Fix #1830 - infer key type after array_key_exists check

src/Psalm/Internal/Type/AssertionReconciler.php

@@ -53,6 +53,7 @@ use Psalm\Type\Atomic\TTrue;
 use function strpos;
 use function substr;
 use Psalm\Issue\InvalidDocblock;
+use Doctrine\Instantiator\Exception\UnexpectedValueException;
 
 class AssertionReconciler extends \Psalm\Type\Reconciler
 {
@@ -191,6 +192,14 @@ class AssertionReconciler extends \Psalm\Type\Reconciler
             return $existing_var_type;
         }
 
+        if (substr($assertion, 0, 9) === 'in-array-') {
+            return self::reconcileInArray(
+                $codebase,
+                $existing_var_type,
+                substr($assertion, 9)
+            );
+        }
+
         if ($assertion === 'falsy' || $assertion === 'empty') {
             return self::reconcileFalsyOrEmpty(
                 $assertion,
@@ -1371,6 +1380,44 @@ class AssertionReconciler extends \Psalm\Type\Reconciler
         return Type::getMixed();
     }
 
+    /**
+     * @param   string[]  $suppressed_issues
+     * @param   0|1|2    $failed_reconciliation
+     */
+    private static function reconcileInArray(
+        Codebase $codebase,
+        Union $existing_var_type,
+        string $assertion
+    ) : Union {
+        if (strpos($assertion, '::')) {
+            list($fq_classlike_name, $const_name) = explode('::', $assertion);
+
+            $class_constant_type = $codebase->classlikes->getConstantForClass(
+                $fq_classlike_name,
+                $const_name,
+                \ReflectionProperty::IS_PRIVATE
+            );
+
+            if ($class_constant_type) {
+                foreach ($class_constant_type->getTypes() as $const_type_atomic) {
+                    if ($const_type_atomic instanceof Type\Atomic\ObjectLike
+                        || $const_type_atomic instanceof Type\Atomic\TArray
+                    ) {
+                        if ($const_type_atomic instanceof Type\Atomic\ObjectLike) {
+                            $const_type_atomic = $const_type_atomic->getGenericArrayType();
+                        }
+
+                        return clone $const_type_atomic->type_params[0];
+                    }
+                }
+            }
+        }
+
+        $existing_var_type->removeType('null');
+
+        return $existing_var_type;
+    }
+
     /**
      * @param   string[]  $suppressed_issues
      * @param   0|1|2    $failed_reconciliation

src/Psalm/Internal/Type/NegatedAssertionReconciler.php

@@ -91,6 +91,8 @@ class NegatedAssertionReconciler extends Reconciler
                 return Type::getNull();
             } elseif ($assertion === 'array-key-exists') {
                 return Type::getEmpty();
+            } elseif (substr($assertion, 0, 9) === 'in-array-') {
+                return $existing_var_type;
             }
         }
 

src/Psalm/Type/Reconciler.php

@@ -84,11 +84,11 @@ class Reconciler
         $suppressed_issues = $statements_analyzer->getSuppressedIssues();
 
         foreach ($new_types as $nk => $type) {
-            if ((strpos($nk, '[') || strpos($nk, '->'))
-                && ($type[0][0] === '=isset'
+            if (strpos($nk, '[') || strpos($nk, '->')) {
+                if ($type[0][0] === '=isset'
                     || $type[0][0] === '!=empty'
                     || $type[0][0] === 'isset'
-                    || $type[0][0] === '!empty')
+                    || $type[0][0] === '!empty'
                 ) {
                     $isset_or_empty = $type[0][0] === 'isset' || $type[0][0] === '=isset'
                         ? '=isset'
@@ -155,6 +155,19 @@ class Reconciler
                     // replace with a less specific check
                     $new_types[$nk][0][0] = $isset_or_empty;
                 }
+
+                if ($type[0][0] === 'array-key-exists') {
+                    $key_parts = Reconciler::breakUpPathIntoParts($nk);
+
+                    if (count($key_parts) === 4 && $key_parts[1] === '[') {
+                        if (isset($new_types[$key_parts[2]])) {
+                            $new_types[$key_parts[2]][] = ['=in-array-' . $key_parts[0]];
+                        } else {
+                            $new_types[$key_parts[2]] = [['=in-array-' . $key_parts[0]]];
+                        }
+                    }
+                }
+            }
         }
 
         // make sure array keys come after base keys

tests/AssertTest.php

@@ -379,6 +379,34 @@ class AssertTest extends TestCase
                         }
                     }'
             ],
+            'assertArrayKeyExistsRefinesType' => [
+                '<?php
+                    class Foo {
+                        /** @var array<int,string> */
+                        public const DAYS = [
+                            1 => "mon",
+                            2 => "tue",
+                            3 => "wed",
+                            4 => "thu",
+                            5 => "fri",
+                            6 => "sat",
+                            7 => "sun",
+                        ];
+
+                        /** @param key-of<self::DAYS> $dayNum*/
+                        private static function doGetDayName(int $dayNum): string {
+                            return self::DAYS[$dayNum];
+                        }
+
+                        /** @throws LogicException */
+                        public static function getDayName(int $dayNum): string {
+                            if (! array_key_exists($dayNum, self::DAYS)) {
+                                throw new \LogicException();
+                            }
+                            return self::doGetDayName($dayNum);
+                        }
+                    }'
+            ],
         ];
     }
 }