d: change YYLocation's type from class to struct

This avoids heap allocation and gives minimal costs for the
creation and destruction of the YYParser.Symbol struct if
the location tracking is active.

Suggested by H. S. Teoh.

* data/skeletons/lalr1.d: Here.
* doc/bison.texi: Document it.
* examples/d/calc/calc.y: Adjust.
* tests/calc.at: Test it.

4 files changed, 34 insertions, 38 deletions

diff --git a/data/skeletons/lalr1.d b/data/skeletons/lalr1.d
index 9fee542e..d126d499 100644
--- a/data/skeletons/lalr1.d
+++ b/data/skeletons/lalr1.d
@@ -139,11 +139,11 @@ static assert(__traits(compiles, (new string[1])[0]=(new ]b4_location_type[[1])[
 
 private immutable bool yy_location_is_class = !__traits(compiles, *(new ]b4_location_type[((new ]b4_position_type[[1])[0])));]], [[
 /**
- * A class defining a pair of positions.  Positions, defined by the
- * <code>]b4_position_type[</code> class, denote a point in the input.
+ * A struct defining a pair of positions.  Positions, defined by the
+ * <code>]b4_position_type[</code> struct, denote a point in the input.
  * Locations represent a part of the input through the beginning
  * and ending positions.  */
-public class ]b4_location_type[
+public struct ]b4_location_type[
 {
   /** The first, inclusive, position in the range.  */
   public ]b4_position_type[ begin;
@@ -159,9 +159,6 @@ public class ]b4_location_type[
     this.begin = this.end = loc;
   }
 
-  public this () {
-  }
-
   /**
    * Create a <code>]b4_location_type[</code> from the endpoints of the range.
    * @@param begin The first position included in the range.
@@ -173,10 +170,9 @@ public class ]b4_location_type[
   }
 
   /**
-   * A representation of the location. For this to be correct,
-   * <code>]b4_position_type[</code> should override the <code>toString</code>
-   * method.  */
-  public override string toString () const {
+   * A representation of the location.
+   */
+  public string toString () const {
     auto end_col = 0 < end.column ? end.column - 1 : 0;
     auto res = begin.toString ();
     if (end.filename && begin.filename != end.filename)
@@ -189,7 +185,7 @@ public class ]b4_location_type[
   }
 }
 
-private immutable bool yy_location_is_class = true;
+private immutable bool yy_location_is_class = false;
 
 ]])])m4_ifdef([b4_user_union_members], [private union YYSemanticType
 {
@@ -438,7 +434,7 @@ b4_symbol_type_define
     /* Error handling.  */
     int yynerrs_ = 0;]b4_locations_if([[
     /// The location where the error started.
-    ]b4_location_type[ yyerrloc = null;
+    ]b4_location_type[ yyerrloc;
 
     /// ]b4_location_type[ of the lookahead.
     ]b4_location_type[ yylloc;
diff --git a/doc/bison.texi b/doc/bison.texi
index 18b5dd2e..959a4039 100644
--- a/doc/bison.texi
+++ b/doc/bison.texi
@@ -13844,8 +13844,8 @@ can be used to print the semantic values.  This however may change
 @c - class Location
 
 When the directive @code{%locations} is used, the D parser supports
-location tracking, see @ref{Tracking Locations}.  The position
-structure and the location class are provided.
+location tracking, see @ref{Tracking Locations}.  The position and
+the location structures are provided.
 
 @deftypeivar {YYLocation} {YYPosition} begin
 @deftypeivarx {YYLocation} {YYPosition} end
diff --git a/examples/d/calc/calc.y b/examples/d/calc/calc.y
index 3f41f048..24ec85d4 100644
--- a/examples/d/calc/calc.y
+++ b/examples/d/calc/calc.y
@@ -127,7 +127,7 @@ if (isInputRange!R && is(ElementType!R : dchar))
     }
 
     if (input.empty)
-      return Calc.Symbol(TokenKind.YYEOF, new YYLocation(startPos, endPos));
+      return Calc.Symbol(TokenKind.YYEOF, YYLocation(startPos, endPos));
 
     // Numbers.
     if (input.front.isNumber)
@@ -143,7 +143,7 @@ if (isInputRange!R && is(ElementType!R : dchar))
       }
       start = end;
       end.column += lenChars;
-      return Calc.Symbol(TokenKind.NUM, semanticVal_.ival, new YYLocation(startPos, endPos));
+      return Calc.Symbol(TokenKind.NUM, semanticVal_.ival, YYLocation(startPos, endPos));
     }
 
     // Individual characters
@@ -153,17 +153,17 @@ if (isInputRange!R && is(ElementType!R : dchar))
     end.column++;
     switch (ch)
     {
-      case '+':  return Calc.Symbol(TokenKind.PLUS, new YYLocation(startPos, endPos));
-      case '-':  return Calc.Symbol(TokenKind.MINUS, new YYLocation(startPos, endPos));
-      case '*':  return Calc.Symbol(TokenKind.STAR, new YYLocation(startPos, endPos));
-      case '/':  return Calc.Symbol(TokenKind.SLASH, new YYLocation(startPos, endPos));
-      case '(':  return Calc.Symbol(TokenKind.LPAR, new YYLocation(startPos, endPos));
-      case ')':  return Calc.Symbol(TokenKind.RPAR, new YYLocation(startPos, endPos));
+      case '+':  return Calc.Symbol(TokenKind.PLUS, YYLocation(startPos, endPos));
+      case '-':  return Calc.Symbol(TokenKind.MINUS, YYLocation(startPos, endPos));
+      case '*':  return Calc.Symbol(TokenKind.STAR, YYLocation(startPos, endPos));
+      case '/':  return Calc.Symbol(TokenKind.SLASH, YYLocation(startPos, endPos));
+      case '(':  return Calc.Symbol(TokenKind.LPAR, YYLocation(startPos, endPos));
+      case ')':  return Calc.Symbol(TokenKind.RPAR, YYLocation(startPos, endPos));
       case '\n':
       {
         end.line++;
         end.column = 1;
-        return Calc.Symbol(TokenKind.EOL, new YYLocation(startPos, endPos));
+        return Calc.Symbol(TokenKind.EOL, YYLocation(startPos, endPos));
       }
       default: assert(0);
     }
diff --git a/tests/calc.at b/tests/calc.at
index d1a9d030..ae8d29de 100644
--- a/tests/calc.at
+++ b/tests/calc.at
@@ -560,7 +560,7 @@ class CalcLexer(R) : Lexer
   ]AT_YYERROR_DEFINE[
 
   YYSemanticType semanticVal_;]AT_LOCATION_IF([[
-  YYLocation location = new YYLocation;
+  YYLocation location;
 
   public final @property YYPosition startPos()
   {
@@ -606,13 +606,13 @@ class CalcLexer(R) : Lexer
 
     // EOF.
     if (input.empty)
-      return YYParser.Symbol(TokenKind.]AT_TOKEN_PREFIX[EOF]AT_LOCATION_IF([[, new YYLocation(startPos, endPos)]])[);
+      return YYParser.Symbol(TokenKind.]AT_TOKEN_PREFIX[EOF]AT_LOCATION_IF([[, YYLocation(startPos, endPos)]])[);
 
     // Numbers.
     if (input.front.isNumber)
       {
         semanticVal_.ival = parseInt;
-        return YYParser.Symbol(TokenKind.]AT_TOKEN_PREFIX[NUM, semanticVal_.ival]AT_LOCATION_IF([[, new YYLocation(startPos, endPos)]])[);
+        return YYParser.Symbol(TokenKind.]AT_TOKEN_PREFIX[NUM, semanticVal_.ival]AT_LOCATION_IF([[, YYLocation(startPos, endPos)]])[);
       }
 
     // Individual characters
@@ -630,22 +630,22 @@ class CalcLexer(R) : Lexer
     if (c == '#')
       {
         stderr.writeln (]AT_LOCATION_IF([location, ": ", ])["syntax error: invalid character: '#'");
-        return YYParser.Symbol(TokenKind.]AT_TOKEN_PREFIX[YYerror]AT_LOCATION_IF([[, new YYLocation(startPos, endPos)]])[);
+        return YYParser.Symbol(TokenKind.]AT_TOKEN_PREFIX[YYerror]AT_LOCATION_IF([[, YYLocation(startPos, endPos)]])[);
       }
 
     switch (c)
     {
-      case '+':  return YYParser.Symbol(TokenKind.]AT_TOKEN_PREFIX[PLUS]AT_LOCATION_IF([[, new YYLocation(startPos, endPos)]])[);
-      case '-':  return YYParser.Symbol(TokenKind.]AT_TOKEN_PREFIX[MINUS]AT_LOCATION_IF([[, new YYLocation(startPos, endPos)]])[);
-      case '*':  return YYParser.Symbol(TokenKind.]AT_TOKEN_PREFIX[STAR]AT_LOCATION_IF([[, new YYLocation(startPos, endPos)]])[);
-      case '/':  return YYParser.Symbol(TokenKind.]AT_TOKEN_PREFIX[SLASH]AT_LOCATION_IF([[, new YYLocation(startPos, endPos)]])[);
-      case '(':  return YYParser.Symbol(TokenKind.]AT_TOKEN_PREFIX[LPAR]AT_LOCATION_IF([[, new YYLocation(startPos, endPos)]])[);
-      case ')':  return YYParser.Symbol(TokenKind.]AT_TOKEN_PREFIX[RPAR]AT_LOCATION_IF([[, new YYLocation(startPos, endPos)]])[);
-      case '\n': return YYParser.Symbol(TokenKind.]AT_TOKEN_PREFIX[EOL]AT_LOCATION_IF([[, new YYLocation(startPos, endPos)]])[);
-      case '=':  return YYParser.Symbol(TokenKind.]AT_TOKEN_PREFIX[EQUAL]AT_LOCATION_IF([[, new YYLocation(startPos, endPos)]])[);
-      case '^':  return YYParser.Symbol(TokenKind.]AT_TOKEN_PREFIX[POW]AT_LOCATION_IF([[, new YYLocation(startPos, endPos)]])[);
-      case '!':  return YYParser.Symbol(TokenKind.]AT_TOKEN_PREFIX[NOT]AT_LOCATION_IF([[, new YYLocation(startPos, endPos)]])[);
-      default:   return YYParser.Symbol(TokenKind.]AT_TOKEN_PREFIX[YYUNDEF]AT_LOCATION_IF([[, new YYLocation(startPos, endPos)]])[);
+      case '+':  return YYParser.Symbol(TokenKind.]AT_TOKEN_PREFIX[PLUS]AT_LOCATION_IF([[, YYLocation(startPos, endPos)]])[);
+      case '-':  return YYParser.Symbol(TokenKind.]AT_TOKEN_PREFIX[MINUS]AT_LOCATION_IF([[, YYLocation(startPos, endPos)]])[);
+      case '*':  return YYParser.Symbol(TokenKind.]AT_TOKEN_PREFIX[STAR]AT_LOCATION_IF([[, YYLocation(startPos, endPos)]])[);
+      case '/':  return YYParser.Symbol(TokenKind.]AT_TOKEN_PREFIX[SLASH]AT_LOCATION_IF([[, YYLocation(startPos, endPos)]])[);
+      case '(':  return YYParser.Symbol(TokenKind.]AT_TOKEN_PREFIX[LPAR]AT_LOCATION_IF([[, YYLocation(startPos, endPos)]])[);
+      case ')':  return YYParser.Symbol(TokenKind.]AT_TOKEN_PREFIX[RPAR]AT_LOCATION_IF([[, YYLocation(startPos, endPos)]])[);
+      case '\n': return YYParser.Symbol(TokenKind.]AT_TOKEN_PREFIX[EOL]AT_LOCATION_IF([[, YYLocation(startPos, endPos)]])[);
+      case '=':  return YYParser.Symbol(TokenKind.]AT_TOKEN_PREFIX[EQUAL]AT_LOCATION_IF([[, YYLocation(startPos, endPos)]])[);
+      case '^':  return YYParser.Symbol(TokenKind.]AT_TOKEN_PREFIX[POW]AT_LOCATION_IF([[, YYLocation(startPos, endPos)]])[);
+      case '!':  return YYParser.Symbol(TokenKind.]AT_TOKEN_PREFIX[NOT]AT_LOCATION_IF([[, YYLocation(startPos, endPos)]])[);
+      default:   return YYParser.Symbol(TokenKind.]AT_TOKEN_PREFIX[YYUNDEF]AT_LOCATION_IF([[, YYLocation(startPos, endPos)]])[);
     }
   }
 }