From ec0dc9e6dc5b28653e06e63a3fde6bf734e91304 Mon Sep 17 00:00:00 2001
From: robchett <robchett@gmail.com>
Date: Sun, 8 Oct 2023 16:56:03 +0100
Subject: [PATCH] Correct decrement min/max ranges

---
 .../BinaryOp/ArithmeticOpAnalyzer.php           | 11 +++++++++--
 tests/BinaryOperationTest.php                   | 17 +++++++++++++++++
 2 files changed, 26 insertions(+), 2 deletions(-)

diff --git a/src/Psalm/Internal/Analyzer/Statements/Expression/BinaryOp/ArithmeticOpAnalyzer.php b/src/Psalm/Internal/Analyzer/Statements/Expression/BinaryOp/ArithmeticOpAnalyzer.php
index e6155f74710..bdce30f40cf 100644
--- a/src/Psalm/Internal/Analyzer/Statements/Expression/BinaryOp/ArithmeticOpAnalyzer.php
+++ b/src/Psalm/Internal/Analyzer/Statements/Expression/BinaryOp/ArithmeticOpAnalyzer.php
@@ -22,6 +22,8 @@
 use Psalm\Issue\PossiblyNullOperand;
 use Psalm\Issue\StringIncrement;
 use Psalm\IssueBuffer;
+use Psalm\Node\Expr\BinaryOp\VirtualMinus;
+use Psalm\Node\Expr\BinaryOp\VirtualPlus;
 use Psalm\StatementsSource;
 use Psalm\Type;
 use Psalm\Type\Atomic;
@@ -826,10 +828,15 @@ private static function analyzeOperands(
                                 $result_type = Type::getInt();
                             }
                         }
-                    } else {
+                    } elseif ($parent instanceof VirtualPlus) {
+                        $start = $left_type_part instanceof TLiteralInt ? $left_type_part->value : 1;
+                        $result_type = Type::combineUnionTypes(Type::getIntRange($start, null), $result_type);
+                    } elseif ($parent instanceof VirtualMinus) {
                         $start = $left_type_part instanceof TLiteralInt ? $left_type_part->value : 1;
+                        $result_type = Type::combineUnionTypes(Type::getIntRange(null, $start), $result_type);
+                    } else {
                         $result_type = Type::combineUnionTypes(
-                            $always_positive ? Type::getIntRange($start, null) : Type::getInt(true),
+                            $always_positive ? Type::getIntRange(1, null) : Type::getInt(true),
                             $result_type,
                         );
                     }
diff --git a/tests/BinaryOperationTest.php b/tests/BinaryOperationTest.php
index 7a69480005b..637a480a928 100644
--- a/tests/BinaryOperationTest.php
+++ b/tests/BinaryOperationTest.php
@@ -970,6 +970,23 @@ function scope(array $a): int|float {
                     '$j' => 'int<100, 110>',
                 ],
             ],
+            'decrementInLoop' => [
+                'code' => '<?php
+                    for ($i = 10; $i > 0; $i--) {
+                        if (rand(0,1)) {
+                            break;
+                        }
+                    }
+                    for ($j = 110; $j > 100; $j--) {
+                        if (rand(0,1)) {
+                            break;
+                        }
+                    }',
+                'assertions' => [
+                    '$i' => 'int<0, 10>',
+                    '$j' => 'int<100, 110>',
+                ],
+            ],
             'coalesceFilterOutNullEvenWithTernary' => [
                 'code' => '<?php