Do not create conditional expression when holder and guard have the same type and guard overlaps with other branch

src/Analyser/MutatingScope.php

@@ -3776,6 +3776,11 @@ private function createConditionalExpressions(
 							&& !$guardHolder->getType()->isSuperTypeOf($theirExpressionTypes[$guardExprString]->getType())->no()
 						)
 						|| $guardHolder->getType()->isSuperTypeOf($theirExpressionTypes[$guardExprString]->getType())->yes()
+						|| (
+							!array_key_exists($exprString, $theirExpressionTypes)
+							&& $holder->getType()->equals($guardHolder->getType())
+							&& !$guardHolder->getType()->isSuperTypeOf($theirExpressionTypes[$guardExprString]->getType())->no()
+						)
 					)
 				) {
 					continue;

tests/PHPStan/Analyser/nsrt/bug-14469.php

@@ -0,0 +1,19 @@
+<?php declare(strict_types = 1);
+
+namespace Bug14469Nsrt;
+
+use function PHPStan\Testing\assertType;
+
+function testConditionalExpressionOverNarrowing(array $R, bool $var1, object $user): void {
+    $aa = null;
+
+    if ($var1) {
+        $aa = $user->id === 10 ? 2 : null;
+    } elseif ($R['aa']) {
+        $aa = $R['aa'];
+    }
+
+    if ($aa) {
+        assertType('mixed', $R['aa']);
+    }
+}

tests/PHPStan/Rules/Comparison/BooleanNotConstantConditionRuleTest.php

@@ -245,4 +245,10 @@ public function testBug12852(): void
 		]);
 	}
 
+	public function testBug14469(): void
+	{
+		$this->treatPhpDocTypesAsCertain = true;
+		$this->analyse([__DIR__ . '/data/bug-14469.php'], []);
+	}
+
 }

tests/PHPStan/Rules/Comparison/data/bug-14469.php

@@ -0,0 +1,88 @@
+<?php declare(strict_types = 1);
+
+namespace Bug14469;
+
+function t(array $R, bool $var1, object $user, bool $is): array {
+    $aa = null;
+
+    if ($var1) {
+        $aa = $user->id  === 10 ? 2 : null;
+    } elseif ($R['aa']) {
+        $aa = $R['aa'];
+    }
+
+    if ($aa) {
+        if (!$R['aa']) {
+            return [];
+        }
+    }
+	return $R;
+}
+
+function testIfConstantCondition(array $R, bool $var1, object $user): void {
+    $aa = null;
+
+    if ($var1) {
+        $aa = $user->id === 10 ? 2 : null;
+    } elseif ($R['aa']) {
+        $aa = $R['aa'];
+    }
+
+    if ($aa) {
+        if ($R['aa']) {
+            // not always true
+        }
+    }
+}
+
+function testFalseyBranch(array $R, bool $var1, object $user): void {
+    $bb = 'default';
+
+    if ($var1) {
+        $bb = $user->id === 10 ? null : 'active';
+    } elseif (!$R['bb']) {
+        $bb = $R['bb'];
+    }
+
+    if (!$bb) {
+        if ($R['bb']) {
+            return;
+        }
+    }
+}
+
+function testWithElse(array $R, bool $var1, object $user): void {
+    $aa = null;
+
+    if ($var1) {
+        $aa = $user->id === 10 ? 2 : null;
+    } elseif ($R['aa']) {
+        $aa = $R['aa'];
+    } else {
+        $aa = 0;
+    }
+
+    if ($aa) {
+        if (!$R['aa']) {
+            return;
+        }
+    }
+}
+
+function testMultipleElseif(array $R, bool $var1, bool $var2, object $user): void {
+    $aa = null;
+
+    if ($var1) {
+        $aa = $user->id === 10 ? 2 : null;
+    } elseif ($var2) {
+        $aa = 42;
+    } elseif ($R['aa']) {
+        $aa = $R['aa'];
+    }
+
+    if ($aa) {
+        if (!$R['aa']) {
+            return;
+        }
+    }
+}