Add regression tests for phpstan/phpstan#7704 and phpstan/phpstan#9360

Both issues report the same underlying bug: unresolvable template type
errors when calling functions with variadic template parameters without
providing any variadic arguments.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

Author: phpstan-bot

tests/PHPStan/Analyser/nsrt/bug-7704.php

@@ -0,0 +1,30 @@
+<?php declare(strict_types = 1);
+
+namespace Bug7704;
+
+use function PHPStan\Testing\assertType;
+
+/**
+ * @template T
+ * @template TRest
+ *
+ * @param T $first
+ * @param TRest ...$rest
+ *
+ * @return T|TRest
+ */
+function intersection($first, ...$rest)
+{
+	$ret = $first;
+	foreach ($rest as $item) {
+		if (rand(0, 1)) {
+			$ret = $item;
+		}
+	}
+	return $ret;
+}
+
+assertType("'a'", intersection("a"));
+assertType("'a'|'b'|'c'", intersection("a", "b", "c"));
+assertType('1', intersection(1));
+assertType('1|2|3', intersection(1, 2, 3));

tests/PHPStan/Analyser/nsrt/bug-9360.php

@@ -0,0 +1,24 @@
+<?php declare(strict_types = 1);
+
+namespace Bug9360;
+
+use function PHPStan\Testing\assertType;
+
+/**
+ * @template T of string|bool
+ *
+ * @param T ...$args
+ *
+ * @return (T is string ? string : bool)
+ */
+function environment(string|bool ...$args): string|bool
+{
+	if (count($args) === 0) {
+		return true;
+	}
+	return (string) $args[0];
+}
+
+assertType('string', environment());
+assertType('string', environment('APP_ENV'));
+assertType('string', environment('APP_ENV', 'production'));

tests/PHPStan/Rules/Functions/CallToFunctionParametersRuleTest.php

@@ -2696,6 +2696,16 @@ public function testBug2572(): void
 		$this->analyse([__DIR__ . '/../../Analyser/nsrt/bug-2572.php'], []);
 	}
 
+	public function testBug7704(): void
+	{
+		$this->analyse([__DIR__ . '/../../Analyser/nsrt/bug-7704.php'], []);
+	}
+
+	public function testBug9360(): void
+	{
+		$this->analyse([__DIR__ . '/../../Analyser/nsrt/bug-9360.php'], []);
+	}
+
 	public function testDumpFunctions(): void
 	{
 		$this->analyse([__DIR__ . '/data/dump-functions.php'], [