Removed TEmpty

docs/annotating_code/type_syntax/atomic_types.md

@@ -52,19 +52,20 @@ Atomic types are the basic building block of all type information used in Psalm.
 - `value-of<Foo\Bar::ARRAY_CONST>`
 - `T[K]`
 
-## Top types, bottom types and empty
+## Top types, bottom types
 
 ### `mixed`
 
 This is the _top type_ in PHP's type system, and represents a lack of type information. Psalm warns about `mixed` types when the `totallyTyped` flag is turned on, or when you're on level 1.
 
 ### `never`
+It can be aliased to `no-return` or `never-return` in docblocks. Note: it replaced the old `empty` type that used to exist in Psalm
 
-This is the _bottom type_ in PHP's type system, and usually represents a return type for a function that can never actually return, such as `die()`, `exit()`, or a function that always throws an exception. It may also be written in docblocks as `no-return` or `never-return`.
-
-### `empty`
-
-A type that's equivalent to a "coming soon" sign. Psalm uses this type when it’s awaiting more information — a good example is the type of the empty array `[]`, which Psalm types as `array<empty, empty>`. Psalm treats `empty` in a somewhat similar fashion to `never` when combining types together — `empty|int` becomes `int`, just as `never|string` becomes `string`.
+This is the _bottom type_ in PHP's type system. It's used to describe a type that has no possible value. It can happen in multiple cases:
+- the actual `never` type from PHP 8.1 (can be used in docblocks for older versions). This type can be used as a return type for functions that will never return, either because they always throw exceptions or always exit()
+- an union type that have been stripped for all its possible types. (For example, if a variable is `string|int` and we perform a is_bool() check in a condition, the type of the variable in the condition will be `never` as the condition will never be entered)
+- it can represent a placeholder for types yet to come — a good example is the type of the empty array `[]`, which Psalm types as `array<never, never>`, the content of the array is void so it can accept any content
+- it can also happen in the same context as the line above for templates that have yet to be defined
 
 ## Other
 

docs/running_psalm/plugins/plugins_type_system.md

@@ -27,16 +27,14 @@ The classes are as follows:
 
 `TNull` - denotes the `null` type
 
-`TNever` - denotes the `no-return`/`never-return` type for functions that never return, either throwing an exception or terminating (like the builtin `exit()`).
+`TNever` - denotes the `no-return`/`never-return` type for functions that never return, either throwing an exception or terminating (like the builtin `exit()`). Also used for union types that can have no possible types (impossible intersections for example).  Empty arrays `[]` have the type `array<never, never>`.
 
 `TMixed` - denotes the `mixed` type, used when you don’t know the type of an expression.
 
 `TNonEmptyMixed `- as above, but not empty. Generated for `$x` inside the `if` statement `if ($x) {...}` when `$x` is `mixed` outside.
 
 `TEmptyMixed` - as above, but empty. Generated for `$x` inside the `if` statement `if (!$x) {...}` when `$x` is `mixed` outside.
 
-`TEmpty` - denotes the `empty` type, used to describe a type corresponding to no value whatsoever. Empty arrays `[]` have the type `array<empty, empty>`.
-
 `TIterable` - denotes the [`iterable` type](https://www.php.net/manual/en/language.types.iterable.php) (which can also result from an `is_iterable` check).
 
 `TResource` - denotes the `resource` type (e.g. a file handle).

src/Psalm/Internal/Analyzer/ClassAnalyzer.php

@@ -1553,7 +1553,7 @@ private function checkForMissingPropertyType(
 
         if ($suggested_type && !$suggested_type->isNull()) {
             $message .= ' - consider ' . str_replace(
-                ['<array-key, mixed>', '<empty, empty>'],
+                ['<array-key, mixed>', '<never, never>'],
                 '',
                 (string)$suggested_type
             );

src/Psalm/Internal/Analyzer/ClassLikeAnalyzer.php

@@ -50,7 +50,7 @@ abstract class ClassLikeAnalyzer extends SourceAnalyzer
         'bool' => 'bool',
         'false' => 'false',
         'object' => 'object',
-        'empty' => 'empty',
+        'never' => 'never',
         'callable' => 'callable',
         'array' => 'array',
         'iterable' => 'iterable',

src/Psalm/Internal/Analyzer/FunctionLike/ReturnTypeAnalyzer.php

@@ -237,12 +237,12 @@ public static function verifyReturnType(
         }
 
         $number_of_types = count($inferred_return_type_parts);
-        // we filter TNever and TEmpty that have no bearing on the return type
+        // we filter TNever that have no bearing on the return type
         if ($number_of_types > 1) {
             $inferred_return_type_parts = array_filter(
                 $inferred_return_type_parts,
                 static function (Union $union_type): bool {
-                    return !($union_type->isNever() || $union_type->isEmpty());
+                    return !$union_type->isNever();
                 }
             );
         }
@@ -490,7 +490,7 @@ static function (Union $union_type): bool {
                 return null;
             }
 
-            if ($inferred_return_type->hasMixed() || $inferred_return_type->isEmpty()) {
+            if ($inferred_return_type->hasMixed()) {
                 if (IssueBuffer::accepts(
                     new MixedInferredReturnType(
                         'Could not verify return type \'' . $declared_return_type . '\' for ' .

src/Psalm/Internal/Analyzer/FunctionLikeAnalyzer.php

@@ -503,7 +503,7 @@ public function analyze(
                 && !$inferred_return_type->isSingleIntLiteral()
                 && !$inferred_return_type->isSingleStringLiteral()
                 && !$inferred_return_type->isTrue()
-                && $inferred_return_type->getId() !== 'array<empty, empty>'
+                && $inferred_return_type->getId() !== 'array<never, never>'
             ) {
                 $manipulator->makePure();
             }

src/Psalm/Internal/Analyzer/Statements/Block/ForeachAnalyzer.php

@@ -49,6 +49,7 @@
 use Psalm\Type\Atomic\TList;
 use Psalm\Type\Atomic\TMixed;
 use Psalm\Type\Atomic\TNamedObject;
+use Psalm\Type\Atomic\TNever;
 use Psalm\Type\Atomic\TNonEmptyArray;
 use Psalm\Type\Atomic\TNonEmptyList;
 use Psalm\Type\Atomic\TNull;
@@ -434,9 +435,7 @@ public static function checkIteratorType(
             }
 
             // if it's an empty array, we cannot iterate over it
-            if ($iterator_atomic_type instanceof TArray
-                && $iterator_atomic_type->type_params[1]->isEmpty()
-            ) {
+            if ($iterator_atomic_type instanceof TArray && $iterator_atomic_type->isEmptyArray()) {
                 $always_non_empty_array = false;
                 $has_valid_iterator = true;
                 continue;
@@ -505,7 +504,10 @@ public static function checkIteratorType(
                 $invalid_iterator_types[] = $iterator_atomic_type->getKey();
 
                 $value_type = Type::getMixed();
-            } elseif ($iterator_atomic_type instanceof TObject || $iterator_atomic_type instanceof TMixed) {
+            } elseif ($iterator_atomic_type instanceof TObject ||
+                $iterator_atomic_type instanceof TMixed ||
+                $iterator_atomic_type instanceof TNever
+            ) {
                 $has_valid_iterator = true;
                 $value_type = Type::getMixed();
                 $key_type = Type::getMixed();

src/Psalm/Internal/Analyzer/Statements/Block/SwitchAnalyzer.php

@@ -171,7 +171,7 @@ public static function analyze(
                     );
 
                 if (isset($case_vars_in_scope_reconciled[$switch_var_id])
-                    && $case_vars_in_scope_reconciled[$switch_var_id]->isEmpty()
+                    && $case_vars_in_scope_reconciled[$switch_var_id]->isNever()
                 ) {
                     $all_options_matched = true;
                 }

src/Psalm/Internal/Analyzer/Statements/Block/SwitchCaseAnalyzer.php

@@ -591,7 +591,7 @@ private static function handleNonReturningCase(
         if (!$case->cond
             && $switch_var_id
             && isset($case_context->vars_in_scope[$switch_var_id])
-            && $case_context->vars_in_scope[$switch_var_id]->isEmpty()
+            && $case_context->vars_in_scope[$switch_var_id]->isNever()
         ) {
             if (IssueBuffer::accepts(
                 new ParadoxicalCondition(

src/Psalm/Internal/Analyzer/Statements/Expression/ArrayAnalyzer.php

@@ -547,7 +547,7 @@ private static function handleUnpackedArray(
                         && count($unpacked_atomic_type->type_params) === 2
                 )) {
                     /** @psalm-suppress PossiblyUndefinedArrayOffset provably true, but Psalm can’t see it */
-                    if ($unpacked_atomic_type->type_params[1]->isEmpty()) {
+                    if ($unpacked_atomic_type->type_params[1]->isNever()) {
                         continue;
                     }
                     $array_creation_info->can_create_objectlike = false;
@@ -579,7 +579,7 @@ private static function handleUnpackedArray(
                         )
                     );
                 } elseif ($unpacked_atomic_type instanceof TList) {
-                    if ($unpacked_atomic_type->type_param->isEmpty()) {
+                    if ($unpacked_atomic_type->type_param->isNever()) {
                         continue;
                     }
                     $array_creation_info->can_create_objectlike = false;

src/Psalm/Internal/Analyzer/Statements/Expression/Assignment/ArrayAssignmentAnalyzer.php

@@ -739,7 +739,7 @@ private static function analyzeNestedArrayAssignment(
                 return;
             }
 
-            if ($child_stmt_var_type->isEmpty()) {
+            if ($child_stmt_var_type->isNever()) {
                 $child_stmt_var_type = Type::getEmptyArray();
                 $statements_analyzer->node_data->setType($child_stmt->var, $child_stmt_var_type);
             }

src/Psalm/Internal/Analyzer/Statements/Expression/AssignmentAnalyzer.php

@@ -569,7 +569,7 @@ public static function analyze(
                     return false;
                 }
 
-                $context->vars_in_scope[$var_id] = Type::getEmpty();
+                $context->vars_in_scope[$var_id] = Type::getNever();
 
                 $context->inside_assignment = $was_in_assignment;
 
@@ -1024,11 +1024,11 @@ public static function assignByRefParam(
                     $by_ref_out_type->parent_nodes += $existing_type->parent_nodes;
                 }
 
-                if ($existing_type->getId() !== 'array<empty, empty>') {
+                if ($existing_type->getId() !== 'array<never, never>') {
                     $context->vars_in_scope[$var_id] = $by_ref_out_type;
 
                     if (!($stmt_type = $statements_analyzer->node_data->getType($stmt))
-                        || $stmt_type->isEmpty()
+                        || $stmt_type->isNever()
                     ) {
                         $statements_analyzer->node_data->setType($stmt, clone $by_ref_type);
                     }
@@ -1043,7 +1043,7 @@ public static function assignByRefParam(
 
             $stmt_type = $statements_analyzer->node_data->getType($stmt);
 
-            if (!$stmt_type || $stmt_type->isEmpty()) {
+            if (!$stmt_type || $stmt_type->isNever()) {
                 $statements_analyzer->node_data->setType($stmt, clone $by_ref_type);
             }
 

src/Psalm/Internal/Analyzer/Statements/Expression/BinaryOp/ArithmeticOpAnalyzer.php

@@ -75,9 +75,9 @@ public static function analyze(
         $right_type = $nodes->getType($right);
         $config = Config::getInstance();
 
-        if ($left_type && $left_type->isEmpty()) {
+        if ($left_type && $left_type->isNever()) {
             $left_type = $right_type;
-        } elseif ($right_type && $right_type->isEmpty()) {
+        } elseif ($right_type && $right_type->isNever()) {
             $right_type = $left_type;
         }
 
@@ -896,7 +896,7 @@ public static function arithmeticOperation(
             $result = $operand1 - $operand2;
         } elseif ($operation instanceof PhpParser\Node\Expr\BinaryOp\Mod) {
             if ($operand2 === 0) {
-                return Type::getEmpty();
+                return Type::getNever();
             }
 
             $result = $operand1 % $operand2;
@@ -916,7 +916,7 @@ public static function arithmeticOperation(
             $result = $operand1 >> $operand2;
         } elseif ($operation instanceof PhpParser\Node\Expr\BinaryOp\Div) {
             if ($operand2 === 0) {
-                return Type::getEmpty();
+                return Type::getNever();
             }
 
             $result = $operand1 / $operand2;
@@ -1269,9 +1269,11 @@ private static function analyzePowBetweenIntRange(
                 $new_result_type = Type::getInt(true, 0);
             } elseif ($right_type_part->min_bound === 0 && $right_type_part->max_bound === 0) {
                 $new_result_type = Type::getInt(true, 1);
+            } elseif ($right_type_part->isNegative()) {
+                $new_result_type = Type::getFloat();
             } else {
-                //technically could be a float(INF)...
-                $new_result_type = Type::getEmpty();
+                $new_result_type = new Union([new TFloat(), new TLiteralInt(0), new TLiteralInt(1)]);
+                $new_result_type->from_calculation = true;
             }
         } else {
             //$left_type_part may be a mix of positive, negative and 0
@@ -1305,7 +1307,7 @@ private static function analyzeModBetweenIntRange(
         if ($right_type_part->min_bound !== null && $right_type_part->min_bound === $right_type_part->max_bound) {
             //if the second operand is a literal, we can be pretty detailed
             if ($right_type_part->max_bound === 0) {
-                $new_result_type = Type::getEmpty();
+                $new_result_type = Type::getNever();
             } else {
                 if ($left_type_part->isPositiveOrZero()) {
                     if ($right_type_part->isPositive()) {

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

@@ -1360,7 +1360,7 @@ private static function coerceValueAfterGatekeeperArgument(
                             && $input_atomic_type->value === $param_atomic_type->value
                         ) {
                             foreach ($input_atomic_type->type_params as $i => $type_param) {
-                                if ($type_param->isEmpty() && isset($param_atomic_type->type_params[$i])) {
+                                if ($type_param->isNever() && isset($param_atomic_type->type_params[$i])) {
                                     $input_type_changed = true;
 
                                     $input_atomic_type->type_params[$i] = clone $param_atomic_type->type_params[$i];

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

@@ -1207,7 +1207,7 @@ private static function evaluateArbitraryParam(
                 );
 
                 foreach ($context->vars_in_scope[$var_id]->getAtomicTypes() as $type) {
-                    if ($type instanceof TArray && $type->type_params[1]->isEmpty()) {
+                    if ($type instanceof TArray && $type->isEmptyArray()) {
                         $context->vars_in_scope[$var_id]->removeType('array');
                         $context->vars_in_scope[$var_id]->addType(
                             new TArray(

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

@@ -33,9 +33,9 @@
 use Psalm\Type\Atomic\TArray;
 use Psalm\Type\Atomic\TCallable;
 use Psalm\Type\Atomic\TClosure;
-use Psalm\Type\Atomic\TEmpty;
 use Psalm\Type\Atomic\TKeyedArray;
 use Psalm\Type\Atomic\TList;
+use Psalm\Type\Atomic\TNever;
 use Psalm\Type\Atomic\TNonEmptyArray;
 use Psalm\Type\Atomic\TNonEmptyList;
 use Psalm\Type\Union;
@@ -544,8 +544,8 @@ public static function handleByRefArrayAdjustment(
                             if ($array_atomic_type->count === 0) {
                                 $array_atomic_type = new TArray(
                                     [
-                                        new Union([new TEmpty]),
-                                        new Union([new TEmpty]),
+                                        new Union([new TNever]),
+                                        new Union([new TNever]),
                                     ]
                                 );
                             } else {
@@ -561,8 +561,8 @@ public static function handleByRefArrayAdjustment(
                             if ($array_atomic_type->count === 0) {
                                 $array_atomic_type = new TArray(
                                     [
-                                        new Union([new TEmpty]),
-                                        new Union([new TEmpty]),
+                                        new Union([new TNever]),
+                                        new Union([new TNever]),
                                     ]
                                 );
                             } else {

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

@@ -144,7 +144,7 @@ public static function fetch(
                                 $template_result->lower_bounds[$template_name] = [
                                     'fn-' . $function_id => [
                                         new TemplateBound(
-                                            Type::getEmpty()
+                                            Type::getNever()
                                         )
                                     ]
                                 ];
@@ -390,14 +390,13 @@ private static function getReturnTypeFromCallMapWithArgs(
                                     foreach ($atomic_types['array']->properties as $property) {
                                         // empty, never and possibly undefined can't count for min value
                                         if (!$property->possibly_undefined
-                                            && !$property->isEmpty()
                                             && !$property->isNever()
                                         ) {
                                             $min++;
                                         }
 
-                                        //empty and never can't count for max value because we know keys are undefined
-                                        if (!$property->isEmpty() && !$property->isNever()) {
+                                        //never can't count for max value because we know keys are undefined
+                                        if (!$property->isNever()) {
                                             $max++;
                                         }
                                     }
@@ -416,8 +415,7 @@ private static function getReturnTypeFromCallMapWithArgs(
                                 }
 
                                 if ($atomic_types['array'] instanceof TArray
-                                    && $atomic_types['array']->type_params[0]->isEmpty()
-                                    && $atomic_types['array']->type_params[1]->isEmpty()
+                                    && $atomic_types['array']->isEmptyArray()
                                 ) {
                                     return Type::getInt(false, 0);
                                 }

src/Psalm/Internal/Analyzer/Statements/Expression/Call/Method/AtomicMethodCallAnalyzer.php

@@ -27,12 +27,12 @@
 use Psalm\Storage\ClassLikeStorage;
 use Psalm\Type;
 use Psalm\Type\Atomic;
-use Psalm\Type\Atomic\TEmpty;
 use Psalm\Type\Atomic\TEmptyMixed;
 use Psalm\Type\Atomic\TFalse;
 use Psalm\Type\Atomic\TGenericObject;
 use Psalm\Type\Atomic\TMixed;
 use Psalm\Type\Atomic\TNamedObject;
+use Psalm\Type\Atomic\TNever;
 use Psalm\Type\Atomic\TNonEmptyMixed;
 use Psalm\Type\Atomic\TNull;
 use Psalm\Type\Atomic\TObject;
@@ -571,7 +571,7 @@ private static function handleInvalidClass(
 
             case TTemplateParam::class:
             case TEmptyMixed::class:
-            case TEmpty::class:
+            case TNever::class:
             case TMixed::class:
             case TNonEmptyMixed::class:
             case TObject::class:

src/Psalm/Internal/Analyzer/Statements/Expression/Call/Method/MethodCallReturnTypeFetcher.php

@@ -588,7 +588,7 @@ public static function replaceTemplateTypes(
                     } else {
                         $template_result->lower_bounds[$template_type->param_name] = [
                             ($template_type->defining_class) => [
-                                new TemplateBound(Type::getEmpty())
+                                new TemplateBound(Type::getNever())
                             ]
                         ];
                     }

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

@@ -516,7 +516,7 @@ function ($bounds) use ($codebase) {
                         );
                     } else {
                         if ($fq_class_name === 'SplObjectStorage') {
-                            $generic_param_type = Type::getEmpty();
+                            $generic_param_type = Type::getNever();
                         } else {
                             $generic_param_type = clone array_values($base_type)[0];
                         }