[AST] Fix a crash on invalid bitwidth exprs when preserving the recoveryexprs.

Summary:
If the bitwith expr contains errors, we mark the field decl invalid.

This patch also tweaks the behavior of ObjCInterfaceDecl to be consistent with
existing RecordDecl -- getObjCLayout method is only called with valid decls.

Reviewers: sammccall

Subscribers: cfe-commits

Tags: #clang

Differential Revision: https://reviews.llvm.org/D76953
diff --git a/clang/lib/AST/ASTContext.cpp b/clang/lib/AST/ASTContext.cpp
index 19f67fc..461b155 100644
--- a/clang/lib/AST/ASTContext.cpp
+++ b/clang/lib/AST/ASTContext.cpp
@@ -2161,6 +2161,11 @@
     return getTypeInfo(cast<AdjustedType>(T)->getAdjustedType().getTypePtr());
   case Type::ObjCInterface: {
     const auto *ObjCI = cast<ObjCInterfaceType>(T);
+    if (ObjCI->getDecl()->isInvalidDecl()) {
+      Width = 8;
+      Align = 8;
+      break;
+    }
     const ASTRecordLayout &Layout = getASTObjCInterfaceLayout(ObjCI->getDecl());
     Width = toBits(Layout.getSize());
     Align = toBits(Layout.getAlignment());