Add @psalm-check-type and @psalm-check-type-exact.

config.xsd

@@ -193,6 +193,7 @@
             <xs:element name="AmbiguousConstantInheritance" type="ClassConstantIssueHandlerType" minOccurs="0" />
             <xs:element name="ArgumentTypeCoercion" type="ArgumentIssueHandlerType" minOccurs="0" />
             <xs:element name="AssignmentToVoid" type="IssueHandlerType" minOccurs="0" />
+            <xs:element name="CheckType" type="IssueHandlerType" minOccurs="0" />
             <xs:element name="CircularReference" type="IssueHandlerType" minOccurs="0" />
             <xs:element name="ComplexFunction" type="IssueHandlerType" minOccurs="0" />
             <xs:element name="ComplexMethod" type="IssueHandlerType" minOccurs="0" />

docs/annotating_code/supported_annotations.md

@@ -448,6 +448,31 @@ $username = $_GET['username']; // prints something like "test.php:4 $username: m
 
 *Note*: it throws [special low-level issue](../running_psalm/issues/Trace.md), so you have to set errorLevel to 1, override it in config or invoke Psalm with `--show-info=true`.
 
+### `@psalm-check-type`
+
+You can use this annotation to ensure the inferred type matches what you expect.
+
+```php
+<?php
+
+/** @psalm-check-type $foo = int */
+$foo = 1; // No issue
+
+/** @psalm-check-type $bar = int */
+$bar = "not-an-int"; // Checked variable $bar = int does not match $bar = 'not-an-int'
+```
+
+### `@psalm-check-type-exact`
+
+Like `@psalm-check-type`, but checks the exact type of the variable without allowing subtypes.
+
+```php
+<?php
+
+/** @psalm-check-type-exact $foo = int */
+$foo = 1; // Checked variable $foo = int does not match $foo = 1
+```
+
 ### `@psalm-taint-*`
 
 See [Security Analysis annotations](../security_analysis/annotations.md).

docs/running_psalm/issues.md

@@ -5,6 +5,7 @@
  - [AmbiguousConstantInheritance](issues/AmbiguousConstantInheritance.md)
  - [ArgumentTypeCoercion](issues/ArgumentTypeCoercion.md)
  - [AssignmentToVoid](issues/AssignmentToVoid.md)
+ - [CheckType](issues/CheckType.md)
  - [CircularReference](issues/CircularReference.md)
  - [ComplexFunction](issues/ComplexFunction.md)
  - [ComplexMethod](issues/ComplexMethod.md)

docs/running_psalm/issues/CheckType.md

@@ -0,0 +1,19 @@
+# CheckType
+
+Checks if a variable matches a specific type.
+Similar to [Trace](./Trace.md), but only shows if the type does not match the expected type.
+
+```php
+<?php
+
+/** @psalm-check-type $x = 1 */
+$x = 2; // Checked variable $x = 1 does not match $x = 2
+```
+
+
+```php
+<?php
+
+/** @psalm-check-type-exact $x = int */
+$x = 2; // Checked variable $x = int does not match $x = 2
+```

src/Psalm/DocComment.php

@@ -32,7 +32,7 @@ final class DocComment
         'yield', 'trace', 'import-type', 'flow', 'taint-specialize', 'taint-escape',
         'taint-unescape', 'self-out', 'consistent-constructor', 'stub-override',
         'require-extends', 'require-implements', 'param-out', 'ignore-var',
-        'consistent-templates', 'if-this-is', 'this-out'
+        'consistent-templates', 'if-this-is', 'this-out', 'check-type', 'check-type-exact',
     ];
 
     /**

src/Psalm/Internal/Analyzer/StatementsAnalyzer.php

@@ -10,6 +10,7 @@
 use Psalm\DocComment;
 use Psalm\Exception\DocblockParseException;
 use Psalm\Exception\IncorrectDocblockException;
+use Psalm\Exception\TypeParseTreeException;
 use Psalm\FileManipulation;
 use Psalm\Internal\Analyzer\Statements\Block\DoAnalyzer;
 use Psalm\Internal\Analyzer\Statements\Block\ForAnalyzer;
@@ -42,6 +43,8 @@
 use Psalm\Internal\Provider\NodeDataProvider;
 use Psalm\Internal\ReferenceConstraint;
 use Psalm\Internal\Scanner\ParsedDocblock;
+use Psalm\Internal\Type\Comparator\UnionTypeComparator;
+use Psalm\Issue\CheckType;
 use Psalm\Issue\ComplexFunction;
 use Psalm\Issue\ComplexMethod;
 use Psalm\Issue\InvalidDocblock;
@@ -64,9 +67,11 @@
 use function array_column;
 use function array_combine;
 use function array_keys;
+use function array_map;
 use function array_merge;
 use function array_search;
 use function count;
+use function explode;
 use function fwrite;
 use function get_class;
 use function in_array;
@@ -370,6 +375,7 @@ private static function analyzeStatement(
         $new_issues = null;
         $traced_variables = [];
 
+        $checked_types = [];
         if ($docblock = $stmt->getDocComment()) {
             $statements_analyzer->parseStatementDocblock($docblock, $stmt, $context);
 
@@ -387,6 +393,13 @@ private static function analyzeStatement(
                 }
             }
 
+            foreach ($statements_analyzer->parsed_docblock->tags['psalm-check-type'] ?? [] as $inexact_check) {
+                $checked_types[] = [$inexact_check, false];
+            }
+            foreach ($statements_analyzer->parsed_docblock->tags['psalm-check-type-exact'] ?? [] as $exact_check) {
+                $checked_types[] = [$exact_check, true];
+            }
+
             if (isset($statements_analyzer->parsed_docblock->tags['psalm-ignore-variable-method'])) {
                 $context->ignore_variable_method = $ignore_variable_method = true;
             }
@@ -660,6 +673,66 @@ private static function analyzeStatement(
             }
         }
 
+        foreach ($checked_types as [$check_type_line, $is_exact]) {
+            /** @var string|null $check_type_string (incorrectly inferred) */
+            [$checked_var, $check_type_string] = array_map('trim', explode('=', $check_type_line));
+
+            if ($check_type_string === null) {
+                IssueBuffer::maybeAdd(
+                    new InvalidDocblock(
+                        "Invalid format for @psalm-check-type" . ($is_exact ? "-exact" : ""),
+                        new CodeLocation($statements_analyzer->source, $stmt),
+                    ),
+                    $statements_analyzer->getSuppressedIssues(),
+                );
+            } else {
+                $checked_var_id = $checked_var;
+                $possibly_undefined = strrpos($checked_var_id, "?") === strlen($checked_var_id) - 1;
+                if ($possibly_undefined) {
+                    $checked_var_id = substr($checked_var_id, 0, strlen($checked_var_id) - 1);
+                }
+
+                if (!isset($context->vars_in_scope[$checked_var_id])) {
+                    IssueBuffer::maybeAdd(
+                        new InvalidDocblock(
+                            "Attempt to check undefined variable $checked_var_id",
+                            new CodeLocation($statements_analyzer->source, $stmt),
+                        ),
+                        $statements_analyzer->getSuppressedIssues(),
+                    );
+                } else {
+                    try {
+                        $checked_type = $context->vars_in_scope[$checked_var_id];
+                        $check_type = Type::parseString($check_type_string);
+                        $check_type->possibly_undefined = $possibly_undefined;
+
+                        if ($check_type->possibly_undefined !== $checked_type->possibly_undefined
+                            || !UnionTypeComparator::isContainedBy($codebase, $checked_type, $check_type)
+                            || ($is_exact && !UnionTypeComparator::isContainedBy($codebase, $check_type, $checked_type))
+                        ) {
+                            $check_var = $checked_var_id . ($checked_type->possibly_undefined ? "?" : "");
+                            IssueBuffer::maybeAdd(
+                                new CheckType(
+                                    "Checked variable $checked_var = {$check_type->getId()} does not match "
+                                        . "$check_var = {$checked_type->getId()}",
+                                    new CodeLocation($statements_analyzer->source, $stmt),
+                                ),
+                                $statements_analyzer->getSuppressedIssues(),
+                            );
+                        }
+                    } catch (TypeParseTreeException $e) {
+                        IssueBuffer::maybeAdd(
+                            new InvalidDocblock(
+                                $e->getMessage(),
+                                new CodeLocation($statements_analyzer->source, $stmt),
+                            ),
+                            $statements_analyzer->getSuppressedIssues(),
+                        );
+                    }
+                }
+            }
+        }
+
         return null;
     }
 

src/Psalm/Issue/CheckType.php

@@ -0,0 +1,9 @@
+<?php
+
+namespace Psalm\Issue;
+
+final class CheckType extends CodeIssue
+{
+    public const ERROR_LEVEL = 8;
+    public const SHORTCODE = 311;
+}

tests/CheckTypeTest.php

@@ -0,0 +1,74 @@
+<?php
+
+namespace Psalm\Tests;
+
+use Psalm\Tests\Traits\InvalidCodeAnalysisTestTrait;
+use Psalm\Tests\Traits\ValidCodeAnalysisTestTrait;
+
+class CheckTypeTest extends TestCase
+{
+    use InvalidCodeAnalysisTestTrait;
+    use ValidCodeAnalysisTestTrait;
+
+    /**
+     * @return iterable<string,array{code:string,assertions?:array<string,string>,ignored_issues?:list<string>,php_version?:string}>
+     */
+    public function providerValidCodeParse(): iterable
+    {
+        yield 'allowSubtype' => [
+            'code' => '<?php
+                /** @psalm-check-type $foo = int */
+                $foo = 1;
+            ',
+        ];
+    }
+
+    /**
+     * @return iterable<string,array{code:string,error_message:string,ignored_issues?:list<string>,php_version?:string}>
+     */
+    public function providerInvalidCodeParse(): iterable
+    {
+        yield 'checkType' => [
+            'code' => '<?php
+                $foo = 1;
+                /** @psalm-check-type $foo = 2 */;
+            ',
+            'error_message' => 'CheckType',
+        ];
+        yield 'checkTypeExact' => [
+            'code' => '<?php
+                /** @psalm-check-type-exact $foo = int */
+                $foo = 1;
+            ',
+            'error_message' => 'CheckType',
+        ];
+        yield 'checkMultipleTypesFirstCorrect' => [
+            'code' => '<?php
+                $foo = 1;
+                $bar = 2;
+                /**
+                 * @psalm-check-type $foo = 1
+                 * @psalm-check-type $bar = 3
+                 */;
+            ',
+            'error_message' => 'CheckType',
+        ];
+        yield 'possiblyUnset' => [
+            'code' => '<?php
+                try {
+                    $foo = 1;
+                } catch (Exception $_) {
+                }
+                /** @psalm-check-type $foo = 1 */;
+            ',
+            'error_message' => 'Checked variable $foo = 1 does not match $foo? = 1',
+        ];
+        yield 'notPossiblyUnset' => [
+            'code' => '<?php
+                $foo = 1;
+                /** @psalm-check-type $foo? = 1 */;
+            ',
+            'error_message' => 'Checked variable $foo? = 1 does not match $foo = 1',
+        ];
+    }
+}