Improve printing of destructuring with local open.

HISTORY.md

@@ -1,5 +1,6 @@
 ## 3.9 (unreleased)
 
+- Improve printing of destructuring with local open. [#2684](https://github.com/reasonml/reason/pull/2684)
 - Reduce the amount of parentheses around functor usage. [#2683](https://github.com/reasonml/reason/pull/2683)
 - Print module type body on separate line (@SanderSpies) [#2709](https://github.com/reasonml/reason/pull/2709)
 - Fix missing patterns around contraint pattern (a pattern with a type annotation).

src/reason-parser/reason_pprint_ast.ml

@@ -5296,6 +5296,34 @@ let printer = object(self:'self)
  forms of explicit polymorphic annotations in the parse tree, and how
  we must recover them here.
  *)
+ | [], (Ppat_open (lid, {ppat_desc = Ppat_record(l, closed); _})) -> 
+ (* 
+ Special case handling for: 
+
+ let Foo.{
+ destruct1,
+ destruct2,
+ destruct3,
+ destruct4,
+ destruct5,
+ } = bar;
+ *)
+
+ let upUntilEqual =
+ let pat = self#patternRecord l closed in
+ label
+ (label ~space:true 
+ (atom "let") 
+ (label 
+ (self#longident_loc lid) 
+ (atom ("."))
+ )
+ )
+ pat
+ in
+ let appTerms = self#unparseExprApplicationItems expr in
+ let includingEqual = makeList ~postSpace:true [upUntilEqual; atom "="] in
+ formatAttachmentApplication applicationFinalWrapping (Some (true, includingEqual)) appTerms
  | [], (Ppat_constraint(p, ty)) -> (
  (* Locally abstract forall types are *seriously* mangled by the parsing
  stage, and we have to be very smart about how to recover it.

test/general-syntax-re.t/input.re

@@ -1246,6 +1246,14 @@ let testCallNamedArgs = (foo: ((~a: int, ~b: int=?) => int), a, b) =>
 let Foo.{name} = bar;
 let Foo.Bar.{name} = bar;
 
+let Foo.{
+ destruct1, 
+ destruct2, 
+ destruct3, 
+ destruct4, 
+ destruct5, 
+} = fooBar;
+
 let Foo.[ name ] = bar;
 let Foo.Bar.[ name ] = bar;
 

test/general-syntax-re.t/run.t

@@ -1432,6 +1432,14 @@ Format general implementation syntax
  let Foo.{name} = bar;
  let Foo.Bar.{name} = bar;
 
+ let Foo.{
+ destruct1,
+ destruct2,
+ destruct3,
+ destruct4,
+ destruct5,
+ } = fooBar;
+
  let Foo.[name] = bar;
  let Foo.Bar.[name] = bar;