Fix infinite loop when resolving method call with superclass cycle (#656)

Author: pynicolas

php-frontend/src/main/java/org/sonar/php/tree/symbols/SymbolUsageVisitor.java

@@ -20,7 +20,9 @@
 package org.sonar.php.tree.symbols;
 
 import java.util.ArrayDeque;
+import java.util.HashSet;
 import java.util.Optional;
+import java.util.Set;
 import org.sonar.php.symbols.ClassSymbol;
 import org.sonar.php.symbols.ClassSymbolIndex;
 import org.sonar.php.symbols.FunctionSymbol;
@@ -99,7 +101,8 @@ private void resolveMethodCall(FunctionCallTree tree, MemberAccessTree callee) {
       String methodName = ((NameIdentifierTree) callee.member()).text();
       MethodSymbol methodSymbol = receiverSymbol.getDeclaredMethod(methodName);
       Optional<ClassSymbol> superClass = receiverSymbol.superClass();
-      while (superClass.isPresent() && methodSymbol.isUnknownSymbol()) {
+      Set<ClassSymbol> processedClasses = new HashSet<>();
+      while (superClass.isPresent() && methodSymbol.isUnknownSymbol() && processedClasses.add(superClass.get())) {
         methodSymbol = superClass.get().getDeclaredMethod(methodName);
         superClass = superClass.get().superClass();
       }

php-frontend/src/test/java/org/sonar/php/symbols/MethodCallResolutionTest.java

@@ -50,6 +50,13 @@ public void resolve_this_with_inheritance() {
       "class B extends A { function f(){ $this->f(); } }")).isKnown("B::f");
   }
 
+  @Test
+  public void resolve_with_superclass_cycle() {
+    assertThat(callSymbol("<?php ",
+      "class A extends B { }",
+      "class B extends A { function g(){ $this->f(); } }")).isUnknown();
+  }
+
   @Test
   public void resolve_self_and_static() {
     assertThat(callSymbol("<?php class A { function f(){} function g(){ self::f(); } }")).isKnown("A::f");