OCaml spacing error (#536)

* Spacing after function keywords.

* [OCaml] open `function_definition` scope more often

---------

Co-authored-by: Nicolas BACQUEY <nicolas.bacquey@tweag.io>

topiary/languages/ocaml.scm

@@ -154,6 +154,8 @@
     "external"
     (floating_attribute)
     "for"
+    "fun"
+    "function"
     "if"
     "in"
     "include"
@@ -783,18 +785,13 @@
   ) @end_scope
   (#scope_id! "function_definition")
 )
-(parenthesized_expression
-  (function_expression
-    "function" @append_spaced_scoped_softline
-  ) @begin_scope @end_scope
-  (#scope_id! "function_definition")
-)
+; The following is the general case, which should happen anywhere except in let bindings
 (
-  (_) @begin_scope
+  "="? @do_nothing
   .
   (function_expression
     "function" @append_spaced_scoped_softline
-  ) @end_scope
+  ) @begin_scope @end_scope
   (#scope_id! "function_definition")
 )
 (function_expression

topiary/tests/samples/expected/ocaml.ml

@@ -13,6 +13,24 @@
 (*                                                                        *)
 (**************************************************************************)
 
+(* Issue 529 *)
+
+let id1 = if true then Fun.id else function x -> x
+
+let id2 = if true then Fun.id else function x -> x | y -> y
+
+let id3 =
+  if true then
+    Fun.id
+  else
+    function x -> x
+
+let id4 = function x -> x
+
+let id5 = if true then Fun.id else function x -> x
+
+let id6 = function x -> x
+
 (* Extensible buffers *)
 
 type t = (* Multi-

topiary/tests/samples/input/ocaml.ml

@@ -13,6 +13,25 @@
 (*                                                                        *)
 (**************************************************************************)
 
+(* Issue 529 *)
+
+let id1 = if true then Fun.id else function x -> x
+
+let id2 = if true then Fun.id else function x -> x | y -> y
+
+let id3 = if 
+true 
+then 
+Fun.id 
+else 
+function x -> x
+
+let id4 = function x -> x
+
+let id5 = if true then Fun.id else function | x -> x
+
+let id6 = function | x -> x
+
 (* Extensible buffers *)
 
 type t =      (* Multi-