Fix #1313 - don’t allow mixed function calls

config.xsd

@@ -221,6 +221,7 @@
             <xs:element name="MixedArrayAssignment" type="IssueHandlerType" minOccurs="0" />
             <xs:element name="MixedArrayOffset" type="IssueHandlerType" minOccurs="0" />
             <xs:element name="MixedAssignment" type="IssueHandlerType" minOccurs="0" />
+            <xs:element name="MixedFunctionCall" type="IssueHandlerType" minOccurs="0" />
             <xs:element name="MixedInferredReturnType" type="IssueHandlerType" minOccurs="0" />
             <xs:element name="MixedMethodCall" type="IssueHandlerType" minOccurs="0" />
             <xs:element name="MixedOperand" type="IssueHandlerType" minOccurs="0" />

docs/issues.md

@@ -1023,6 +1023,16 @@ Emitted when assigning a variable to a value for which Psalm cannot infer a type
 $a = $_GET['foo'];
 ```
 
+### MixedFunctionCall
+
+Emitted when calling a function on a value whose type Psalm cannot infer.
+
+```php
+/** @psalm-suppress MixedAssignment */
+$a = $_GET['foo'];
+$a();
+```
+
 ### MixedInferredReturnType
 
 Emitted when Psalm cannot determine a function's return type

src/Psalm/Config.php

@@ -38,6 +38,7 @@ class Config
         'MixedArrayAssignment',
         'MixedArrayOffset',
         'MixedAssignment',
+        'MixedFunctionCall',
         'MixedInferredReturnType',
         'MixedMethodCall',
         'MixedOperand',

src/Psalm/Internal/Analyzer/Statements/Expression/Call/FunctionCallAnalyzer.php

@@ -12,6 +12,7 @@ use Psalm\CodeLocation;
 use Psalm\Context;
 use Psalm\Internal\FileManipulation\FileManipulationBuffer;
 use Psalm\Issue\ForbiddenCode;
+use Psalm\Issue\MixedFunctionCall;
 use Psalm\Issue\InvalidFunctionCall;
 use Psalm\Issue\NullFunctionCall;
 use Psalm\Issue\PossiblyInvalidFunctionCall;
@@ -119,7 +120,16 @@ class FunctionCallAnalyzer extends \Psalm\Internal\Analyzer\Statements\Expressio
                         $has_valid_function_call_type = true;
                     } elseif ($var_type_part instanceof TMixed || $var_type_part instanceof TGenericParam) {
                         $has_valid_function_call_type = true;
-                        // @todo maybe emit issue here
+
+                        if (IssueBuffer::accepts(
+                            new MixedFunctionCall(
+                                'Cannot call function on mixed',
+                                new CodeLocation($statements_analyzer->getSource(), $stmt)
+                            ),
+                            $statements_analyzer->getSuppressedIssues()
+                        )) {
+                            // fall through
+                        }
                     } elseif ($var_type_part instanceof TCallableObject
                         || $var_type_part instanceof TCallableString
                     ) {

src/Psalm/Issue/MixedFunctionCall.php

@@ -0,0 +1,7 @@
+<?php
+
+namespace Psalm\Issue;
+
+class MixedFunctionCall extends CodeIssue
+{
+}

tests/CallableTest.php

@@ -804,7 +804,10 @@ class CallableTest extends TestCase
 
 
                     $foo =
-                        /** @param mixed $bar */
+                        /**
+                         * @param mixed $bar
+                         * @psalm-suppress MixedFunctionCall
+                         */
                         function ($bar) use (&$foo): string
                         {
                             if (is_array($bar)) {

tests/FunctionCallTest.php

@@ -1882,6 +1882,16 @@ class FunctionCallTest extends TestCase
                     usort($a, "strcmp");',
                 'error_message' => 'InvalidArgument',
             ],
+            'functionCallOnMixed' => [
+                '<?php
+                    /**
+                     * @var mixed $s
+                     * @psalm-suppress MixedAssignment
+                     */
+                    $s = 1;
+                    $s();',
+                'error_message' => 'MixedFunctionCall',
+            ],
         ];
     }
 }