implemented ConstantStringType inference for str_repeat

Author: staabm

src/Type/Php/StrRepeatFunctionReturnTypeExtension.php

@@ -12,9 +12,11 @@
 use PHPStan\Type\DynamicFunctionReturnTypeExtension;
 use PHPStan\Type\IntegerRangeType;
 use PHPStan\Type\IntersectionType;
+use PHPStan\Type\NeverType;
 use PHPStan\Type\StringType;
 use PHPStan\Type\Type;
 use function count;
+use function str_repeat;
 
 class StrRepeatFunctionReturnTypeExtension implements DynamicFunctionReturnTypeExtension
 {
@@ -42,6 +44,14 @@ public function getTypeFromFunctionCall(
 			return new ConstantStringType('');
 		}
 
+		if ($multiplierType instanceof ConstantIntegerType && $multiplierType->getValue() < 0) {
+			return new NeverType();
+		}
+
+		if ($inputType instanceof ConstantStringType && $multiplierType instanceof ConstantIntegerType) {
+			return new ConstantStringType(str_repeat($inputType->getValue(), $multiplierType->getValue()));
+		}
+
 		$accessoryTypes = [];
 		if ($inputType->isNonEmptyString()->yes()) {
 			if (IntegerRangeType::fromInterval(1, null)->isSuperTypeOf($multiplierType)->yes()) {

tests/PHPStan/Analyser/data/literal-string.php

@@ -25,8 +25,10 @@ public function doFoo($literalString, string $string)
 
 		assertType('string', str_repeat($string, 10));
 		assertType('literal-string', str_repeat($literalString, 10));
-		assertType('literal-string', str_repeat('', 10));
-		assertType('literal-string&non-empty-string', str_repeat('foo', 10));
+		assertType("''", str_repeat('', 10));
+		assertType("'foofoofoofoofoofoofoofoofoofoo'", str_repeat('foo', 10));
+		assertType("'?,?,?,'", str_repeat('?,', 3));
+		assertType("*NEVER*", str_repeat('?,', -3));
 
 		assertType('non-empty-string', str_pad($string, 5, $string));
 		assertType('non-empty-string', str_pad($literalString, 5, $string));