Fix redundant type cast dropping type narrowing in comparisons

- Unwrap redundant cast expressions in Smaller/SmallerOrEqual type specifying
  so that narrowing propagates to the inner variable instead of the cast expr
- When a cast produces the same type as its inner expression (e.g. (int) on
  an int variable), the narrowing is now applied to the original variable
- New regression test in tests/PHPStan/Analyser/nsrt/bug-7858.php

Closes phpstan/phpstan#7858

Author: github-actions[bot]

src/Analyser/TypeSpecifier.php

@@ -492,42 +492,59 @@ public function specifyTypesInCondition(
 				}
 			}
 
+			$leftExpr = $expr->left;
+			if ($leftExpr instanceof Expr\Cast) {
+				$castedType = $scope->getType($leftExpr);
+				$innerType = $scope->getType($leftExpr->expr);
+				if ($castedType->equals($innerType)) {
+					$leftExpr = $leftExpr->expr;
+				}
+			}
+			$rightExpr = $expr->right;
+			if ($rightExpr instanceof Expr\Cast) {
+				$castedType = $scope->getType($rightExpr);
+				$innerType = $scope->getType($rightExpr->expr);
+				if ($castedType->equals($innerType)) {
+					$rightExpr = $rightExpr->expr;
+				}
+			}
+
 			if ($context->true()) {
-				if (!$expr->left instanceof Node\Scalar) {
+				if (!$leftExpr instanceof Node\Scalar) {
 					$result = $result->unionWith(
 						$this->create(
-							$expr->left,
+							$leftExpr,
 							$orEqual ? $rightType->getSmallerOrEqualType($this->phpVersion) : $rightType->getSmallerType($this->phpVersion),
 							TypeSpecifierContext::createTruthy(),
 							$scope,
 						)->setRootExpr($expr),
 					);
 				}
-				if (!$expr->right instanceof Node\Scalar) {
+				if (!$rightExpr instanceof Node\Scalar) {
 					$result = $result->unionWith(
 						$this->create(
-							$expr->right,
+							$rightExpr,
 							$orEqual ? $leftType->getGreaterOrEqualType($this->phpVersion) : $leftType->getGreaterType($this->phpVersion),
 							TypeSpecifierContext::createTruthy(),
 							$scope,
 						)->setRootExpr($expr),
 					);
 				}
 			} elseif ($context->false()) {
-				if (!$expr->left instanceof Node\Scalar) {
+				if (!$leftExpr instanceof Node\Scalar) {
 					$result = $result->unionWith(
 						$this->create(
-							$expr->left,
+							$leftExpr,
 							$orEqual ? $rightType->getGreaterType($this->phpVersion) : $rightType->getGreaterOrEqualType($this->phpVersion),
 							TypeSpecifierContext::createTruthy(),
 							$scope,
 						)->setRootExpr($expr),
 					);
 				}
-				if (!$expr->right instanceof Node\Scalar) {
+				if (!$rightExpr instanceof Node\Scalar) {
 					$result = $result->unionWith(
 						$this->create(
-							$expr->right,
+							$rightExpr,
 							$orEqual ? $leftType->getSmallerType($this->phpVersion) : $leftType->getSmallerOrEqualType($this->phpVersion),
 							TypeSpecifierContext::createTruthy(),
 							$scope,

tests/PHPStan/Analyser/nsrt/bug-7858.php

@@ -0,0 +1,21 @@
+<?php declare(strict_types = 1);
+
+namespace Bug7858;
+
+use function PHPStan\Testing\assertType;
+
+function foo(int $year): void
+{
+	if (!ctype_digit($year) || (int) $year < 2022) {
+		throw new \RuntimeException();
+	}
+	assertType('int<2022, max>', $year);
+}
+
+function bar(int $year): void
+{
+	if (!ctype_digit($year) || $year < 2022) {
+		throw new \RuntimeException();
+	}
+	assertType('int<2022, max>', $year);
+}