Question: CompileType::ToAbstractType may ignore nullability?

[akemimadoka]

sdk/runtime/vm/compiler/backend/type_propagator.cc

Line 858 in 3f6db11

type_ = &AbstractType::ZoneHandle(type_class.RareType());

This function converts a CompileType to an AbstractType using RareType, but does not use is_nullable, so the result is always non-nullable, is this expected behavior?

[mraleph]

I would say that this is expected though maybe there are places where this can be misused. Maybe we should change this. Did you encounter a code path where this causes problems?

The code predates NNBD. CompileType::cid_ represents concrete runtime type of a value if it is not null (CompileType::can_be_null_ tracks whether the value can be null or not). CompileType::type_ acts as a counterpart of cid_ - with nullability split into can_be_null_.

[a-siva]

Closing as I believe question has been answered.

[akemimadoka]

Thank you @mraleph. The problem I encountered is solved in 36054ee, but the solution doesn't make CompileType::ToAbstractType return a nullable type; instead, it uses ctype directly. Would it be better to use nullable types here instead?