Report inheritance cycles with a rule instead of a reflection error

A class that extends itself, interfaces that extend each other and
traits that use each other cannot be declared in PHP. A class on a
parent class cycle now has no parent instead of throwing
CircularReference, and a trait inside a trait on a cycle processes only
the traits reflection says it uses. CircularInheritanceRule reports the
cycle on each of its members, at level 0.

Co-Authored-By: Claude Opus 5.5 (1M context) <noreply@anthropic.com>

Author: SanderMuller

.github/workflows/e2e-tests.yml

@@ -1403,6 +1403,26 @@ jobs:
               echo "$OUTPUT"
               ../bashunit assert contains 'Result cache was not saved because of non-ignorable exception: Class ResultCacheE2EInternalError\Missing was not found' "$OUTPUT"
               test ! -f tmp/resultCache.php
+          - script: |
+              cd e2e/result-cache-circular-inheritance
+              # src/First.php, src/Second.php and src/Third.php extend each other in a cycle. src/TraitA.php
+              # uses TraitB, which uses TraitC, without a cycle.
+              OUTPUT=$(../bashunit assert exit_code "1" "../../bin/phpstan analyse -vv --error-format raw")
+              echo "$OUTPUT"
+              ../bashunit assert contains 'First.php:5:Class ResultCacheE2ECircularInheritance\First extends ResultCacheE2ECircularInheritance\Second, which extends ResultCacheE2ECircularInheritance\Third, which extends ResultCacheE2ECircularInheritance\First.' "$OUTPUT"
+              ../bashunit assert not_contains 'TraitA' "$OUTPUT"
+              # The cycle is reported by a rule and is not a reflection error, so the result cache is saved.
+              ../bashunit assert contains 'Result cache is saved.' "$OUTPUT"
+              # Breaking the cycle in src/Third.php has to re-analyse src/First.php, although a class on a
+              # cycle has no parents and the file depends only on its direct parent otherwise.
+              cp patched/Third.php src/Third.php
+              # src/TraitC.php now uses TraitA, which closes a cycle. A trait declaration is not analysed on
+              # its own, so src/TraitA.php depends on the traits it uses only through the rule.
+              cp patched/TraitC.php src/TraitC.php
+              OUTPUT=$(../bashunit assert exit_code "1" "../../bin/phpstan analyse -vv --error-format raw")
+              echo "$OUTPUT"
+              ../bashunit assert not_contains 'First.php' "$OUTPUT"
+              ../bashunit assert contains 'TraitA.php:5:Trait ResultCacheE2ECircularInheritance\TraitA uses ResultCacheE2ECircularInheritance\TraitB, which uses ResultCacheE2ECircularInheritance\TraitC, which uses ResultCacheE2ECircularInheritance\TraitA.' "$OUTPUT"
           - script: |
               cd e2e/result-cache-string-class
               ../../bin/phpstan analyse

e2e/result-cache-circular-inheritance/patched/Third.php

@@ -0,0 +1,8 @@
+<?php declare(strict_types = 1);
+
+namespace ResultCacheE2ECircularInheritance;
+
+class Third
+{
+
+}

e2e/result-cache-circular-inheritance/patched/TraitC.php

@@ -0,0 +1,10 @@
+<?php declare(strict_types = 1);
+
+namespace ResultCacheE2ECircularInheritance;
+
+trait TraitC
+{
+
+	use TraitA;
+
+}

e2e/result-cache-circular-inheritance/phpstan.neon

@@ -0,0 +1,5 @@
+parameters:
+	level: 0
+	tmpDir: tmp
+	paths:
+		- src

e2e/result-cache-circular-inheritance/src/First.php

@@ -0,0 +1,8 @@
+<?php declare(strict_types = 1);
+
+namespace ResultCacheE2ECircularInheritance;
+
+class First extends Second
+{
+
+}

e2e/result-cache-circular-inheritance/src/Second.php

@@ -0,0 +1,8 @@
+<?php declare(strict_types = 1);
+
+namespace ResultCacheE2ECircularInheritance;
+
+class Second extends Third
+{
+
+}

e2e/result-cache-circular-inheritance/src/Third.php

@@ -0,0 +1,8 @@
+<?php declare(strict_types = 1);
+
+namespace ResultCacheE2ECircularInheritance;
+
+class Third extends First
+{
+
+}

e2e/result-cache-circular-inheritance/src/TraitA.php

@@ -0,0 +1,10 @@
+<?php declare(strict_types = 1);
+
+namespace ResultCacheE2ECircularInheritance;
+
+trait TraitA
+{
+
+	use TraitB;
+
+}

e2e/result-cache-circular-inheritance/src/TraitB.php

@@ -0,0 +1,10 @@
+<?php declare(strict_types = 1);
+
+namespace ResultCacheE2ECircularInheritance;
+
+trait TraitB
+{
+
+	use TraitC;
+
+}

e2e/result-cache-circular-inheritance/src/TraitC.php

@@ -0,0 +1,8 @@
+<?php declare(strict_types = 1);
+
+namespace ResultCacheE2ECircularInheritance;
+
+trait TraitC
+{
+
+}