Don't drop "?" on nullable empty record types. (#1229)

Fix #1224.

CHANGELOG.md

@@ -7,6 +7,7 @@
 * Don't split before `.` following a record literal (#1213).
 * Don't force split on a line comment before a switch expression case (#1215).
 * Require `package:analyzer` `^5.12.0`.
+* Preserve `?` on nullable empty record types (#1224).
 
 # 2.3.1
 

lib/src/source_visitor.dart

@@ -2505,6 +2505,7 @@ class SourceVisitor extends ThrowingAstVisitor {
       if (node.rightParenthesis.precedingComments != null) soloZeroSplit();
 
       token(node.rightParenthesis);
+      token(node.question);
       return;
     }
 

test/whitespace/record_types.unit

@@ -47,4 +47,8 @@
 >>> nullable record type
 (  int  ,   bool  )   ?  x;
 <<<
-(int, bool)? x;
+(int, bool)? x;
+>>> empty nullable record type
+(  )  ?   x;
+<<<
+()? x;