Move Type.Data.ip_index and .either to Type

[FnControlOption]

The is_type_val field is redundant for ip_index and either, so let's turn Type into a tagged union with those and the original struct as the possible variants. Currently, I've named the new variant as dynamic, but I'm open to suggestions!

Before

After

pub const Type = struct { data: Data, is_type_val: bool, pub const Data = union(enum) { // ... compile_error: NodeWithHandle, either: []const EitherEntry, ip_index: struct { node: ?NodeWithHandle = null, index: InternPool.Index, }, pub const EitherEntry = struct { type_data: Data, descriptor: []const u8, }; }; // ... pub const TypeWithDescriptor = struct { type: Type, descriptor: []const u8, }; // ... };

pub const Type = union(enum) { dynamic: struct { data: Data, is_type_val: bool, }, ip_index: struct { node: ?NodeWithHandle = null, index: InternPool.Index, }, either: []const TypeWithDescriptor, pub const Data = union(enum) { // ... compile_error: NodeWithHandle, }; // ... pub const TypeWithDescriptor = struct { type: Type, descriptor: []const u8, }; // ... };

[Techatrix]

What exactly is this PR trying to improve? The PR description implies code quality by removing a redundant field but the code now requires analysis to switch twice every time it want to extract some information out of Type. Having is_type_val is not a big issue for ip_index and either since it avoids computing it (which happens quite often) and the rest of the code remains more readable. Hypothetically, if ZLS was already in the "After" state, I would accept a PR that would change it to the "Before" state.

This change will also conflicts with #2180 since it tries to add a new field to Type.