More precise MixedType::toString() with subtracted type

Author: staabm

src/Type/MixedType.php

@@ -27,7 +27,9 @@
 use PHPStan\Type\Accessory\OversizedArrayType;
 use PHPStan\Type\Constant\ConstantArrayType;
 use PHPStan\Type\Constant\ConstantBooleanType;
+use PHPStan\Type\Constant\ConstantFloatType;
 use PHPStan\Type\Constant\ConstantIntegerType;
+use PHPStan\Type\Constant\ConstantStringType;
 use PHPStan\Type\Generic\TemplateMixedType;
 use PHPStan\Type\Generic\TemplateType;
 use PHPStan\Type\Traits\NonGeneralizableTypeTrait;
@@ -504,7 +506,7 @@ public function toInteger(): Type
 			new ConstantIntegerType(0),
 			new ConstantArrayType([], []),
 			new StringType(),
-			new FloatType(),
+			new FloatType(), // every 0.x float casts to int(0)
 		]);
 		if (
 			$this->subtractedType !== null
@@ -526,6 +528,32 @@ public function toFloat(): Type
 
 	public function toString(): Type
 	{
+		if ($this->subtractedType !== null) {
+			$castsToEmptyString = new UnionType([
+				new NullType(),
+				new ConstantBooleanType(false),
+				new ConstantStringType(''),
+			]);
+			if ($this->subtractedType->isSuperTypeOf($castsToEmptyString)->yes()) {
+				$accessories = [
+					new StringType(),
+					new AccessoryNonEmptyStringType(),
+				];
+
+				$castsToZeroString = new UnionType([
+					new ConstantFloatType(0.0),
+					new ConstantStringType('0'),
+					new ConstantIntegerType(0),
+				]);
+				if ($this->subtractedType->isSuperTypeOf($castsToZeroString)->yes()) {
+					$accessories[] = new AccessoryNonFalsyStringType();
+				}
+				return new IntersectionType(
+					$accessories,
+				);
+			}
+		}
+
 		return new StringType();
 	}
 

tests/PHPStan/Analyser/nsrt/non-empty-string.php

@@ -408,4 +408,40 @@ function multiplesPrintfFormats(string $s) {
 		assertType('non-empty-string', sprintf($nonEmpty, $s));
 		assertType('non-falsy-string', sprintf($nonFalsy, $s));
 	}
+
+	function subtract($m) {
+		if ($m) {
+			assertType("mixed~(0|0.0|''|'0'|array{}|false|null)", $m);
+			assertType('non-falsy-string', (string) $m);
+		}
+		if ($m != '') {
+			assertType("mixed", $m);
+			assertType('string', (string) $m);
+		}
+		if ($m !== '') {
+			assertType("mixed~''", $m);
+			assertType('string', (string) $m);
+		}
+		if (!is_string($m)) {
+			assertType("mixed~string", $m);
+			assertType('string', (string) $m);
+		}
+
+		if ($m !== true) {
+			assertType("mixed~true", $m);
+			assertType('string', (string) $m);
+		}
+		if ($m !== false) {
+			assertType("mixed~false", $m);
+			assertType('string', (string) $m);
+		}
+		if ($m !== false && $m !== '' && $m !== null) {
+			assertType("mixed~(''|false|null)", $m);
+			assertType('non-empty-string', (string) $m);
+		}
+		if (!is_bool($m) && $m !== '' && $m !== null) {
+			assertType("mixed~(''|bool|null)", $m);
+			assertType('non-empty-string', (string) $m);
+		}
+	}
 }