After trim($s) !== '' the $s can still be mixed

Author: ondrejmirtes

src/Analyser/TypeSpecifier.php

@@ -1314,15 +1314,19 @@ private function specifyTypesForConstantStringBinaryExpression(
 			&& isset($exprNode->getArgs()[0])
 			&& $constantStringValue === ''
 		) {
-			return $this->create(
-				$exprNode->getArgs()[0]->value,
-				TypeCombinator::intersect(
-					new StringType(),
-					new AccessoryNonEmptyStringType(),
-				),
-				$context->negate(),
-				$scope,
-			)->setRootExpr($rootExpr);
+			$argValue = $exprNode->getArgs()[0]->value;
+			$argType = $scope->getType($argValue);
+			if ($argType->isString()->yes()) {
+				return $this->create(
+					$argValue,
+					TypeCombinator::intersect(
+						new StringType(),
+						new AccessoryNonEmptyStringType(),
+					),
+					$context->negate(),
+					$scope,
+				)->setRootExpr($rootExpr);
+			}
 		}
 
 		return null;

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

@@ -9,21 +9,21 @@ function mbtrim($value): void
 	if (mb_trim($value) === '') {
 		assertType('mixed', $value);
 	} else {
-		assertType('non-empty-string', $value);
+		assertType('mixed', $value);
 	}
 	assertType('mixed', $value);
 
 	if (mb_ltrim($value) === '') {
 		assertType('mixed', $value);
 	} else {
-		assertType('non-empty-string', $value);
+		assertType('mixed', $value);
 	}
 	assertType('mixed', $value);
 
 	if (mb_rtrim($value) === '') {
 		assertType('mixed', $value);
 	} else {
-		assertType('non-empty-string', $value);
+		assertType('mixed', $value);
 	}
 	assertType('mixed', $value);
 }

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

@@ -21,7 +21,7 @@ function trimMixed($value): void
 	if (trim($value) === '') {
 		assertType('mixed', $value);
 	} else {
-		assertType('non-empty-string', $value);
+		assertType('mixed', $value);
 	}
 	assertType('mixed', $value);
 

tests/PHPStan/Analyser/nsrt/bug-13552.php

@@ -0,0 +1,13 @@
+<?php // lint >= 8.0
+
+namespace Bug13552;
+
+use function PHPStan\Testing\assertType;
+
+function doSomething(mixed $value): void
+{
+	if (trim($value) === '') {
+		return;
+	}
+	assertType('mixed', $value);
+}