Infer mixed array shape merges

Use the generic key and value approximation when constant shapes are merged with generic arrays. Preserve the guaranteed array fallback for unioned constant shapes, with coverage for named, optional, numeric, and union cases.

Author: jbboehr

src/ArrayMergeType.php

@@ -200,7 +200,7 @@ protected function getResult(): Type
             return $builder->getArray();
         }
 
-        if ($nConstantLists + $nOtherArrays === count($this->types)) {
+        if ($nConstantArrays + $nOtherArrays === count($this->types)) {
             $allIntegerKeys = true;
             $atLeastOneNonEmpty = false;
             $combinedKeyType = null;
@@ -209,7 +209,7 @@ protected function getResult(): Type
             foreach ($this->types as $type) {
                 /** @TODO don't handle more than one atm */
                 if (count($type->getArrays()) !== 1) {
-                    return new MixedType();
+                    return new ArrayType(new MixedType(true), new MixedType(true));
                 }
 
                 if ($type->isIterableAtLeastOnce()->yes()) {

tests/ArrayMergeTypeNodeResolverExtensionTest.php

@@ -42,6 +42,7 @@ public static function dataFileProvider(): \Generator
         yield [__DIR__ . '/data/generic.php'];
         yield [__DIR__ . '/data/generic-constant-list.php'];
         yield [__DIR__ . '/data/generic-const.php'];
+        yield [__DIR__ . '/data/mixed-shapes.php'];
         yield [__DIR__ . '/data/mixed-lists.php'];
         yield [__DIR__ . '/data/multi-const-var.php'];
         yield [__DIR__ . '/data/nested.php'];

tests/data/mixed-shapes.php

@@ -0,0 +1,20 @@
+<?php
+
+namespace jbboehr\PHPStan\ArrayMerge\Tests\Data;
+
+use function PHPStan\Testing\assertType;
+
+/** @phpstan-var array-merge<array{fixed: int}, array<string, string>> $constantFirst */
+assertType('non-empty-array<string, int|string>', $constantFirst);
+
+/** @phpstan-var array-merge<array<string, string>, array{fixed: int}> $constantLast */
+assertType('non-empty-array<string, int|string>', $constantLast);
+
+/** @phpstan-var array-merge<array{fixed?: int}, array<string, string>> $possiblyEmpty */
+assertType('array<string, int|string>', $possiblyEmpty);
+
+/** @phpstan-var array-merge<array{2: int}, array<int, string>> $numericKeys */
+assertType('non-empty-list<int|string>', $numericKeys);
+
+/** @phpstan-var array-merge<array{a: int}|array{b: string}, array<string, bool>> $unionedShapes */
+assertType('array<mixed, mixed>', $unionedShapes);