Fix phpstan/phpstan#4296: false positive on isset() with numeric string offset on string-keyed array

- In ArrayType::hasOffsetValueType() and getOffsetValueType(), numeric string offsets
  like '1234' are converted to integers by toArrayKey(), then rejected because
  IntegerType is not a supertype of StringType key
- Added check against original (pre-coercion) offset type so numeric strings are
  recognized as valid string keys
- New regression test in tests/PHPStan/Rules/Variables/data/bug-4296.php

Author: VincentLanglet

src/Type/ArrayType.php

@@ -268,6 +268,7 @@ public function looseCompare(Type $type, PhpVersion $phpVersion): BooleanType
 
 	public function hasOffsetValueType(Type $offsetType): TrinaryLogic
 	{
+		$originalOffsetType = $offsetType;
 		$offsetArrayKeyType = $offsetType->toArrayKey();
 		if ($offsetArrayKeyType instanceof ErrorType) {
 			$allowedArrayKeys = AllowedArrayKeysTypes::getType();
@@ -279,6 +280,7 @@ public function hasOffsetValueType(Type $offsetType): TrinaryLogic
 		$offsetType = $offsetArrayKeyType;
 
 		if ($this->getKeyType()->isSuperTypeOf($offsetType)->no()
+			&& $this->getKeyType()->isSuperTypeOf($originalOffsetType)->no()
 			&& ($offsetType->isString()->no() || !$offsetType->isConstantScalarValue()->no())
 		) {
 			return TrinaryLogic::createNo();
@@ -289,8 +291,10 @@ public function hasOffsetValueType(Type $offsetType): TrinaryLogic
 
 	public function getOffsetValueType(Type $offsetType): Type
 	{
+		$originalOffsetType = $offsetType;
 		$offsetType = $offsetType->toArrayKey();
 		if ($this->getKeyType()->isSuperTypeOf($offsetType)->no()
+			&& $this->getKeyType()->isSuperTypeOf($originalOffsetType)->no()
 			&& ($offsetType->isString()->no() || !$offsetType->isConstantScalarValue()->no())
 		) {
 			return new ErrorType();

tests/PHPStan/Rules/Arrays/NonexistentOffsetInArrayDimFetchRuleTest.php

@@ -63,10 +63,6 @@ public function testRule(): void
 				'Offset 0 does not exist on array<string, string>.',
 				111,
 			],
-			[
-				'Offset \'0\' does not exist on array<string, string>.',
-				112,
-			],
 			[
 				'Offset int does not exist on array<string, string>.',
 				114,

tests/PHPStan/Rules/Variables/IssetRuleTest.php

@@ -513,4 +513,11 @@ public function testBug9503(): void
 		$this->analyse([__DIR__ . '/data/bug-9503.php'], []);
 	}
 
+	public function testBug4296(): void
+	{
+		$this->treatPhpDocTypesAsCertain = true;
+
+		$this->analyse([__DIR__ . '/data/bug-4296.php'], []);
+	}
+
 }

tests/PHPStan/Rules/Variables/data/bug-4296.php

@@ -0,0 +1,28 @@
+<?php declare(strict_types = 1);
+
+namespace Bug4296;
+
+class Test {
+    private string $id;
+
+    public function __construct(string $id)
+    {
+        $this->id = $id;
+    }
+
+    public function getId(): string
+    {
+        return $this->id;
+    }
+}
+
+$map = [];
+foreach ([new Test('1234')] as $test) {
+    $map[$test->getId()] = $test;
+}
+
+foreach (['1234'] as $value) {
+    if (isset($map[$value])) {
+        $found = 1;
+    }
+}