Fix phpstan/phpstan#14394: NAN ==/=== anything is always evaluated as false

src/Analyser/ExprHandler/BinaryOpHandler.php

@@ -109,7 +109,10 @@ public function resolveType(MutatingScope $scope, Expr $expr): Type
 				&& is_string($expr->right->name)
 				&& $expr->left->name === $expr->right->name
 			) {
-				return new ConstantBooleanType(true);
+				$varType = $scope->getType($expr->left);
+				if (!$this->initializerExprTypeResolver->containsNan($varType)) {
+					return new ConstantBooleanType(true);
+				}
 			}
 
 			$leftType = $scope->getType($expr->left);

src/Analyser/RicherScopeGetTypeHelper.php

@@ -36,7 +36,10 @@ public function getIdenticalResult(Scope $scope, Identical $expr): TypeResult
 			&& is_string($expr->right->name)
 			&& $expr->left->name === $expr->right->name
 		) {
-			return new TypeResult(new ConstantBooleanType(true), []);
+			$varType = $scope->getType($expr->left);
+			if (!$this->initializerExprTypeResolver->containsNan($varType)) {
+				return new TypeResult(new ConstantBooleanType(true), []);
+			}
 		}
 
 		$leftType = $scope->getType($expr->left);

src/Reflection/InitializerExprTypeResolver.php

@@ -114,6 +114,7 @@
 use function is_finite;
 use function is_float;
 use function is_int;
+use function is_nan;
 use function is_numeric;
 use function is_string;
 use function max;
@@ -1944,6 +1945,10 @@ public function resolveIdenticalType(Type $leftType, Type $rightType): TypeResul
 			return new TypeResult(new ConstantBooleanType(false), []);
 		}
 
+		if ($this->containsNan($leftType) || $this->containsNan($rightType)) {
+			return new TypeResult(new ConstantBooleanType(false), []);
+		}
+
 		if ($leftType instanceof ConstantScalarType && $rightType instanceof ConstantScalarType) {
 			return new TypeResult(new ConstantBooleanType($leftType->getValue() === $rightType->getValue()), []);
 		}
@@ -1972,6 +1977,10 @@ public function resolveIdenticalType(Type $leftType, Type $rightType): TypeResul
 	 */
 	public function resolveEqualType(Type $leftType, Type $rightType): TypeResult
 	{
+		if ($this->containsNan($leftType) || $this->containsNan($rightType)) {
+			return new TypeResult(new ConstantBooleanType(false), []);
+		}
+
 		if (
 			($leftType->isEnum()->yes() && $rightType->isTrue()->no())
 			|| ($rightType->isEnum()->yes() && $leftType->isTrue()->no())
@@ -2061,6 +2070,37 @@ private function resolveConstantArrayTypeComparison(ConstantArrayType $leftType,
 		return new TypeResult($resultType->toBoolean(), []);
 	}
 
+	public function containsNan(Type $type): bool
+	{
+		if ($type instanceof ConstantFloatType && is_nan($type->getValue())) {
+			return true;
+		}
+
+		$constantArrays = $type->getConstantArrays();
+		if ($constantArrays !== []) {
+			foreach ($constantArrays as $constantArray) {
+				$optionalKeys = $constantArray->getOptionalKeys();
+				$hasNan = false;
+				foreach ($constantArray->getValueTypes() as $index => $valueType) {
+					if (in_array($index, $optionalKeys, true)) {
+						continue;
+					}
+					if ($this->containsNan($valueType)) {
+						$hasNan = true;
+						break;
+					}
+				}
+				if (!$hasNan) {
+					return false;
+				}
+			}
+
+			return true;
+		}
+
+		return false;
+	}
+
 	/**
 	 * @param BinaryOp\Plus|BinaryOp\Minus|BinaryOp\Mul|BinaryOp\Div|BinaryOp\ShiftLeft|BinaryOp\ShiftRight $expr
 	 */

tests/PHPStan/Rules/Comparison/ConstantLooseComparisonRuleTest.php

@@ -248,4 +248,27 @@ public function testBug13098(): void
 		$this->analyse([__DIR__ . '/data/bug-13098.php'], []);
 	}
 
+	public function testBug14394(): void
+	{
+		$this->treatPhpDocTypesAsCertain = true;
+		$this->analyse([__DIR__ . '/data/bug-14394.php'], [
+			[
+				'Loose comparison using == between float and NAN will always evaluate to false.',
+				8,
+			],
+			[
+				'Loose comparison using == between list<mixed> and array{NAN} will always evaluate to false.',
+				10,
+			],
+			[
+				'Loose comparison using == between NAN and NAN will always evaluate to false.',
+				16,
+			],
+			[
+				'Loose comparison using == between array{NAN} and array{NAN} will always evaluate to false.',
+				18,
+			],
+		]);
+	}
+
 }

tests/PHPStan/Rules/Comparison/StrictComparisonOfDifferentTypesRuleTest.php

@@ -1164,11 +1164,45 @@ public function testPossiblyImpureTip(): void
 	public function testBug11054(): void
 	{
 		$this->analyse([__DIR__ . '/data/bug-11054.php'], [
+			[
+				'Strict comparison using === between mixed and array{NAN} will always evaluate to false.',
+				24,
+			],
+			[
+				'Strict comparison using === between mixed and array{NAN} will always evaluate to false.',
+				28,
+			],
 			[
 				'Strict comparison using === between mixed and array{INF} will always evaluate to false.',
 				47,
 				'Type array{INF} has already been eliminated from mixed.',
 			],
+			[
+				'Strict comparison using === between mixed and array{NAN} will always evaluate to false.',
+				55,
+			],
+		]);
+	}
+
+	public function testBug14394(): void
+	{
+		$this->analyse([__DIR__ . '/data/bug-14394.php'], [
+			[
+				'Strict comparison using === between float and NAN will always evaluate to false.',
+				9,
+			],
+			[
+				'Strict comparison using === between list<mixed> and array{NAN} will always evaluate to false.',
+				11,
+			],
+			[
+				'Strict comparison using === between NAN and NAN will always evaluate to false.',
+				17,
+			],
+			[
+				'Strict comparison using === between array{NAN} and array{NAN} will always evaluate to false.',
+				19,
+			],
 		]);
 	}
 

tests/PHPStan/Rules/Comparison/data/bug-14394.php

@@ -0,0 +1,27 @@
+<?php declare(strict_types = 1);
+
+namespace Bug14394;
+
+class Cl {
+	/** @param list<mixed> $v2 */
+	public static function test(float $v1, array $v2): void {
+		if ($v1 == NAN) { echo "never reached\n"; }
+		if ($v1 === NAN) { echo "never reached\n"; }
+		if ($v2 == [NAN]) { echo "never reached\n"; }
+		if ($v2 === [NAN]) { echo "never reached\n"; }
+	}
+
+	public static function testSameVariable(): void {
+		$a = NAN;
+		if ($a == $a) { echo "never reached\n"; }
+		if ($a === $a) { echo "never reached\n"; }
+		if ([$a] == [$a]) { echo "never reached\n"; }
+		if ([$a] === [$a]) { echo "never reached\n"; }
+	}
+
+	/** @param array{NAN}|array{1} $v */
+	public static function testUnionArrayNotAlwaysFalse(array $v): void {
+		if ($v === [1]) { echo "maybe reached\n"; }
+		if ($v == [1]) { echo "maybe reached\n"; }
+	}
+}