Sema: Don't set "validation started" bit on typealiases in the ITC

This appears to do nothing except cause a crash.

Author: slavapestov

lib/Sema/ITCDecl.cpp

@@ -342,8 +342,6 @@ void IterativeTypeChecker::processResolveTypeDecl(
   if (auto typeAliasDecl = dyn_cast<TypeAliasDecl>(typeDecl)) {
     if (typeAliasDecl->getDeclContext()->isModuleScopeContext() &&
         typeAliasDecl->getGenericParams() == nullptr) {
-      typeAliasDecl->setValidationStarted();
-
       TypeResolutionOptions options = TR_TypeAliasUnderlyingType;
       if (typeAliasDecl->getFormalAccess() <= Accessibility::FilePrivate)
         options |= TR_KnownNonCascadingDependency;

validation-test/compiler_crashers/28728-d-isbeingvalidated-d-hasvalidsignature.swift renamed to validation-test/compiler_crashers_fixed/28728-d-isbeingvalidated-d-hasvalidsignature.swift

@@ -6,6 +6,6 @@
 // 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
 typealias e:a
 struct A:a{}typealias a=A