; }
 
-  [[nodiscard]] Position SavePosition() const {
-    return Position{position_, at_end_, done_, error_};
-  }
+  [[nodiscard]] int32_t SavePosition() const { return position_; }
 
-  void RestorePosition(const Position& position) {
-    position_ = position.position;
-    at_end_ = position.at_end;
-    done_ = position.done;
-    error_ = position.error;
+  void RestorePosition(int32_t position) {
+    ABSL_DCHECK_GE(position, 0);
+    ABSL_DCHECK_LE(position, static_cast<int32_t>(content_.size()));
+    position_ = position;
+    error_ = LexerError{};
   }
 
  private:
@@ -201,9 +192,6 @@ class Lexer final {
   }
 
   [[nodiscard]] Token MakeToken(TokenType type, int32_t start, int32_t end) {
-    if (ABSL_PREDICT_FALSE(at_end_)) {
-      AtEndTokenCreated();
-    }
     return Token{.type = type, .start = start, .end = end};
   }
 
@@ -214,8 +202,6 @@ class Lexer final {
     return Token{.type = TokenType::kError, .start = start, .end = end};
   }
 
-  void AtEndTokenCreated() { done_ = true; }
-
   // Consumes characters up to and including the first occurrence of character
   // `c` without interpreting backslashes as escapes. Returns true if `c` was
   // found and consumed; false if end of input was reached.
@@ -294,8 +280,6 @@ class Lexer final {
 
   cel::SourceContentView content_;
   int32_t position_ = 0;
-  bool at_end_ = false;
-  bool done_ = false;
   LexerError error_;
 };
 
diff --git a/parser/internal/lexer_test.cc b/parser/internal/lexer_test.cc
index ebe0011d3..9cdfbd45d 100644
--- a/parser/internal/lexer_test.cc
+++ b/parser/internal/lexer_test.cc
@@ -14,6 +14,7 @@
 
 #include "parser/internal/lexer.h"
 
+#include <cstdint>
 #include <string>
 #include <string_view>
 #include <utility>
@@ -506,7 +507,7 @@ TEST(LexerPositionTest, SaveAndRestorePosition) {
   EXPECT_EQ(tok2.type, TokenType::kWhitespace);
 
   // Save position before '+'
-  Lexer::Position saved = lexer.SavePosition();
+  int32_t saved = lexer.SavePosition();
 
   Token tok3 = lexer.Lex();
   EXPECT_EQ(tok3.type, TokenType::kPlus);
diff --git a/parser/internal/pratt_parser_worker.h b/parser/internal/pratt_parser_worker.h
index e1608a3a2..2cfe84b79 100644
--- a/parser/internal/pratt_parser_worker.h
+++ b/parser/internal/pratt_parser_worker.h
@@ -1222,7 +1222,7 @@ int PrattParserWorker<ExprNode>::CountGroupingParentheses() {
   }
 
   // Save lexer position to restore after scanning ahead.
-  const Lexer::Position saved_pos = lexer_.SavePosition();
+  const int32_t saved_pos = lexer_.SavePosition();
   auto restore_lexer = absl::MakeCleanup(
       [this, saved_pos] { lexer_.RestorePosition(saved_pos); });