diff --git a/frontend/include/chpl/framework/ErrorWriter.h b/frontend/include/chpl/framework/ErrorWriter.h
index 2c2d567a7b41..2cd7d40b2c22 100644
--- a/frontend/include/chpl/framework/ErrorWriter.h
+++ b/frontend/include/chpl/framework/ErrorWriter.h
@@ -134,7 +134,7 @@ struct Writer<errordetail::AsFileName<T>> {
 template <>
 struct Writer<const types::Type*> {
   void operator()(Context* context, std::ostream& oss, const types::Type* type) {
-    if (type->isUnknownType()) {
+    if (!type || type->isUnknownType()) {
       oss << "unknown type";
     } else {
       stringify<const types::Type*> str;
diff --git a/frontend/lib/resolution/Resolver.cpp b/frontend/lib/resolution/Resolver.cpp
index eeeb3403b1d7..241139ce17c4 100644
--- a/frontend/lib/resolution/Resolver.cpp
+++ b/frontend/lib/resolution/Resolver.cpp
@@ -2208,8 +2208,6 @@ QualifiedType Resolver::typeForId(const ID& id, bool localGenericToUnknown) {
     }
   }
 
-  CHPL_ASSERT(ct); // or else, pattern not handled yet
-
   if (ct) {
     auto newDefaultsPolicy = defaultsPolicy;
     if (defaultsPolicy == DefaultsPolicy::USE_DEFAULTS_OTHER_FIELDS &&
@@ -2240,7 +2238,7 @@ QualifiedType Resolver::typeForId(const ID& id, bool localGenericToUnknown) {
 
   // Otherwise it is a case not handled yet
   // TODO: handle outer function variables
-  CHPL_ASSERT(false && "not yet handled");
+  CHPL_UNIMPL("not yet handled");
   auto unknownType = UnknownType::get(context);
   return QualifiedType(QualifiedType::UNKNOWN, unknownType);
 }
diff --git a/frontend/lib/resolution/call-init-deinit.cpp b/frontend/lib/resolution/call-init-deinit.cpp
index 8ffcaf26d1bd..8e5d2ea3faae 100644
--- a/frontend/lib/resolution/call-init-deinit.cpp
+++ b/frontend/lib/resolution/call-init-deinit.cpp
@@ -509,6 +509,11 @@ void CallInitDeinit::resolveAssign(const AstNode* ast,
                                    const QualifiedType& lhsType,
                                    const QualifiedType& rhsType,
                                    RV& rv) {
+  if (lhsType.isUnknown() || lhsType.isErroneousType() ||
+      rhsType.isUnknown() || rhsType.isErroneousType()) {
+    return;
+  }
+
   std::vector<CallInfoActual> actuals;
   actuals.push_back(CallInfoActual(lhsType, UniqueString()));
   actuals.push_back(CallInfoActual(rhsType, UniqueString()));
diff --git a/frontend/lib/resolution/default-functions.cpp b/frontend/lib/resolution/default-functions.cpp
index 60e31e743c97..23cc586d8f4d 100644
--- a/frontend/lib/resolution/default-functions.cpp
+++ b/frontend/lib/resolution/default-functions.cpp
@@ -227,7 +227,8 @@ generateInitSignature(Context* context, const CompositeType* inCompType) {
 
   // TODO: generic types
   if (rf.isGeneric()) {
-    CHPL_ASSERT(false && "Not handled yet!");
+    CHPL_UNIMPL("generating 'init' signatures for generic types is not yet supported");
+    return nullptr;
   }
 
   // TODO: super fields and invoking super
@@ -745,16 +746,16 @@ getCompilerGeneratedMethodQuery(Context* context, const Type* type,
       } else if (name == USTR("=")) {
         result = generateRecordAssignment(context, recordType);
       } else {
-        CHPL_ASSERT(false && "record method not implemented yet!");
+        CHPL_UNIMPL("record method not implemented yet!");
       }
     } else if (auto cPtrType = type->toCPtrType()) {
       result = generateCPtrMethod(context, cPtrType, name);
     } else {
-      CHPL_ASSERT(false && "should not be reachable");
+      CHPL_UNIMPL("should not be reachable");
     }
   }
 
-  CHPL_ASSERT(result->untyped()->name() == name);
+  CHPL_ASSERT(result == nullptr || result->untyped()->name() == name);
 
   return QUERY_END(result);
 }
diff --git a/frontend/lib/resolution/resolution-queries.cpp b/frontend/lib/resolution/resolution-queries.cpp
index 4482667e8c7f..4d8c838a960b 100644
--- a/frontend/lib/resolution/resolution-queries.cpp
+++ b/frontend/lib/resolution/resolution-queries.cpp
@@ -3353,7 +3353,6 @@ considerCompilerGeneratedMethods(Context* context,
   // get the compiler-generated function, may be generic
   auto tfs = getCompilerGeneratedMethod(context, receiverType, ci.name(),
                                         ci.isParenless());
-  CHPL_ASSERT(tfs);
   return tfs;
 }
 
diff --git a/frontend/lib/util/assertions.cpp b/frontend/lib/util/assertions.cpp
index 14305f1ebd31..505900bdc416 100644
--- a/frontend/lib/util/assertions.cpp
+++ b/frontend/lib/util/assertions.cpp
@@ -67,8 +67,8 @@ void chpl_unimpl(const char* filename, const char* func, int lineno,
                  const char* msg) {
   std::string fname(filename);
   auto front = fname.substr(fname.find("frontend"), std::string::npos);
-  printf("[%s:%d in %s] Unimplemented: %s\n", front.c_str(), lineno,
-         func, msg);
+  fprintf(stderr, "[%s:%d in %s] Unimplemented: %s\n", front.c_str(), lineno,
+          func, msg);
 };