fixes #940

Author: wumpz

src/main/jjtree/net/sf/jsqlparser/parser/JSqlParserCC.jjt

@@ -2969,7 +2969,7 @@ Expression PrimaryExpression() #PrimaryExpression:
         | LOOKAHEAD(2) retval=CastExpression()
 
         // support timestamp expressions
-        | token=<K_TIME_KEY_EXPR> { retval = new TimeKeyExpression(token.image); }
+        | (token=<K_TIME_KEY_EXPR> | token=<K_CURRENT>) { retval = new TimeKeyExpression(token.image); }
 
         | LOOKAHEAD(2) retval=DateTimeLiteralExpression()
 
@@ -3225,7 +3225,7 @@ WindowOffset WindowOffset():
 											<K_FOLLOWING> { offset.setType(WindowOffset.Type.FOLLOWING); } )
 		) 
 		|
-		( <K_CURRENT> <K_ROW> { offset.setType(WindowOffset.Type.CURRENT); } ) 
+		LOOKAHEAD(2) ( <K_CURRENT> <K_ROW> { offset.setType(WindowOffset.Type.CURRENT); } ) 
 		|
 		( expr = SimpleExpression() {
 			offset.setType(WindowOffset.Type.EXPR); 

src/test/java/net/sf/jsqlparser/statement/select/SelectTest.java

@@ -4059,4 +4059,9 @@ public void testKeyWordCreateIssue941() throws JSQLParserException {
     public void testKeyWordCreateIssue941_2() throws JSQLParserException {
         assertSqlCanBeParsedAndDeparsed("select f.select from `from` f", true);
     }
+    
+    @Test
+    public void testCurrentIssue940() throws JSQLParserException {
+        assertSqlCanBeParsedAndDeparsed("SELECT date(current) AS test_date FROM systables WHERE tabid = 1");
+    }
 }