Added regression test

Author: staabm

tests/PHPStan/Rules/Functions/ReturnTypeRuleTest.php

@@ -370,4 +370,12 @@ public function testBug9401(): void
 		]);
 	}
 
+	public function testBug7076(): void
+	{
+		$this->checkExplicitMixed = true;
+		$this->checkNullables = true;
+
+		$this->analyse([__DIR__ . '/data/bug-7076.php'], []);
+	}
+
 }

tests/PHPStan/Rules/Functions/data/bug-7076.php

@@ -0,0 +1,63 @@
+<?php declare(strict_types=1);
+
+namespace Bug7076;
+
+/**
+ * @param array<string, mixed> $param
+ * @return array<string, mixed>
+ */
+function expectsStringKey(array $param): array
+{
+	return $param;
+}
+
+/**
+ * @param array<int|string, mixed> $arguments
+ * @return array<string, mixed>
+ */
+function foo(array $arguments): array
+{
+	foreach ($arguments as $key => $argument) {
+		if (!is_string($key)) {
+			throw new \Exception('Key must be a string');
+		}
+	}
+
+	return $arguments;
+}
+
+/**
+ * @return array<string, mixed>
+ */
+function bar(mixed ...$arguments): array
+{
+	foreach ($arguments as $key => $argument) {
+		if (!is_string($key)) {
+			throw new \Exception('Key must be a string');
+		}
+
+		if (is_int($key)) {
+			echo 'int';
+		}
+	}
+
+	return $arguments;
+}
+
+/**
+ * @return array<string, mixed>
+ */
+function baz(mixed ...$arguments): array
+{
+	foreach ($arguments as $key => $argument) {
+		if (is_string($key)) {
+			continue;
+		}
+
+		throw new \Exception('Key must be a string');
+	}
+
+	return $arguments;
+}
+
+