Detect more possibly-impossible offset

src/Rules/Arrays/NonexistentOffsetInArrayDimFetchCheck.php

@@ -14,7 +14,6 @@
 use PHPStan\Type\ErrorType;
 use PHPStan\Type\Type;
 use PHPStan\Type\TypeUtils;
-use PHPStan\Type\UnionType;
 use PHPStan\Type\VerbosityLevel;
 use function count;
 use function sprintf;
@@ -76,6 +75,7 @@ public function check(
 			} else {
 				$flattenedTypes = TypeUtils::flattenTypes($type);
 			}
+
 			foreach ($flattenedTypes as $innerType) {
 				if (
 					$this->reportPossiblyNonexistentGeneralArrayOffset
@@ -94,15 +94,15 @@ public function check(
 					$report = true;
 					break;
 				}
-				if ($dimType instanceof UnionType) {
-					if ($innerType->hasOffsetValueType($dimType)->no()) {
-						$report = true;
-						break;
-					}
-					continue;
+				if ($dimType instanceof BenevolentUnionType) {
+					$flattenedInnerTypes = [$dimType];
+				} else {
+					$flattenedInnerTypes = TypeUtils::flattenTypes($dimType);
 				}
-				foreach (TypeUtils::flattenTypes($dimType) as $innerDimType) {
-					if ($innerType->hasOffsetValueType($innerDimType)->no()) {
+				foreach ($flattenedInnerTypes as $innerDimType) {
+					if (
+						$innerType->hasOffsetValueType($innerDimType)->no()
+					) {
 						$report = true;
 						break 2;
 					}

tests/PHPStan/Levels/data/stringOffsetAccess-7.json

@@ -1,4 +1,9 @@
 [
+    {
+        "message": "Offset int|object might not exist on 'foo'.",
+        "line": 19,
+        "ignorable": true
+    },
     {
         "message": "Offset 'foo' might not exist on array|string.",
         "line": 27,
@@ -9,6 +14,11 @@
         "line": 31,
         "ignorable": true
     },
+    {
+        "message": "Offset int|object might not exist on array|string.",
+        "line": 35,
+        "ignorable": true
+    },
     {
         "message": "Possibly invalid array key type int|object.",
         "line": 35,

tests/PHPStan/Rules/Arrays/NonexistentOffsetInArrayDimFetchRuleTest.php

@@ -119,6 +119,10 @@ public function testRule(): void
 				'Cannot access offset \'a\' on array{a: 1, b: 1}|(Closure(): void).',
 				258,
 			],
+			[
+				'Offset int|null might not exist on array<int, string>.',
+				309,
+			],
 			[
 				'Offset null does not exist on array<int, string>.',
 				310,
@@ -127,6 +131,10 @@ public function testRule(): void
 				'Offset int does not exist on array<string, string>.',
 				312,
 			],
+			[
+				'Offset int|null might not exist on array<string, string>.',
+				314,
+			],
 			[
 				'Offset \'baz\' might not exist on array{bar: 1, baz?: 2}.',
 				344,
@@ -185,6 +193,10 @@ public function testStrings(): void
 				'Offset 12.34 does not exist on \'foo\'.',
 				13,
 			],
+			[
+				'Offset int|object might not exist on \'foo\'.',
+				16,
+			],
 			[
 				'Offset \'foo\' might not exist on array|string.',
 				24,
@@ -193,6 +205,10 @@ public function testStrings(): void
 				'Offset 12.34 might not exist on array|string.',
 				28,
 			],
+			[
+				'Offset int|object might not exist on array|string.',
+				32,
+			],
 		]);
 	}
 
@@ -949,4 +965,14 @@ public function testBug12447(): void
 		]);
 	}
 
+	public function testBug1061(): void
+	{
+		$this->analyse([__DIR__ . '/data/bug-1061.php'], [
+			[
+				"Offset 'one'|'two' might not exist on array{two: 1, three: 2}.",
+				14,
+			],
+		]);
+	}
+
 }

tests/PHPStan/Rules/Arrays/data/bug-1061.php

@@ -0,0 +1,15 @@
+<?php declare(strict_types = 1);
+
+namespace Bug1061;
+
+class A {
+	const KEYS = ["one", "two"];
+	const ARR = [
+		"two" => 1,
+		"three" => 2
+	];
+}
+
+foreach (A::KEYS as $key) {
+	echo A::ARR[$key];
+}