Add unsealed-array variants of array_flip/array_fill_keys union-value tests

Mirror the sealed bug-14656 cases with unsealed array shapes (`...<int, V>`
tails) to lock in the per-key value precision across the unsealed extras:
a finite union tail decomposes into optional explicit slots merged with the
explicit keys, while a non-finite tail (e.g. `string`) survives as unsealed
extras with overlapping explicit values widened.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

Author: phpstan-bot

tests/PHPStan/Analyser/nsrt/bug-14656.php

@@ -45,3 +45,57 @@ public function mixedUnionAndConstant(array $a): void
 		assertType("array{a?: 'x', b?: 'x', c: 'x'}", array_fill_keys($a, 'x'));
 	}
 }
+
+class ArrayFlipUnsealedUnionValues
+{
+	/** @param array{0: 'a'|'b'|'c', 1: 'a'|'b'|'c', 2: 'a'|'b'|'c', ...<int, 'a'|'b'|'c'>} $a */
+	public function allUnion(array $a): void
+	{
+		assertType("non-empty-array{a?: int, b?: int, c?: int}", array_flip($a));
+	}
+
+	/** @param array{0: 'a'|'b', 1: 'b'|'c', ...<int, 'a'|'b'|'c'>} $a */
+	public function overlappingUnion(array $a): void
+	{
+		assertType("non-empty-array{a?: int, b?: int, c?: int}", array_flip($a));
+	}
+
+	/** @param array{0: 'a'|'b', 1: 'c', ...<int, 'a'|'b'>} $a */
+	public function mixedUnionAndConstant(array $a): void
+	{
+		assertType("array{a?: int, b?: int, c: 1}", array_flip($a));
+	}
+
+	/** @param array{0: 'a'|'b', 1: 'c', ...<int, string>} $a */
+	public function nonFiniteTail(array $a): void
+	{
+		assertType("array{a?: int, b?: int, c: int, ...<string, int>}", array_flip($a));
+	}
+}
+
+class ArrayFillKeysUnsealedUnionValues
+{
+	/** @param array{0: 'a'|'b', 1: 'b'|'c', ...<int, 'a'|'b'|'c'>} $a */
+	public function overlappingUnion(array $a): void
+	{
+		assertType("non-empty-array{a?: 'x', b?: 'x', c?: 'x'}", array_fill_keys($a, 'x'));
+	}
+
+	/** @param array{0: 'a'|'b'|'c', 1: 'a'|'b'|'c', 2: 'a'|'b'|'c', ...<int, 'a'|'b'|'c'>} $a */
+	public function allUnion(array $a): void
+	{
+		assertType("non-empty-array{a?: 'x', b?: 'x', c?: 'x'}", array_fill_keys($a, 'x'));
+	}
+
+	/** @param array{0: 'a'|'b', 1: 'c', ...<int, 'a'|'b'>} $a */
+	public function mixedUnionAndConstant(array $a): void
+	{
+		assertType("array{a?: 'x', b?: 'x', c: 'x'}", array_fill_keys($a, 'x'));
+	}
+
+	/** @param array{0: 'a'|'b', 1: 'c', ...<int, string>} $a */
+	public function nonFiniteTail(array $a): void
+	{
+		assertType("array{a?: 'x', b?: 'x', c: 'x', ...<string, 'x'>}", array_fill_keys($a, 'x'));
+	}
+}