Add TypeCombinatorTest cases for object shape intersection edge cases

Tests for: object{foo: int}&object{foo?: int}, object{foo: int}&object{foo: int|null},
object{foo: int}&object{foo?: int|null}, object{foo: int}&object{bar?: int},
and object{foo: int}&object{foo?: string}.

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

Author: phpstan-bot

tests/PHPStan/Type/TypeCombinatorTest.php

@@ -4619,6 +4619,46 @@ public static function dataIntersect(): iterable
 			ObjectShapeType::class,
 			'object{bar: string, foo: int}',
 		];
+		yield [
+			[
+				new ObjectShapeType(['foo' => new IntegerType()], []),
+				new ObjectShapeType(['foo' => new IntegerType()], ['foo']),
+			],
+			ObjectShapeType::class,
+			'object{foo: int}',
+		];
+		yield [
+			[
+				new ObjectShapeType(['foo' => new IntegerType()], []),
+				new ObjectShapeType(['foo' => TypeCombinator::union(new IntegerType(), new NullType())], []),
+			],
+			ObjectShapeType::class,
+			'object{foo: int}',
+		];
+		yield [
+			[
+				new ObjectShapeType(['foo' => new IntegerType()], []),
+				new ObjectShapeType(['foo' => TypeCombinator::union(new IntegerType(), new NullType())], ['foo']),
+			],
+			ObjectShapeType::class,
+			'object{foo: int}',
+		];
+		yield [
+			[
+				new ObjectShapeType(['foo' => new IntegerType()], []),
+				new ObjectShapeType(['bar' => new IntegerType()], ['bar']),
+			],
+			ObjectShapeType::class,
+			'object{bar?: int, foo: int}',
+		];
+		yield [
+			[
+				new ObjectShapeType(['foo' => new IntegerType()], []),
+				new ObjectShapeType(['foo' => new StringType()], ['foo']),
+			],
+			NeverType::class,
+			'*NEVER*=implicit',
+		];
 		yield [
 			[
 				new ObjectShapeType(['foo' => new IntegerType()], []),