Support arrays with union value-types in implode()

phpstan-baseline.neon

@@ -1362,11 +1362,6 @@ parameters:
 			count: 1
 			path: src/Type/Php/FunctionExistsFunctionTypeSpecifyingExtension.php
 
-		-
-			message: "#^Doing instanceof PHPStan\\\\Type\\\\ConstantScalarType is error\\-prone and deprecated\\. Use Type\\:\\:isConstantScalarValue\\(\\) or Type\\:\\:getConstantScalarTypes\\(\\) or Type\\:\\:getConstantScalarValues\\(\\) instead\\.$#"
-			count: 1
-			path: src/Type/Php/ImplodeFunctionReturnTypeExtension.php
-
 		-
 			message: """
 				#^Call to deprecated method getConstantScalars\\(\\) of class PHPStan\\\\Type\\\\TypeUtils\\:

src/Type/Php/ImplodeFunctionReturnTypeExtension.php

@@ -4,15 +4,16 @@
 
 use PhpParser\Node\Expr\FuncCall;
 use PHPStan\Analyser\Scope;
+use PHPStan\Internal\CombinationsHelper;
 use PHPStan\Reflection\FunctionReflection;
+use PHPStan\Reflection\InitializerExprTypeResolver;
 use PHPStan\Type\Accessory\AccessoryLiteralStringType;
 use PHPStan\Type\Accessory\AccessoryLowercaseStringType;
 use PHPStan\Type\Accessory\AccessoryNonEmptyStringType;
 use PHPStan\Type\Accessory\AccessoryNonFalsyStringType;
 use PHPStan\Type\Accessory\AccessoryUppercaseStringType;
 use PHPStan\Type\Constant\ConstantArrayType;
 use PHPStan\Type\Constant\ConstantStringType;
-use PHPStan\Type\ConstantScalarType;
 use PHPStan\Type\DynamicFunctionReturnTypeExtension;
 use PHPStan\Type\IntersectionType;
 use PHPStan\Type\StringType;
@@ -114,14 +115,28 @@ private function inferConstantType(ConstantArrayType $arrayType, ConstantStringT
 			$valueTypes = $array->getValueTypes();
 
 			$arrayValues = [];
+			$combinationsCount = 1;
 			foreach ($valueTypes as $valueType) {
-				if (!$valueType instanceof ConstantScalarType) {
+				$constScalars = $valueType->getConstantScalarValues();
+				if (count($constScalars) === 0) {
 					return null;
 				}
-				$arrayValues[] = $valueType->getValue();
+				$arrayValues[] = $constScalars;
+				$combinationsCount *= count($constScalars);
 			}
 
-			$strings[] = new ConstantStringType(implode($separatorType->getValue(), $arrayValues));
+			if ($combinationsCount > InitializerExprTypeResolver::CALCULATE_SCALARS_LIMIT) {
+				return null;
+			}
+
+			$combinations = CombinationsHelper::combinations($arrayValues);
+			foreach ($combinations as $combination) {
+				$strings[] = new ConstantStringType(implode($separatorType->getValue(), $combination));
+			}
+		}
+
+		if (count($strings) > InitializerExprTypeResolver::CALCULATE_SCALARS_LIMIT) {
+			return null;
 		}
 
 		return TypeCombinator::union(...$strings);

tests/PHPStan/Analyser/nsrt/bug-11854.php

@@ -0,0 +1,18 @@
+<?php declare(strict_types = 1);
+
+namespace Bug11854;
+
+use function PHPStan\Testing\assertType;
+
+class HelloWorld
+{
+	public function sayHello(): void
+	{
+		$arr = [];
+		$arr[] = rand(0,1) ? 'A' : 'B';
+		$arr[] = rand(0,1) ? 'C' : '';
+
+		assertType("array{'A'|'B', ''|'C'}", $arr);
+		assertType("'A '|'A C'|'B '|'B C'", implode(' ', $arr));
+	}
+}

tests/PHPStan/Analyser/nsrt/implode.php

@@ -21,4 +21,34 @@ public function constants() {
 		assertType("'x,345'", join(',', [self::X, '345']));
 		assertType("'1,345'", join(',', [self::ONE, '345']));
 	}
+
+	/** @param array{0: 1|2, 1: 'a'|'b'} $constArr */
+	public function constArrays($constArr) {
+		assertType("'1a'|'1b'|'2a'|'2b'", implode('', $constArr));
+	}
+
+	/** @param array{0: 1|2|3, 1: 'a'|'b'|'c'} $constArr */
+	public function constArrays2($constArr) {
+		assertType("'1a'|'1b'|'1c'|'2a'|'2b'|'2c'|'3a'|'3b'|'3c'", implode('', $constArr));
+	}
+
+	/** @param array{0: 1, 1: 'a'|'b', 2: 'x'|'y'} $constArr */
+	public function constArrays3($constArr) {
+		assertType("'1ax'|'1ay'|'1bx'|'1by'", implode('', $constArr));
+	}
+
+	/** @param array{0: 1, 1: 'a'|'b', 2?: 'x'|'y'} $constArr */
+	public function constArrays4($constArr) {
+		assertType("'1a'|'1ax'|'1ay'|'1b'|'1bx'|'1by'", implode('', $constArr));
+	}
+
+	/** @param array{10: 1|2|3, xy: 'a'|'b'|'c'} $constArr */
+	public function constArrays5($constArr) {
+		assertType("'1a'|'1b'|'1c'|'2a'|'2b'|'2c'|'3a'|'3b'|'3c'", implode('', $constArr));
+	}
+
+	/** @param array{0: 1, 1: 'a'|'b', 3?: 'c'|'d', 4?: 'e'|'f', 5?: 'g'|'h', 6?: 'x'|'y'} $constArr */
+	public function constArrays6($constArr) {
+		assertType("string", implode('', $constArr));
+	}
 }