String offset access leads non-empty-string (single character)

Author: ondrejmirtes

src/Type/StringType.php

@@ -72,7 +72,10 @@ public function getOffsetValueType(Type $offsetType): Type
 			return new ErrorType();
 		}
 
-		return new StringType();
+		return new IntersectionType([
+			new StringType(),
+			new AccessoryNonEmptyStringType(),
+		]);
 	}
 
 	public function setOffsetValueType(?Type $offsetType, Type $valueType, bool $unionValues = true): Type
@@ -87,7 +90,10 @@ public function setOffsetValueType(?Type $offsetType, Type $valueType, bool $uni
 		}
 
 		if ($offsetType->isInteger()->yes() || $offsetType instanceof MixedType) {
-			return new StringType();
+			return new IntersectionType([
+				new StringType(),
+				new AccessoryNonEmptyStringType(),
+			]);
 		}
 
 		return new ErrorType();

tests/PHPStan/Analyser/LegacyNodeScopeResolverTest.php

@@ -1073,7 +1073,7 @@ public function dataArrayDestructuring(): array
 				'$secondStringArray',
 			],
 			[
-				'string',
+				'non-empty-string',
 				'$thirdStringArray',
 			],
 			[
@@ -1089,43 +1089,43 @@ public function dataArrayDestructuring(): array
 				'$secondStringArrayList',
 			],
 			[
-				'string',
+				'non-empty-string',
 				'$thirdStringArrayList',
 			],
 			[
 				'string',
 				'$fourthStringArrayList',
 			],
 			[
-				'string',
+				'non-empty-string',
 				'$firstStringArrayForeach',
 			],
 			[
-				'string',
+				'non-empty-string',
 				'$secondStringArrayForeach',
 			],
 			[
-				'string',
+				'non-empty-string',
 				'$thirdStringArrayForeach',
 			],
 			[
-				'string',
+				'non-empty-string',
 				'$fourthStringArrayForeach',
 			],
 			[
-				'string',
+				'non-empty-string',
 				'$firstStringArrayForeachList',
 			],
 			[
-				'string',
+				'non-empty-string',
 				'$secondStringArrayForeachList',
 			],
 			[
-				'string',
+				'non-empty-string',
 				'$thirdStringArrayForeachList',
 			],
 			[
-				'string',
+				'non-empty-string',
 				'$fourthStringArrayForeachList',
 			],
 			[
@@ -2904,7 +2904,7 @@ public function dataBinaryOperations(): array
 				'$fooString[4]',
 			],
 			[
-				'string',
+				'non-empty-string',
 				'$fooString[$integer]',
 			],
 			[

tests/PHPStan/Analyser/nsrt/bug-3981.php

@@ -18,8 +18,8 @@ public function doFoo(string $s, string $nonEmptyString): void
 		assertType('false', strtok('', ' '));
 
 		assertType('non-empty-string', $nonEmptyString[0]);
-		assertType('string', $nonEmptyString[1]);
-		assertType('string', $s[0]);
+		assertType('non-empty-string', $nonEmptyString[1]);
+		assertType('non-empty-string', $s[0]);
 	}
 
 }

tests/PHPStan/Rules/Functions/CallToFunctionParametersRuleTest.php

@@ -1716,4 +1716,9 @@ public function testCountArrayShift(): void
 		$this->analyse([__DIR__ . '/data/count-array-shift.php'], $errors);
 	}
 
+	public function testBug11506(): void
+	{
+		$this->analyse([__DIR__ . '/data/bug-11506.php'], []);
+	}
+
 }

tests/PHPStan/Rules/Functions/data/bug-11506.php

@@ -0,0 +1,13 @@
+<?php
+
+namespace Bug11506;
+
+function (): void {
+	$brandName         = 'Mercedes-Benz';
+	$enabledChars      = './-';
+	$enabledCharsCount = \strlen($enabledChars);
+
+	for ($i = 0; $i < $enabledCharsCount; $i++) {
+		$parts = \explode($enabledChars[$i], $brandName);
+	}
+};