Fix count()-based type narrowing on unions of constant array shapes

When narrowing a union of constant array shapes (e.g.
`array{bool}|array{mixed, string|null, mixed}`) via count() comparisons,
the narrowed type was applied via intersection with the original type.
This failed to filter out non-matching union members because
ConstantArrayType::isSuperTypeOf() uses open-shape semantics.

Fix: use setAlwaysOverwriteTypes() when the type being narrowed is a
constant array union, so the precisely-computed result from
specifyTypesForCountFuncCall() directly replaces the original type
instead of being intersected with it.

This also improves precision for arrays with optional keys: when
count === N is known, optional keys that can't be present at that
count are now correctly removed from the narrowed type.

Closes phpstan/phpstan#14301

Author: phpstan-bot

src/Analyser/TypeSpecifier.php

@@ -2586,6 +2586,9 @@ private function resolveNormalizedIdentical(Expr\BinaryOp\Identical $expr, Scope
 
 			$specifiedTypes = $this->specifyTypesForCountFuncCall($unwrappedLeftExpr, $argType, $rightType, $context, $scope, $expr);
 			if ($specifiedTypes !== null) {
+				if ($argType->isConstantArray()->yes()) {
+					return $specifiedTypes->setAlwaysOverwriteTypes();
+				}
 				return $specifiedTypes;
 			}
 

tests/PHPStan/Analyser/nsrt/bug-14301.php

@@ -0,0 +1,50 @@
+<?php declare(strict_types = 1);
+
+namespace Bug14301;
+
+use function PHPStan\Testing\assertType;
+
+class Foo
+{
+	/**
+	 * @param array{bool}|array{mixed, string|null, mixed} $row
+	 */
+	protected function testNotEquals(array $row): string
+	{
+		if (count($row) !== 1) {
+			assertType('array{mixed, string|null, mixed}', $row);
+
+			[$field, $operator, $value] = $row;
+			assertType('string|null', $operator);
+			return $operator ?? '=';
+		} else {
+			assertType('array{bool}', $row);
+		}
+
+		return '';
+	}
+
+	/**
+	 * @param array{bool}|array{mixed, string|null, mixed} $row
+	 */
+	protected function testEquals(array $row): void
+	{
+		if (count($row) === 3) {
+			assertType('array{mixed, string|null, mixed}', $row);
+		} else {
+			assertType('array{bool}', $row);
+		}
+	}
+
+	/**
+	 * @param array{bool}|array{mixed, string|null, mixed} $row
+	 */
+	protected function testEquals1(array $row): void
+	{
+		if (count($row) === 1) {
+			assertType('array{bool}', $row);
+		} else {
+			assertType('array{mixed, string|null, mixed}', $row);
+		}
+	}
+}

tests/PHPStan/Analyser/nsrt/list-count.php

@@ -291,15 +291,15 @@ protected function testOptionalKeysInListsOfTaggedUnion($row): void
 		}
 
 		if (count($row) === 1) {
-			assertType('array{0: int, 1?: string|null}|array{string}', $row);
+			assertType('array{int}|array{string}', $row);
 		} else {
 			assertType('array{int, string|null}', $row);
 		}
 
 		if (count($row) === 2) {
 			assertType('array{int, string|null}', $row);
 		} else {
-			assertType('array{0: int, 1?: string|null}|array{string}', $row);
+			assertType('array{int}|array{string}', $row);
 		}
 
 		if (count($row) === 3) {

tests/PHPStan/Analyser/nsrt/narrow-tagged-union.php

@@ -101,7 +101,7 @@ public function arrayIntRangeSize(): void
 		}
 
 		if (count($x) === 1) {
-			assertType("array{'xy'}|array{0: 'ab', 1?: 'xy'}", $x);
+			assertType("array{'ab'}|array{'xy'}", $x);
 		} else {
 			assertType("array{}|array{0: 'ab', 1?: 'xy'}", $x);
 		}