From 85f2083acb7dcb09d636baae3912cdb6bb7e9c2d Mon Sep 17 00:00:00 2001
From: Bruce Weirdan <weirdan@gmail.com>
Date: Thu, 11 Nov 2021 00:44:17 +0200
Subject: [PATCH] Flag duplicate constants

Fixes vimeo/psalm#6882
Addresses p1 from vimeo/psalm#6471
---
 config.xsd                                    |  1 +
 docs/running_psalm/issues.md                  |  1 +
 .../running_psalm/issues/DuplicateConstant.md | 16 +++++++++
 .../Reflector/ClassLikeNodeScanner.php        | 25 ++++++++++++++
 src/Psalm/Issue/DuplicateConstant.php         |  9 +++++
 tests/ConstantTest.php                        | 33 +++++++++++++++++++
 6 files changed, 85 insertions(+)
 create mode 100644 docs/running_psalm/issues/DuplicateConstant.md
 create mode 100644 src/Psalm/Issue/DuplicateConstant.php

diff --git a/config.xsd b/config.xsd
index 9682ba657..ab37ca2dc 100644
--- a/config.xsd
+++ b/config.xsd
@@ -240,6 +240,7 @@
             <xs:element name="DocblockTypeContradiction" type="IssueHandlerType" minOccurs="0" />
             <xs:element name="DuplicateArrayKey" type="IssueHandlerType" minOccurs="0" />
             <xs:element name="DuplicateClass" type="IssueHandlerType" minOccurs="0" />
+            <xs:element name="DuplicateConstant" type="ClassIssueHandlerType" minOccurs="0" />
             <xs:element name="DuplicateEnumCase" type="ClassIssueHandlerType" minOccurs="0" />
             <xs:element name="DuplicateEnumCaseValue" type="ClassIssueHandlerType" minOccurs="0" />
             <xs:element name="DuplicateFunction" type="IssueHandlerType" minOccurs="0" />
diff --git a/docs/running_psalm/issues.md b/docs/running_psalm/issues.md
index 7e986f76d..43838dafc 100644
--- a/docs/running_psalm/issues.md
+++ b/docs/running_psalm/issues.md
@@ -20,6 +20,7 @@
  - [DocblockTypeContradiction](issues/DocblockTypeContradiction.md)
  - [DuplicateArrayKey](issues/DuplicateArrayKey.md)
  - [DuplicateClass](issues/DuplicateClass.md)
+ - [DuplicateConstant](issues/DuplicateConstant.md)
  - [DuplicateFunction](issues/DuplicateFunction.md)
  - [DuplicateMethod](issues/DuplicateMethod.md)
  - [DuplicateParam](issues/DuplicateParam.md)
diff --git a/docs/running_psalm/issues/DuplicateConstant.md b/docs/running_psalm/issues/DuplicateConstant.md
new file mode 100644
index 000000000..44a2d0b51
--- /dev/null
+++ b/docs/running_psalm/issues/DuplicateConstant.md
@@ -0,0 +1,16 @@
+# DuplicateConstant
+
+Emitted when a constant is defined twice in a single class or when there's a
+clash between a constant and an enum case.
+
+```php
+<?php
+class C {
+    public const A = 1;
+    public const A = 2;
+}
+```
+
+## Why this is bad
+
+The above code won’t compile.
diff --git a/src/Psalm/Internal/PhpVisitor/Reflector/ClassLikeNodeScanner.php b/src/Psalm/Internal/PhpVisitor/Reflector/ClassLikeNodeScanner.php
index e32b945ce..bb39e3af3 100644
--- a/src/Psalm/Internal/PhpVisitor/Reflector/ClassLikeNodeScanner.php
+++ b/src/Psalm/Internal/PhpVisitor/Reflector/ClassLikeNodeScanner.php
@@ -28,6 +28,7 @@ use Psalm\Internal\Type\TypeAlias;
 use Psalm\Internal\Type\TypeParser;
 use Psalm\Internal\Type\TypeTokenizer;
 use Psalm\Issue\DuplicateClass;
+use Psalm\Issue\DuplicateConstant;
 use Psalm\Issue\DuplicateEnumCase;
 use Psalm\Issue\InvalidDocblock;
 use Psalm\Issue\InvalidEnumBackingType;
@@ -1193,6 +1194,19 @@ class ClassLikeNodeScanner
                 $fq_classlike_name
             );
 
+            if (isset($storage->constants[$const->name->name])
+                || isset($storage->enum_cases[$const->name->name])
+            ) {
+                if (IssueBuffer::accepts(new DuplicateConstant(
+                    'Constant names should be unique',
+                    new CodeLocation($this->file_scanner, $const),
+                    $fq_classlike_name
+                ))) {
+                    // fall through
+                }
+                continue;
+            }
+
             $storage->constants[$const->name->name] = $constant_storage = new \Psalm\Storage\ClassConstantStorage(
                 $const_type,
                 $stmt->isProtected()
@@ -1271,6 +1285,17 @@ class ClassLikeNodeScanner
         ClassLikeStorage $storage,
         string $fq_classlike_name
     ): void {
+        if (isset($storage->constants[$stmt->name->name])) {
+            if (IssueBuffer::accepts(new DuplicateConstant(
+                'Constant names should be unique',
+                new CodeLocation($this->file_scanner, $stmt),
+                $fq_classlike_name
+            ))) {
+                // fall through
+            }
+            return;
+        }
+
         $enum_value = null;
 
         if ($stmt->expr !== null) {
diff --git a/src/Psalm/Issue/DuplicateConstant.php b/src/Psalm/Issue/DuplicateConstant.php
new file mode 100644
index 000000000..73783e321
--- /dev/null
+++ b/src/Psalm/Issue/DuplicateConstant.php
@@ -0,0 +1,9 @@
+<?php
+
+namespace Psalm\Issue;
+
+class DuplicateConstant extends ClassIssue
+{
+    public const ERROR_LEVEL = -1;
+    public const SHORTCODE = 302;
+}
diff --git a/tests/ConstantTest.php b/tests/ConstantTest.php
index 378f61337..6daedba4b 100644
--- a/tests/ConstantTest.php
+++ b/tests/ConstantTest.php
@@ -1430,6 +1430,39 @@ class ConstantTest extends TestCase
                     }',
                 'error_message' => 'UndefinedClass',
             ],
+            'duplicateConstants' => [
+                '<?php
+                    class A {
+                        public const B = 1;
+                        public const B = 2;
+                    }
+                ',
+                'error_message' => 'DuplicateConstant',
+            ],
+            'constantDuplicatesEnumCase' => [
+                '<?php
+                    enum State {
+                        case Open;
+                        public const Open = 1;
+                    }
+                ',
+                'error_message' => 'DuplicateConstant',
+                [],
+                false,
+                '8.1',
+            ],
+            'enumCaseDuplicatesConstant' => [
+                '<?php
+                    enum State {
+                        public const Open = 1;
+                        case Open;
+                    }
+                ',
+                'error_message' => 'DuplicateConstant',
+                [],
+                false,
+                '8.1',
+            ],
         ];
     }
 }