From e9b0a926d6411e88d8bca8ce158610f093951eb1 Mon Sep 17 00:00:00 2001
From: Guillaume Petiot <guillaume@tarides.com>
Date: Thu, 29 Aug 2019 22:04:22 +0700
Subject: [PATCH] Fix crash on extension sequence (#992)

---
 src/Fmt_ast.ml                              | 3 ++-
 test/passing/extensions-indent.ml.ref       | 2 ++
 test/passing/extensions-sugar_always.ml.ref | 2 ++
 test/passing/extensions.ml                  | 2 ++
 test/passing/extensions.ml.ref              | 2 ++
 5 files changed, 10 insertions(+), 1 deletion(-)

diff --git a/src/Fmt_ast.ml b/src/Fmt_ast.ml
index e46c948a57..576a762ec1 100644
--- a/src/Fmt_ast.ml
+++ b/src/Fmt_ast.ml
@@ -2251,7 +2251,8 @@ and fmt_expression c ?(box = true) ?pro ?epi ?eol ?parens ?(indent_wrap = 0)
             ; pstr_loc= _ } ] )
     when List.is_empty pexp_attributes
          && ( Poly.(c.conf.extension_sugar = `Always)
-            || Source.extension_using_sugar ~name:ext ~payload:e1 ) ->
+            || Source.extension_using_sugar ~name:ext ~payload:e1
+               && List.length (Sugar.sequence c.conf c.cmts xexp) > 1 ) ->
       fmt_sequence c parens width xexp pexp_loc fmt_atrs ~ext
   | Pexp_sequence _ ->
       fmt_sequence c parens width xexp pexp_loc fmt_atrs ?ext
diff --git a/test/passing/extensions-indent.ml.ref b/test/passing/extensions-indent.ml.ref
index bfda087163..2cfc293e33 100644
--- a/test/passing/extensions-indent.ml.ref
+++ b/test/passing/extensions-indent.ml.ref
@@ -177,3 +177,5 @@ let _ =
   [%ext
        let+ a = b in
        c]
+
+let _ = [%ext "foo" ; "bar"]
diff --git a/test/passing/extensions-sugar_always.ml.ref b/test/passing/extensions-sugar_always.ml.ref
index 6d880194e4..8ac02cfd88 100644
--- a/test/passing/extensions-sugar_always.ml.ref
+++ b/test/passing/extensions-sugar_always.ml.ref
@@ -171,3 +171,5 @@ let _ =
   [%ext
     let+ a = b in
     c]
+
+let _ = "foo" ;%ext "bar"
diff --git a/test/passing/extensions.ml b/test/passing/extensions.ml
index 749d52eaba..17100038ac 100644
--- a/test/passing/extensions.ml
+++ b/test/passing/extensions.ml
@@ -186,3 +186,5 @@ let foo =
     foooooooooooooooooooooooooooo]
 
 let _ = [%ext let+ a = b in c]
+
+let _ = (begin%ext "foo"; "bar" end)
diff --git a/test/passing/extensions.ml.ref b/test/passing/extensions.ml.ref
index 8d7b7083d5..81453fbd4f 100644
--- a/test/passing/extensions.ml.ref
+++ b/test/passing/extensions.ml.ref
@@ -177,3 +177,5 @@ let _ =
   [%ext
     let+ a = b in
     c]
+
+let _ = [%ext "foo" ; "bar"]