libexpr: Rename "column" fields to offset

... because that's what they are.

src/libexpr/lexer-helpers.cc

@@ -4,7 +4,7 @@
 
 void nix::lexer::internal::initLoc(YYLTYPE * loc)
 {
-    loc->first_column = loc->last_column = 0;
+    loc->beginOffset = loc->endOffset = 0;
 }
 
 void nix::lexer::internal::adjustLoc(yyscan_t yyscanner, YYLTYPE * loc, const char * s, size_t len)
@@ -16,15 +16,15 @@ void nix::lexer::internal::adjustLoc(yyscan_t yyscanner, YYLTYPE * loc, const ch
     if (lexerState.docCommentDistance == 1) {
         // Preceding token was a doc comment.
         ParserLocation doc;
-        doc.first_column = lexerState.lastDocCommentLoc.first_column;
+        doc.beginOffset = lexerState.lastDocCommentLoc.beginOffset;
         ParserLocation docEnd;
-        docEnd.first_column = lexerState.lastDocCommentLoc.last_column;
+        docEnd.beginOffset = lexerState.lastDocCommentLoc.endOffset;
         DocComment docComment{lexerState.at(doc), lexerState.at(docEnd)};
         PosIdx locPos = lexerState.at(*loc);
         lexerState.positionToDocComment.emplace(locPos, docComment);
     }
     lexerState.docCommentDistance++;
 
-    loc->first_column = loc->last_column;
-    loc->last_column += len;
+    loc->beginOffset = loc->endOffset;
+    loc->endOffset += len;
 }

src/libexpr/lexer.l

@@ -287,8 +287,8 @@ or          { return OR_KW; }
 \/\*\*[^/*]([^*]|\*+[^*/])*\*+\/  /* doc comments */ {
     LexerState & lexerState = *yyget_extra(yyscanner);
     lexerState.docCommentDistance = 0;
-    lexerState.lastDocCommentLoc.first_column = yylloc->first_column;
-    lexerState.lastDocCommentLoc.last_column = yylloc->last_column;
+    lexerState.lastDocCommentLoc.beginOffset = yylloc->beginOffset;
+    lexerState.lastDocCommentLoc.endOffset = yylloc->endOffset;
 }
 
 

src/libexpr/parser-state.hh

@@ -22,20 +22,20 @@ struct StringToken
 
 struct ParserLocation
 {
-    int first_column;
-    int last_column;
+    int beginOffset;
+    int endOffset;
 
     // backup to recover from yyless(0)
-    int stashed_first_column, stashed_last_column;
+    int stashedBeginOffset, stashedEndOffset;
 
     void stash() {
-        stashed_first_column = first_column;
-        stashed_last_column = last_column;
+        stashedBeginOffset = beginOffset;
+        stashedEndOffset = endOffset;
     }
 
     void unstash() {
-        first_column = stashed_first_column;
-        last_column = stashed_last_column;
+        beginOffset = stashedBeginOffset;
+        endOffset = stashedEndOffset;
     }
 
     /** Latest doc comment position, or 0. */
@@ -308,12 +308,12 @@ inline Expr * ParserState::stripIndentation(const PosIdx pos,
 
 inline PosIdx LexerState::at(const ParserLocation & loc)
 {
-    return positions.add(origin, loc.first_column);
+    return positions.add(origin, loc.beginOffset);
 }
 
 inline PosIdx ParserState::at(const ParserLocation & loc)
 {
-    return positions.add(origin, loc.first_column);
+    return positions.add(origin, loc.beginOffset);
 }
 
 }

src/libexpr/parser.y

@@ -36,13 +36,13 @@
     do                                                                  \
       if (N)                                                            \
         {                                                               \
-          (Current).first_column = YYRHSLOC (Rhs, 1).first_column;      \
-          (Current).last_column  = YYRHSLOC (Rhs, N).last_column;       \
+          (Current).beginOffset = YYRHSLOC (Rhs, 1).beginOffset;        \
+          (Current).endOffset  = YYRHSLOC (Rhs, N).endOffset;           \
         }                                                               \
       else                                                              \
         {                                                               \
-          (Current).first_column = (Current).last_column =              \
-            YYRHSLOC (Rhs, 0).last_column;                              \
+          (Current).beginOffset = (Current).endOffset =                 \
+            YYRHSLOC (Rhs, 0).endOffset;                                \
         }                                                               \
     while (0)
 
@@ -83,7 +83,7 @@ using namespace nix;
 void yyerror(YYLTYPE * loc, yyscan_t scanner, ParserState * state, const char * error)
 {
     if (std::string_view(error).starts_with("syntax error, unexpected end of file")) {
-        loc->first_column = loc->last_column;
+        loc->beginOffset = loc->endOffset;
     }
     throw ParseError({
         .msg = HintFmt(error),