allow marking enum cases as @deprecated

src/Psalm/Internal/Analyzer/Statements/Expression/Fetch/ClassConstFetchAnalyzer.php

@@ -218,6 +218,18 @@ class ClassConstFetchAnalyzer
             }
 
             $const_class_storage = $codebase->classlike_storage_provider->get($fq_class_name);
+            if ($const_class_storage->is_enum) {
+                $case = $const_class_storage->enum_cases[(string)$stmt->name] ?? null;
+                if ($case && $case->deprecated) {
+                    IssueBuffer::maybeAdd(
+                        new DeprecatedConstant(
+                            "Enum Case $const_id is marked as deprecated",
+                            new CodeLocation($statements_analyzer->getSource(), $stmt)
+                        ),
+                        $statements_analyzer->getSuppressedIssues()
+                    );
+                }
+            }
 
             if ($fq_class_name === $context->self
                 || (

src/Psalm/Internal/PhpVisitor/Reflector/ClassLikeNodeScanner.php

@@ -1345,10 +1345,20 @@ class ClassLikeNodeScanner
         $case_location = new CodeLocation($this->file_scanner, $stmt);
 
         if (!isset($storage->enum_cases[$stmt->name->name])) {
-            $storage->enum_cases[$stmt->name->name] = new EnumCaseStorage(
+            $case = new EnumCaseStorage(
                 $enum_value,
                 $case_location
             );
+
+            $comment = $stmt->getDocComment();
+            if ($comment) {
+                $comments = DocComment::parsePreservingLength($comment);
+
+                if (isset($comments->tags['deprecated'])) {
+                    $case->deprecated = true;
+                }
+            }
+            $storage->enum_cases[$stmt->name->name] = $case;
         } else {
             if (IssueBuffer::accepts(
                 new DuplicateEnumCase(

src/Psalm/Storage/EnumCaseStorage.php

@@ -14,6 +14,11 @@ class EnumCaseStorage
     /** @var CodeLocation */
     public $stmt_location;
 
+    /**
+     * @var bool
+     */
+    public $deprecated = false;
+
     /**
      * @param int|string|null  $value
      */

tests/DeprecatedAnnotationTest.php

@@ -251,6 +251,22 @@ class DeprecatedAnnotationTest extends TestCase
                     ',
                 'error_message' => 'DeprecatedProperty',
             ],
+            'deprecatedEnumCaseFetch' => [
+                '<?php
+                    enum Foo {
+                        case A;
+
+                        /** @deprecated */
+                        case B;
+                    }
+
+                    Foo::B;
+                ',
+                'error_message' => 'DeprecatedConstant',
+                [],
+                false,
+                '8.1',
+            ]
         ];
     }
 }