Skip non-discriminating guards in createConditionalExpressions even when target is not tracked in the other scope

- In `MutatingScope::createConditionalExpressions`, the filter that skips
  non-discriminating guards previously required the target expression to
  exist in the other scope's expression types. When the target was absent
  (e.g. `$options['multiple']` not explicitly narrowed in the truthy branch),
  the filter did not fire, allowing guards like `$instructions` (an unrelated
  mutable variable) to create spurious conditional expression holders.
- Add an additional check: if the guard variable's type in our scope is
  definitively a supertype of its type in the other scope (`.yes()`), the
  guard is non-discriminating regardless of the target's presence, so skip it.
- The original check (requiring both target and guard in the other scope,
  using `!.no()`) is preserved for cases where the target IS tracked, to
  avoid regressions with `maybe` supertype results (e.g. `Event` vs
  `OrderInterface`).
- Also fixes the same bug with strict comparison (`!==` instead of `!=`).

Author: VincentLanglet

src/Analyser/MutatingScope.php

@@ -3749,11 +3749,16 @@ private function createConditionalExpressions(
 
 			foreach ($variableTypeGuards as $guardExprString => $guardHolder) {
 				if (
-					array_key_exists($exprString, $theirExpressionTypes)
-					&& $theirExpressionTypes[$exprString]->getCertainty()->yes()
-					&& array_key_exists($guardExprString, $theirExpressionTypes)
+					array_key_exists($guardExprString, $theirExpressionTypes)
 					&& $theirExpressionTypes[$guardExprString]->getCertainty()->yes()
-					&& !$guardHolder->getType()->isSuperTypeOf($theirExpressionTypes[$guardExprString]->getType())->no()
+					&& (
+						(
+							array_key_exists($exprString, $theirExpressionTypes)
+							&& $theirExpressionTypes[$exprString]->getCertainty()->yes()
+							&& !$guardHolder->getType()->isSuperTypeOf($theirExpressionTypes[$guardExprString]->getType())->no()
+						)
+						|| $guardHolder->getType()->isSuperTypeOf($theirExpressionTypes[$guardExprString]->getType())->yes()
+					)
 				) {
 					continue;
 				}

tests/PHPStan/Analyser/nsrt/bug-14595.php

@@ -0,0 +1,45 @@
+<?php
+
+namespace Bug14595;
+
+use function PHPStan\Testing\assertType;
+
+/**
+ * @param array{
+ *     multiple: 0|1|2
+ *   , total: bool
+ *  } $options
+ */
+function arrayAppendGuard(array $options): void {
+	$instructions = [ ];
+	$instructions[] = "foo";
+	if ($options['multiple'] != 1 || $options['total'])
+		$instructions[] = "bar";
+	assertType('0|1|2', $options['multiple']);
+	if (!$options['total'])
+		$instructions[] = "baz";
+	assertType('0|1|2', $options['multiple']);
+	if (!$options['total'])
+		$instructions[] = "qux";
+	assertType('0|1|2', $options['multiple']);
+}
+
+/**
+ * @param array{
+ *     multiple: 0|1|2
+ *   , total: bool
+ *  } $options
+ */
+function strictComparisonGuard(array $options): void {
+	$instructions = [ ];
+	$instructions[] = "foo";
+	if ($options['multiple'] !== 1 || $options['total'])
+		$instructions[] = "bar";
+	assertType('0|1|2', $options['multiple']);
+	if (!$options['total'])
+		$instructions[] = "baz";
+	assertType('0|1|2', $options['multiple']);
+	if (!$options['total'])
+		$instructions[] = "qux";
+	assertType('0|1|2', $options['multiple']);
+}