Infer non-empty-ness after count($a) == count($b)

Author: staabm

src/Analyser/TypeSpecifier.php

@@ -2243,7 +2243,7 @@ public function resolveIdentical(Expr\BinaryOp\Identical $expr, Scope $scope, Ty
 
 		$rightType = $scope->getType($rightExpr);
 
-		// (count($a) === $b)
+		// (count($a) === $expr)
 		if (
 			!$context->null()
 			&& $unwrappedLeftExpr instanceof FuncCall
@@ -2252,6 +2252,28 @@ public function resolveIdentical(Expr\BinaryOp\Identical $expr, Scope $scope, Ty
 			&& in_array(strtolower((string) $unwrappedLeftExpr->name), ['count', 'sizeof'], true)
 			&& $rightType->isInteger()->yes()
 		) {
+			// count($a) === count($b)
+			if (
+				$context->true()
+				&& $unwrappedRightExpr instanceof FuncCall
+				&& $unwrappedRightExpr->name instanceof Name
+				&& in_array($unwrappedRightExpr->name->toLowerString(), ['count', 'sizeof'], true)
+				&& count($unwrappedRightExpr->getArgs()) >= 1
+			) {
+				$leftArrayType = $scope->getType($unwrappedLeftExpr->getArgs()[0]->value);
+				$rightArrayType = $scope->getType($unwrappedRightExpr->getArgs()[0]->value);
+
+				if (
+					$leftArrayType->isArray()->yes() && $rightArrayType->isArray()->yes()
+					&& ($leftArrayType->isIterableAtLeastOnce()->yes() || $rightArrayType->isIterableAtLeastOnce()->yes())
+				) {
+					$arrayTypes = $this->create($unwrappedLeftExpr->getArgs()[0]->value, new NonEmptyArrayType(), $context, $scope)->setRootExpr($expr);
+					return $arrayTypes->unionWith(
+						$this->create($unwrappedRightExpr->getArgs()[0]->value, new NonEmptyArrayType(), $context, $scope)->setRootExpr($expr),
+					);
+				}
+			}
+
 			if (IntegerRangeType::fromInterval(null, -1)->isSuperTypeOf($rightType)->yes()) {
 				return $this->create($unwrappedLeftExpr->getArgs()[0]->value, new NeverType(), $context, $scope)->setRootExpr($expr);
 			}

tests/PHPStan/Analyser/nsrt/list-count2.php

@@ -0,0 +1,81 @@
+<?php
+
+namespace ListCount2;
+
+use function PHPStan\dumpType;
+use function PHPStan\debugScope;
+use function PHPStan\Testing\assertType;
+
+class HelloWorld
+{
+	/**
+	 * @param non-empty-list<int> $listA
+	 * @param list<int> $listB
+	 */
+	public function sayIdenticalLists($listA, array $listB): void
+	{
+		if (count($listA) === count($listB)) {
+			assertType('non-empty-list<int>', $listB);
+		}
+		assertType('list<int>', $listB);
+	}
+
+	/**
+	 * @param non-empty-list<int> $listA
+	 */
+	public function sayIdenticalList($listA, array $arrB): void
+	{
+		if (count($listA) === count($arrB)) {
+			assertType('non-empty-array', $arrB);
+		}
+		assertType('array', $arrB);
+	}
+
+	/**
+	 * @param non-empty-array<int> $arrA
+	 */
+	public function sayEqualArray($arrA, array $arrB): void
+	{
+		if (count($arrA) == count($arrB)) {
+			assertType('non-empty-array', $arrB);
+		}
+		assertType('array', $arrB);
+	}
+
+	/**
+	 * @param non-empty-array<int> $arrA
+	 * @param array<int> $arrB
+	 */
+	public function sayEqualIntArray($arrA, array $arrB): void
+	{
+		if (count($arrA) == count($arrB)) {
+			assertType('non-empty-array<int>', $arrB);
+		}
+		assertType('array<int>', $arrB);
+	}
+
+	/**
+	 * @param non-empty-array<int> $arrA
+	 * @param array<string> $arrB
+	 */
+	public function sayEqualStringArray($arrA, array $arrB): void
+	{
+		if (count($arrA) == count($arrB)) {
+			assertType('non-empty-array<string>', $arrB);
+		}
+		assertType('array<string>', $arrB);
+	}
+
+	/**
+	 * @param array<int> $arrA
+	 * @param array<string> $arrB
+	 */
+	public function sayUnknownArray($arrA, array $arrB): void
+	{
+		if (count($arrA) == count($arrB)) {
+			assertType('array<int>', $arrA);
+			assertType('array<string>', $arrB);
+		}
+		assertType('array<string>', $arrB);
+	}
+}