Implement AccessoryDecimalIntegerStringType::tryRemove() and preserve accessories when re-unioning '0'

phpstan-baseline.neon

@@ -777,6 +777,12 @@ parameters:
 			count: 1
 			path: src/Type/Accessory/AccessoryArrayListType.php
 
+		-
+			rawMessage: 'Doing instanceof PHPStan\Type\Constant\ConstantStringType is error-prone and deprecated. Use Type::getConstantStrings() instead.'
+			identifier: phpstanApi.instanceofType
+			count: 1
+			path: src/Type/Accessory/AccessoryDecimalIntegerStringType.php
+
 		-
 			rawMessage: Doing instanceof PHPStan\Type\IntersectionType is error-prone and deprecated.
 			identifier: phpstanApi.instanceofType
@@ -1662,7 +1668,7 @@ parameters:
 		-
 			rawMessage: Doing instanceof PHPStan\Type\IntersectionType is error-prone and deprecated.
 			identifier: phpstanApi.instanceofType
-			count: 6
+			count: 7
 			path: src/Type/TypeCombinator.php
 
 		-

src/Type/Accessory/AccessoryDecimalIntegerStringType.php

@@ -16,6 +16,7 @@
 use PHPStan\Type\Constant\ConstantArrayType;
 use PHPStan\Type\Constant\ConstantBooleanType;
 use PHPStan\Type\Constant\ConstantIntegerType;
+use PHPStan\Type\Constant\ConstantStringType;
 use PHPStan\Type\ErrorType;
 use PHPStan\Type\FloatType;
 use PHPStan\Type\GeneralizePrecision;
@@ -27,7 +28,6 @@
 use PHPStan\Type\Traits\NonGenericTypeTrait;
 use PHPStan\Type\Traits\NonIterableTypeTrait;
 use PHPStan\Type\Traits\NonObjectTypeTrait;
-use PHPStan\Type\Traits\NonRemoveableTypeTrait;
 use PHPStan\Type\Traits\UndecidedComparisonCompoundTypeTrait;
 use PHPStan\Type\Type;
 use PHPStan\Type\TypeCombinator;
@@ -55,7 +55,6 @@ class AccessoryDecimalIntegerStringType implements CompoundType, AccessoryType
 	use NonIterableTypeTrait;
 	use UndecidedComparisonCompoundTypeTrait;
 	use NonGenericTypeTrait;
-	use NonRemoveableTypeTrait;
 
 	/** @api */
 	public function __construct(private bool $inverse = false)
@@ -203,6 +202,19 @@ public function unsetOffset(Type $offsetType): Type
 		return new ErrorType();
 	}
 
+	public function tryRemove(Type $typeToRemove): ?Type
+	{
+		if ($this->inverse) {
+			return null;
+		}
+
+		if ($typeToRemove instanceof ConstantStringType && $typeToRemove->getValue() === '0') {
+			return new IntersectionType([new StringType(), $this, new AccessoryNonFalsyStringType()]);
+		}
+
+		return null;
+	}
+
 	public function toNumber(): Type
 	{
 		if ($this->inverse) {

src/Type/TypeCombinator.php

@@ -7,6 +7,7 @@
 use PHPStan\Type\Accessory\AccessoryDecimalIntegerStringType;
 use PHPStan\Type\Accessory\AccessoryLowercaseStringType;
 use PHPStan\Type\Accessory\AccessoryNonEmptyStringType;
+use PHPStan\Type\Accessory\AccessoryNonFalsyStringType;
 use PHPStan\Type\Accessory\AccessoryType;
 use PHPStan\Type\Accessory\AccessoryUppercaseStringType;
 use PHPStan\Type\Accessory\HasOffsetType;
@@ -600,13 +601,9 @@ private static function compareTypesInUnion(Type $a, Type $b): ?array
 			}
 
 			if ($a->getValue() === '0') {
-				$description = $b->describe(VerbosityLevel::value());
-				if ($description === 'non-falsy-string') {
-					return [null, new IntersectionType([
-						new StringType(),
-						new AccessoryNonEmptyStringType(),
-						...self::getAccessoryCaseStringTypes($b),
-					])];
+				$nonEmpty = self::downgradeNonFalsyStringToNonEmpty($b);
+				if ($nonEmpty !== null) {
+					return [null, $nonEmpty];
 				}
 			}
 		}
@@ -625,13 +622,9 @@ private static function compareTypesInUnion(Type $a, Type $b): ?array
 			}
 
 			if ($b->getValue() === '0') {
-				$description = $a->describe(VerbosityLevel::value());
-				if ($description === 'non-falsy-string') {
-					return [new IntersectionType([
-						new StringType(),
-						new AccessoryNonEmptyStringType(),
-						...self::getAccessoryCaseStringTypes($a),
-					]), null];
+				$nonEmpty = self::downgradeNonFalsyStringToNonEmpty($a);
+				if ($nonEmpty !== null) {
+					return [$nonEmpty, null];
 				}
 			}
 		}
@@ -673,6 +666,43 @@ private static function getAccessoryCaseStringTypes(Type $type): array
 		return $accessory;
 	}
 
+	/**
+	 * Turns a non-falsy-string type into its non-empty-string counterpart by
+	 * downgrading the non-falsy accessory while preserving every other accessory
+	 * (numeric-string, decimal-int-string, lowercase-string, …). Used to simplify
+	 * `'0' | non-falsy-string-X` back to `non-empty-string-X`, since `"0"` is the
+	 * only value that separates the two. Returns null when $type is not a
+	 * non-constant non-falsy-string built from an intersection.
+	 */
+	private static function downgradeNonFalsyStringToNonEmpty(Type $type): ?Type
+	{
+		if (!$type instanceof IntersectionType || $type->isNonFalsyString()->no()) {
+			return null;
+		}
+
+		$newTypes = [];
+		$found = false;
+		foreach ($type->getTypes() as $innerType) {
+			if ($innerType instanceof AccessoryNonFalsyStringType) {
+				$found = true;
+				continue;
+			}
+
+			$newTypes[] = $innerType;
+		}
+
+		if (!$found) {
+			return null;
+		}
+
+		$withoutNonFalsy = self::intersect(...$newTypes);
+		if ($withoutNonFalsy->isNonEmptyString()->yes()) {
+			return $withoutNonFalsy;
+		}
+
+		return self::intersect($withoutNonFalsy, new AccessoryNonEmptyStringType());
+	}
+
 	private static function removeDecimalIntStringAccessory(Type $type): Type
 	{
 		if (!$type instanceof IntersectionType) {

tests/PHPStan/Analyser/nsrt/decimal-int-string.php

@@ -55,4 +55,118 @@ public function emptyStringIsNonDecimal(string $s): void
 		}
 	}
 
+	/**
+	 * @param decimal-int-string $s
+	 */
+	public function removingZeroMakesNonFalsy(string $s): void
+	{
+		if ($s !== '0') {
+			assertType('decimal-int-string&non-falsy-string', $s);
+		} else {
+			assertType("'0'", $s);
+		}
+
+		if ($s != '0') {
+			assertType('decimal-int-string&non-falsy-string', $s);
+		}
+
+		if ($s) {
+			assertType('decimal-int-string&non-falsy-string', $s);
+		} else {
+			assertType("'0'", $s);
+		}
+	}
+
+	/**
+	 * @param numeric-string $s
+	 */
+	public function removingZeroMakesNumericNonFalsy(string $s): void
+	{
+		if ($s !== '0') {
+			assertType('non-falsy-string&numeric-string', $s);
+		} else {
+			assertType("'0'", $s);
+		}
+	}
+
+	/**
+	 * @param non-decimal-int-string $s
+	 */
+	public function removingZeroFromNonDecimal(string $s): void
+	{
+		// '0' is a decimal-int-string, so it is not part of non-decimal-int-string
+		if ($s !== '0') {
+			assertType('non-decimal-int-string', $s);
+		}
+	}
+
+	/**
+	 * @param decimal-int-string $s
+	 */
+	public function unionWithZeroRoundTrips(string $s): void
+	{
+		$t = $s !== '0' ? $s : '0';
+		assertType('decimal-int-string', $t);
+	}
+
+	/**
+	 * @param numeric-string $s
+	 */
+	public function numericUnionWithZeroRoundTrips(string $s): void
+	{
+		$t = $s !== '0' ? $s : '0';
+		assertType('numeric-string', $t);
+	}
+
+	/**
+	 * @param non-empty-string $s
+	 */
+	public function nonEmptyUnionWithZeroRoundTrips(string $s): void
+	{
+		$t = $s !== '0' ? $s : '0';
+		assertType('non-empty-string', $t);
+	}
+
+	/**
+	 * @param uppercase-string $s
+	 */
+	public function removingZeroFromUppercase(string $s): void
+	{
+		// '' is a falsy uppercase-string too, so removing '0' alone does not
+		// make an uppercase-string non-falsy.
+		if ($s !== '0') {
+			assertType('uppercase-string', $s);
+		}
+	}
+
+	/**
+	 * @param uppercase-string $s
+	 */
+	public function uppercaseUnionWithZeroRoundTrips(string $s): void
+	{
+		$t = $s !== '0' ? $s : '0';
+		assertType('uppercase-string', $t);
+	}
+
+	/**
+	 * @param lowercase-string $s
+	 */
+	public function removingZeroFromLowercase(string $s): void
+	{
+		// '' is a falsy lowercase-string too, so removing '0' alone does not
+		// make a lowercase-string non-falsy.
+		if ($s !== '0') {
+			assertType('lowercase-string', $s);
+		}
+	}
+
+	/**
+	 * @param lowercase-string $s
+	 */
+	public function lowercaseUnionWithZeroRoundTrips(string $s): void
+	{
+		$t = $s !== '0' ? $s : '0';
+		assertType('lowercase-string', $t);
+	}
+
 }