AST: Fix crash when doing name lookup into class with circular inheritance

Author: slavapestov

lib/AST/ConformanceLookupTable.cpp

@@ -319,6 +319,10 @@ void ConformanceLookupTable::updateLookupTable(NominalTypeDecl *nominal,
           return;
         llvm::SaveAndRestore<bool> visiting(VisitingSuperclass, true);
 
+        // Don't update our own lookup table if we inherit from ourselves.
+        if (classDecl == superclassDecl)
+          break;
+
         // Resolve the conformances of the superclass.
         superclassDecl->prepareConformanceTable();
         superclassDecl->ConformanceTable->updateLookupTable(

test/decl/class/circular_inheritance.swift

@@ -6,7 +6,7 @@
 // RUN: %FileCheck -check-prefix CHECK-DOT %s  < %t.dot
 
 // Check that we produced superclass type requests.
-// RUN: %{python} %utils/process-stats-dir.py --evaluate 'SuperclassTypeRequest == 16' %t/stats-dir
+// RUN: %{python} %utils/process-stats-dir.py --evaluate 'SuperclassTypeRequest == 17' %t/stats-dir
 
 class Left
     : Right.Hand {
@@ -59,3 +59,19 @@ class Outer3
 
 // CHECK-DOT: digraph Dependencies
 // CHECK-DOT: label="InheritedTypeRequest
+
+protocol Initable {
+  init()
+  // expected-note@-1 {{protocol requires initializer 'init()' with type '()'; do you want to add a stub?}}
+}
+
+protocol Shape : Circle {}
+
+class Circle : Initable & Circle {}
+// expected-error@-1 {{'Circle' inherits from itself}}
+// expected-error@-2 {{type 'Circle' does not conform to protocol 'Initable'}}
+
+func crash() {
+  Circle()
+  // expected-error@-1 {{'Circle' cannot be constructed because it has no accessible initializers}}
+}

validation-test/compiler_crashers/28833-foundintype-isexistentialtype.swift renamed to validation-test/compiler_crashers_fixed/28833-foundintype-isexistentialtype.swift

@@ -5,8 +5,8 @@
 // See https://swift.org/LICENSE.txt for license information
 // See https://swift.org/CONTRIBUTORS.txt for the list of Swift project authors
 
-// REQUIRES: asserts
-// RUN: not --crash %target-swift-frontend %s -emit-ir
+
+// RUN: not %target-swift-frontend %s -emit-ir
 protocol A:a{}class a:RangeReplaceableCollection
 & a
 func<a