Move collectOffsetSetUsage() from NodeScopeResolver to AssignHandler

AssignHandler is its only caller, so it becomes a private method there,
observing through the handler's own TemplateArgumentObserver.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_014hgcbwfKQnye2coQXtX5XU

Author: ondrejmirtes

src/Analyser/ExprHandler/AssignHandler.php

@@ -36,6 +36,7 @@
 use PHPStan\Analyser\ExprHandler\Helper\MethodThrowPointHelper;
 use PHPStan\Analyser\ExprHandler\Helper\NonNullabilityHelper;
 use PHPStan\Analyser\ExprHandler\Helper\VirtualExprResultHelper;
+use PHPStan\Analyser\Generics\TemplateArgumentConstraints;
 use PHPStan\Analyser\Generics\TemplateArgumentObserver;
 use PHPStan\Analyser\ImpurePoint;
 use PHPStan\Analyser\InternalThrowPoint;
@@ -1492,7 +1493,8 @@ public function applyWrite(
 				&& !$setVarType->isArray()->yes()
 				&& !(new ObjectType(ArrayAccess::class))->isSuperTypeOf($setVarType)->no()
 			) {
-				$scope = $scope->addTemplateArgumentConstraints($nodeScopeResolver->collectOffsetSetUsage(
+				$scope = $scope->addTemplateArgumentConstraints($this->collectOffsetSetUsage(
+					$nodeScopeResolver,
 					$scope,
 					$setVarType,
 					$offsetTypes[count($offsetTypes) - 1][0],
@@ -1813,6 +1815,32 @@ public function applyWrite(
 		);
 	}
 
+	/**
+	 * A write through ArrayAccess (`$storage[$key] = $value`) reaches the
+	 * object's template arguments exactly like the offsetSet() call it stands
+	 * for, so observe both the key and the written value against that method's
+	 * parameters resolved on the receiver.
+	 */
+	private function collectOffsetSetUsage(NodeScopeResolver $nodeScopeResolver, MutatingScope $scope, Type $receiverType, ?Type $keyType, Type $valueType): TemplateArgumentConstraints
+	{
+		$constraints = TemplateArgumentConstraints::createEmpty();
+		$frame = $nodeScopeResolver->observingTemplateArgumentFrame($scope);
+		if ($frame === null || !$receiverType->hasMethod('offsetSet')->yes()) {
+			return $constraints;
+		}
+
+		$parameters = $receiverType->getMethod('offsetSet', $scope)->getOnlyVariant()->getParameters();
+		if ($keyType !== null && isset($parameters[0])) {
+			$constraints = $constraints->merge($this->templateArgumentObserver->collectArgument($parameters[0]->getType(), $keyType));
+		}
+		if (!isset($parameters[1])) {
+			return $constraints;
+		}
+
+		$constraints = $constraints->merge($this->templateArgumentObserver->collectArgument($parameters[1]->getType(), $valueType));
+		return $constraints;
+	}
+
 	private function createArrayDimFetchConditionalExpressionHolder(
 		Expr\Variable $keyVar,
 		Expr $arrayArg,

src/Analyser/NodeScopeResolver.php

@@ -1067,30 +1067,4 @@ public function collectReturnSend(MutatingScope $scope, ExpressionResult $return
 		return $this->templateArgumentObserver->collectSend($declaredReturnType, $returnedResult->getType());
 	}
 
-	/**
-	 * A write through ArrayAccess (`$storage[$key] = $value`) reaches the
-	 * object's template arguments exactly like the offsetSet() call it stands
-	 * for, so observe both the key and the written value against that method's
-	 * parameters resolved on the receiver.
-	 */
-	public function collectOffsetSetUsage(MutatingScope $scope, Type $receiverType, ?Type $keyType, Type $valueType): TemplateArgumentConstraints
-	{
-		$constraints = TemplateArgumentConstraints::createEmpty();
-		$frame = $this->observingTemplateArgumentFrame($scope);
-		if ($frame === null || !$receiverType->hasMethod('offsetSet')->yes()) {
-			return $constraints;
-		}
-
-		$parameters = $receiverType->getMethod('offsetSet', $scope)->getOnlyVariant()->getParameters();
-		if ($keyType !== null && isset($parameters[0])) {
-			$constraints = $constraints->merge($this->templateArgumentObserver->collectArgument($parameters[0]->getType(), $keyType));
-		}
-		if (!isset($parameters[1])) {
-			return $constraints;
-		}
-
-		$constraints = $constraints->merge($this->templateArgumentObserver->collectArgument($parameters[1]->getType(), $valueType));
-		return $constraints;
-	}
-
 }