@@ -256,7 +256,6 @@ public static function doUnion(Type ...$types): Type
 		$alreadyNormalizedCounter = 0;
 
 		$benevolentTypes = [];
-		$benevolentUnionObject = null;
 		$neverCount = 0;
 		// transform A | (B | C) to A | B | C
 		for ($i = 0; $i < $typesCount; $i++) {
@@ -273,8 +272,8 @@ public static function doUnion(Type ...$types): Type
 				continue;
 			}
 			if ($types[$i] instanceof BenevolentUnionType) {
-				if ($types[$i] instanceof TemplateBenevolentUnionType && $benevolentUnionObject === null) {
-					$benevolentUnionObject = $types[$i];
+				if ($types[$i] instanceof TemplateType) {
+					continue;
 				}
 				$benevolentTypesCount = 0;
 				$typesInner = $types[$i]->getTypes();
@@ -528,10 +527,6 @@ public static function doUnion(Type ...$types): Type
 			}
 
 			if ($tempTypes === []) {
-				if ($benevolentUnionObject instanceof TemplateBenevolentUnionType) {
-					return $benevolentUnionObject->withTypes(array_values($types));
-				}
-
 				return new BenevolentUnionType(array_values($types), true);
 			}
 		}
 
@@ -0,0 +1,35 @@
+<?php
+
+namespace TemplateArrayKeyUnionFalse;
+
+use function PHPStan\Testing\assertType;
+
+/**
+ * @template TKey of array-key
+ * @template TValue
+ */
+class Collection
+{
+
+	/**
+	 * @param TValue|callable(TValue, TKey): bool $value
+	 * @return TKey|false
+	 */
+	public function search($value, bool $strict = false)
+	{
+		return false;
+	}
+
+}
+
+/**
+ * @param Collection<int, string> $ints
+ * @param Collection<string, string> $strings
+ * @param Collection<int|string, string> $keys
+ */
+function test(Collection $ints, Collection $strings, Collection $keys): void
+{
+	assertType('int|false', $ints->search('foo'));
+	assertType('string|false', $strings->search('foo'));
+	assertType('int|string|false', $keys->search('foo'));
+}
@@ -1982,6 +1982,14 @@ public static function dataUnion(): iterable
 				TemplateBenevolentUnionType::class,
 				'T of (int|string) (function foo(), parameter)',
 			],
+			[
+				[
+					TemplateTypeFactory::create(TemplateTypeScope::createWithFunction('foo'), 'T', new BenevolentUnionType([new IntegerType(), new StringType()]), TemplateTypeVariance::createInvariant()),
+					new ConstantBooleanType(false),
+				],
+				UnionType::class,
+				'T of (int|string) (function foo(), parameter)|false',
+			],
 			[
 				[
 					new ConstantStringType(''),
Original file line number	Diff line number	Diff line change
`@@ -256,7 +256,6 @@ public static function doUnion(Type ...$types): Type`
`256`	`256`	`$alreadyNormalizedCounter = 0;`
`257`	`257`
`258`	`258`	`$benevolentTypes = [];`
`259`		`- $benevolentUnionObject = null;`
`260`	`259`	`$neverCount = 0;`
`261`	`260`	`// transform A \| (B \| C) to A \| B \| C`
`262`	`261`	`for ($i = 0; $i < $typesCount; $i++) {`
`@@ -273,8 +272,8 @@ public static function doUnion(Type ...$types): Type`
`273`	`272`	`continue;`
`274`	`273`	`}`
`275`	`274`	`if ($types[$i] instanceof BenevolentUnionType) {`
`276`		`- if ($types[$i] instanceof TemplateBenevolentUnionType && $benevolentUnionObject === null) {`
`277`		`- $benevolentUnionObject = $types[$i];`
	`275`	`+ if ($types[$i] instanceof TemplateType) {`
	`276`	`+ continue;`
`278`	`277`	`}`
`279`	`278`	`$benevolentTypesCount = 0;`
`280`	`279`	`$typesInner = $types[$i]->getTypes();`
`@@ -528,10 +527,6 @@ public static function doUnion(Type ...$types): Type`
`528`	`527`	`}`
`529`	`528`
`530`	`529`	`if ($tempTypes === []) {`
`531`		`- if ($benevolentUnionObject instanceof TemplateBenevolentUnionType) {`
`532`		`- return $benevolentUnionObject->withTypes(array_values($types));`
`533`		`- }`
`534`		`-`
`535`	`530`	`return new BenevolentUnionType(array_values($types), true);`
`536`	`531`	`}`
`537`	`532`	`}`