Allow tuples in untagged variants (#6550)

fixes #6544

Author: tsnobip

CHANGELOG.md

@@ -16,6 +16,7 @@
 
 - GenType: support `@deriving(accessors)` outputs. https://github.com/rescript-lang/rescript-compiler/pull/6537
 - Allow coercing ints and floats to unboxed variants that have a catch-all unboxed int or float case. https://github.com/rescript-lang/rescript-compiler/pull/6540
+- Allow tuples in untagged variants https://github.com/rescript-lang/rescript-compiler/pull/6550
 
 #### :bug: Bug Fix
 

jscomp/build_tests/super_errors/expected/UntaggedTupleAndArray.res.expected

@@ -0,0 +1,10 @@
+
+  We've found a bug for you!
+  /.../fixtures/UntaggedTupleAndArray.res:4:3-21
+
+  2 │ type t =
+  3 │   | Array(array<int>)
+  4 │   | Tuple((int, int))
+  5 │ 
+
+  This untagged variant definition is invalid: At most one case can be an array or tuple type.

jscomp/build_tests/super_errors/expected/UntaggedUnknown.res.expected

@@ -1,9 +1,9 @@
 
   We've found a bug for you!
-  /.../fixtures/UntaggedUnknown.res:2:10-31
+  /.../fixtures/UntaggedUnknown.res:2:10-26
 
   1 │ @unboxed
-  2 │ type t = Tuple((float, string)) | Float(float)
+  2 │ type t = List(list<float>) | Float(float)
   3 │ 
 
-  This untagged variant definition is invalid: Case Tuple has a payload that is not of one of the recognized shapes (object, array, etc). Then it must be the only case with payloads.
+  This untagged variant definition is invalid: Case List has a payload that is not of one of the recognized shapes (object, array, etc). Then it must be the only case with payloads.

jscomp/build_tests/super_errors/fixtures/UntaggedTupleAndArray.res

@@ -0,0 +1,4 @@
+@unboxed
+type t =
+  | Array(array<int>)
+  | Tuple((int, int))

jscomp/build_tests/super_errors/fixtures/UntaggedUnknown.res

@@ -1,2 +1,2 @@
 @unboxed
-type t = Tuple((float, string)) | Float(float)
+type t = List(list<float>) | Float(float)

jscomp/ml/ast_untagged_variants.ml

@@ -47,6 +47,7 @@ let report_error ppf =
       (match untaggedVariant with
       | OnlyOneUnknown name -> "Case " ^ name ^ " has a payload that is not of one of the recognized shapes (object, array, etc). Then it must be the only case with payloads."
       | AtMostOneObject -> "At most one case can be an object type."
+      | AtMostOneInstance Array -> "At most one case can be an array or tuple type."
       | AtMostOneInstance i -> "At most one case can be a " ^ (Instance.to_string i) ^ " type."
       | AtMostOneFunction -> "At most one case can be a function type."
       | AtMostOneString -> "At most one case can be a string type."
@@ -183,6 +184,7 @@ let get_block_type_from_typ ~env (t: Types.type_expr) : block_type option =
     (match type_to_instanceof_backed_obj t with 
     | None -> None 
     | Some instanceType -> Some (InstanceType instanceType))
+  | {desc = Ttuple _} -> Some (InstanceType Array)
   | _ -> None
 
 let get_block_type ~env (cstr : Types.constructor_declaration) :

jscomp/test/UntaggedVariants.js

@@ -16,3 +16,5 @@ export type MyNullable_t<a> = null | undefined | a;
 export type MyNullableExtended_t<a> = null | undefined | "WhyNotAnotherOne" | a;
 
 export type UntaggedWithBool_t = string | number | boolean | string;
+
+export type UntaggedWithTuple_t = string | [number, number, string];

jscomp/test/variantsMatching.gen.tsx

@@ -286,3 +286,14 @@ module UntaggedWithBool = {
     | Object({name}) => "Object" ++ name
     }
 }
+
+module UntaggedWithTuple = {
+  @unboxed @genType
+  type t = String(string) | Tuple((int, float, string)) 
+
+  let classify = x =>
+    switch x {
+    | String(_) => "string"
+    | Tuple(_) => "tuple"
+    }
+}