Prevent illegal array keys (#4660)

* Emit an issue when an array-key is not legal

* tests

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

@@ -7,6 +7,7 @@ use Psalm\Internal\Analyzer\StatementsAnalyzer;
 use Psalm\CodeLocation;
 use Psalm\Context;
 use Psalm\Issue\DuplicateArrayKey;
+use Psalm\Issue\InvalidArrayOffset;
 use Psalm\IssueBuffer;
 use Psalm\Type;
 use Psalm\Internal\Type\TypeCombiner;
@@ -356,6 +357,30 @@ class ArrayAnalyzer
             return true;
         }
 
+        if ($item_key_type) {
+            foreach ($item_key_type->getAtomicTypes() as $atomic_key_type) {
+                if (!$atomic_key_type instanceof Type\Atomic\TString &&
+                    !$atomic_key_type instanceof Type\Atomic\TInt &&
+                    !$atomic_key_type instanceof Type\Atomic\TArrayKey &&
+                    !$atomic_key_type instanceof Type\Atomic\TMixed &&
+                    !(
+                        $atomic_key_type instanceof Type\Atomic\TObjectWithProperties &&
+                        isset($atomic_key_type->methods['__toString'])
+                    )
+                ) {
+                    if (IssueBuffer::accepts(
+                        new InvalidArrayOffset(
+                            'Cannot create offset of type ' . $item_key_type->getKey() . ', expecting array-key',
+                            new CodeLocation($statements_analyzer->getSource(), $stmt)
+                        ),
+                        $statements_analyzer->getSuppressedIssues()
+                    )) {
+                        $item_key_type = Type::getArrayKey();
+                    }
+                }
+            }
+        }
+
         $array_type = new Type\Atomic\TNonEmptyArray([
             $item_key_type && !$item_key_type->hasMixed() ? $item_key_type : Type::getArrayKey(),
             $item_value_type ?: Type::getMixed(),

tests/ArrayAssignmentTest.php

@@ -2,6 +2,7 @@
 namespace Psalm\Tests;
 
 use Psalm\Context;
+use Psalm\Issue\InvalidArrayOffset;
 
 class ArrayAssignmentTest extends TestCase
 {
@@ -1548,7 +1549,20 @@ class ArrayAssignmentTest extends TestCase
                 {
                     return [...$data];
                 }'
-            ]
+            ],
+            'ArrayCreateOffsetStringable' => [
+                '<?php
+                    $a = new class{public function __toString(){return "";}};
+                    $_a = [$a => "a"];
+                ',
+            ],
+            'ArrayCreateOffsetMixed' => [
+                '<?php
+                    /** @var mixed $b */
+                    $b = "";
+                    $_a = [$b => "a"];
+                ',
+            ],
         ];
     }
 
@@ -1851,7 +1865,25 @@ class ArrayAssignmentTest extends TestCase
                     return [...$data];
                 }',
                 'error_message' => 'DuplicateArrayKey'
-            ]
+            ],
+            'ArrayCreateOffsetObject' => [
+                '<?php
+                    $_a = [new stdClass => "a"];
+                ',
+                'error_message' => 'InvalidArrayOffset'
+            ],
+            'ArrayCreateOffsetResource' => [
+                '<?php
+                    $_a = [fopen("", "") => "a"];
+                ',
+                'error_message' => 'InvalidArrayOffset'
+            ],
+            'ArrayCreateOffsetBool' => [
+                '<?php
+                    $_a = [true => "a"];
+                ',
+                'error_message' => 'InvalidArrayOffset'
+            ],
         ];
     }
 }