WIP Attempt to fix zero

Author: thg2k

src/Analyser/TypeSpecifier.php

@@ -1611,7 +1611,7 @@ private function processBooleanNotSureConditionalTypes(Scope $scope, SpecifiedTy
 	}
 
 	/**
-	 * @return array{Expr, ConstantScalarType}|null
+	 * @return array{Expr, ConstantScalarType, Type}|null
 	 */
 	private function findTypeExpressionsFromBinaryOperation(Scope $scope, Node\Expr\BinaryOp $binaryOperation): ?array
 	{
@@ -1633,13 +1633,13 @@ private function findTypeExpressionsFromBinaryOperation(Scope $scope, Node\Expr\
 			&& !$rightExpr instanceof ConstFetch
 			&& !$rightExpr instanceof ClassConstFetch
 		) {
-			return [$binaryOperation->right, $leftType];
+			return [$binaryOperation->right, $leftType, $rightType];
 		} elseif (
 			$rightType instanceof ConstantScalarType
 			&& !$leftExpr instanceof ConstFetch
 			&& !$leftExpr instanceof ClassConstFetch
 		) {
-			return [$binaryOperation->left, $rightType];
+			return [$binaryOperation->left, $rightType, $leftType];
 		}
 
 		return null;
@@ -1950,6 +1950,7 @@ public function resolveEqual(Expr\BinaryOp\Equal $expr, Scope $scope, TypeSpecif
 		if ($expressions !== null) {
 			$exprNode = $expressions[0];
 			$constantType = $expressions[1];
+			$otherType = $expressions[2];
 
 			if (!$context->null() && $constantType->getValue() === null) {
 				$trueTypes = [
@@ -1981,6 +1982,30 @@ public function resolveEqual(Expr\BinaryOp\Equal $expr, Scope $scope, TypeSpecif
 				);
 			}
 
+			if (!$context->null() && $constantType->getValue() === 0 && !$otherType->isInteger()->yes()) {
+				/* There is a difference between php 7.x and 8.x on the equality
+				 * behavior between zero and the empty string, so to be conservative
+				 * we leave it untouched regardless of the language version */
+				if ($context->true()) {
+					$trueTypes = [
+						new NullType(),
+						new ConstantBooleanType(false),
+						new ConstantIntegerType(0),
+						new ConstantFloatType(0.0),
+						new StringType(),
+					];
+				} else {
+					$trueTypes = [
+						new NullType(),
+						new ConstantBooleanType(false),
+						new ConstantIntegerType(0),
+						new ConstantFloatType(0.0),
+						new ConstantStringType('0'),
+					];
+				}
+				return $this->create($exprNode, new UnionType($trueTypes), $context, false, $scope, $rootExpr);
+			}
+
 			if (!$context->null() && $constantType->getValue() === '') {
 				/* There is a difference between php 7.x and 8.x on the equality
 				 * behavior between zero and the empty string, so to be conservative

tests/PHPStan/Analyser/nsrt/equal-narrow.php

@@ -115,6 +115,38 @@ function doTrue($x, $y, $z): void
 	}
 }
 
+/**
+ * @param 0|0.0|1|''|'0'|'x'|array{}|bool|object|null $x
+ * @param int|string|null $y
+ * @param mixed $z
+ */
+function doZero($x, $y, $z): void
+{
+	// PHP 7.x/8.x compatibility: Keep zero in both cases
+	if ($x == 0) {
+		assertType("0|0.0|''|'0'|'x'|false|null", $x);
+	} else {
+		assertType("1|''|'x'|array{}|object|true", $x);
+	}
+	if (0 != $x) {
+		assertType("1|''|'x'|array{}|object|true", $x);
+	} else {
+		assertType("0|0.0|''|'0'|'x'|false|null", $x);
+	}
+
+	if ($y == 0) {
+		assertType("0|string|null", $y);
+	} else {
+		assertType("int<min, -1>|int<1, max>|string", $y);
+	}
+
+	if ($z == 0) {
+		assertType("0|0.0|string|false|null", $z);
+	} else {
+		assertType("mixed~(0|0.0|'0'|false|null)", $z);
+	}
+}
+
 /**
  * @param 0|0.0|1|''|'0'|'x'|array{}|bool|object|null $x
  * @param int|string|null $y

tests/PHPStan/Analyser/nsrt/integer-range-types.php

@@ -449,7 +449,7 @@ public function zeroIssues($positive, $negative)
 
 function subtract($m) {
 	if ($m != 0) {
-		assertType("mixed", $m); // could be "mixed~0|0.0|''|'0'|array{}|false|null"
+		assertType("mixed~(0|0.0|'0'|false|null)", $m); // could be "mixed~(0|0.0|''|'0'|false|null)"
 		assertType('int', (int) $m);
 	}
 	if ($m !== 0) {