skip zero offset

Author: samsonasik

rules-tests/DowngradePhp80/Rector/FuncCall/DowngradeSubstrFalsyRector/Fixture/skip_zero_offset_with_no_length.php.inc

@@ -0,0 +1,14 @@
+<?php
+
+namespace Rector\Tests\DowngradePhp80\Rector\FuncCall\DowngradeSubstrFalsyRector\Fixture;
+
+/**
+ * zero offset with no length can't be false
+ */
+class SkipZeroOffsetWithNoLength
+{
+    public function run(string $name)
+    {
+        return substr($name, 0);
+    }
+}

rules-tests/DowngradePhp80/Rector/FuncCall/DowngradeSubstrFalsyRector/Fixture/skip_zero_offset_with_positive_length.php.inc

@@ -0,0 +1,14 @@
+<?php
+
+namespace Rector\Tests\DowngradePhp80\Rector\FuncCall\DowngradeSubstrFalsyRector\Fixture;
+
+/**
+ * zero offset with postive length can't be false
+ */
+class SkipZeroOffsetWithPositiveLength
+{
+    public function run(string $name)
+    {
+        return substr($name, 0, 10);
+    }
+}

rules/DowngradePhp80/Rector/FuncCall/DowngradeSubstrFalsyRector.php

@@ -5,6 +5,7 @@
 namespace Rector\DowngradePhp80\Rector\FuncCall;
 
 use PhpParser\Node;
+use PhpParser\Node\Arg;
 use PhpParser\Node\Expr;
 use PhpParser\Node\Expr\BinaryOp\Identical;
 use PhpParser\Node\Expr\BooleanNot;
@@ -13,6 +14,7 @@
 use PhpParser\Node\Expr\Empty_;
 use PhpParser\Node\Expr\FuncCall;
 use PhpParser\Node\Expr\Ternary;
+use PHPStan\Type\Constant\ConstantIntegerType;
 use Rector\PhpParser\Node\Value\ValueResolver;
 use Rector\Rector\AbstractRector;
 use Symplify\RuleDocGenerator\ValueObject\CodeSample\CodeSample;
@@ -94,6 +96,23 @@ public function refactor(Node $node): ?Node
             return null;
         }
 
+        $offset = $node->getArg('offset', 1);
+
+        if ($offset instanceof Arg) {
+            $offsetType = $this->getType($offset->value);
+            if ($offsetType instanceof ConstantIntegerType && $offsetType->getValue() === 0) {
+                return null;
+            }
+
+            $length = $node->getArg('length', 2);
+            if ($length instanceof Arg) {
+                $lengthType = $this->getType($length->value);
+                if ($lengthType instanceof ConstantIntegerType && $lengthType->getValue() >= 0) {
+                    return null;
+                }
+            }
+        }
+
         return new String_($node);
     }
 }