Fix ltrim and trim on numeric string

src/Type/Php/LtrimFunctionReturnTypeExtension.php

@@ -72,7 +72,7 @@ public function getTypeFromFunctionCall(FunctionReflection $functionReflection,
 				} elseif ($trimConstantString->getValue() === '\\' && $string->isClassString()->yes()) {
 					$result[] = new ClassStringType();
 				} elseif (preg_match('/\d/', $trimConstantString->getValue()) === 0 && $string->isNumericString()->yes()) {
-					$result[] = new AccessoryNumericStringType();
+					$result[] = new IntersectionType([new StringType(), new AccessoryNumericStringType()]);
 				} else {
 					return $defaultType;
 				}

src/Type/Php/TrimFunctionDynamicReturnTypeExtension.php

@@ -78,7 +78,7 @@ public function getTypeFromFunctionCall(
 						);
 					}
 				} elseif (preg_match('/\d/', $trimConstantString->getValue()) === 0 && $stringType->isNumericString()->yes()) {
-					$result[] = new AccessoryNumericStringType();
+					$result[] = new IntersectionType([new StringType(), new AccessoryNumericStringType()]);
 				} else {
 					return $defaultType;
 				}

tests/PHPStan/Rules/Functions/CallToFunctionParametersRuleTest.php

@@ -2380,6 +2380,11 @@ public function testBug11863(): void
 		$this->analyse([__DIR__ . '/data/bug-11863.php'], []);
 	}
 
+	public function testBug13784(): void
+	{
+		$this->analyse([__DIR__ . '/data/bug-13784.php'], []);
+	}
+
 	public function testBug13556(): void
 	{
 		$this->checkExplicitMixed = true;

tests/PHPStan/Rules/Functions/data/bug-13784.php

@@ -0,0 +1,22 @@
+<?php declare(strict_types = 1);
+
+namespace Bug13784;
+
+function ok(): int {
+	return strlen(number_format(15, 0, '', ''));
+}
+
+/**
+ * @param numeric-string $str
+ */
+function ok2(string $str): int {
+	return strlen($str);
+}
+
+function fail(): int {
+	return strlen(ltrim(number_format(15, 0, '', ''), '-'));
+}
+
+function fail2(): int {
+	return strlen(trim(number_format(15, 0, '', ''), '-'));
+}