Merge pull request #1421 from informalsystems/gabriela/empty-tuple-type-parsing

Parse the empty tuple type

Author: bugarela

CHANGELOG.md

@@ -12,6 +12,10 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 ### Deprecated
 ### Removed
 ### Fixed
+
+- Fix a problem where empty tuples were not parsed as valid types, only as
+  values (#1421).
+
 ### Security
 
 ## v0.19.1 -- 2024-04-01

quint/src/generated/Quint.g4

@@ -6,7 +6,7 @@
  *  2. Make it expressive enough to capture all of the TLA logic.
  *
  * @author: Igor Konnov, Shon Feder, Gabriela Moreira, Jure Kukovec, Thomas Pani
- *          Informal Systems, 2021-2023
+ *          Informal Systems, 2021-2024
  */
 grammar Quint;
 
@@ -119,6 +119,8 @@ type
     | SET '[' type ']'                                           # typeSet
     // TODO: replace List with general type application
     | LIST '[' type ']'                                          # typeList
+    // Parse tuples of size 0 or 2+, but not 1. (int) should be parsed as int.
+    | '(' ')'                                                    # typeUnit
     | '(' type ',' type (',' type)* ','? ')'                     # typeTuple
     | '{' row? '}'                                               # typeRec
     | 'int'                                                      # typeInt