[Serialization] Skip serializing invalid destructors if allowing errors

Author: bnbarham

lib/Serialization/Serialization.cpp

@@ -3933,6 +3933,9 @@ class Serializer::DeclSerializer : public DeclVisitor<DeclSerializer> {
     using namespace decls_block;
     verifyAttrSerializable(dtor);
 
+    if (S.allowCompilerErrors() && dtor->isInvalid())
+      return;
+
     auto contextID = S.addDeclContextRef(dtor->getDeclContext());
 
     unsigned abbrCode = S.DeclTypeAbbrCodes[DestructorLayout::Code];

validation-test/Serialization/AllowErrors/invalid-deinit.swift

@@ -0,0 +1,8 @@
+// RUN: %empty-directory(%t)
+
+// RUN: %target-swift-frontend -module-name errors -emit-module -o %t/errors.swiftmodule -experimental-allow-module-with-compiler-errors %s
+
+// deinit is only valid on a class, make sure we don't crash when allowing
+// errors
+
+deinit {}