From 4702bd807bf9693181cc9d48ecc7f9ce0fc5e7e0 Mon Sep 17 00:00:00 2001
From: TSUYUSATO Kitsune <make.just.on@gmail.com>
Date: Thu, 21 Dec 2017 20:16:08 +0900
Subject: [PATCH] Fix to work formatting `foo.[bar] = baz`

Fixed #5416
---
 spec/compiler/formatter/formatter_spec.cr |  2 ++
 src/compiler/crystal/tools/formatter.cr   | 27 +++++++++++++++++++++++
 2 files changed, 29 insertions(+)

diff --git a/spec/compiler/formatter/formatter_spec.cr b/spec/compiler/formatter/formatter_spec.cr
index aa9b7451f022..23bfb9612a76 100644
--- a/spec/compiler/formatter/formatter_spec.cr
+++ b/spec/compiler/formatter/formatter_spec.cr
@@ -901,6 +901,8 @@ describe Crystal::Formatter do
 
   assert_format "foo.[]"
   assert_format "foo.[1]"
+  assert_format "foo.[] = 1"
+  assert_format "foo.[1, 2] = 3"
 
   assert_format "@foo : Int32 # comment\n\ndef foo\nend"
   assert_format "getter foo # comment\n\ndef foo\nend"
diff --git a/src/compiler/crystal/tools/formatter.cr b/src/compiler/crystal/tools/formatter.cr
index c8ca96269a24..28bc019e229d 100644
--- a/src/compiler/crystal/tools/formatter.cr
+++ b/src/compiler/crystal/tools/formatter.cr
@@ -2230,6 +2230,33 @@ module Crystal
 
       current_multiline_call_indent = @multiline_call_indent
 
+      # This is for foo.[bar] = baz
+      if node.name == "[]=" && @token.type == :"["
+        write "["
+        next_token_skip_space_or_newline
+        args = node.args
+        last_arg = args.pop
+        format_args args, true, node.named_args
+        write_token :"]"
+        skip_space_or_newline
+        write " ="
+        next_token_skip_space
+        accept_assign_value_after_equals last_arg
+        return false
+      end
+
+      # This is for foo.[] = bar
+      if node.name == "[]=" && @token.type == :"[]"
+        write_token :"[]"
+        next_token_skip_space_or_newline
+        write " ="
+        next_token_skip_space
+        accept_assign_value_after_equals node.args.last
+        return false
+      end
+
+      current_dot_column = @dot_column
+
       assignment = node.name.ends_with?('=') && node.name.chars.any?(&.ascii_letter?)
 
       if assignment