Fix ConstantFloatType::toString

src/Type/Constant/ConstantFloatType.php

@@ -11,6 +11,7 @@
 use PHPStan\Type\Traits\ConstantNumericComparisonTypeTrait;
 use PHPStan\Type\Traits\ConstantScalarTypeTrait;
 use PHPStan\Type\Type;
+use PHPStan\Type\UnionType;
 use PHPStan\Type\VerbosityLevel;
 use function abs;
 use function ini_get;
@@ -69,6 +70,13 @@ public function describe(VerbosityLevel $level): string
 
 	public function toString(): Type
 	{
+		if ($this->value === 0.0) {
+			return new UnionType([
+				new ConstantStringType('0'),
+				new ConstantStringType('-0'),
+			]);
+		}
+
 		return new ConstantStringType((string) $this->value);
 	}
 

tests/PHPStan/Analyser/nsrt/bug-12225.php

@@ -0,0 +1,44 @@
+<?php declare(strict_types = 1);
+
+namespace Bug12225;
+
+use function PHPStan\Testing\assertType;
+
+function floatAsserts(float $num): ?int
+{
+	if ($num === 0.0) {
+		assertType('0.0', $num);
+		assertType("'-0'|'0'", (string) $num);
+	}
+
+	if ($num == 0) {
+		assertType('0.0', $num);
+		assertType("'-0'|'0'", (string) $num);
+	}
+
+	assertType("'-0'|'0'", (string) 0.0); // could be '0'
+	assertType("'-0'|'0'", (string) -0.0); // could be '-0'
+
+	assertType('-0.0', -1.0 * 0.0);
+	assertType('0.0', 1.0 * 0.0);
+	assertType('0.0', -1.0 * -0.0);
+	assertType('-0.0', 1.0 * -0.0);
+
+	assertType('true', 0.0 === -0.0);
+	assertType('true', 0.0 == -0.0);
+
+	return null;
+}
+
+/** @param mixed $num */
+function withMixed($num): ?int
+{
+	if ($num === 0.0) {
+		assertType('0.0', $num);
+		assertType("'-0'|'0'", (string) $num);
+	}
+
+	assertType('true', 0.0 === -0.0);
+
+	return null;
+}