From e7005245b8255c41c52fbaf8f086a6f41411c254 Mon Sep 17 00:00:00 2001
From: hirokinoue <70567194+hirokinoue@users.noreply.github.com>
Date: Sat, 14 May 2022 23:36:51 +0900
Subject: [PATCH 1/3] add test case for implode()

---
 tests/ArrayFunctionCallTest.php | 25 +++++++++++++++++++++++++
 1 file changed, 25 insertions(+)

diff --git a/tests/ArrayFunctionCallTest.php b/tests/ArrayFunctionCallTest.php
index 8ab3396a6de..d6bfc9b41df 100644
--- a/tests/ArrayFunctionCallTest.php
+++ b/tests/ArrayFunctionCallTest.php
@@ -1055,6 +1055,31 @@ function mapdef(string $_a, int $_b = 0): string {
                     '$b===' => 'non-empty-literal-string',
                 ]
             ],
+            'implodeArrayOfNonEmptyStringAndEmptyString' => [
+                '<?php
+                    class Foo {
+                        const DIR = __DIR__;
+                    }
+                    $l = ["a", "b"];
+                    $k = [Foo::DIR];
+                    $a = implode("", $l);
+                    $b = implode("", $k);',
+                [
+                    '$a===' => 'non-empty-literal-string',
+                    '$b===' => 'non-empty-string',
+                ]
+            ],
+            'implodeEmptyArrayAndString' => [
+                '<?php
+                    $l = [""];
+                    $k = [];
+                    $a = implode("", $l);
+                    $b = implode("", $k);',
+                [
+                    '$a===' => 'string',
+                    '$b===' => 'string',
+                ]
+            ],
             'key' => [
                 '<?php
                     $a = ["one" => 1, "two" => 3];

From 91640e7e9098688f0f0c3895b89f8e741b181dc6 Mon Sep 17 00:00:00 2001
From: hirokinoue <70567194+hirokinoue@users.noreply.github.com>
Date: Sat, 14 May 2022 23:44:43 +0900
Subject: [PATCH 2/3] improve @return annotation of implode()

---
 stubs/CoreGenericFunctions.phpstub | 7 ++++++-
 1 file changed, 6 insertions(+), 1 deletion(-)

diff --git a/stubs/CoreGenericFunctions.phpstub b/stubs/CoreGenericFunctions.phpstub
index 6a6a97711d4..60db20e1b5e 100644
--- a/stubs/CoreGenericFunctions.phpstub
+++ b/stubs/CoreGenericFunctions.phpstub
@@ -582,7 +582,12 @@ function rtrim(string $string, string $characters = " \t\n\r\0\x0B") : string {}
  *             : non-empty-string
  *         )
  *         : string)
- *     : string
+ *     : ($array is non-empty-array
+ *         ? ($array is array<non-empty-literal-string|non-empty-string>
+ *             ? ($array is array<non-empty-literal-string> ? non-empty-literal-string : non-empty-string)
+ *             : string
+ *         )
+ *         : string)
  * )
  *
  * @psalm-flow ($separator) -> return

From 4fc34d998b5e0af6a4bbc3fcda2d9e1c20d95833 Mon Sep 17 00:00:00 2001
From: hirokinoue <70567194+hirokinoue@users.noreply.github.com>
Date: Sat, 14 May 2022 23:47:46 +0900
Subject: [PATCH 3/3] improve @return annotation of join()

---
 stubs/CoreGenericFunctions.phpstub | 7 ++++++-
 1 file changed, 6 insertions(+), 1 deletion(-)

diff --git a/stubs/CoreGenericFunctions.phpstub b/stubs/CoreGenericFunctions.phpstub
index 60db20e1b5e..800383c0dfb 100644
--- a/stubs/CoreGenericFunctions.phpstub
+++ b/stubs/CoreGenericFunctions.phpstub
@@ -609,7 +609,12 @@ function implode($separator, array $array = []) : string {}
  *             : non-empty-string
  *         )
  *         : string)
- *     : string
+ *     : ($array is non-empty-array
+ *         ? ($array is array<non-empty-literal-string|non-empty-string>
+ *             ? ($array is array<non-empty-literal-string> ? non-empty-literal-string : non-empty-string)
+ *             : string
+ *         )
+ *         : string)
  * )
  *
  * @psalm-flow ($separator) -> return