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Parse attributes after = private and a doc comment before a manifest (#9115)
Why: `private @attr {x: int}` took the type expression path and rejected the record, and a doc comment right after `=` always started a constructor list, so `/** d */ int` failed. Both now use the lookahead that attributes after `=` already had: past attributes and doc comments, a record, `..`, `|` or constructor is a representation, anything else a manifest. AST modified (doc comment before a manifest): Example: type z = /** d */ int Before (diagnostic): Did you mean `Int` instead of `int`? After (parse): type_declaration "z" ptype_kind = Ptype_abstract ptype_private = Public ptype_manifest = Some core_type attribute "res.doc" … Ptyp_constr "int" Format modified (attribute after `private`): Example: type t = private @attr {x: int} type u = private /** d */ int Before (diagnostic): An inline record type declaration is only allowed in a variant constructor's declaration or nested inside of a record type declaration After (rescript): @attr type t = private {x: int} type u = private /** d */ int Review: Does a leading doc comment change any form that parsed before? No. After a doc comment the lookahead keeps the representation for every start the constructor and record parsers accept (`|`, a constructor, `...base`, `{...`, a record, `..`); only starts they rejected, such as `int`, `M.t`, `'a`, `(a, b)`, `[#A]`, `{.}` or `{"a": int}`, become a manifest. A differential run over 672 declarations (prefixes x bodies, with and without `private`, .res and .resi) gives the same tree as before for every one that parsed. Fixes #9106 Claude-Session: https://claude.ai/code/session_01Kbf3gGkPma9LAZimuQjnrP Signed-off-by: Christoph Knittel <ck@cca.io> Co-authored-by: Claude Opus 5.5 <noreply@anthropic.com>
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Lines changed: 218 additions & 39 deletions

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‎changes/private-attr-doc-comment-type.fix.md‎

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- Accept attributes and doc comments after `= private`, and a doc comment after `=` in front of a type expression such as `int`.

‎compiler/syntax/src/res_core.ml‎

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@@ -5799,6 +5799,11 @@ and parse_private_eq_or_repr p =
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| Bar | DotDot ->
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let _, kind, attrs = parse_type_representation p in
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(None, Asttypes.Private, kind, attrs)
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| (At | DocComment _) when is_representation_after_attrs p ->
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let _, kind, attrs = parse_type_representation p in
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(None, Asttypes.Private, kind, attrs)
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| DocComment _ ->
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(Some (parse_typ_expr p), Asttypes.Private, Parsetree.Ptype_abstract, [])
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| t when Grammar.is_typ_expr_start t ->
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(Some (parse_typ_expr p), Asttypes.Private, Parsetree.Ptype_abstract, [])
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| _ ->
@@ -6019,6 +6024,55 @@ and parse_polymorphic_variant_type_args p =
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Parser.expect Rparen p;
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Location.mkloc args (mk_loc start_pos (Parser.position p))
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(* Attributes and doc comments after `=` (or `= private`) can start a
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representation (variant/record/open variant) or a manifest. Look ahead past
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them: if a representation-like token follows, it is a representation;
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otherwise a manifest type expression. *)
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and is_representation_after_attrs p =
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let starts_with_doc_comment =
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match Parser.peek p with
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| DocComment _ -> true
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| _ -> false
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in
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Parser.lookahead p (fun state ->
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ignore (parse_attributes state);
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(* optionally skip a run of doc comments before deciding *)
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skip_doc_comments state;
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match Parser.peek state with
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| Lbrace -> (
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(* Disambiguate record declaration vs object type.
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Peek inside the braces; if it looks like an object (String/Dot/DotDot/DotDotDot),
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then this is a manifest type expression, not a representation. If it looks like
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a record field (e.g. Lident or attributes before one), treat as representation. *)
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Parser.next state;
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(* consume Lbrace *)
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ignore (parse_attributes state);
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skip_doc_comments state;
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match Parser.peek state with
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| String _ | Dot | DotDot -> false (* object type => manifest *)
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| DotDotDot ->
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(* A spread (`{...base, y: int}`) after a leading doc comment has
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always been parsed as a record declaration, and after a leading
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attribute as an object type. *)
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starts_with_doc_comment
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| _ -> true
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(* record decl => representation *))
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| Bar -> true (* variant constructor list *)
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| DotDot -> true (* extensible/open variant ".." *)
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| DotDotDot ->
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(* A variant spread (`...base | C`) after a leading doc comment has
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always been parsed as a constructor list. *)
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starts_with_doc_comment
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| Uident _ -> (
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(* constructor vs module-qualified manifest *)
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Parser.next state;
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match Parser.peek state with
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| Dot -> false (* M.t => manifest *)
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| _ -> true
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(* Uident starting a constructor *))
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| DocComment _ -> true (* doc before constructor list *)
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| _ -> false)
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and parse_type_equation_and_representation ?current_type_name_path
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?inline_types_context p =
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match Parser.peek p with
@@ -6034,49 +6088,14 @@ and parse_type_equation_and_representation ?current_type_name_path
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in
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(manifest, priv, kind, [])
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| Private -> parse_private_eq_or_repr p
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| Bar | DotDot | DocComment _ ->
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| Bar | DotDot ->
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let priv, kind, attrs =
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parse_type_representation ?current_type_name_path ?inline_types_context
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p
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in
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(None, priv, kind, attrs)
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| At -> (
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(* Attributes can start a representation (variant/record/open variant) or a manifest.
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Look ahead past attributes (and doc comments). If a representation-like token follows,
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parse it as a representation; otherwise treat as a manifest. *)
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let is_representation_after_attrs =
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Parser.lookahead p (fun state ->
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ignore (parse_attributes state);
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(* optionally skip a run of doc comments before deciding *)
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skip_doc_comments state;
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match Parser.peek state with
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| Lbrace -> (
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(* Disambiguate record declaration vs object type.
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Peek inside the braces; if it looks like an object (String/Dot/DotDot/DotDotDot),
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then this is a manifest type expression, not a representation. If it looks like
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a record field (e.g. Lident or attributes before one), treat as representation. *)
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Parser.next state;
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(* consume Lbrace *)
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ignore (parse_attributes state);
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skip_doc_comments state;
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match Parser.peek state with
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| String _ | Dot | DotDot | DotDotDot ->
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false (* object type => manifest *)
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| _ -> true
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(* record decl => representation *))
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| Bar -> true (* variant constructor list *)
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| DotDot -> true (* extensible/open variant ".." *)
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| Uident _ -> (
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(* constructor vs module-qualified manifest *)
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Parser.next state;
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match Parser.peek state with
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| Dot -> false (* M.t => manifest *)
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| _ -> true
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(* Uident starting a constructor *))
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| DocComment _ -> true (* doc before constructor list *)
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| _ -> false)
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in
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if is_representation_after_attrs then
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| At | DocComment _ -> (
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if is_representation_after_attrs p then
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let priv, kind, attrs =
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parse_type_representation ?current_type_name_path
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?inline_types_context p

‎tests/syntax_tests/data/parsing/grammar/typedefinition/expected/typeRepresentation.res.txt‎

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@@ -79,4 +79,73 @@ type nonrec t =
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| B [@res.doc {js|doc2|js}]
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type nonrec t =
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| A [@res.doc {js|doc|js}][@attr ]
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| B
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| B
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type nonrec t = private {
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x: int }[@@attr ]
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type nonrec t = private ..[@@attr ]
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type nonrec t = private
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| A [@attr ]
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| B
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type nonrec t = private ((int)[@attr ])
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type nonrec t = private ((< a: int > )[@attr ])
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type nonrec t = private ((int)[@res.doc {js|doc|js}])
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type nonrec t = private ((M.t)[@res.doc {js|doc|js}])
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type nonrec t = private
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| A [@res.doc {js|doc|js}]
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| B
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type nonrec t = private {
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x: int }[@@res.doc {js|doc|js}][@@attr ]
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type nonrec t = ((int)[@res.doc {js|doc|js}])
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type nonrec t = ((< a: int > )[@res.doc {js|doc|js}])
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type nonrec t = (((int * int))[@res.doc {js|doc|js}])
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type nonrec t = (([ `A ])[@res.doc {js|doc|js}])
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type nonrec t = ((M.t)[@res.doc {js|doc|js}])
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type nonrec t = ((M.t)[@res.doc {js|doc|js}]) =
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| A
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| B
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type nonrec t = ((int)[@res.doc {js|doc|js}][@attr ])
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type nonrec t = {
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...: base ;
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y: int }[@@res.doc {js|doc|js}]
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type nonrec t = {
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...: base }[@@res.doc {js|doc|js}]
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type nonrec t = {
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...: base ;
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y: int }[@@res.doc {js|doc|js}][@@attr ]
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type nonrec t = ((< .. > )[@res.doc {js|doc|js}])
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type nonrec t = ((< > )[@res.doc {js|doc|js}])
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type nonrec t = ((< a: int ;.. > )[@res.doc {js|doc|js}])
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type nonrec t = ((< base ;y: int > )[@attr ])
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type nonrec t = ((< base > )[@attr ])
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type nonrec t = private {
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...: base ;
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y: int }[@@res.doc {js|doc|js}]
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type nonrec t = private {
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...: base }[@@res.doc {js|doc|js}]
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type nonrec t = private {
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...: base ;
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y: int }[@@res.doc {js|doc|js}][@@attr ]
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type nonrec t = private ((< .. > )[@res.doc {js|doc|js}])
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type nonrec t = private ((< a: int ;.. > )[@res.doc {js|doc|js}])
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type nonrec t = private ((< base ;y: int > )[@attr ])
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type nonrec t = private ((< base > )[@attr ])
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type nonrec t =
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| ... of base [@res.doc {js|doc|js}]
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| C
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type nonrec t =
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| ... of base [@res.doc {js|doc|js}][@res.doc {js|doc2|js}]
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| C
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type nonrec t =
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| ... of base [@res.doc {js|doc|js}][@attr ]
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| C
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type nonrec t = private
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| ... of base [@res.doc {js|doc|js}]
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| C
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type nonrec t = private
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| ... of base [@res.doc {js|doc|js}][@attr ]
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| C
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type nonrec t = (('a)[@res.doc {js|doc|js}])
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type nonrec t = ((int)[@res.doc {js|doc|js}]) -> int (a:1)
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type nonrec t = ((M.t)[@res.doc {js|doc|js}]) = {
150+
x: int }
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type nonrec t = private (('a Dict.t)[@res.doc {js|doc|js}])

‎tests/syntax_tests/data/parsing/grammar/typedefinition/typeRepresentation.res‎

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@@ -45,3 +45,45 @@ type t = private /**doc*/ {x: int}
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type t = /**doc*/ A | B
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type t = /**doc*/ | A | /**doc2*/ B
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type t = /**doc*/ @attr A | B
48+
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// attributes and doc comments after `private`, and doc comments before a manifest
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type t = private @attr {x: int}
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type t = private @attr ..
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type t = private @attr A | B
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type t = private @attr int
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type t = private @attr {"a": int}
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type t = private /**doc*/ int
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type t = private /**doc*/ M.t
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type t = private /**doc*/ A | B
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type t = private /**doc*/ @attr {x: int}
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type t = /**doc*/ int
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type t = /**doc*/ {"a": int}
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type t = /**doc*/ (int, int)
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type t = /**doc*/ [#A]
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type t = /**doc*/ M.t
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type t = /**doc*/ M.t = A | B
65+
type t = /**doc*/ @attr int
66+
type t = /**doc*/ {...base, y: int}
67+
type t = /**doc*/ {...base}
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type t = /**doc*/ @attr {...base, y: int}
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type t = /**doc*/ {..}
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type t = /**doc*/ {.}
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type t = /**doc*/ {.. "a": int}
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type t = @attr {...base, "y": int}
73+
type t = @attr {...base}
74+
type t = private /**doc*/ {...base, y: int}
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type t = private /**doc*/ {...base}
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type t = private /**doc*/ @attr {...base, y: int}
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type t = private /**doc*/ {..}
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type t = private /**doc*/ {.. "a": int}
79+
type t = private @attr {...base, "y": int}
80+
type t = private @attr {...base}
81+
type t = /**doc*/ ...base | C
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type t = /**doc*/ /**doc2*/ ...base | C
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type t = /**doc*/ @attr ...base | C
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type t = private /**doc*/ ...base | C
85+
type t = private /**doc*/ @attr ...base | C
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type t = /**doc*/ 'a
87+
type t = /**doc*/ int => int
88+
type t = /**doc*/ M.t = {x: int}
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type t = private /**doc*/ Dict.t<'a>

‎tests/syntax_tests/data/printer/typeDef/attributes.res‎

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@@ -27,3 +27,20 @@ type t = /** d1 */ @attr /** d2 */ {x: int}
2727
type t = /* c1 */ /** doc */ /* c2 */ {x: int} // trail
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type t = /** doc */ A | B
2929
type t = | /** doc */ A | /** doc2 */ B
30+
type t = private @attr {x: int}
31+
type t = private /** doc */ @attr ..
32+
type t = private @attr int
33+
type t = private /** doc */ int
34+
type t = private /** doc */ A | B
35+
type t = /** doc */ int
36+
type t = /** doc */ {"a": int}
37+
type t = /** doc */ (int, int)
38+
type t = /** doc */ [#A]
39+
type t = /** doc */ M.t = A | B
40+
type t = /** doc */ {...base, y: int}
41+
type t = /** doc */ {.. "a": int}
42+
type t = private /** doc */ {...base, y: int}
43+
type t = private /** doc */ {.}
44+
type t = /** doc */ ...base | C
45+
type t = private /** doc */ ...base | C
46+
type t = /** doc */ 'a

‎tests/syntax_tests/data/printer/typeDef/expected/attributes.res.txt‎

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Original file line numberDiff line numberDiff line change
@@ -44,3 +44,34 @@ type t =
4444
| A
4545
/** doc2 */
4646
| B
47+
@attr type t = private {x: int}
48+
/** doc */
49+
@attr type t = private ..
50+
type t = private @attr int
51+
type t = private /** doc */ int
52+
type t =
53+
private
54+
/** doc */
55+
| A
56+
| B
57+
type t = /** doc */ int
58+
type t = /** doc */ {"a": int}
59+
type t = /** doc */ (int, int)
60+
type t = /** doc */ [#A]
61+
type t = /** doc */ M.t = A | B
62+
/** doc */
63+
type t = {...base, y: int}
64+
type t = /** doc */ {.."a": int}
65+
/** doc */
66+
type t = private {...base, y: int}
67+
type t = private /** doc */ {.}
68+
type t =
69+
/** doc */
70+
| ...base
71+
| C
72+
type t =
73+
private
74+
/** doc */
75+
| ...base
76+
| C
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type t = /** doc */ 'a

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