Fix special case for type doc in lexer

unison-src/transcripts/doc2markdown.md

@@ -92,3 +92,20 @@ Table
 ```ucm
 .> debug.doc-to-markdown fulldoc
 ```
+
+You can add docs to a term or type with a top-level doc literal above the binding:
+
+```unison
+{{ This is a term doc }}
+myTerm = 10
+
+-- Regression tests for https://github.com/unisonweb/unison/issues/4634
+{{ This is a type doc }}
+type MyType = MyType
+
+{{ This is a unique type doc }}
+unique type MyUniqueType = MyUniqueType
+
+{{ This is a structural type doc }}
+structural type MyStructuralType = MyStructuralType
+```

unison-src/transcripts/doc2markdown.output.md

@@ -156,4 +156,42 @@ Table
 
 
 
+```
+You can add docs to a term or type with a top-level doc literal above the binding:
+
+```unison
+{{ This is a term doc }}
+myTerm = 10
+
+-- Regression tests for https://github.com/unisonweb/unison/issues/4634
+{{ This is a type doc }}
+type MyType = MyType
+
+{{ This is a unique type doc }}
+unique type MyUniqueType = MyUniqueType
+
+{{ This is a structural type doc }}
+structural type MyStructuralType = MyStructuralType
+```
+
+```ucm
+
+  Loading changes detected in scratch.u.
+
+  I found and typechecked these definitions in scratch.u. If you
+  do an `add` or `update`, here's how your codebase would
+  change:
+  
+    ⍟ These new definitions are ok to `add`:
+    
+      structural type MyStructuralType
+        (also named builtin.Unit)
+      type MyType
+      type MyUniqueType
+      MyStructuralType.doc : Doc2
+      MyType.doc           : Doc2
+      MyUniqueType.doc     : Doc2
+      myTerm               : Nat
+      myTerm.doc           : Doc2
+
 ```

unison-syntax/src/Unison/Syntax/Lexer.hs

@@ -403,7 +403,7 @@ lexemes' eof =
           let lit' s = lit s <* sp
           let modifier = typeModifiersAlt lit'
           let typeOrAbility' = typeOrAbilityAlt wordyKw
-          _ <- modifier <* typeOrAbility' *> sp
+          _ <- optional modifier *> typeOrAbility' *> sp
           wordyId
         ignore _ _ _ = []
         body = join <$> P.many (sectionElem <* CP.space)