Rename `ReturnInfo` to `ReturnTypeInfo`. Move it and `InitRepr` into
`type_info.h` alongside `ValueRepr`. Replace `ReturnSlot` with
`InitRepr`, and extend `InitRepr` to be able to represent the
incomplete-type case instead of CHECK-failing. Remove `has_return_slot`
from `InitRepr` and instead only provide that as part of
`ReturnTypeInfo`.
The caching isn't buying us much, and is adding complexity and
divergence between the codepaths for generic and non-generic functions.
This means we no longer suppress diagnostics for the second or
subsequent time we call a function with an incomplete return type. If we
want to add that back, it might be worth considering moving the
suppression to `TryToCompleteType` and only diagnosing that a type is
incomplete once, regardless of why we're requiring it to be complete.
As discussed in toolchain meeting, we want to avoid overloading the
meaning of "instance", and "specific" was the best name we found. It's a
little unorthodox and inventive, but hopefully over time will become as
unsurprising as the term "generic" is.
Require mapping from a `ConstantId` to an `InstId` to go through the
`ConstantValueStore`.
This is a preparatory step for an upcoming generics change where
symbolic `ConstantId`s are no longer just a thin wrapper around an
`InstId` but instead are indexes into a table with additional
information about the symbolic constant beyond its `InstId`.
Instead of redundantly storing both the `return_type_id` and
`return_storage_id`, where the declared return type is just the type of
the return storage, store only the `return_storage_id`.
Add a convenience property to get the declared return type of the
function.
In addition to avoiding storing redundant information, this is a
preparatory step for an upcoming change for generics support that will
make it more expensive and awkward to store `TypeId`s in places other
than the type of an instruction.
This removes the builtin FunctionType, replacing it with a FunctionType
instruction. The constant for a FunctionDecl is now a StructValue with
type of FunctionType.
Note this means a function declaration produces _both_ a type, and a
value of the type. This has some consequences in terms of circularity,
and makes the importing of function declarations a little more complex.
It'll get particularly peculiar for imports because of the behavior of
the reference, but that's a known issue due to other things such as
`alias`. The impact will hopefully be contained to
ResolvePrevInstForMerge (and ImportRefs).
To note a small formatting change in diagnostics:
```
- // CHECK:STDERR: fail_member_lookup.carbon:[[@LINE+4]]:3: ERROR: Value of type `<associated <function> in Interface>` is not callable.
+ // CHECK:STDERR: fail_member_lookup.carbon:[[@LINE+4]]:3: ERROR: Value of type `<associated F in Interface>` is not callable.
- // CHECK:STDERR: fail_todo_facet_lookup.carbon:[[@LINE+4]]:3: ERROR: Value of type `<associated <function> in Interface>` is not callable.
+ // CHECK:STDERR: fail_todo_facet_lookup.carbon:[[@LINE+4]]:3: ERROR: Value of type `<associated F in Interface>` is not callable.
```
---------
Co-authored-by: Richard Smith <richard@metafoo.co.uk>
Richard Smith
Jon Ross-PerkinsandRichard Smith