The purpose of using path digest was to reference a file in a
serializable manner. Now that there is a stable index associated with
files, it is a superior way to accomplish that goal, since removes one
layer of indirection, and makes TrackedInst 8 bytes instead of 20.
The saved Zig Compiler State file for "hello world" goes from 1.3M to
1.2M with this change.
Primarily, this commit removes 2 fields from File, relying on the data
being stored in the `files` field, with the key as the path digest, and
the value as the struct decl corresponding to the File. This table is
serialized into the compiler state that survives between incremental
updates.
Meanwhile, the File struct remains ephemeral data that can be
reconstructed the first time it is needed by the compiler process, as
well as operated on by independent worker threads.
A key outcome of this commit is that there is now a stable index that
can be used to refer to a File. This will be needed when serializing
error messages to survive incremental compilation updates.
I'm so sorry.
This commit was just meant to be making all types fully resolve by
queueing resolution at the moment of their creation. Unfortunately, a
lot of dominoes ended up falling. Here's what happened:
* I added a work queue job to fully resolve a type.
* I realised that from here we could eliminate `Sema.types_to_resolve`
if we made function codegen a separate job. This is desirable for
simplicity of both spec and implementation.
* This led to a new AIR traversal to detect whether any required type is
unresolved. If a type in the AIR failed to resolve, then we can't run
codegen.
* Because full type resolution now occurs by the work queue job, a bug
was exposed whereby error messages for type resolution were associated
with the wrong `Decl`, resulting in duplicate error messages when the
type was also resolved "by" its owner `Decl` (which really *all*
resolution should be done on).
* A correct fix for this requires using a different `Sema` when
performing type resolution: we need a `Sema` owned by the type. Also
note that this fix is necessary for incremental compilation.
* This means a whole bunch of functions no longer need to take `Sema`s.
* First-order effects: `resolveTypeFields`, `resolveTypeLayout`, etc
* Second-order effects: `Type.abiAlignmentAdvanced`, `Value.orderAgainstZeroAdvanced`, etc
The end result of this is, in short, a more correct compiler and a
simpler language specification. This regressed a few error notes in the
test cases, but nothing that seems worth blocking this change.
Oh, also, I ripped out the old code in `test/src/Cases.zig` which
introduced a dependency on `Compilation`. This dependency was
problematic at best, and this code has been unused for a while. When we
re-enable incremental test cases, we must rewrite their executor to use
the compiler server protocol.
