Fix a couple of cases where the plpgsql grammar looked for T_WORD and

failed to consider the possibility that it would get T_SCALAR, T_RECORD,
or T_ROW instead because the word happens to match a plpgsql variable name.
In particular, give "duplicate declaration" rather than generic "syntax error"
if the same identifier is declared twice in the same block, as per my recent
complaint.  Also behave more sanely when decl_aliasitem or proc_condition or
opt_lblname is coincidentally not T_WORD.  Refactor the related productions a
bit to reduce duplication.

This is a longstanding bug, but it doesn't seem critical enough to
back-patch.

src/pl/plpgsql/src/gram.y

@@ -9,7 +9,7 @@
  *
  *
  * IDENTIFICATION
- *	  $PostgreSQL: pgsql/src/pl/plpgsql/src/gram.y,v 1.123 2009/04/19 21:50:09 tgl Exp $
+ *	  $PostgreSQL: pgsql/src/pl/plpgsql/src/gram.y,v 1.124 2009/05/01 23:57:34 tgl Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -144,7 +144,7 @@ static List				*read_raise_options(void);
 %type <forvariable>	for_variable
 %type <stmt>	for_control
 
-%type <str>		opt_lblname opt_block_label opt_label
+%type <str>		any_identifier any_name opt_block_label opt_label
 %type <str>		execsql_start
 
 %type <list>	proc_sect proc_stmts stmt_else
@@ -331,7 +331,7 @@ decl_stmts		: decl_stmts decl_stmt
 					{	$$ = $1;	}
 				;
 
-decl_stmt		: '<' '<' opt_lblname '>' '>'
+decl_stmt		: '<' '<' any_name '>' '>'
 					{	$$ = $3;	}
 				| K_DECLARE
 					{	$$ = NULL;	}
@@ -512,12 +512,12 @@ decl_cursor_arg : decl_varname decl_datatype
 decl_is_for		:	K_IS |		/* Oracle */
 					K_FOR;		/* ANSI */
 
-decl_aliasitem	: T_WORD
+decl_aliasitem	: any_identifier
 					{
 						char	*name;
 						PLpgSQL_nsitem *nsi;
 
-						plpgsql_convert_ident(yytext, &name, 1);
+						plpgsql_convert_ident($1, &name, 1);
 						if (name[0] != '$')
 							yyerror("only positional parameters can be aliased");
 
@@ -549,8 +549,27 @@ decl_varname	: T_WORD
 						$$.name = name;
 						$$.lineno  = plpgsql_scanner_lineno();
 					}
+				| T_SCALAR
+					{
+						/*
+						 * Since the scanner is only searching the topmost
+						 * namestack entry, getting T_SCALAR etc can only
+						 * happen if the name is already declared in this
+						 * block.
+						 */
+						yyerror("duplicate declaration");
+					}
+				| T_ROW
+					{
+						yyerror("duplicate declaration");
+					}
+				| T_RECORD
+					{
+						yyerror("duplicate declaration");
+					}
 				;
 
+/* XXX this is broken because it doesn't allow for T_SCALAR,T_ROW,T_RECORD */
 decl_renname	: T_WORD
 					{
 						char	*name;
@@ -1752,25 +1771,17 @@ proc_conditions	: proc_conditions K_OR proc_condition
 						}
 				;
 
-proc_condition	: opt_lblname
+proc_condition	: any_name
+						{
+							if (strcmp($1, "sqlstate") != 0)
 							{
 								$$ = plpgsql_parse_err_condition($1);
 							}
-				| T_SCALAR
+							else
 							{
-							/*
-							 * Because we know the special sqlstate variable
-							 * is at the top of the namestack (see the
-							 * exception_sect production), the SQLSTATE
-							 * keyword will always lex as T_SCALAR.  This
-							 * might not be true in other parsing contexts!
-							 */
 								PLpgSQL_condition *new;
 								char   *sqlstatestr;
 
-							if (pg_strcasecmp(yytext, "sqlstate") != 0)
-								yyerror("syntax error");
-
 								/* next token should be a string literal */
 								if (yylex() != T_STRING)
 									yyerror("syntax error");
@@ -1782,7 +1793,8 @@ proc_condition	: opt_lblname
 									yyerror("invalid SQLSTATE code");
 
 								new = palloc(sizeof(PLpgSQL_condition));
-							new->sqlerrstate = MAKE_SQLSTATE(sqlstatestr[0],
+								new->sqlerrstate =
+									MAKE_SQLSTATE(sqlstatestr[0],
 												  sqlstatestr[1],
 												  sqlstatestr[2],
 												  sqlstatestr[3],
@@ -1792,6 +1804,7 @@ proc_condition	: opt_lblname
 
 								$$ = new;
 							}
+						}
 				;
 
 expr_until_semi :
@@ -1815,49 +1828,55 @@ opt_block_label	:
 						plpgsql_ns_push(NULL);
 						$$ = NULL;
 					}
-				| '<' '<' opt_lblname '>' '>'
+				| '<' '<' any_name '>' '>'
 					{
 						plpgsql_ns_push($3);
 						$$ = $3;
 					}
 				;
 
-/*
- * need all the options because scanner will have tried to resolve as variable
- */
 opt_label	:
 					{
 						$$ = NULL;
 					}
-				| T_WORD
+				| any_identifier
+					{
+						$$ = check_label($1);
+					}
+				;
+
+opt_exitcond	: ';'
+					{ $$ = NULL; }
+				| K_WHEN expr_until_semi
+					{ $$ = $2; }
+				;
+
+/*
+ * need all the options because scanner will have tried to resolve as variable
+ */
+any_identifier	: T_WORD
 					{
-						$$ = check_label(yytext);
+						$$ = yytext;
 					}
 				| T_SCALAR
 					{
-						$$ = check_label(yytext);
+						$$ = yytext;
 					}
 				| T_RECORD
 					{
-						$$ = check_label(yytext);
+						$$ = yytext;
 					}
 				| T_ROW
 					{
-						$$ = check_label(yytext);
+						$$ = yytext;
 					}
 				;
 
-opt_exitcond	: ';'
-					{ $$ = NULL; }
-				| K_WHEN expr_until_semi
-					{ $$ = $2; }
-				;
-
-opt_lblname		: T_WORD
+any_name		: any_identifier
 					{
 						char	*name;
 
-						plpgsql_convert_ident(yytext, &name, 1);
+						plpgsql_convert_ident($1, &name, 1);
 						$$ = name;
 					}
 				;