[Sema] Fixes infinite recursion when inheriting from a member of the same type

Author: manavgabhawala

lib/Sema/TypeCheckType.cpp

@@ -1134,10 +1134,25 @@ static Type resolveIdentTypeComponent(
                                             diagnoseErrors, resolver,
                                             unsatisfiedDependency);
   if (!parentTy || parentTy->is<ErrorType>()) return parentTy;
-
-  // Resolve the nested type.
+  
   SourceRange parentRange(parentComps.front()->getIdLoc(),
                           parentComps.back()->getSourceRange().End);
+  
+  // Don't resolve the nested type if the parent is equal to the decl context
+  // we are looking in.
+  auto selfTypeBase = DC->getSelfTypeInContext().getPointer();
+  if (DC->getAsClassOrClassExtensionContext() &&
+      selfTypeBase && selfTypeBase->isEqual(parentTy)) {
+    if (diagnoseErrors) {
+      TC.diagnose(parentComps.front()->getStartLoc(),
+                  diag::circular_class_inheritance,
+                  parentComps.front()->getIdentifier().str())
+        .fixItRemove(parentRange);
+    }
+    return ErrorType::get(TC.Context);
+  }
+  
+  // Resolve the nested type.
   return resolveNestedIdentTypeComponent(TC, DC, parentTy,
                                          parentRange, comp,
                                          options, diagnoseErrors,

validation-test/compiler_crashers/08008-swift-typechecker-typecheckexpression.swift renamed to validation-test/compiler_crashers_2_fixed/08008-swift-typechecker-typecheckexpression.swift

@@ -5,6 +5,6 @@
 // See http://swift.org/LICENSE.txt for license information
 // See http://swift.org/CONTRIBUTORS.txt for the list of Swift project authors
 
-// RUN: not --crash %target-swift-frontend %s -parse
+// RUN: not %target-swift-frontend %s -parse
 // ASAN Output: stack-overflow on address 0x7fffe2a98fd8 (pc 0x000001e12adb bp 0x7fffe2a992d0 sp 0x7fffe2a98f60 T0)
 class A:A.b{let b=Void{

validation-test/compiler_crashers/21765-vtable.swift renamed to validation-test/compiler_crashers_fixed/21765-vtable.swift

@@ -5,7 +5,7 @@
 // See http://swift.org/LICENSE.txt for license information
 // See http://swift.org/CONTRIBUTORS.txt for the list of Swift project authors
 
-// RUN: not --crash %target-swift-frontend %s -parse
+// RUN: not %target-swift-frontend %s -parse
 // ASAN Output: stack-overflow on address 0x7ffe8def3f70 (pc 0x000001cf1268 bp 0x7ffe8def48f0 sp 0x7ffe8def3f00 T0)
 func b<T {
 class A : A.e {

validation-test/compiler_crashers/27939-vtable.swift renamed to validation-test/compiler_crashers_fixed/27939-vtable.swift

@@ -5,7 +5,7 @@
 // See http://swift.org/LICENSE.txt for license information
 // See http://swift.org/CONTRIBUTORS.txt for the list of Swift project authors
 
-// RUN: not --crash %target-swift-frontend %s -parse
+// RUN: not %target-swift-frontend %s -parse
 // ASAN Output: stack-overflow on address 0x7ffdad0b1cd0 (pc 0x000001cf1268 bp 0x7ffdad0b2650 sp 0x7ffdad0b1c60 T0)
 func b<T {
 class A : A.e {