idl: Fix defined types with unsupported fields not producing an error

[acheroncrypto]

Problem

As mentioned in #4073, defined types (structs and enums) do not get included in the IDL if they contain unsupported type(s).

For example, with the following type:

pub struct BrokenType {
    x: (u32, u32),
}

IDL build successfully, but there is no type definition for BrokenType in the types section. This is not only unintuitive, but it also breaks other parts of the framework e.g. declare_program! and TS package usage.

Summary of changes

Make unsupported field types of defined types produce an error instead of omitting the type definition altogether.

Example error output:

error: Unsupported type
  --> programs/name/src/lib.rs:37:8
   |
37 |     x: (u32, u32),
   |        ^^^^^^^^^^

Note: This is a fix but also a breaking change because, although unlikely, programs that compiled before this change might not compile after this change if they are using unsupported types in their public API.

Fixes #4073

[vercel]

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