From 5d447cb520145cc85461070db9d3dbf38fdbc953 Mon Sep 17 00:00:00 2001
From: Alexander Nutz <alexander.nutz@vxcc.dev>
Date: Fri, 12 Sep 2025 10:20:24 +0200
Subject: [PATCH] v0.0.3: no untagged or mixed tagged unions anymore

---
 spec.md | 20 ++++++++++----------
 1 file changed, 10 insertions(+), 10 deletions(-)

diff --git a/spec.md b/spec.md
index 8f7ae82..45ff57c 100644
--- a/spec.md
+++ b/spec.md
@@ -84,26 +84,26 @@ def example3() : User {
 }
 ```
 
-## mixed-tagged union types
+## (tagged) union types
 ```
 type Option[t] =
-  'Err Unit   # Unit that has tag enum 'Err
-| t           # has no tag
+  'Err        # If no type specified after tag, defaults to Unit
+| 'Some t
 
-# the tags of unions are weakly attached to the types, but won't decay unless they have to *)
+# the tags of unions are weakly attached to the types, but won't decay unless they have to
 def example(n: Num) : Num {
   let x = 'MyTag n  # type of x is 'MyTag Num
   x                 # tag gets removed because target type is Num
 }
 
 def example2(n: Num) : Option[Num] {
-  n    # this works, because the `t` is not tagged in option
+  'Some n
 }
 
 def example3-invalid() : Option[Num] {
-  Unit   # error: can't convert type `Unit` into type `'Err Unit | t`
+  Unit   # error: can't convert type `Unit` into type `'Err Unit | 'Some Num`
          #        Either label the expression with 'Err,
-         #        or change the return type to Option[Unit]
+         #        or change the return type to Option[Unit], and label the expression with 'Some
 }
 
 def exampe4(): Option[Num] {
@@ -116,8 +116,8 @@ def exampe4(): Option[Num] {
 def example5-error(): Option[Num] {
   let x = ( 'Err Unit ) :: Option[Unit]
   x
-  # error: can't convert type `'Err Unit | Unit` into type `'Err Unit | Num`
-  #        The case `Unit` does not exist in the target `'Err Unit | Num`
+  # error: can't convert type `'Err Unit | 'Some Unit` into type `'Err Unit | 'Some Num`
+  #        The case `'Some Unit` does not exist in the target `'Err Unit | 'Some Num`
 }
 
 def example6-error(): Option[Unit] {
@@ -126,7 +126,7 @@ def example6-error(): Option[Unit] {
   # in this case, the enum tag does not decay, like in `example`,
   # because we are casting to an enum
 
-  # error: can't convert type `'Error Unit` into type `'Err Unit | Num``
+  # error: can't convert type `'Error Unit` into type `'Err Unit | 'Some Num``
   #        1st possible solution: manually cast to just `Unit` (via `expr :: Unit`), so that it can convert to the second case of the target
   #        2nd possible solution: pattern match against the enum, to rename the tag from 'Error to 'Err
 }