Fix #4794 - invvalidate dependent types when their variables change

src/Psalm/Context.php

@@ -656,10 +656,18 @@ class Context
             $statements_analyzer
         );
 
-        foreach ($this->vars_in_scope as $var_id => $_) {
+        foreach ($this->vars_in_scope as $var_id => $type) {
             if (preg_match('/' . preg_quote($remove_var_id, '/') . '[\]\[\-]/', $var_id)) {
                 unset($this->vars_in_scope[$var_id]);
             }
+
+            foreach ($type->getAtomicTypes() as $atomic_type) {
+                if ($atomic_type instanceof Type\Atomic\DependentType
+                    && $atomic_type->getVarId() === $remove_var_id
+                ) {
+                    $type->addType($atomic_type->getReplacement());
+                }
+            }
         }
     }
 

src/Psalm/Type/Atomic/DependentType.php

@@ -0,0 +1,12 @@
+<?php
+namespace Psalm\Type\Atomic;
+
+interface DependentType
+{
+    public function getVarId() : string;
+
+    /**
+     * This returns a replacement type for when the dependent data is invalidated
+     */
+    public function getReplacement() : \Psalm\Type\Atomic;
+}

src/Psalm/Type/Atomic/TDependentGetClass.php

@@ -6,7 +6,7 @@ use Psalm\Type\Union;
 /**
  * Represents a string whose value is a fully-qualified class found by get_class($var)
  */
-class TDependentGetClass extends TString
+class TDependentGetClass extends TString implements DependentType
 {
     /**
      * Used to hold information as to what this refers to
@@ -37,6 +37,23 @@ class TDependentGetClass extends TString
             : 'class-string<' . $this->as_type->getId() . '>';
     }
 
+    public function getKey(bool $include_extra = true): string
+    {
+        return 'get-class-of<' . $this->typeof
+            . (!$this->as_type->isMixed() && !$this->as_type->hasObject() ? ', ' . $this->as_type->getId() : '')
+            . '>';
+    }
+
+    public function getVarId() : string
+    {
+        return $this->typeof;
+    }
+
+    public function getReplacement() : \Psalm\Type\Atomic
+    {
+        return new TClassString();
+    }
+
     public function canBeFullyExpressedInPhp(int $php_major_version, int $php_minor_version): bool
     {
         return false;

src/Psalm/Type/Atomic/TDependentGetDebugType.php

@@ -4,7 +4,7 @@ namespace Psalm\Type\Atomic;
 /**
  * Represents a string whose value is that of a type found by get_debug_type($var)
  */
-class TDependentGetDebugType extends TString
+class TDependentGetDebugType extends TString implements DependentType
 {
     /**
      * Used to hold information as to what this refers to
@@ -21,6 +21,21 @@ class TDependentGetDebugType extends TString
         $this->typeof = $typeof;
     }
 
+    public function getKey(bool $include_extra = true): string
+    {
+        return 'get-debug-type-of<' . $this->typeof . '>';
+    }
+
+    public function getVarId() : string
+    {
+        return $this->typeof;
+    }
+
+    public function getReplacement() : \Psalm\Type\Atomic
+    {
+        return new TString();
+    }
+
     public function canBeFullyExpressedInPhp(int $php_major_version, int $php_minor_version): bool
     {
         return false;

tests/SwitchTypeTest.php

@@ -1301,6 +1301,28 @@ class SwitchTypeTest extends TestCase
                     }',
                 'error_message' => 'InvalidReturnType'
             ],
+            'clearDependentTypeWhenAssigning' => [
+                '<?php
+                    class A {}
+
+                    class AChild extends A {
+                        public function bar() : void {}
+                    }
+
+                    class B {}
+
+                    function foo(A $a) : void {
+                        $a_class = get_class($a);
+
+                        $a = new B();
+
+                        switch ($a_class) {
+                            case AChild::class:
+                                $a->bar();
+                        }
+                    }',
+                'error_message' => 'UndefinedMethod'
+            ],
         ];
     }
 }