Fix precision handling for some COERCE_SQL_SYNTAX functions

f193883 has been incorrectly setting up the precision used in the
timestamp compilations returned by the following functions:
- LOCALTIME
- LOCALTIMESTAMP
- CURRENT_TIME
- CURRENT_TIMESTAMP

Specifying an out-of-range precision for CURRENT_TIMESTAMP and
LOCALTIMESTAMP was raising a WARNING without adjusting the precision,
leading to a subsequent error.  LOCALTIME and CURRENT_TIME raised a
WARNING without an error, still the precision given to the internal
routines was not correct, so let's be clean.

Ian has reported the problems in timestamp.c, while I have noticed the
ones in date.c.  Regression tests are added for all of them with
precisions high enough to provide coverage for the warnings, something
that went missing up to this commit.

Author: Ian Lawrence Barwick, Michael Paquier
Discussion: https://postgr.es/m/CAB8KJ=jQEnn9sYG+N752spt68wMrhmT-ocHCh4oeNmHF82QMWA@mail.gmail.com

src/backend/utils/adt/date.c

@@ -347,10 +347,7 @@ current_time(PG_FUNCTION_ARGS)
 	int32		typmod = -1;
 
 	if (!PG_ARGISNULL(0))
-	{
-		typmod = PG_GETARG_INT32(0);
-		anytime_typmod_check(true, typmod);
-	}
+		typmod = anytime_typmod_check(true, PG_GETARG_INT32(0));
 
 	GetCurrentTimeUsec(tm, &fsec, &tz);
 
@@ -375,10 +372,7 @@ sql_localtime(PG_FUNCTION_ARGS)
 	int32		typmod = -1;
 
 	if (!PG_ARGISNULL(0))
-	{
-		typmod = PG_GETARG_INT32(0);
-		anytime_typmod_check(false, typmod);
-	}
+		typmod = anytime_typmod_check(false, PG_GETARG_INT32(0));
 
 	GetCurrentTimeUsec(tm, &fsec, &tz);
 

src/backend/utils/adt/timestamp.c

@@ -1606,10 +1606,7 @@ current_timestamp(PG_FUNCTION_ARGS)
 	int32		typmod = -1;
 
 	if (!PG_ARGISNULL(0))
-	{
-		typmod = PG_GETARG_INT32(0);
-		anytimestamp_typmod_check(true, typmod);
-	}
+		typmod = anytimestamp_typmod_check(true, PG_GETARG_INT32(0));
 
 	ts = GetCurrentTransactionStartTimestamp();
 	if (typmod >= 0)
@@ -1627,10 +1624,7 @@ sql_localtimestamp(PG_FUNCTION_ARGS)
 	int32		typmod = -1;
 
 	if (!PG_ARGISNULL(0))
-	{
-		typmod = PG_GETARG_INT32(0);
-		anytimestamp_typmod_check(false, typmod);
-	}
+		typmod = anytimestamp_typmod_check(false, PG_GETARG_INT32(0));
 
 	ts = timestamptz2timestamp(GetCurrentTransactionStartTimestamp());
 	if (typmod >= 0)

src/test/regress/expected/expressions.out

@@ -36,7 +36,7 @@ SELECT now()::time(3)::text = localtime(3)::text;
  t
 (1 row)
 
--- current_timestamp / localtimestamp (always matches because of transactional behaviour)
+-- current_time[stamp]/ localtime[stamp] (always matches because of transactional behaviour)
 SELECT current_timestamp = NOW();
  ?column? 
 ----------
@@ -57,6 +57,35 @@ SELECT now()::timestamp::text = localtimestamp::text;
  t
 (1 row)
 
+-- precision overflow
+SELECT current_time = current_time(7);
+WARNING:  TIME(7) WITH TIME ZONE precision reduced to maximum allowed, 6
+ ?column? 
+----------
+ t
+(1 row)
+
+SELECT current_timestamp = current_timestamp(7);
+WARNING:  TIMESTAMP(7) WITH TIME ZONE precision reduced to maximum allowed, 6
+ ?column? 
+----------
+ t
+(1 row)
+
+SELECT localtime = localtime(7);
+WARNING:  TIME(7) precision reduced to maximum allowed, 6
+ ?column? 
+----------
+ t
+(1 row)
+
+SELECT localtimestamp = localtimestamp(7);
+WARNING:  TIMESTAMP(7) precision reduced to maximum allowed, 6
+ ?column? 
+----------
+ t
+(1 row)
+
 -- current_role/user/user is tested in rolnames.sql
 -- current database / catalog
 SELECT current_catalog = current_database();

src/test/regress/sql/expressions.sql

@@ -17,12 +17,17 @@ SELECT now()::timetz(4)::text = current_time(4)::text;
 SELECT now()::time::text = localtime::text;
 SELECT now()::time(3)::text = localtime(3)::text;
 
--- current_timestamp / localtimestamp (always matches because of transactional behaviour)
+-- current_time[stamp]/ localtime[stamp] (always matches because of transactional behaviour)
 SELECT current_timestamp = NOW();
 -- precision
 SELECT length(current_timestamp::text) >= length(current_timestamp(0)::text);
 -- localtimestamp
 SELECT now()::timestamp::text = localtimestamp::text;
+-- precision overflow
+SELECT current_time = current_time(7);
+SELECT current_timestamp = current_timestamp(7);
+SELECT localtime = localtime(7);
+SELECT localtimestamp = localtimestamp(7);
 
 -- current_role/user/user is tested in rolnames.sql