fix-empty-list-location.patch

diff --git a/src/backend/parser/gram.y b/src/backend/parser/gram.y
index 7feadeac1693e7ff46f44ef3ad9ea2fa86bf46a8..e4ff76e66e0990d91790ccc54615c26dd64a143e 100644
*** a/src/backend/parser/gram.y
--- b/src/backend/parser/gram.y
***************
*** 67,82 ****
  #include "utils/xml.h"
  
  
! /* Location tracking support --- simpler than bison's default */
  #define YYLLOC_DEFAULT(Current, Rhs, N) \
  	do { \
! 		if (N) \
  			(Current) = (Rhs)[1]; \
  		else \
! 			(Current) = (Rhs)[0]; \
  	} while (0)
  
  /*
   * Bison doesn't allocate anything that needs to live across parser calls,
   * so we can easily have it use palloc instead of malloc.  This prevents
   * memory leaks if we error out during parsing.  Note this only works with
--- 67,100 ----
  #include "utils/xml.h"
  
  
! /*
!  * Location tracking support --- simpler than bison's default, since we only
!  * want to track the start position not the end position of each nonterminal.
!  */
  #define YYLLOC_DEFAULT(Current, Rhs, N) \
  	do { \
! 		if ((N) > 0) \
  			(Current) = (Rhs)[1]; \
  		else \
! 			(Current) = (-1); \
  	} while (0)
  
  /*
+  * The above macro assigns -1 (unknown) as the parse location of any
+  * nonterminal that was reduced from an empty rule.  This is problematic
+  * for nonterminals defined like
+  *		OptFooList: / * EMPTY * / { ... } | OptFooList Foo { ... } ;
+  * because we'll set -1 as the location during the first reduction and then
+  * copy it during each subsequent reduction, leaving us with -1 for the
+  * location even when the list is not empty.  To fix that, do this in the
+  * action for the nonempty rule(s):
+  *		if (@$ < 0) @$ = @2;
+  * (Although we have many nonterminals that follow this pattern, we only
+  * bother with fixing @$ like this when the nonterminal's parse location
+  * is actually referenced in some rule.)
+  */
+ 
+ /*
   * Bison doesn't allocate anything that needs to live across parser calls,
   * so we can easily have it use palloc instead of malloc.  This prevents
   * memory leaks if we error out during parsing.  Note this only works with
*************** OptSchemaName:
*** 1223,1230 ****
  		;
  
  OptSchemaEltList:
! 			OptSchemaEltList schema_stmt			{ $$ = lappend($1, $2); }
! 			| /* EMPTY */							{ $$ = NIL; }
  		;
  
  /*
--- 1241,1254 ----
  		;
  
  OptSchemaEltList:
! 			OptSchemaEltList schema_stmt
! 				{
! 					if (@$ < 0)			/* see comments for YYLLOC_DEFAULT */
! 						@$ = @2;
! 					$$ = lappend($1, $2);
! 				}
! 			| /* EMPTY */
! 				{ $$ = NIL; }
  		;
  
  /*
diff --git a/src/test/regress/expected/namespace.out b/src/test/regress/expected/namespace.out
index 5fcd46daf42705147f53599d657e52d8fe7b5b1f..9187c8126a3ffa32e365400816b262daf3b6f2d5 100644
*** a/src/test/regress/expected/namespace.out
--- b/src/test/regress/expected/namespace.out
*************** CREATE SCHEMA IF NOT EXISTS test_schema_
*** 47,54 ****
                b int UNIQUE
         );
  ERROR:  CREATE SCHEMA IF NOT EXISTS cannot include schema elements
! LINE 1: CREATE SCHEMA IF NOT EXISTS test_schema_1 
!                                     ^
  DROP SCHEMA test_schema_1 CASCADE;
  NOTICE:  drop cascades to 2 other objects
  DETAIL:  drop cascades to table test_schema_1.abc
--- 47,54 ----
                b int UNIQUE
         );
  ERROR:  CREATE SCHEMA IF NOT EXISTS cannot include schema elements
! LINE 2:        CREATE TABLE abc (
!                ^
  DROP SCHEMA test_schema_1 CASCADE;
  NOTICE:  drop cascades to 2 other objects
  DETAIL:  drop cascades to table test_schema_1.abc