Make GenericDialect support trailing commas in projections (apache#1921)

Author: simonvandel

src/dialect/generic.rs

@@ -116,6 +116,10 @@ impl Dialect for GenericDialect {
         true
     }
 
+    fn supports_projection_trailing_commas(&self) -> bool {
+        true
+    }
+
     fn supports_asc_desc_in_column_definition(&self) -> bool {
         true
     }

tests/sqlparser_common.rs

@@ -11184,7 +11184,7 @@ fn parse_trailing_comma() {
     trailing_commas.verified_stmt(r#"SELECT "from" FROM "from""#);
 
     // doesn't allow any trailing commas
-    let trailing_commas = TestedDialects::new(vec![Box::new(GenericDialect {})]);
+    let trailing_commas = TestedDialects::new(vec![Box::new(PostgreSqlDialect {})]);
 
     assert_eq!(
         trailing_commas