enforceNativeReturnTypehint fix false positive for unions with template type (#325)

Author: mspirkov

src/Rule/EnforceNativeReturnTypehintRule.php

@@ -117,7 +117,7 @@ private function getTypehintByType(
         bool $topLevel
     ): ?string
     {
-        if ($type instanceof MixedType) {
+        if ($type instanceof MixedType || $this->isUnionTypeWithMixed($type)) {
             return $this->phpVersion->getVersionId() >= 80_000 ? 'mixed' : null;
         }
 
@@ -351,4 +351,19 @@ private function alwaysThrowsException(ReturnStatementsNode $node): bool
         return $exitPoints !== [];
     }
 
+    private function isUnionTypeWithMixed(Type $type): bool
+    {
+        if (!$type instanceof UnionType) {
+            return false;
+        }
+
+        foreach ($type->getTypes() as $innerType) {
+            if ($innerType instanceof MixedType) {
+                return true;
+            }
+        }
+
+        return false;
+    }
+
 }

tests/Rule/data/EnforceNativeReturnTypehintRule/code-74.php

@@ -80,6 +80,13 @@ public function requireMixed3() {}
     /** @return mixed|int|null */
     public function requireMixed4() {}
 
+    /**
+     * @template T
+     * @param callable(): T $function
+     * @return T|false
+     */
+    public function requireMixed5(callable $function) {}
+
     /** @return void */
     public function requireVoid() {} // error: Missing native return typehint void
 

tests/Rule/data/EnforceNativeReturnTypehintRule/code-80.php

@@ -80,6 +80,13 @@ public function requireMixed3() {} // error: Missing native return typehint mixe
     /** @return mixed|int|null */
     public function requireMixed4() {} // error: Missing native return typehint mixed
 
+    /**
+     * @template T
+     * @param callable(): T $function
+     * @return T|false
+     */
+    public function requireMixed5(callable $function) {} // error: Missing native return typehint mixed
+
     /** @return void */
     public function requireVoid() {} // error: Missing native return typehint void
 

tests/Rule/data/EnforceNativeReturnTypehintRule/code-81.php

@@ -80,6 +80,13 @@ public function requireMixed3() {} // error: Missing native return typehint mixe
     /** @return mixed|int|null */
     public function requireMixed4() {} // error: Missing native return typehint mixed
 
+    /**
+     * @template T
+     * @param callable(): T $function
+     * @return T|false
+     */
+    public function requireMixed5(callable $function) {} // error: Missing native return typehint mixed
+
     /** @return void */
     public function requireVoid() {} // error: Missing native return typehint void
 

tests/Rule/data/EnforceNativeReturnTypehintRule/code-82.php

@@ -80,6 +80,13 @@ public function requireMixed3() {} // error: Missing native return typehint mixe
     /** @return mixed|int|null */
     public function requireMixed4() {} // error: Missing native return typehint mixed
 
+    /**
+     * @template T
+     * @param callable(): T $function
+     * @return T|false
+     */
+    public function requireMixed5(callable $function) {} // error: Missing native return typehint mixed
+
     /** @return void */
     public function requireVoid() {} // error: Missing native return typehint void