Parse doc comments in type parameters.

CHANGELOG.md

@@ -18,6 +18,7 @@
 - Fix issue where spreading record types with optional labels would not have their labels preserved as optional. https://github.com/rescript-lang/rescript-compiler/pull/6154
 - Fix error location to be the type with the spreads when spreading record types with duplicate labels. https://github.com/rescript-lang/rescript-compiler/pull/6157
 - Disable warning on `@inline` attibute on uncurried functions. https://github.com/rescript-lang/rescript-compiler/pull/6152
+- Support doc comments on arguments of function types. https://github.com/rescript-lang/rescript-compiler/pull/6161
 
 # 11.0.0-alpha.3
 

res_syntax/src/res_core.ml

@@ -4125,14 +4125,21 @@ and parseTypeAlias p typ =
    *  | . type_parameter
 *)
 and parseTypeParameter p =
+  let docAttr : Parsetree.attributes =
+    match p.Parser.token with
+    | DocComment (loc, s) ->
+      Parser.next p;
+      [docCommentToAttribute loc s]
+    | _ -> []
+  in
   if
     p.Parser.token = Token.Tilde
     || p.token = Dot
     || Grammar.isTypExprStart p.token
   then
     let startPos = p.Parser.startPos in
     let dotted = Parser.optional p Dot in
-    let attrs = parseAttributes p in
+    let attrs = docAttr @ parseAttributes p in
     match p.Parser.token with
     | Tilde -> (
       Parser.next p;
@@ -4236,6 +4243,7 @@ and parseEs6ArrowType ~attrs p =
     let returnType = parseTypExpr ~alias:false p in
     let loc = mkLoc startPos p.prevEndPos in
     Ast_helper.Typ.arrow ~loc ~attrs arg typ returnType
+  | DocComment _ -> assert false
   | _ ->
     let parameters = parseTypeParameters p in
     Parser.expect EqualGreater p;
@@ -6399,15 +6407,17 @@ and parseAttribute p =
     Some (attrId, payload)
   | DocComment (loc, s) ->
     Parser.next p;
-    Some
-      ( {txt = "res.doc"; loc},
-        PStr
-          [
-            Ast_helper.Str.eval ~loc
-              (Ast_helper.Exp.constant ~loc (Pconst_string (s, None)));
-          ] )
+    Some (docCommentToAttribute loc s)
   | _ -> None
 
+and docCommentToAttribute loc s : Parsetree.attribute =
+  ( {txt = "res.doc"; loc},
+    PStr
+      [
+        Ast_helper.Str.eval ~loc
+          (Ast_helper.Exp.constant ~loc (Pconst_string (s, None)));
+      ] )
+
 and parseAttributes p =
   parseRegion p ~grammar:Grammar.Attribute ~f:parseAttribute
 

res_syntax/tests/printer/expr/DocComments.res

@@ -0,0 +1,13 @@
+let doc1: (/** ddd */ ~x: int) => int = (~x) => x + 1
+let doc2: @res.doc(" ddd ") int => int = x => x + 1
+let doc3: /** ddd */ int => int = x => x + 1
+let doc4: (/** ddd */ ~x: int, /** eee */ n) => int = (~x) => x + 1
+
+module M : {
+    let foo : (/** xxdoc */ ~x:int, /** yydoc */ ~y:int) => int
+} = {
+    let foo= (~x, ~y) => x+y
+}
+
+@val
+external ex : (/** ddd */ ~x: int, /** eee */ n) => int = "ex"

res_syntax/tests/printer/expr/expected/DocComments.res.txt

@@ -0,0 +1,13 @@
+let doc1: (/** ddd */ ~x: int) => int = (~x) => x + 1
+let doc2: /** ddd */ int => int = x => x + 1
+let doc3: /** ddd */ int => int = x => x + 1
+let doc4: (/** ddd */ ~x: int, /** eee */ n) => int = (~x) => x + 1
+
+module M: {
+  let foo: (/** xxdoc */ ~x: int, /** yydoc */ ~y: int) => int
+} = {
+  let foo = (~x, ~y) => x + y
+}
+
+@val
+external ex: (/** ddd */ ~x: int, /** eee */ n) => int = "ex"