infer non-falsy-string in sscanf()

Author: staabm

src/Type/Php/SscanfFunctionDynamicReturnTypeExtension.php

@@ -6,6 +6,7 @@
 use PHPStan\Analyser\Scope;
 use PHPStan\Reflection\FunctionReflection;
 use PHPStan\Type\Accessory\AccessoryNonEmptyStringType;
+use PHPStan\Type\Accessory\AccessoryNonFalsyStringType;
 use PHPStan\Type\Constant\ConstantArrayTypeBuilder;
 use PHPStan\Type\Constant\ConstantIntegerType;
 use PHPStan\Type\Constant\ConstantStringType;
@@ -54,10 +55,17 @@ public function getTypeFromFunctionCall(
 
 				$type = new StringType();
 				if ($length !== '') {
-					$type = new IntersectionType([
-						$type,
-						new AccessoryNonEmptyStringType(),
-					]);
+					if (((int) $length) > 1) {
+						$type = new IntersectionType([
+							$type,
+							new AccessoryNonFalsyStringType(),
+						]);
+					} else {
+						$type = new IntersectionType([
+							$type,
+							new AccessoryNonEmptyStringType(),
+						]);
+					}
 				}
 
 				if (in_array($specifier, ['d', 'o', 'u', 'x'], true)) {

tests/PHPStan/Analyser/data/sscanf.php

@@ -37,8 +37,14 @@ function fscanfFormatInference($r) {
 	assertType('int|null', $year);
 }
 
-function fooo() {
+function fooo(string $s) {
+	// %0s returns the whole string
+	assertType('array{non-empty-string|null}|null', sscanf( "0" , "%0s"));
 	assertType('array{non-empty-string|null}|null', sscanf( "123456" , "%0s"));
-	assertType('array{non-empty-string|null}|null', sscanf( "123456" , "%3s"));
+
+	assertType('array{non-empty-string|null}|null', sscanf( "123456" , "%1s"));
+	assertType('array{non-falsy-string|null}|null', sscanf( "123456" , "%2s"));
+	assertType('array{non-falsy-string|null}|null', sscanf( "123456" , "%3s"));
+
 	assertType('array{int|null, int|null, int|null}|null', sscanf('00ccff', '%2x%2x%2x'));
 }