support mb_r/l/trim

Author: staabm

src/Analyser/TypeSpecifier.php

@@ -1307,7 +1307,10 @@ private function specifyTypesForConstantStringBinaryExpression(
 			$context->false()
 			&& $exprNode instanceof FuncCall
 			&& $exprNode->name instanceof Name
-			&& in_array(strtolower((string) $exprNode->name), ['trim', 'ltrim', 'rtrim'], true)
+			&& in_array(strtolower((string) $exprNode->name), [
+				'trim', 'ltrim', 'rtrim',
+				'mb_trim', 'mb_ltrim', 'mb_rtrim',
+			], true)
 			&& isset($exprNode->getArgs()[0])
 			&& $constantStringValue === ''
 		) {

tests/PHPStan/Analyser/nsrt/bug-12973-php84.php

@@ -0,0 +1,29 @@
+<?php // lint >= 8.4
+
+namespace Bug12973Php84;
+
+use function PHPStan\Testing\assertType;
+
+function mbtrim($value): void
+{
+	if (mb_trim($value) === '') {
+		assertType('mixed', $value);
+	} else {
+		assertType('non-empty-string', $value);
+	}
+	assertType('mixed', $value);
+
+	if (mb_ltrim($value) === '') {
+		assertType('mixed', $value);
+	} else {
+		assertType('non-empty-string', $value);
+	}
+	assertType('mixed', $value);
+
+	if (mb_rtrim($value) === '') {
+		assertType('mixed', $value);
+	} else {
+		assertType('non-empty-string', $value);
+	}
+	assertType('mixed', $value);
+}