From 77e9f9ee82db9c77ef67f3916df746383ff451c3 Mon Sep 17 00:00:00 2001
From: Robert Hensing <robert@roberthensing.nl>
Date: Thu, 11 Jul 2024 12:58:20 +0200
Subject: [PATCH] libexpr: Get rid of unused line tracking fields

---
 src/libexpr/lexer-helpers.cc |  1 -
 src/libexpr/lexer.l          |  1 -
 src/libexpr/parser-state.hh  |  6 +++---
 src/libexpr/parser.y         | 16 +++++++++++++++-
 4 files changed, 18 insertions(+), 6 deletions(-)

diff --git a/src/libexpr/lexer-helpers.cc b/src/libexpr/lexer-helpers.cc
index 87c514c71..f7d1017c3 100644
--- a/src/libexpr/lexer-helpers.cc
+++ b/src/libexpr/lexer-helpers.cc
@@ -4,7 +4,6 @@
 
 void nix::lexer::internal::initLoc(YYLTYPE * loc)
 {
-    loc->first_line = loc->last_line = 0;
     loc->first_column = loc->last_column = 0;
 }
 
diff --git a/src/libexpr/lexer.l b/src/libexpr/lexer.l
index 7d4e6963f..b1b87b96a 100644
--- a/src/libexpr/lexer.l
+++ b/src/libexpr/lexer.l
@@ -287,7 +287,6 @@ or          { return OR_KW; }
 \/\*\*[^/*]([^*]|\*+[^*/])*\*+\/  /* doc comments */ {
     LexerState & lexerState = *yyget_extra(yyscanner);
     lexerState.docCommentDistance = 0;
-    lexerState.lastDocCommentLoc.first_line = yylloc->first_line;
     lexerState.lastDocCommentLoc.first_column = yylloc->first_column;
     lexerState.lastDocCommentLoc.last_column = yylloc->last_column;
 }
diff --git a/src/libexpr/parser-state.hh b/src/libexpr/parser-state.hh
index 1df64e73d..3e801c13a 100644
--- a/src/libexpr/parser-state.hh
+++ b/src/libexpr/parser-state.hh
@@ -22,8 +22,8 @@ struct StringToken
 
 struct ParserLocation
 {
-    int first_line, first_column;
-    int last_line, last_column;
+    int first_column;
+    int last_column;
 
     // backup to recover from yyless(0)
     int stashed_first_column, stashed_last_column;
@@ -39,7 +39,7 @@ struct ParserLocation
     }
 
     /** Latest doc comment position, or 0. */
-    int doc_comment_first_line, doc_comment_first_column, doc_comment_last_column;
+    int doc_comment_first_column, doc_comment_last_column;
 };
 
 struct LexerState
diff --git a/src/libexpr/parser.y b/src/libexpr/parser.y
index a25c6dd87..76190c0fa 100644
--- a/src/libexpr/parser.y
+++ b/src/libexpr/parser.y
@@ -31,6 +31,21 @@
 #define YY_DECL int yylex \
     (YYSTYPE * yylval_param, YYLTYPE * yylloc_param, yyscan_t yyscanner, nix::ParserState * state)
 
+// For efficiency, we only track offsets; not line,column coordinates
+# define YYLLOC_DEFAULT(Current, Rhs, N)                                \
+    do                                                                  \
+      if (N)                                                            \
+        {                                                               \
+          (Current).first_column = YYRHSLOC (Rhs, 1).first_column;      \
+          (Current).last_column  = YYRHSLOC (Rhs, N).last_column;       \
+        }                                                               \
+      else                                                              \
+        {                                                               \
+          (Current).first_column = (Current).last_column =              \
+            YYRHSLOC (Rhs, 0).last_column;                              \
+        }                                                               \
+    while (0)
+
 namespace nix {
 
 typedef std::map<PosIdx, DocComment> DocCommentMap;
@@ -69,7 +84,6 @@ void yyerror(YYLTYPE * loc, yyscan_t scanner, ParserState * state, const char *
 {
     if (std::string_view(error).starts_with("syntax error, unexpected end of file")) {
         loc->first_column = loc->last_column;
-        loc->first_line = loc->last_line;
     }
     throw ParseError({
         .msg = HintFmt(error),