Fix #12222: Unecessary nullsafe operator reported on nullable array index

CLAUDE.md

@@ -280,6 +280,10 @@ Fixes typically involve `ConstantArrayType`, `TypeSpecifier` (for narrowing afte
 
 The degradation loses specific key information. To preserve it, `getArrayType()` tracks `HasOffsetValueType` accessories for non-optional keys from constant array spreads with string keys. After building, these are intersected with the degraded result. When a non-constant spread appears later that could overwrite tracked keys (its key type is a supertype of the tracked offsets), those entries are invalidated. This ensures correct handling of PHP's spread ordering semantics where later spreads override earlier ones for same-named string keys.
 
+### Nullsafe operator and ensureShallowNonNullability / revertNonNullability
+
+`NodeScopeResolver` handles `NullsafeMethodCall` and `NullsafePropertyFetch` by temporarily removing null from the variable's type (`ensureShallowNonNullability`), processing the inner expression, then restoring the original nullable type (`revertNonNullability`). When the expression is an `ArrayDimFetch` (e.g. `$arr['key']?->method()`), `specifyExpressionType` recursively narrows the parent array type via `TypeCombinator::intersect` with `HasOffsetValueType`. This intersection only narrows and cannot widen, so `revertNonNullability` fails to restore the parent array's offset type. The fix is to also save and restore the parent expression's type in `ensureShallowNonNullability`. Without this, subsequent uses of the same nullsafe call are falsely reported as "Using nullsafe method call on non-nullable type" because the parent array retains the narrowed (non-null) offset type.
+
 ### Loop analysis: foreach, for, while
 
 Loops are a frequent source of false positives because PHPStan must reason about types across iterations:

src/Analyser/NodeScopeResolver.php

@@ -214,6 +214,7 @@
 use function array_pop;
 use function array_reverse;
 use function array_slice;
+use function array_unshift;
 use function array_values;
 use function base64_decode;
 use function count;
@@ -2462,6 +2463,29 @@ private function ensureShallowNonNullability(MutatingScope $scope, Scope $origin
 		}
 
 		$nativeType = $scope->getNativeType($exprToSpecify);
+
+		$specifiedExpressions = [
+			new EnsuredNonNullabilityResultExpression($exprToSpecify, $exprType, $nativeType, $certainty),
+		];
+
+		// When narrowing an ArrayDimFetch, specifyExpressionType also recursively
+		// narrows the parent array's offset type via intersection with HasOffsetValueType.
+		// To properly revert this, we must also save and restore the parent expression's type.
+		if ($exprToSpecify instanceof Expr\ArrayDimFetch && $exprToSpecify->dim !== null) {
+			$parentExpr = $exprToSpecify->var;
+			$parentCertainty = TrinaryLogic::createYes();
+			$hasParentExpressionType = $originalScope->hasExpressionType($parentExpr);
+			if (!$hasParentExpressionType->no()) {
+				$parentCertainty = $hasParentExpressionType;
+			}
+			array_unshift($specifiedExpressions, new EnsuredNonNullabilityResultExpression(
+				$parentExpr,
+				$scope->getType($parentExpr),
+				$scope->getNativeType($parentExpr),
+				$parentCertainty,
+			));
+		}
+
 		$scope = $scope->specifyExpressionType(
 			$exprToSpecify,
 			$exprTypeWithoutNull,
@@ -2471,9 +2495,7 @@ private function ensureShallowNonNullability(MutatingScope $scope, Scope $origin
 
 		return new EnsuredNonNullabilityResult(
 			$scope,
-			[
-				new EnsuredNonNullabilityResultExpression($exprToSpecify, $exprType, $nativeType, $certainty),
-			],
+			$specifiedExpressions,
 		);
 	}
 

tests/PHPStan/Analyser/nsrt/bug-12222.php

@@ -0,0 +1,63 @@
+<?php // lint >= 8.1
+
+namespace Bug12222;
+
+use function PHPStan\Testing\assertType;
+
+enum ContractStatus: string
+{
+	case ACTIVE = 'A';
+	case BEING_TERMINATED = 'B';
+	case TERMINATED = 'C';
+
+	public function isActive(): bool
+	{
+		return $this === self::ACTIVE;
+	}
+
+	public function isBeingTerminated(): bool
+	{
+		return $this === self::BEING_TERMINATED;
+	}
+
+	public function isTerminated(): bool
+	{
+		return $this === self::TERMINATED;
+	}
+}
+
+/**
+ * @phpstan-type Contract array{
+ *     reference: string,
+ *     status: null|ContractStatus,
+ *     startDate: string,
+ *     isActive: bool,
+ *     isBeingTerminated: bool,
+ *     isTerminated: bool
+ * }
+ */
+class DataProcessor
+{
+	/**
+	 * @param mixed[] $data
+	 * @return Contract
+	 */
+	public function process(array $data): array
+	{
+		/** @var Contract $contract */
+		$contract = [
+			'reference' => $data['reference'],
+			'status' => '' !== $data['status'] ? ContractStatus::from($data['status']) : null,
+			'startDate' => $data['startDate'],
+		];
+
+		assertType('Bug12222\ContractStatus|null', $contract['status']);
+		$contract['isActive'] = $contract['status']?->isActive();
+		assertType('Bug12222\ContractStatus|null', $contract['status']);
+		$contract['isBeingTerminated'] = $contract['status']?->isBeingTerminated();
+		assertType('Bug12222\ContractStatus|null', $contract['status']);
+		$contract['isTerminated'] = $contract['status']?->isTerminated();
+
+		return $contract;
+	}
+}

tests/PHPStan/Rules/Methods/NullsafeMethodCallRuleTest.php

@@ -64,4 +64,10 @@ public function testBug8523c(): void
 		$this->analyse([__DIR__ . '/data/bug-8523c.php'], []);
 	}
 
+	#[RequiresPhp('>= 8.1')]
+	public function testBug12222(): void
+	{
+		$this->analyse([__DIR__ . '/data/bug-12222.php'], []);
+	}
+
 }

tests/PHPStan/Rules/Methods/data/bug-12222.php

@@ -0,0 +1,58 @@
+<?php // lint >= 8.1
+
+namespace Bug12222;
+
+enum ContractStatus: string
+{
+	case ACTIVE = 'A';
+	case BEING_TERMINATED = 'B';
+	case TERMINATED = 'C';
+
+	public function isActive(): bool
+	{
+		return $this === self::ACTIVE;
+	}
+
+	public function isBeingTerminated(): bool
+	{
+		return $this === self::BEING_TERMINATED;
+	}
+
+	public function isTerminated(): bool
+	{
+		return $this === self::TERMINATED;
+	}
+}
+
+/**
+ * @phpstan-type Contract array{
+ *     reference: string,
+ *     status: null|ContractStatus,
+ *     startDate: string,
+ *     isActive: bool,
+ *     isBeingTerminated: bool,
+ *     isTerminated: bool
+ * }
+ */
+class DataProcessor
+{
+	/**
+	 * @param mixed[] $data
+	 * @return Contract
+	 */
+	public function process(array $data): array
+	{
+		/** @var Contract $contract */
+		$contract = [
+			'reference' => $data['reference'],
+			'status' => '' !== $data['status'] ? ContractStatus::from($data['status']) : null,
+			'startDate' => $data['startDate'],
+		];
+
+		$contract['isActive'] = $contract['status']?->isActive();
+		$contract['isBeingTerminated'] = $contract['status']?->isBeingTerminated();
+		$contract['isTerminated'] = $contract['status']?->isTerminated();
+
+		return $contract;
+	}
+}