diff --git a/tests/PHPStan/Analyser/nsrt/bug-10025.php b/tests/PHPStan/Analyser/nsrt/bug-10025.php
new file mode 100644
index 0000000000..4d172f2aac
--- /dev/null
+++ b/tests/PHPStan/Analyser/nsrt/bug-10025.php
@@ -0,0 +1,36 @@
+<?php declare(strict_types=1);
+
+namespace Bug10025;
+
+use function PHPStan\Testing\assertType;
+
+class MyClass
+{
+	public int $groupId;
+}
+
+/**
+ * @param list<MyClass> $foos
+ * @param list<MyClass> $bars
+ */
+function x(array $foos, array $bars): void
+{
+	$arr = [];
+	foreach ($foos as $foo) {
+		$arr[$foo->groupId]['foo'][] = $foo;
+	}
+	foreach ($bars as $bar) {
+		$arr[$bar->groupId]['bar'][] = $bar;
+	}
+
+	assertType('array<int, non-empty-array{foo?: non-empty-list<Bug10025\MyClass>, bar?: non-empty-list<Bug10025\MyClass>}>', $arr);
+	foreach ($arr as $groupId => $group) {
+		if (isset($group['foo'])) {
+		}
+		if (isset($group['bar'])) {
+		}
+	}
+
+	assertType('array<int, non-empty-array{foo?: non-empty-list<Bug10025\MyClass>, bar?: non-empty-list<Bug10025\MyClass>}>', $arr);
+}
+
diff --git a/tests/PHPStan/Analyser/nsrt/bug-10640.php b/tests/PHPStan/Analyser/nsrt/bug-10640.php
new file mode 100644
index 0000000000..12452341c6
--- /dev/null
+++ b/tests/PHPStan/Analyser/nsrt/bug-10640.php
@@ -0,0 +1,31 @@
+<?php declare(strict_types=1);
+
+namespace Bug10640;
+
+use function PHPStan\Testing\assertType;
+
+$changes = [];
+foreach (toAdd() as $add) {
+	$changes[$add['id']]['add'][] = doSomething($add);
+}
+assertType('array<array{add: non-empty-list}>', $changes);
+
+foreach (toRem() as $del) {
+	$changes[$add['id']]['del'][] = doSomething($del);
+}
+assertType('array<non-empty-array{add?: non-empty-list, del?: non-empty-list}>', $changes);
+
+foreach ($changes as $changeSet) {
+	if (isset($changeSet['del'])) {
+		doDel($changeSet['del']);
+	}
+	if (isset($changeSet['add'])) {
+		doAdd($changeSet['add']);
+	}
+}
+
+function doSomething($s) {}
+function toAdd($s) {}
+function toRem($s) {}
+function doDel($s) {}
+function doAdd($s) {}
diff --git a/tests/PHPStan/Analyser/nsrt/bug-12078.php b/tests/PHPStan/Analyser/nsrt/bug-12078.php
new file mode 100644
index 0000000000..c1d22c1ab1
--- /dev/null
+++ b/tests/PHPStan/Analyser/nsrt/bug-12078.php
@@ -0,0 +1,67 @@
+<?php declare(strict_types=1);
+
+namespace Bug12078;
+
+use function PHPStan\Testing\assertType;
+
+/**
+ * @return array <string,string>
+ */
+function returnsData6M(): array
+{
+	return ["A" => 'data A', "B" => 'Data B'];
+}
+
+/**
+ * @return array <string,string>
+ */
+function returnsData3M(): array
+{
+	return ["A" => 'data A', "C" => 'Data C'];
+}
+
+function main()
+{
+	$arrDataByKey = [];
+
+	$arrData6M = returnsData6M();
+	if ([] === $arrData6M) {
+		echo "No data for 6M\n";
+	} else {
+		foreach ($arrData6M as $key => $data) {
+			$arrDataByKey[$key]['6M'][] = $data;
+		}
+	}
+
+	$arrData3M = returnsData3M();
+	if ([] === $arrData3M) {
+		echo "No data for 3M\n";
+	} else {
+		foreach ($arrData3M as $key => $data) {
+			$arrDataByKey[$key]['3M'][] = $data;
+		}
+	}
+	/*
+	So $arrDataByKey looks like
+	[
+		'A'=>[
+			'6M'=>['data A'],
+			'3M'=>['data A']
+		],
+		'B'=>[
+			'6M'=>['data B']
+		],
+		'C'=>[
+			'3M'=>['data C']
+		]
+	]
+	*/
+
+	assertType("array<string, non-empty-array{'6M'?: non-empty-list<string>, '3M'?: non-empty-list<string>}>", $arrDataByKey);
+	foreach ($arrDataByKey as $key => $arrDataByKeyForKey) {
+		assertType("non-empty-array{'6M'?: non-empty-list<string>, '3M'?: non-empty-list<string>}", $arrDataByKeyForKey);
+		echo [] === ($arrDataByKeyForKey['6M'] ?? []) ? 'No 6M data for key ' . $key . "\n" : 'We got 6M data for key ' . $key . "\n";
+		echo [] === ($arrDataByKeyForKey['3M'] ?? []) ? 'No 3M data for key ' . $key . "\n" : 'We got 3M data for key ' . $key . "\n";
+		assertType("non-empty-array{'6M'?: non-empty-list<string>, '3M'?: non-empty-list<string>}", $arrDataByKeyForKey);
+	}
+}
diff --git a/tests/PHPStan/Analyser/nsrt/bug-6173.php b/tests/PHPStan/Analyser/nsrt/bug-6173.php
new file mode 100644
index 0000000000..41ced55a63
--- /dev/null
+++ b/tests/PHPStan/Analyser/nsrt/bug-6173.php
@@ -0,0 +1,32 @@
+<?php declare(strict_types=1);
+
+namespace Bug6173;
+
+use function PHPStan\Testing\assertType;
+
+class HelloWorld
+{
+	/**
+	 * @param int[] $ids1
+	 * @param int[] $ids2
+	 */
+	public function sayHello(array $ids1, array $ids2): bool
+	{
+		$res = [];
+		foreach ($ids1 as $id) {
+			$res[$id]['foo'] = $id;
+		}
+
+		foreach ($ids2 as $id) {
+			$res[$id]['bar'] = $id;
+		}
+
+		assertType('array<int, non-empty-array{foo?: int, bar?: int}>', $res);
+		foreach ($res as $id => $r) {
+			assertType('non-empty-array{foo?: int, bar?: int}', $r);
+			return isset($r['foo']);
+		}
+
+		return false;
+	}
+}
diff --git a/tests/PHPStan/Rules/Variables/IssetRuleTest.php b/tests/PHPStan/Rules/Variables/IssetRuleTest.php
index da52dc925f..40b837c134 100644
--- a/tests/PHPStan/Rules/Variables/IssetRuleTest.php
+++ b/tests/PHPStan/Rules/Variables/IssetRuleTest.php
@@ -504,4 +504,11 @@ public function testPr4374(): void
 		]);
 	}
 
+	public function testBug10640(): void
+	{
+		$this->treatPhpDocTypesAsCertain = true;
+
+		$this->analyse([__DIR__ . '/../../Analyser/nsrt/bug-10640.php'], []);
+	}
+
 }