diff --git a/dictionaries/scripts/update_signaturemap_from_other_tool.php b/dictionaries/scripts/update_signaturemap_from_other_tool.php
index 21fb61166d5..d50e88ee0a8 100644
--- a/dictionaries/scripts/update_signaturemap_from_other_tool.php
+++ b/dictionaries/scripts/update_signaturemap_from_other_tool.php
@@ -30,7 +30,7 @@
     $removed_foreign_functions
 );
 
-uksort($new_local, fn($a, $b) => strtolower($a) <=> strtolower($b));
+uksort($new_local, static fn($a, $b) => strtolower($a) <=> strtolower($b));
 
 foreach ($new_local as $name => $data) {
     if (!is_array($data)) {
diff --git a/examples/plugins/ClassUnqualifier.php b/examples/plugins/ClassUnqualifier.php
index 3f4f14f517a..57a9f86da08 100644
--- a/examples/plugins/ClassUnqualifier.php
+++ b/examples/plugins/ClassUnqualifier.php
@@ -44,7 +44,7 @@ public static function afterClassLikeExistenceCheck(
             $new_candidate_type = implode(
                 '',
                 array_map(
-                    fn($f) => $f[0],
+                    static fn($f) => $f[0],
                     $type_tokens,
                 ),
             );
diff --git a/src/Psalm/Codebase.php b/src/Psalm/Codebase.php
index d2b5d54ceae..e1c2f017090 100644
--- a/src/Psalm/Codebase.php
+++ b/src/Psalm/Codebase.php
@@ -69,7 +69,6 @@
 use UnexpectedValueException;
 
 use function array_combine;
-use function array_merge;
 use function array_pop;
 use function array_reverse;
 use function array_values;
@@ -1917,7 +1916,7 @@ public function getCompletionItemsForClassishThing(
                         );
                     }
 
-                    $completion_items = array_merge($completion_items, array_values($pseudo_property_types));
+                    $completion_items = [...$completion_items, ...array_values($pseudo_property_types)];
 
                     foreach ($class_storage->declaring_property_ids as $property_name => $declaring_class) {
                         $property_storage = $this->properties->getStorage(
diff --git a/src/Psalm/Internal/Analyzer/ClassLikeAnalyzer.php b/src/Psalm/Internal/Analyzer/ClassLikeAnalyzer.php
index 3ee68c6582f..bc20c08f8ae 100644
--- a/src/Psalm/Internal/Analyzer/ClassLikeAnalyzer.php
+++ b/src/Psalm/Internal/Analyzer/ClassLikeAnalyzer.php
@@ -707,7 +707,7 @@ protected function checkTemplateParams(
                                 && $storage->template_types
                                 && $storage->template_covariants
                                 && ($local_offset
-                                    = array_search($t->param_name, array_keys($storage->template_types)))
+                                    = array_search($t->param_name, array_keys($storage->template_types), true))
                                     !== false
                                 && !empty($storage->template_covariants[$local_offset])
                             ) {
diff --git a/src/Psalm/Internal/Analyzer/CommentAnalyzer.php b/src/Psalm/Internal/Analyzer/CommentAnalyzer.php
index 9668f292417..65915d1f34c 100644
--- a/src/Psalm/Internal/Analyzer/CommentAnalyzer.php
+++ b/src/Psalm/Internal/Analyzer/CommentAnalyzer.php
@@ -25,7 +25,6 @@
 use Psalm\Type\Union;
 use UnexpectedValueException;
 
-use function array_merge;
 use function count;
 use function is_string;
 use function preg_match;
@@ -400,7 +399,7 @@ public static function splitDocLine(string $return_block): array
                 $remaining = trim(preg_replace('@^[ \t]*\* *@m', ' ', substr($return_block, $i + 1)));
 
                 if ($remaining) {
-                    return array_merge([rtrim($type)], preg_split('/\s+/', $remaining) ?: []);
+                    return [rtrim($type), ...preg_split('/\s+/', $remaining) ?: []];
                 }
 
                 return [$type];
diff --git a/src/Psalm/Internal/Analyzer/Statements/Block/ForeachAnalyzer.php b/src/Psalm/Internal/Analyzer/Statements/Block/ForeachAnalyzer.php
index 905dc3d8a80..128eaada6ef 100644
--- a/src/Psalm/Internal/Analyzer/Statements/Block/ForeachAnalyzer.php
+++ b/src/Psalm/Internal/Analyzer/Statements/Block/ForeachAnalyzer.php
@@ -1096,7 +1096,7 @@ private static function getExtendedType(
     ): ?Union {
         if ($calling_class === $template_class) {
             if (isset($class_template_types[$template_name]) && $calling_type_params) {
-                $offset = array_search($template_name, array_keys($class_template_types));
+                $offset = array_search($template_name, array_keys($class_template_types), true);
 
                 if ($offset !== false && isset($calling_type_params[$offset])) {
                     return $calling_type_params[$offset];
diff --git a/src/Psalm/Internal/Analyzer/Statements/Expression/Call/Method/AtomicMethodCallAnalyzer.php b/src/Psalm/Internal/Analyzer/Statements/Expression/Call/Method/AtomicMethodCallAnalyzer.php
index fca21662783..5997ac82efa 100644
--- a/src/Psalm/Internal/Analyzer/Statements/Expression/Call/Method/AtomicMethodCallAnalyzer.php
+++ b/src/Psalm/Internal/Analyzer/Statements/Expression/Call/Method/AtomicMethodCallAnalyzer.php
@@ -751,6 +751,7 @@ private static function handleTemplatedMixins(
                 $param_position = array_search(
                     $mixin->param_name,
                     $template_type_keys,
+                    true,
                 );
 
                 if ($param_position !== false
diff --git a/src/Psalm/Internal/Analyzer/Statements/Expression/CastAnalyzer.php b/src/Psalm/Internal/Analyzer/Statements/Expression/CastAnalyzer.php
index 12285e2432e..99f045d71c6 100644
--- a/src/Psalm/Internal/Analyzer/Statements/Expression/CastAnalyzer.php
+++ b/src/Psalm/Internal/Analyzer/Statements/Expression/CastAnalyzer.php
@@ -476,7 +476,7 @@ public static function castIntAttempt(
             // todo: emit error here
         }
 
-        $valid_types = array_merge($valid_ints, $castable_types);
+        $valid_types = [...$valid_ints, ...$castable_types];
 
         if (!$valid_types) {
             $int_type = Type::getInt();
@@ -661,7 +661,7 @@ public static function castFloatAttempt(
             // todo: emit error here
         }
 
-        $valid_types = array_merge($valid_floats, $castable_types);
+        $valid_types = [...$valid_floats, ...$castable_types];
 
         if (!$valid_types) {
             $float_type = Type::getFloat();
@@ -804,10 +804,7 @@ public static function castStringAttempt(
                                 $parent_nodes = array_merge($return_type->parent_nodes, $parent_nodes);
                             }
 
-                            $castable_types = array_merge(
-                                $castable_types,
-                                array_values($return_type->getAtomicTypes()),
-                            );
+                            $castable_types = [...$castable_types, ...array_values($return_type->getAtomicTypes())];
 
                             continue 2;
                         }
diff --git a/src/Psalm/Internal/Analyzer/Statements/Expression/Fetch/AtomicPropertyFetchAnalyzer.php b/src/Psalm/Internal/Analyzer/Statements/Expression/Fetch/AtomicPropertyFetchAnalyzer.php
index d6289b6687b..ff14ed24273 100644
--- a/src/Psalm/Internal/Analyzer/Statements/Expression/Fetch/AtomicPropertyFetchAnalyzer.php
+++ b/src/Psalm/Internal/Analyzer/Statements/Expression/Fetch/AtomicPropertyFetchAnalyzer.php
@@ -788,6 +788,7 @@ public static function localizePropertyType(
                             $position = array_search(
                                 $param_name,
                                 array_keys($property_class_storage->template_types),
+                                true,
                             );
                         }
 
@@ -1000,7 +1001,7 @@ private static function handleEnumName(
             empty($relevant_enum_case_names)
                 ? Type::getNonEmptyString()
                 : new Union(array_map(
-                    fn(string $name): TString => Type::getAtomicStringFromLiteral($name),
+                    static fn(string $name): TString => Type::getAtomicStringFromLiteral($name),
                     $relevant_enum_case_names,
                 )),
         );
diff --git a/src/Psalm/Internal/Analyzer/StatementsAnalyzer.php b/src/Psalm/Internal/Analyzer/StatementsAnalyzer.php
index 55e80d44643..fc75e1631eb 100644
--- a/src/Psalm/Internal/Analyzer/StatementsAnalyzer.php
+++ b/src/Psalm/Internal/Analyzer/StatementsAnalyzer.php
@@ -869,7 +869,7 @@ public function checkUnreferencedVars(array $stmts, Context $context): void
             }
 
             if ($function_storage) {
-                $param_index = array_search(substr($var_id, 1), array_keys($function_storage->param_lookup));
+                $param_index = array_search(substr($var_id, 1), array_keys($function_storage->param_lookup), true);
                 if ($param_index !== false) {
                     $param = $function_storage->params[$param_index];
 
diff --git a/src/Psalm/Internal/Codebase/Populator.php b/src/Psalm/Internal/Codebase/Populator.php
index 022cc684e46..69aa208044e 100644
--- a/src/Psalm/Internal/Codebase/Populator.php
+++ b/src/Psalm/Internal/Codebase/Populator.php
@@ -931,10 +931,10 @@ protected function inheritMethodsFromParent(
             if ($parent_storage->is_trait
                 && $storage->trait_alias_map
             ) {
-                $aliased_method_names = array_merge(
-                    $aliased_method_names,
-                    array_keys($storage->trait_alias_map, $method_name_lc, true),
-                );
+                $aliased_method_names = [
+                    ...$aliased_method_names,
+                    ...array_keys($storage->trait_alias_map, $method_name_lc, true),
+                ];
             }
 
             foreach ($aliased_method_names as $aliased_method_name) {
@@ -1001,10 +1001,10 @@ protected function inheritMethodsFromParent(
             if ($parent_storage->is_trait
                 && $storage->trait_alias_map
             ) {
-                $aliased_method_names = array_merge(
-                    $aliased_method_names,
-                    array_keys($storage->trait_alias_map, $method_name_lc, true),
-                );
+                $aliased_method_names = [
+                    ...$aliased_method_names,
+                    ...array_keys($storage->trait_alias_map, $method_name_lc, true),
+                ];
             }
 
             foreach ($aliased_method_names as $aliased_method_name) {
diff --git a/src/Psalm/Internal/FileManipulation/FunctionDocblockManipulator.php b/src/Psalm/Internal/FileManipulation/FunctionDocblockManipulator.php
index b04952c0581..f10a42379e2 100644
--- a/src/Psalm/Internal/FileManipulation/FunctionDocblockManipulator.php
+++ b/src/Psalm/Internal/FileManipulation/FunctionDocblockManipulator.php
@@ -44,7 +44,7 @@ class FunctionDocblockManipulator
     private static array $manipulators = [];
 
     /** @var Closure|Function_|ClassMethod|ArrowFunction */
-    private $stmt;
+    private FunctionLike $stmt;
 
     private int $docblock_start;
 
@@ -415,7 +415,7 @@ private function getDocblock(): string
             $modified_docblock = true;
             $inferredThrowsClause = array_reduce(
                 $this->throwsExceptions,
-                fn(string $throwsClause, string $exception) => $throwsClause === ''
+                static fn(string $throwsClause, string $exception) => $throwsClause === ''
                     ? $exception
                     : $throwsClause.'|'.$exception,
                 '',
diff --git a/src/Psalm/Internal/LanguageServer/LanguageServer.php b/src/Psalm/Internal/LanguageServer/LanguageServer.php
index ed6b879dcbe..fde6b541395 100644
--- a/src/Psalm/Internal/LanguageServer/LanguageServer.php
+++ b/src/Psalm/Internal/LanguageServer/LanguageServer.php
@@ -237,7 +237,7 @@ function (Message $msg): Generator {
 
         $this->protocolReader->on(
             'readMessageGroup',
-            function (): void {
+            static function (): void {
                 //$this->verboseLog('Received message group');
                 //$this->doAnalysis();
             },
@@ -765,7 +765,7 @@ function (IssueData $issue_data): Diagnostic {
                     return $diagnostic;
                 },
                 array_filter(
-                    array_map(function (IssueData $issue_data) use (&$issue_baseline) {
+                    array_map(static function (IssueData $issue_data) use (&$issue_baseline) {
                         if (empty($issue_baseline)) {
                             return $issue_data;
                         }
diff --git a/src/Psalm/Internal/Provider/ReturnTypeProvider/ArrayMapReturnTypeProvider.php b/src/Psalm/Internal/Provider/ReturnTypeProvider/ArrayMapReturnTypeProvider.php
index 92397ebb69f..910c5d5c9e6 100644
--- a/src/Psalm/Internal/Provider/ReturnTypeProvider/ArrayMapReturnTypeProvider.php
+++ b/src/Psalm/Internal/Provider/ReturnTypeProvider/ArrayMapReturnTypeProvider.php
@@ -113,9 +113,9 @@ public static function getFunctionReturnType(FunctionReturnTypeProviderEvent $ev
             $array_arg_types = array_map(null, ...$array_arg_types);
             $array_arg_types = array_map(
                 /** @param non-empty-array<?Union> $sub */
-                function (array $sub) use ($null) {
+                static function (array $sub) use ($null) {
                     $sub = array_map(
-                        fn(?Union $t) => $t ?? $null,
+                        static fn(?Union $t) => $t ?? $null,
                         $sub,
                     );
                     return new Union([new TKeyedArray($sub, null, null, true)]);
diff --git a/src/Psalm/Internal/Type/SimpleAssertionReconciler.php b/src/Psalm/Internal/Type/SimpleAssertionReconciler.php
index 5e0d0a827ed..aa606ec8f89 100644
--- a/src/Psalm/Internal/Type/SimpleAssertionReconciler.php
+++ b/src/Psalm/Internal/Type/SimpleAssertionReconciler.php
@@ -686,7 +686,7 @@ private static function reconcileNonEmptyCountable(
                         $existing_var_type->removeType('array');
                         $existing_var_type->addType($array_atomic_type->setProperties(
                             array_map(
-                                fn(Union $union) => $union->setPossiblyUndefined(false),
+                                static fn(Union $union) => $union->setPossiblyUndefined(false),
                                 $array_atomic_type->properties,
                             ),
                         ));
@@ -806,7 +806,7 @@ private static function reconcileExactlyCountable(
                         $existing_var_type->removeType('array');
                         $existing_var_type->addType($array_atomic_type->setProperties(
                             array_map(
-                                fn(Union $union) => $union->setPossiblyUndefined(false),
+                                static fn(Union $union) => $union->setPossiblyUndefined(false),
                                 $array_atomic_type->properties,
                             ),
                         ));
diff --git a/src/Psalm/Internal/Type/TemplateInferredTypeReplacer.php b/src/Psalm/Internal/Type/TemplateInferredTypeReplacer.php
index fc8573ab418..259aedd9521 100644
--- a/src/Psalm/Internal/Type/TemplateInferredTypeReplacer.php
+++ b/src/Psalm/Internal/Type/TemplateInferredTypeReplacer.php
@@ -226,7 +226,7 @@ public static function replace(
             )->freeze();
         }
 
-        $atomic_types = array_merge($types, $new_types);
+        $atomic_types = [...$types, ...$new_types];
         if (!$atomic_types) {
             throw new UnexpectedValueException('This array should be full');
         }
diff --git a/src/Psalm/Internal/Type/TemplateStandinTypeReplacer.php b/src/Psalm/Internal/Type/TemplateStandinTypeReplacer.php
index 9fa51c420cd..bbab4e24b7b 100644
--- a/src/Psalm/Internal/Type/TemplateStandinTypeReplacer.php
+++ b/src/Psalm/Internal/Type/TemplateStandinTypeReplacer.php
@@ -1343,6 +1343,7 @@ public static function getMappedGenericTypeParams(
                                 $old_params_offset = (int) array_search(
                                     $template->param_name,
                                     array_keys($input_class_storage->template_types),
+                                    true,
                                 );
 
                                 $candidate_param_types[] = ($input_type_params[$old_params_offset] ?? Type::getMixed())
diff --git a/src/Psalm/Internal/Type/TypeParser.php b/src/Psalm/Internal/Type/TypeParser.php
index 99cf82a4d51..0287ab4d6bd 100644
--- a/src/Psalm/Internal/Type/TypeParser.php
+++ b/src/Psalm/Internal/Type/TypeParser.php
@@ -958,7 +958,11 @@ private static function getTypeFromGenericTree(
             }
             assert(count($parse_tree->children) === 2);
 
-            $get_int_range_bound = function (ParseTree $parse_tree, Union $generic_param, string $bound_name): ?int {
+            $get_int_range_bound = static function (
+                ParseTree $parse_tree,
+                Union $generic_param,
+                string $bound_name
+            ): ?int {
                 if (!$parse_tree instanceof Value
                     || count($generic_param->getAtomicTypes()) > 1
                     || (!$generic_param->getSingleAtomic() instanceof TLiteralInt
@@ -970,7 +974,6 @@ private static function getTypeFromGenericTree(
                         "Invalid type \"{$generic_param->getId()}\" as int $bound_name boundary",
                     );
                 }
-
                 $generic_param_atomic = $generic_param->getSingleAtomic();
                 return $generic_param_atomic instanceof TLiteralInt ? $generic_param_atomic->value : null;
             };
diff --git a/src/Psalm/IssueBuffer.php b/src/Psalm/IssueBuffer.php
index 1460c53f7c8..9ca29ef701b 100644
--- a/src/Psalm/IssueBuffer.php
+++ b/src/Psalm/IssueBuffer.php
@@ -190,7 +190,7 @@ public static function isSuppressed(CodeIssue $e, array $suppressed_issues = [])
             return true;
         }
 
-        $suppressed_issue_position = array_search($issue_type, $suppressed_issues);
+        $suppressed_issue_position = array_search($issue_type, $suppressed_issues, true);
 
         if ($suppressed_issue_position !== false) {
             if (is_int($suppressed_issue_position)) {
@@ -203,7 +203,7 @@ public static function isSuppressed(CodeIssue $e, array $suppressed_issues = [])
         $parent_issue_type = Config::getParentIssueType($issue_type);
 
         if ($parent_issue_type) {
-            $suppressed_issue_position = array_search($parent_issue_type, $suppressed_issues);
+            $suppressed_issue_position = array_search($parent_issue_type, $suppressed_issues, true);
 
             if ($suppressed_issue_position !== false) {
                 if (is_int($suppressed_issue_position)) {
@@ -216,7 +216,7 @@ public static function isSuppressed(CodeIssue $e, array $suppressed_issues = [])
 
         $suppress_all_position = $config->disable_suppress_all
             ? false
-            : array_search('all', $suppressed_issues);
+            : array_search('all', $suppressed_issues, true);
 
         if ($suppress_all_position !== false) {
             if (is_int($suppress_all_position)) {
diff --git a/src/Psalm/Plugin/EventHandler/Event/AfterMethodCallAnalysisEvent.php b/src/Psalm/Plugin/EventHandler/Event/AfterMethodCallAnalysisEvent.php
index b0ad1ef31d5..f699a6d4e03 100644
--- a/src/Psalm/Plugin/EventHandler/Event/AfterMethodCallAnalysisEvent.php
+++ b/src/Psalm/Plugin/EventHandler/Event/AfterMethodCallAnalysisEvent.php
@@ -16,7 +16,7 @@ final class AfterMethodCallAnalysisEvent
     /**
      * @var MethodCall|StaticCall
      */
-    private $expr;
+    private Expr $expr;
     private string $method_id;
     private string $appearing_method_id;
     private string $declaring_method_id;
diff --git a/src/Psalm/Report/ByIssueLevelAndTypeReport.php b/src/Psalm/Report/ByIssueLevelAndTypeReport.php
index c657b415749..36aeb60221b 100644
--- a/src/Psalm/Report/ByIssueLevelAndTypeReport.php
+++ b/src/Psalm/Report/ByIssueLevelAndTypeReport.php
@@ -181,7 +181,7 @@ private function sortIssuesByLevelAndType(): void
     {
         usort(
             $this->issues_data,
-            fn(IssueData $left, IssueData $right): int => [$left->error_level > 0, -$left->error_level,
+            static fn(IssueData $left, IssueData $right): int => [$left->error_level > 0, -$left->error_level,
                     $left->type, $left->file_path, $left->file_name, $left->line_from]
                 <=> [$right->error_level > 0, -$right->error_level, $right->type, $right->file_path, $right->file_name,
                     $right->line_from],
diff --git a/src/Psalm/Report/CountReport.php b/src/Psalm/Report/CountReport.php
index b044d851651..4321789d44b 100644
--- a/src/Psalm/Report/CountReport.php
+++ b/src/Psalm/Report/CountReport.php
@@ -21,7 +21,7 @@ public function create(): string
                 $issue_type_counts[$issue_data->type] = 1;
             }
         }
-        uksort($issue_type_counts, function (string $a, string $b) use ($issue_type_counts): int {
+        uksort($issue_type_counts, static function (string $a, string $b) use ($issue_type_counts): int {
             $cmp_result = $issue_type_counts[$a] <=> $issue_type_counts[$b];
             if ($cmp_result === 0) {
                 return $a <=> $b;
diff --git a/src/Psalm/Storage/FunctionLikeStorage.php b/src/Psalm/Storage/FunctionLikeStorage.php
index 929e2b84d7a..7be91f80434 100644
--- a/src/Psalm/Storage/FunctionLikeStorage.php
+++ b/src/Psalm/Storage/FunctionLikeStorage.php
@@ -254,7 +254,7 @@ public function getHoverMarkdown(): string
         $params = count($this->params) > 0 ? "\n" . implode(
             ",\n",
             array_map(
-                function (FunctionLikeParameter $param): string {
+                static function (FunctionLikeParameter $param): string {
                     $realType = $param->type ?: 'mixed';
                     return "    {$realType} \${$param->name}";
                 },
@@ -289,7 +289,7 @@ public function getCompletionSignature(): string
         $symbol_text = 'function ' . $this->cased_name . '('   . implode(
             ',',
             array_map(
-                fn(FunctionLikeParameter $param): string => ($param->type ?: 'mixed') . ' $' . $param->name,
+                static fn(FunctionLikeParameter $param): string => ($param->type ?: 'mixed') . ' $' . $param->name,
                 $this->params,
             ),
         ) .  ') : ' . ($this->return_type ?: 'mixed');
diff --git a/src/Psalm/Type/Atomic/TClosure.php b/src/Psalm/Type/Atomic/TClosure.php
index 97949adc967..94ee9446d44 100644
--- a/src/Psalm/Type/Atomic/TClosure.php
+++ b/src/Psalm/Type/Atomic/TClosure.php
@@ -9,8 +9,6 @@
 use Psalm\Type\Atomic;
 use Psalm\Type\Union;
 
-use function array_merge;
-
 /**
  * Represents a closure where we know the return type and params
  *
@@ -131,6 +129,6 @@ public function replaceTemplateTypesWithStandins(
 
     protected function getChildNodeKeys(): array
     {
-        return array_merge(parent::getChildNodeKeys(), $this->getCallableChildNodeKeys());
+        return [...parent::getChildNodeKeys(), ...$this->getCallableChildNodeKeys()];
     }
 }
diff --git a/src/Psalm/Type/Atomic/TGenericObject.php b/src/Psalm/Type/Atomic/TGenericObject.php
index 45aa50b8cee..c362085f565 100644
--- a/src/Psalm/Type/Atomic/TGenericObject.php
+++ b/src/Psalm/Type/Atomic/TGenericObject.php
@@ -8,7 +8,6 @@
 use Psalm\Type\Atomic;
 use Psalm\Type\Union;
 
-use function array_merge;
 use function count;
 use function implode;
 use function strrpos;
@@ -127,7 +126,7 @@ public function getAssertionString(): string
 
     protected function getChildNodeKeys(): array
     {
-        return array_merge(parent::getChildNodeKeys(), ['type_params']);
+        return [...parent::getChildNodeKeys(), 'type_params'];
     }
 
     /**
diff --git a/src/Psalm/Type/Atomic/TValueOf.php b/src/Psalm/Type/Atomic/TValueOf.php
index 9220c079dee..59941bc61e5 100644
--- a/src/Psalm/Type/Atomic/TValueOf.php
+++ b/src/Psalm/Type/Atomic/TValueOf.php
@@ -42,8 +42,9 @@ private static function getValueTypeForNamedObject(array $cases, TNamedObject $a
         }
 
         return new Union(array_map(
-            function (EnumCaseStorage $case): Atomic {
-                assert($case->value !== null); // Backed enum must have a value
+            static function (EnumCaseStorage $case): Atomic {
+                assert($case->value !== null);
+                // Backed enum must have a value
                 return ConstantTypeResolver::getLiteralTypeFromScalarValue($case->value);
             },
             array_values($cases),
diff --git a/src/Psalm/Type/UnionTrait.php b/src/Psalm/Type/UnionTrait.php
index 3361c2ba873..a500789cf41 100644
--- a/src/Psalm/Type/UnionTrait.php
+++ b/src/Psalm/Type/UnionTrait.php
@@ -43,7 +43,6 @@
 use Psalm\Type\Atomic\TTrue;
 
 use function array_filter;
-use function array_merge;
 use function array_unique;
 use function count;
 use function get_class;
@@ -273,13 +272,13 @@ public function toNamespacedString(
         }
 
         if (count($literal_ints) <= 3 && !$has_non_literal_int) {
-            $other_types = array_merge($other_types, $literal_ints);
+            $other_types = [...$other_types, ...$literal_ints];
         } else {
             $other_types[] = 'int';
         }
 
         if (count($literal_strings) <= 3 && !$has_non_literal_string) {
-            $other_types = array_merge($other_types, $literal_strings);
+            $other_types = [...$other_types, ...$literal_strings];
         } else {
             $other_types[] = 'string';
         }
diff --git a/tests/AsyncTestCase.php b/tests/AsyncTestCase.php
index e9834d7af89..b459c42414b 100644
--- a/tests/AsyncTestCase.php
+++ b/tests/AsyncTestCase.php
@@ -152,7 +152,7 @@ public static function assertArrayKeysAreStrings(array $array, string $message =
      */
     public static function assertArrayKeysAreZeroOrString(array $array, string $message = ''): void
     {
-        $isZeroOrString = /** @param mixed $key */ fn($key): bool => $key === 0 || is_string($key);
+        $isZeroOrString = /** @param mixed $key */ static fn($key): bool => $key === 0 || is_string($key);
         $validKeys = array_filter($array, $isZeroOrString, ARRAY_FILTER_USE_KEY);
         self::assertTrue(count($array) === count($validKeys), $message);
     }
diff --git a/tests/CodebaseTest.php b/tests/CodebaseTest.php
index 81e7a7786b8..f5291649826 100644
--- a/tests/CodebaseTest.php
+++ b/tests/CodebaseTest.php
@@ -159,7 +159,7 @@ public static function afterClassLikeVisit(AfterClassLikeVisitEvent $event)
                         ? (string)$stmt->extends->getAttribute('resolvedName')
                         : '';
                     $storage->custom_metadata['implements'] = array_map(
-                        fn(Name $aspect): string => (string)$aspect->getAttribute('resolvedName'),
+                        static fn(Name $aspect): string => (string)$aspect->getAttribute('resolvedName'),
                         $stmt->implements,
                     );
                     $storage->custom_metadata['a'] = 'b';
diff --git a/tests/Config/ConfigTest.php b/tests/Config/ConfigTest.php
index 17d6a2e5c5e..88273122b36 100644
--- a/tests/Config/ConfigTest.php
+++ b/tests/Config/ConfigTest.php
@@ -1106,7 +1106,7 @@ public function testAllPossibleIssues(): void
                  * @param string $issue_name
                  * @return string
                  */
-                fn($issue_name): string => '<' . $issue_name . ' errorLevel="suppress" />' . "\n",
+                static fn($issue_name): string => '<' . $issue_name . ' errorLevel="suppress" />' . "\n",
                 IssueHandler::getAllIssueTypes(),
             ),
         );
diff --git a/tests/Config/Plugin/Hook/CustomArrayMapFunctionStorageProvider.php b/tests/Config/Plugin/Hook/CustomArrayMapFunctionStorageProvider.php
index a491d9ecf1b..87da0a93636 100644
--- a/tests/Config/Plugin/Hook/CustomArrayMapFunctionStorageProvider.php
+++ b/tests/Config/Plugin/Hook/CustomArrayMapFunctionStorageProvider.php
@@ -54,11 +54,10 @@ public static function getFunctionStorage(DynamicFunctionStorageProviderEvent $e
         $custom_array_map_storage->return_type = self::createReturnType($all_expected_callables);
         $custom_array_map_storage->params = [
             ...array_map(
-                function (TCallable $expected, int $offset) {
+                static function (TCallable $expected, int $offset) {
                     $t = new Union([$expected]);
                     $param = new FunctionLikeParameter('fn' . $offset, false, $t, $t);
                     $param->is_optional = false;
-
                     return $param;
                 },
                 $all_expected_callables,
diff --git a/tests/DocumentationTest.php b/tests/DocumentationTest.php
index 653e25f2004..26b734c803a 100644
--- a/tests/DocumentationTest.php
+++ b/tests/DocumentationTest.php
@@ -342,7 +342,7 @@ public function testShortcodesAreUnique(): void
 
         $duplicate_shortcodes = array_filter(
             $all_shortcodes,
-            fn($issues): bool => count($issues) > 1
+            static fn($issues): bool => count($issues) > 1
         );
 
         $this->assertEquals(
diff --git a/tests/FileDiffTest.php b/tests/FileDiffTest.php
index acc84f404bb..345e1d98b3b 100644
--- a/tests/FileDiffTest.php
+++ b/tests/FileDiffTest.php
@@ -62,7 +62,7 @@ public function testCode(
              * @param array{0: int, 1: int, 2: int, 3: int} $arr
              * @return array{0: int, 1: int}
              */
-            fn(array $arr): array => [$arr[2], $arr[3]],
+            static fn(array $arr): array => [$arr[2], $arr[3]],
             $diff[3],
         );
 
@@ -133,7 +133,7 @@ public function testPartialAstDiff(
              * @param array{0: int, 1: int, 2: int, 3: int} $arr
              * @return array{0: int, 1: int}
              */
-            fn(array $arr): array => [$arr[2], $arr[3]],
+            static fn(array $arr): array => [$arr[2], $arr[3]],
             $diff[3],
         );
 
diff --git a/tests/TaintTest.php b/tests/TaintTest.php
index faa299957d4..9f62160edb2 100644
--- a/tests/TaintTest.php
+++ b/tests/TaintTest.php
@@ -2528,7 +2528,7 @@ public function multipleTaintIssuesAreDetected(string $code, array $expectedIssu
         $this->analyzeFile($filePath, new Context(), false);
 
         $actualIssueTypes = array_map(
-            fn(IssueData $issue): string => $issue->type . '{ ' . trim($issue->snippet) . ' }',
+            static fn(IssueData $issue): string => $issue->type . '{ ' . trim($issue->snippet) . ' }',
             IssueBuffer::getIssuesDataForFile($filePath),
         );
         self::assertSame($expectedIssuesTypes, $actualIssueTypes);
diff --git a/tests/TestCase.php b/tests/TestCase.php
index 00739cbccb0..d0d285eb9e3 100644
--- a/tests/TestCase.php
+++ b/tests/TestCase.php
@@ -149,7 +149,7 @@ public static function assertArrayKeysAreStrings(array $array, string $message =
 
     public static function assertArrayKeysAreZeroOrString(array $array, string $message = ''): void
     {
-        $isZeroOrString = /** @param mixed $key */ fn($key): bool => $key === 0 || is_string($key);
+        $isZeroOrString = /** @param mixed $key */ static fn($key): bool => $key === 0 || is_string($key);
         $validKeys = array_filter($array, $isZeroOrString, ARRAY_FILTER_USE_KEY);
         self::assertTrue(count($array) === count($validKeys), $message);
     }
diff --git a/tests/TypeComparatorTest.php b/tests/TypeComparatorTest.php
index 6a2d093f511..0e21e5e7880 100644
--- a/tests/TypeComparatorTest.php
+++ b/tests/TypeComparatorTest.php
@@ -88,7 +88,7 @@ public function getAllBasicTypes(): array
         $basic_types['list{123}'] = true;
 
         return array_map(
-            fn($type) => [$type],
+            static fn($type) => [$type],
             array_keys($basic_types),
         );
     }
diff --git a/tests/fixtures/DestructiveAutoloader/autoloader.php b/tests/fixtures/DestructiveAutoloader/autoloader.php
index 17cb0a152c5..37a8624de36 100644
--- a/tests/fixtures/DestructiveAutoloader/autoloader.php
+++ b/tests/fixtures/DestructiveAutoloader/autoloader.php
@@ -9,7 +9,7 @@
     $GLOBALS[$key] = new Exception;
 }
 
-spl_autoload_register(function() {
+spl_autoload_register(static function () {
     // and destroy vars again
     // this will run during scanning (?)
     foreach ($GLOBALS as $key => $_) {
diff --git a/tests/fixtures/SuicidalAutoloader/autoloader.php b/tests/fixtures/SuicidalAutoloader/autoloader.php
index 365fa7b723e..d506219c141 100644
--- a/tests/fixtures/SuicidalAutoloader/autoloader.php
+++ b/tests/fixtures/SuicidalAutoloader/autoloader.php
@@ -3,7 +3,7 @@
 use React\Promise\PromiseInterface as ReactPromise;
 use Composer\InstalledVersions;
 
-spl_autoload_register(function (string $className) {
+spl_autoload_register(static function (string $className) {
     $knownBadClasses = [
         ReactPromise::class, // amphp/amp
         ResourceBundle::class, // symfony/polyfill-php73
@@ -25,11 +25,9 @@
         'Symfony\Component\String\s',
         'Symfony\Component\Translation\t',
     ];
-
     if (in_array($className, $knownBadClasses)) {
         return;
     }
-
     $ex = new RuntimeException('Attempted to load ' . $className);
     echo $ex->__toString() . "\n\n" . $ex->getTraceAsString() . "\n\n";
     exit(70);