Improve handling of coerced-to-array strings in array_splice

src/Psalm/Checker/Statements/Expression/CallChecker.php

@@ -391,6 +391,16 @@ class CallChecker
                 return false;
             }
 
+            if (isset($replacement_arg->inferredType)
+                && !$replacement_arg->inferredType->hasArray()
+                && $replacement_arg->inferredType->hasString()
+                && $replacement_arg->inferredType->isSingle()
+            ) {
+                $replacement_arg->inferredType = new Type\Union([
+                    new Type\Atomic\TArray([Type::getInt(), $replacement_arg->inferredType])
+                ]);
+            }
+
             if (isset($array_arg->inferredType)
                 && $array_arg->inferredType->hasArray()
                 && isset($replacement_arg->inferredType)
@@ -419,8 +429,18 @@ class CallChecker
                     $context,
                     false
                 );
+
+                return;
             }
 
+            ExpressionChecker::assignByRefParam(
+                $statements_checker,
+                $array_arg,
+                Type::getArray(),
+                $context,
+                false
+            );
+
             return;
         }
 

tests/FunctionCallTest.php

@@ -920,6 +920,14 @@ class FunctionCallTest extends TestCase
                     '$c' => 'array{0:int, 1:int, 2:int}',
                 ],
             ],
+            'arraySpliceOtherType' => [
+                '<?php
+                    $d = [["red"], ["green"], ["blue"]];
+                    array_splice($d, -1, 1, "foo");',
+                'assertions' => [
+                    '$d' => 'array<int, array{0:string}|string>',
+                ],
+            ],
         ];
     }