[VM/runtime] Tighten asserts and do not allow duplicate canonical recursive types.

Several improvements in previous CLs should have eliminated duplicate canonical recursive types.

TEST=existing ones

Change-Id: Ic7ef6ea614baa678a9aa99d3f2cae4ceadc71396
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/200884
Reviewed-by: Alexander Markov <[email protected]>
Commit-Queue: Régis Crelier <[email protected]>

Author: crelier

runtime/vm/class_finalizer.cc

@@ -1653,8 +1653,7 @@ void ClassFinalizer::RehashTypes() {
   for (intptr_t i = 0; i < types.Length(); i++) {
     type ^= types.At(i);
     bool present = types_table.Insert(type);
-    // Two recursive types with different topology (and hashes) may be equal.
-    ASSERT(!present || type.IsRecursive());
+    ASSERT(!present);
   }
   object_store->set_canonical_types(types_table.Release());
 
@@ -1674,8 +1673,7 @@ void ClassFinalizer::RehashTypes() {
   for (intptr_t i = 0; i < function_types.Length(); i++) {
     function_type ^= function_types.At(i);
     bool present = function_types_table.Insert(function_type);
-    // Two recursive types with different topology (and hashes) may be equal.
-    ASSERT(!present || function_type.IsRecursive());
+    ASSERT(!present);
   }
   object_store->set_canonical_function_types(function_types_table.Release());
 
@@ -1695,8 +1693,7 @@ void ClassFinalizer::RehashTypes() {
   for (intptr_t i = 0; i < typeparams.Length(); i++) {
     typeparam ^= typeparams.At(i);
     bool present = typeparams_table.Insert(typeparam);
-    // Two recursive types with different topology (and hashes) may be equal.
-    ASSERT(!present || typeparam.IsRecursive());
+    ASSERT(!present);
   }
   object_store->set_canonical_type_parameters(typeparams_table.Release());
 
@@ -1720,8 +1717,7 @@ void ClassFinalizer::RehashTypes() {
   for (intptr_t i = 0; i < typeargs.Length(); i++) {
     typearg ^= typeargs.At(i);
     bool present = typeargs_table.Insert(typearg);
-    // Two recursive types with different topology (and hashes) may be equal.
-    ASSERT(!present || typearg.IsRecursive());
+    ASSERT(!present);
   }
   object_store->set_canonical_type_arguments(typeargs_table.Release());
 }

runtime/vm/clustered_snapshot.cc

@@ -533,14 +533,8 @@ class CanonicalSetSerializationCluster : public SerializationCluster {
         element ^= ptr;
         intptr_t entry = -1;
         const bool present = table.FindKeyOrDeletedOrUnused(element, &entry);
-        if (!present) {
-          table.InsertKey(entry, element);
-        } else {
-          // Two recursive types with different topology (and hashes)
-          // may be equal.
-          ASSERT(element.IsRecursive());
-          objects_[num_occupied++] = ptr;
-        }
+        ASSERT(!present);
+        table.InsertKey(entry, element);
       } else {
         objects_[num_occupied++] = ptr;
       }