Cover non-empty-string in substr

conf/config.neon

@@ -1275,6 +1275,11 @@ services:
 		tags:
 			- phpstan.broker.dynamicFunctionReturnTypeExtension
 
+	-
+		class: PHPStan\Type\Php\SubstrDynamicReturnTypeExtension
+		tags:
+			- phpstan.broker.dynamicFunctionReturnTypeExtension
+
 	-
 		class: PHPStan\Type\Php\ParseUrlFunctionDynamicReturnTypeExtension
 		tags:

src/Type/Php/SubstrDynamicReturnTypeExtension.php

@@ -0,0 +1,59 @@
+<?php declare(strict_types = 1);
+
+namespace PHPStan\Type\Php;
+
+use PhpParser\Node\Expr\FuncCall;
+use PHPStan\Analyser\Scope;
+use PHPStan\Reflection\FunctionReflection;
+use PHPStan\Reflection\ParametersAcceptorSelector;
+use PHPStan\Type\Accessory\AccessoryNonEmptyStringType;
+use PHPStan\Type\Constant\ConstantIntegerType;
+use PHPStan\Type\DynamicFunctionReturnTypeExtension;
+use PHPStan\Type\IntegerRangeType;
+use PHPStan\Type\IntersectionType;
+use PHPStan\Type\StringType;
+
+class SubstrDynamicReturnTypeExtension implements DynamicFunctionReturnTypeExtension
+{
+
+	public function isFunctionSupported(FunctionReflection $functionReflection): bool
+	{
+		return $functionReflection->getName() === 'substr';
+	}
+
+	public function getTypeFromFunctionCall(
+		FunctionReflection $functionReflection,
+		FuncCall $functionCall,
+		Scope $scope
+	): \PHPStan\Type\Type
+	{
+		$args = $functionCall->args;
+		if (count($args) === 0) {
+			return ParametersAcceptorSelector::selectSingle($functionReflection->getVariants())->getReturnType();
+		}
+
+		if (count($args) >= 2) {
+			$string = $scope->getType($args[0]->value);
+			$offset = $scope->getType($args[1]->value);
+
+			$negativeOffset = IntegerRangeType::fromInterval(null, -1)->isSuperTypeOf($offset)->yes();
+			$zeroOffset = (new ConstantIntegerType(0))->isSuperTypeOf($offset)->yes();
+			$positiveLength = false;
+
+			if (count($args) === 3) {
+				$length = $scope->getType($args[2]->value);
+				$positiveLength = IntegerRangeType::fromInterval(1, null)->isSuperTypeOf($length)->yes();
+			}
+
+			if ($string->isNonEmptyString()->yes() && ($negativeOffset || $zeroOffset && $positiveLength)) {
+				  return new IntersectionType([
+					  new StringType(),
+					  new AccessoryNonEmptyStringType(),
+				  ]);
+			}
+		}
+
+		return new StringType();
+	}
+
+}

tests/PHPStan/Analyser/data/non-empty-string.php

@@ -134,6 +134,29 @@ public function doEmpty2(string $s): void
 		}
 	}
 
+	/**
+	 * @param non-empty-string $nonEmpty
+	 * @param positive-int $positiveInt
+	 * @param 1|2|3 $postiveRange
+	 * @param -1|-2|-3 $negativeRange
+	 */
+	public function doSubstr(string $s, $nonEmpty, $positiveInt, $postiveRange, $negativeRange): void
+	{
+		assertType('string', substr($s, 5));
+
+		assertType('string', substr($s, -5));
+		assertType('non-empty-string', substr($nonEmpty, -5));
+		assertType('non-empty-string', substr($nonEmpty, $negativeRange));
+
+		assertType('string', substr($s, 0, 5));
+		assertType('non-empty-string', substr($nonEmpty, 0, 5));
+		assertType('non-empty-string', substr($nonEmpty, 0, $postiveRange));
+
+		assertType('string', substr($nonEmpty, 0, -5));
+
+		assertType('string', substr($s, 0, $positiveInt));
+		assertType('non-empty-string', substr($nonEmpty, 0, $positiveInt));
+	}
 }
 
 class ImplodingStrings
@@ -186,15 +209,16 @@ public function doFoo4(string $s, array $nonEmptyArrayWithNonEmptyStrings): void
 	public function sayHello(): void
 	{
 		// coming from issue #5291
-		$s = array(1,2);
+		$s = array(1, 2);
 
 		assertType('non-empty-string', implode("a", $s));
 	}
 
 	/**
 	 * @param non-empty-string $glue
 	 */
-	public function nonE($glue, array $a) {
+	public function nonE($glue, array $a)
+	{
 		// coming from issue #5291
 		if (empty($a)) {
 			return "xyz";
@@ -206,15 +230,16 @@ public function nonE($glue, array $a) {
 	public function sayHello2(): void
 	{
 		// coming from issue #5291
-		$s = array(1,2);
+		$s = array(1, 2);
 
 		assertType('non-empty-string', join("a", $s));
 	}
 
 	/**
 	 * @param non-empty-string $glue
 	 */
-	public function nonE2($glue, array $a) {
+	public function nonE2($glue, array $a)
+	{
 		// coming from issue #5291
 		if (empty($a)) {
 			return "xyz";
@@ -228,7 +253,8 @@ public function nonE2($glue, array $a) {
 class LiteralString
 {
 
-	function x(string $tableName, string $original): void {
+	function x(string $tableName, string $original): void
+	{
 		assertType('non-empty-string', "from `$tableName`");
 	}
 
@@ -297,7 +323,7 @@ public function doFoo(string $s, string $nonEmpty, int $i)
 		assertType('non-empty-string', htmlspecialchars($nonEmpty));
 		assertType('string', htmlentities($s));
 		assertType('non-empty-string', htmlentities($nonEmpty));
-		
+
 		assertType('string', urlencode($s));
 		assertType('non-empty-string', urlencode($nonEmpty));
 		assertType('string', urldecode($s));