Remove useSubtypeForConditionMatching flag, use two-pass matching instead

Instead of a flag on ConditionalExpressionHolder to control whether
condition matching uses equals() or isSuperTypeOf(), use a two-pass
approach in filterBySpecifiedTypes():

Pass 1: exact matching via equals() (existing behavior)
Pass 2: isSuperTypeOf for condition types with finite types (fallback)

Pass 2 only runs when pass 1 found no matches for a target expression.
This handles conditional parameter types where the condition is a union
(e.g. 'value1'|'value2') that can't match a narrowed type ('value1')
via equals(), but should match via isSuperTypeOf.

The two-pass approach avoids regressions from using isSuperTypeOf
globally: when scope merging creates both a specific condition (e.g.
"if $key=2, then $value is Yes") and a broader condition (e.g. "if
$key=0|2, then $value is Maybe"), exact matching in pass 1 prevents
the broader condition from degrading variable certainty through
extremeIdentity.

The bug-5051 test expectations are updated to reflect more precise
type narrowing: when narrowing $data to a specific constant, PHPStan
now correctly determines which branch was taken and narrows related
variables accordingly (e.g. $update becomes 'false' instead of 'bool'
when $data === 1 because that branch always sets $update = false).

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

Author: phpstan-bot

src/Analyser/ConditionalExpressionHolder.php

@@ -17,7 +17,6 @@ final class ConditionalExpressionHolder
 	public function __construct(
 		private array $conditionExpressionTypeHolders,
 		private ExpressionTypeHolder $typeHolder,
-		private bool $useSubtypeForConditionMatching = false,
 	)
 	{
 		if (count($conditionExpressionTypeHolders) === 0) {
@@ -38,11 +37,6 @@ public function getTypeHolder(): ExpressionTypeHolder
 		return $this->typeHolder;
 	}
 
-	public function useSubtypeForConditionMatching(): bool
-	{
-		return $this->useSubtypeForConditionMatching;
-	}
-
 	public function getKey(): string
 	{
 		$parts = [];

src/Analyser/MutatingScope.php

@@ -1760,12 +1760,12 @@ private function enterFunctionLike(
 
 					$holder = new ConditionalExpressionHolder([
 						$parameterType->getParameterName() => ExpressionTypeHolder::createYes(new Variable($targetParameterName), TypeCombinator::intersect($targetParameter->getType(), $parameterType->getTarget())),
-					], ExpressionTypeHolder::createYes(new Variable($parameter->getName()), $ifType), true);
+					], ExpressionTypeHolder::createYes(new Variable($parameter->getName()), $ifType));
 					$conditionalTypes['$' . $parameter->getName()][$holder->getKey()] = $holder;
 
 					$holder = new ConditionalExpressionHolder([
 						$parameterType->getParameterName() => ExpressionTypeHolder::createYes(new Variable($targetParameterName), TypeCombinator::remove($targetParameter->getType(), $parameterType->getTarget())),
-					], ExpressionTypeHolder::createYes(new Variable($parameter->getName()), $elseType), true);
+					], ExpressionTypeHolder::createYes(new Variable($parameter->getName()), $elseType));
 					$conditionalTypes['$' . $parameter->getName()][$holder->getKey()] = $holder;
 				}
 			}
@@ -3216,28 +3216,46 @@ public function filterBySpecifiedTypes(SpecifiedTypes $specifiedTypes): self
 				if (array_key_exists($conditionalExprString, $conditions)) {
 					continue;
 				}
+
+				// Pass 1: exact matching via equals()
 				foreach ($conditionalExpressions as $conditionalExpression) {
 					foreach ($conditionalExpression->getConditionExpressionTypeHolders() as $holderExprString => $conditionalTypeHolder) {
-						if (!array_key_exists($holderExprString, $specifiedExpressions)) {
-							continue 2;
-						}
-						$specifiedHolder = $specifiedExpressions[$holderExprString];
-						if (!$specifiedHolder->getCertainty()->equals($conditionalTypeHolder->getCertainty())) {
+						if (!array_key_exists($holderExprString, $specifiedExpressions) || !$specifiedExpressions[$holderExprString]->equals($conditionalTypeHolder)) {
 							continue 2;
 						}
-						if ($conditionalExpression->useSubtypeForConditionMatching()) {
-							if (!$conditionalTypeHolder->getType()->isSuperTypeOf($specifiedHolder->getType())->yes()) {
+					}
+
+					$conditions[$conditionalExprString][] = $conditionalExpression;
+					$specifiedExpressions[$conditionalExprString] = $conditionalExpression->getTypeHolder();
+				}
+
+				// Pass 2: for condition types with finite types, use isSuperTypeOf
+				// This handles cases like conditional parameter types where the condition
+				// is a union (e.g. 'value1'|'value2') that won't match a narrowed type
+				// (e.g. 'value1') via equals(), but should match via isSuperTypeOf.
+				// Only attempted when pass 1 found no matches, to avoid conflicts with
+				// broader conditions that have lower certainty from scope merging.
+				if (!array_key_exists($conditionalExprString, $conditions)) {
+					foreach ($conditionalExpressions as $conditionalExpression) {
+						foreach ($conditionalExpression->getConditionExpressionTypeHolders() as $holderExprString => $conditionalTypeHolder) {
+							if (!array_key_exists($holderExprString, $specifiedExpressions)) {
 								continue 2;
 							}
-						} else {
-							if (!$specifiedHolder->equals($conditionalTypeHolder)) {
+							$specifiedHolder = $specifiedExpressions[$holderExprString];
+							if (!$specifiedHolder->getCertainty()->equals($conditionalTypeHolder->getCertainty())) {
+								continue 2;
+							}
+							if (count($conditionalTypeHolder->getType()->getFiniteTypes()) === 0) {
+								continue 2;
+							}
+							if (!$conditionalTypeHolder->getType()->isSuperTypeOf($specifiedHolder->getType())->yes()) {
 								continue 2;
 							}
 						}
-					}
 
-					$conditions[$conditionalExprString][] = $conditionalExpression;
-					$specifiedExpressions[$conditionalExprString] = $conditionalExpression->getTypeHolder();
+						$conditions[$conditionalExprString][] = $conditionalExpression;
+						$specifiedExpressions[$conditionalExprString] = $conditionalExpression->getTypeHolder();
+					}
 				}
 			}
 		}

tests/PHPStan/Analyser/nsrt/bug-5051.php

@@ -60,35 +60,35 @@ public function testWithBooleans($data): void
 			assertType('bool', $update);
 		} else {
 			assertType('1|2', $data);
-			assertType('bool', $update);
+			assertType('false', $update);
 		}
 
 		if ($data === 1) {
-			assertType('bool', $update);
-			assertType('bool', $foo);
+			assertType('false', $update);
+			assertType('false', $foo);
 		} else {
 			assertType('bool', $update);
 			assertType('bool', $foo);
 		}
 
 		if ($data === 2) {
-			assertType('bool', $update);
-			assertType('bool', $foo);
+			assertType('false', $update);
+			assertType('false', $foo);
 		} else {
 			assertType('bool', $update);
 			assertType('bool', $foo);
 		}
 
 		if ($data === 3) {
-			assertType('bool', $update);
+			assertType('false', $update);
 			assertType('true', $foo);
 		} else {
 			assertType('bool', $update);
 			assertType('bool', $foo);
 		}
 
 		if ($data === 1 || $data === 2) {
-			assertType('bool', $update);
+			assertType('false', $update);
 			assertType('false', $foo);
 		} else {
 			assertType('bool', $update);