diff --git a/src/Psalm/Internal/Analyzer/Statements/Expression/AssertionFinder.php b/src/Psalm/Internal/Analyzer/Statements/Expression/AssertionFinder.php
index b3affb3f0..20f87bd55 100644
--- a/src/Psalm/Internal/Analyzer/Statements/Expression/AssertionFinder.php
+++ b/src/Psalm/Internal/Analyzer/Statements/Expression/AssertionFinder.php
@@ -2016,22 +2016,15 @@ class AssertionFinder
             return;
         }
 
-        $always_contains = TypeAnalyzer::isContainedBy(
-            $codebase,
-            $expected_type,
-            $first_var_type
-        );
-
-        $never_contains = !TypeAnalyzer::isContainedBy(
+        if (!TypeAnalyzer::isContainedBy(
             $codebase,
             $first_var_type,
             $expected_type
-        );
+        )) {
+            return;
+        }
 
-        /** @psalm-suppress ParadoxicalCondition */
-        if (($always_contains && !$negate)
-            || ($never_contains && $negate)
-        ) {
+        if (!$negate) {
             if ($first_var_type->from_docblock) {
                 if (IssueBuffer::accepts(
                     new RedundantConditionGivenDocblockType(
@@ -2053,9 +2046,7 @@ class AssertionFinder
                     // fall through
                 }
             }
-        } elseif (($always_contains && $negate)
-            || ($never_contains && !$negate)
-        ) {
+        } else {
             if ($first_var_type->from_docblock) {
                 if (IssueBuffer::accepts(
                     new DocblockTypeContradiction(
diff --git a/src/Psalm/Internal/Analyzer/TypeAnalyzer.php b/src/Psalm/Internal/Analyzer/TypeAnalyzer.php
index 0a5b036c5..c42369e9f 100644
--- a/src/Psalm/Internal/Analyzer/TypeAnalyzer.php
+++ b/src/Psalm/Internal/Analyzer/TypeAnalyzer.php
@@ -1047,7 +1047,7 @@ class TypeAnalyzer
         }
 
         if ($container_type_part instanceof TNumeric &&
-            ($input_type_part->isNumericType() || $input_type_part instanceof TString)
+            $input_type_part->isNumericType()
         ) {
             return true;
         }
diff --git a/tests/TypeCombinationTest.php b/tests/TypeCombinationTest.php
index ad2889992..865d0677f 100644
--- a/tests/TypeCombinationTest.php
+++ b/tests/TypeCombinationTest.php
@@ -188,7 +188,7 @@ class TypeCombinationTest extends TestCase
                 ],
             ],
             'arrayMixedOrStringKeys' => [
-                'array<int|mixed|string, string>',
+                'array<array-key, string>',
                 [
                     'array<int|string,string>',
                     'array<mixed,string>',
diff --git a/tests/TypeParseTest.php b/tests/TypeParseTest.php
index d49a054cc..d8f0547d5 100644
--- a/tests/TypeParseTest.php
+++ b/tests/TypeParseTest.php
@@ -816,7 +816,7 @@ class TypeParseTest extends TestCase
      */
     public function testVeryLargeType()
     {
-        $very_large_type = 'array{a: Closure():(array<mixed, mixed>|null), b?: Closure():array<mixed, mixed>, c?: Closure():array<mixed, mixed>, d?: Closure():array<mixed, mixed>, e?: Closure():(array{f: null|string, g: null|string, h: null|string, i: string, j: mixed, k: mixed, l: mixed, m: mixed, n: bool, o?: array{0: string}}|null), p?: Closure():(array{f: null|string, g: null|string, h: null|string, i: string, j: mixed, k: mixed, l: mixed, m: mixed, n: bool, o?: array{0: string}}|null), q: string, r?: Closure():(array<mixed, mixed>|null), s: array<mixed, mixed>}|null';
+        $very_large_type = 'array{a: Closure():(array<array-key, mixed>|null), b?: Closure():array<array-key, mixed>, c?: Closure():array<array-key, mixed>, d?: Closure():array<array-key, mixed>, e?: Closure():(array{f: null|string, g: null|string, h: null|string, i: string, j: mixed, k: mixed, l: mixed, m: mixed, n: bool, o?: array{0: string}}|null), p?: Closure():(array{f: null|string, g: null|string, h: null|string, i: string, j: mixed, k: mixed, l: mixed, m: mixed, n: bool, o?: array{0: string}}|null), q: string, r?: Closure():(array<array-key, mixed>|null), s: array<array-key, mixed>}|null';
 
         $this->assertSame(
             $very_large_type,
diff --git a/tests/TypeReconciliation/ReconcilerTest.php b/tests/TypeReconciliation/ReconcilerTest.php
index 9477d8a36..f4cf67171 100644
--- a/tests/TypeReconciliation/ReconcilerTest.php
+++ b/tests/TypeReconciliation/ReconcilerTest.php
@@ -59,9 +59,7 @@ class ReconcilerTest extends \Psalm\Tests\TestCase
             $reconciled->getId()
         );
 
-        if (is_array($reconciled->getAtomicTypes())) {
-            $this->assertContainsOnlyInstancesOf('Psalm\Type\Atomic', $reconciled->getAtomicTypes());
-        }
+        $this->assertContainsOnlyInstancesOf('Psalm\Type\Atomic', $reconciled->getAtomicTypes());
     }
 
     /**
diff --git a/tests/TypeReconciliation/RedundantConditionTest.php b/tests/TypeReconciliation/RedundantConditionTest.php
index 96a61ea25..59c3c712e 100644
--- a/tests/TypeReconciliation/RedundantConditionTest.php
+++ b/tests/TypeReconciliation/RedundantConditionTest.php
@@ -773,6 +773,16 @@ class RedundantConditionTest extends \Psalm\Tests\TestCase
                     '$fp' => 'closed-resource',
                 ]
             ],
+            'allowCheckOnReturnTypeUnion' => [
+                '<?php
+                    /** @return int|string */
+                    function returnsInt() {
+                        return rand(0, 1) ? 1 : "hello";
+                    }
+
+                    if (is_int(returnsInt())) {}
+                    if (!is_int(returnsInt())) {}',
+            ],
         ];
     }
 
@@ -1260,6 +1270,27 @@ class RedundantConditionTest extends \Psalm\Tests\TestCase
                     if (is_int(returnsInt())) {}',
                 'error_message' => 'RedundantCondition',
             ],
+            'preventAlwaysReturningSpecificInt' => [
+                '<?php
+                    /**
+                     * @return 3|4
+                     */
+                    function returnsInt(): int {
+                        return rand(0, 1) ? 3 : 4;
+                    }
+
+                    if (is_int(returnsInt())) {}',
+                'error_message' => 'RedundantConditionGivenDocblockType',
+            ],
+            'preventNotAlwaysReturningInt' => [
+                '<?php
+                    function returnsInt(): int {
+                        return 3;
+                    }
+
+                    if (!is_int(returnsInt())) {}',
+                'error_message' => 'TypeDoesNotContainType',
+            ],
         ];
     }
 }