Improve plural handling in error message

This does not use the normal plural handling, because no numbers appear
in the actual message.

src/backend/parser/parse_oper.c

@@ -723,7 +723,10 @@ op_error(ParseState *pstate, List *op, char oprkind,
 				(errcode(ERRCODE_UNDEFINED_FUNCTION),
 				 errmsg("operator does not exist: %s",
 						op_signature_string(op, oprkind, arg1, arg2)),
-				 errhint("No operator matches the given name and argument type(s). "
+				 (!arg1 || !arg2) ?
+				 errhint("No operator matches the given name and argument type. "
+						 "You might need to add an explicit type cast.") :
+				 errhint("No operator matches the given name and argument types. "
 						 "You might need to add explicit type casts."),
 				 parser_errposition(pstate, location)));
 }

src/test/regress/expected/alter_table.out

@@ -1895,7 +1895,7 @@ alter table anothertab alter column atcol1 drop default;
 alter table anothertab alter column atcol1 type boolean
         using case when atcol1 % 2 = 0 then true else false end; -- fails
 ERROR:  operator does not exist: boolean <= integer
-HINT:  No operator matches the given name and argument type(s). You might need to add explicit type casts.
+HINT:  No operator matches the given name and argument types. You might need to add explicit type casts.
 alter table anothertab drop constraint anothertab_chk;
 alter table anothertab drop constraint anothertab_chk; -- fails
 ERROR:  constraint "anothertab_chk" of relation "anothertab" does not exist

src/test/regress/expected/create_view.out

@@ -1605,7 +1605,7 @@ select 'foo'::text = any((select array['abc','def','foo']::text[]));  -- fail
 ERROR:  operator does not exist: text = text[]
 LINE 1: select 'foo'::text = any((select array['abc','def','foo']::t...
                            ^
-HINT:  No operator matches the given name and argument type(s). You might need to add explicit type casts.
+HINT:  No operator matches the given name and argument types. You might need to add explicit type casts.
 select 'foo'::text = any((select array['abc','def','foo']::text[])::text[]);
  ?column? 
 ----------

src/test/regress/expected/geometry.out

@@ -107,7 +107,7 @@ SELECT '' AS count, p.f1, l.s, l.s # p.f1 AS intersection
 ERROR:  operator does not exist: lseg # point
 LINE 1: SELECT '' AS count, p.f1, l.s, l.s # p.f1 AS intersection
                                            ^
-HINT:  No operator matches the given name and argument type(s). You might need to add explicit type casts.
+HINT:  No operator matches the given name and argument types. You might need to add explicit type casts.
 -- closest point
 SELECT '' AS thirty, p.f1, l.s, p.f1 ## l.s AS closest
    FROM LSEG_TBL l, POINT_TBL p;

src/test/regress/expected/horology.out

@@ -321,7 +321,7 @@ SELECT date '1991-02-03' - time with time zone '04:05:06 UTC' AS "Subtract Time
 ERROR:  operator does not exist: date - time with time zone
 LINE 1: SELECT date '1991-02-03' - time with time zone '04:05:06 UTC...
                                  ^
-HINT:  No operator matches the given name and argument type(s). You might need to add explicit type casts.
+HINT:  No operator matches the given name and argument types. You might need to add explicit type casts.
 --
 -- timestamp, interval arithmetic
 --

src/test/regress/expected/text.out

@@ -50,7 +50,7 @@ select 3 || 4.0;
 ERROR:  operator does not exist: integer || numeric
 LINE 1: select 3 || 4.0;
                  ^
-HINT:  No operator matches the given name and argument type(s). You might need to add explicit type casts.
+HINT:  No operator matches the given name and argument types. You might need to add explicit type casts.
 /*
  * various string functions
  */

src/test/regress/expected/timetz.out

@@ -92,4 +92,4 @@ SELECT f1 + time with time zone '00:01' AS "Illegal" FROM TIMETZ_TBL;
 ERROR:  operator does not exist: time with time zone + time with time zone
 LINE 1: SELECT f1 + time with time zone '00:01' AS "Illegal" FROM TI...
                   ^
-HINT:  No operator matches the given name and argument type(s). You might need to add explicit type casts.
+HINT:  No operator matches the given name and argument types. You might need to add explicit type casts.

src/test/regress/expected/with.out

@@ -166,7 +166,7 @@ SELECT n, n IS OF (int) AS is_int FROM t;
 ERROR:  operator does not exist: text + integer
 LINE 4:     SELECT n+1 FROM t WHERE n < 10
                     ^
-HINT:  No operator matches the given name and argument type(s). You might need to add explicit type casts.
+HINT:  No operator matches the given name and argument types. You might need to add explicit type casts.
 --
 -- Some examples with a tree
 --