Fix #2560 - handle special case of array_filter on single-element array

vimeo · Jan 11, 2020 · bd84612 · bd84612
1 parent 40406c7
commit bd84612
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diff --git a/src/Psalm/Internal/Provider/ReturnTypeProvider/ArrayFilterReturnTypeProvider.php b/src/Psalm/Internal/Provider/ReturnTypeProvider/ArrayFilterReturnTypeProvider.php
@@ -77,6 +77,18 @@ public static function getFunctionReturnType(
                 $statements_source->getSuppressedIssues()
             );
 
+            if ($first_arg_array instanceof Type\Atomic\ObjectLike
+                && $first_arg_array->is_list
+                && $key_type->isSingleIntLiteral()
+                && $key_type->getSingleIntLiteral()->value === 0
+            ) {
+                return new Type\Union([
+                    new Type\Atomic\TList(
+                        $inner_type,
+                    ),
+                ]);
+            }
+
             if ($key_type->getLiteralStrings()) {
                 $key_type->addType(new Type\Atomic\TString);
             }

diff --git a/tests/FunctionCallTest.php b/tests/FunctionCallTest.php
@@ -2422,6 +2422,13 @@ function getCharPairs(string $line) : array {
                     '$array' => 'list<int>',
                 ],
             ],
+            'specialCaseArrayFilterOnSingleEntry' => [
+                '<?php
+                    /** @psalm-return list<int> */
+                    function makeAList(int $ofThisInteger): array {
+                        return array_filter([$ofThisInteger]);
+                    }'
+            ],
         ];
     }