The compiler actually doesn't need any functional changes for this: Sema
does reification based on the tag indices of `std.builtin.Type` already!
So, no zig1.wasm update is necessary.
This change is necessary to disallow name clashes between fields and
decls on a type, which is a prerequisite of #9938.
The type `Zcu.Decl` in the compiler is problematic: over time it has
gained many responsibilities. Every source declaration, container type,
generic instantiation, and `@extern` has a `Decl`. The functions of
these `Decl`s are in some cases entirely disjoint.
After careful analysis, I determined that the two main responsibilities
of `Decl` are as follows:
* A `Decl` acts as the "subject" of semantic analysis at comptime. A
single unit of analysis is either a runtime function body, or a
`Decl`. It registers incremental dependencies, tracks analysis errors,
etc.
* A `Decl` acts as a "global variable": a pointer to it is consistent,
and it may be lowered to a specific symbol by the codegen backend.
This commit eliminates `Decl` and introduces new types to model these
responsibilities: `Cau` (Comptime Analysis Unit) and `Nav` (Named
Addressable Value).
Every source declaration, and every container type requiring resolution
(so *not* including `opaque`), has a `Cau`. For a source declaration,
this `Cau` performs the resolution of its value. (When #131 is
implemented, it is unsolved whether type and value resolution will share
a `Cau` or have two distinct `Cau`s.) For a type, this `Cau` is the
context in which type resolution occurs.
Every non-`comptime` source declaration, every generic instantiation,
and every distinct `extern` has a `Nav`. These are sent to codegen/link:
the backends by definition do not care about `Cau`s.
This commit has some minor technically-breaking changes surrounding
`usingnamespace`. I don't think they'll impact anyone, since the changes
are fixes around semantics which were previously inconsistent (the
behavior changed depending on hashmap iteration order!).
Aside from that, this changeset has no significant user-facing changes.
Instead, it is an internal refactor which makes it easier to correctly
model the responsibilities of different objects, particularly regarding
incremental compilation. The performance impact should be negligible,
but I will take measurements before merging this work into `master`.
Co-authored-by: Jacob Young <jacobly0@users.noreply.github.com>
Co-authored-by: Jakub Konka <kubkon@jakubkonka.com>
I pointed a fuzzer at the tokenizer and it crashed immediately. Upon
inspection, I was dissatisfied with the implementation. This commit
removes several mechanisms:
* Removes the "invalid byte" compile error note.
* Dramatically simplifies tokenizer recovery by making recovery always
occur at newlines, and never otherwise.
* Removes UTF-8 validation.
* Moves some character validation logic to `std.zig.parseCharLiteral`.
Removing UTF-8 validation is a regression of #663, however, the existing
implementation was already buggy. When adding this functionality back,
it must be fuzz-tested while checking the property that it matches an
independent Unicode validation implementation on the same file. While
we're at it, fuzzing should check the other properties of that proposal,
such as no ASCII control characters existing inside the source code.
Other changes included in this commit:
* Deprecate `std.unicode.utf8Decode` and its WTF-8 counterpart. This
function has an awkward API that is too easy to misuse.
* Make `utf8Decode2` and friends use arrays as parameters, eliminating a
runtime assertion in favor of using the type system.
After this commit, the crash found by fuzzing, which was
"\x07\xd5\x80\xc3=o\xda|a\xfc{\x9a\xec\x91\xdf\x0f\\\x1a^\xbe;\x8c\xbf\xee\xea"
no longer causes a crash. However, I did not feel the need to add this
test case because the simplified logic eradicates most crashes of this
nature.
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.
This change seeks to more appropriately model the way semantic analysis
works by drawing a more clear line between errors emitted by analyzing a
`Decl` (in future a `Cau`) and errors emitted by analyzing a runtime
function.
This does change a few compile errors surrounding compile logs by adding
more "also here" notes. The new notes are more technically correct, but
perhaps not so helpful. They're not doing enough harm for me to put
extensive thought into this for now.
`LazySrcLoc` now stores a reference to the "base AST node" to which it
is relative. The previous tagged union is `LazySrcLoc.Offset`. To make
working with this structure convenient, `Sema.Block` contains a
convenience `src` method which takes an `Offset` and returns a
`LazySrcLoc`.
The "base node" of a source location is no longer given by a `Decl`, but
rather a `TrackedInst` representing either a `declaration`,
`struct_decl`, `union_decl`, `enum_decl`, or `opaque_decl`. This is a
more appropriate model, and removes an unnecessary responsibility from
`Decl` in preparation for the upcoming refactor which will split it into
`Nav` and `Cau`.
As a part of these `Decl` reworks, the `src_node` field is eliminated.
This change aids incremental compilation, and simplifies `Decl`. In some
cases -- particularly in backends -- the source location of a
declaration is desired. This was previously `Decl.srcLoc` and worked for
any `Decl`. Now, it is `Decl.navSrcLoc` in reference to the upcoming
refactor, since the set of `Decl`s this works for precisely corresponds
to what will in future become a `Nav` -- that is, source-level
declarations and generic function instantiations, but *not* type owner
Decls.
This commit introduces more tags to `LazySrcLoc.Offset` so as to
eliminate the concept of `error.NeededSourceLocation`. Now, `.unneeded`
should only be used to assert that an error path is unreachable. In the
future, uses of `.unneeded` can probably be replaced with `undefined`.
The `src_decl` field of `Sema.Block` no longer has a role in type
resolution. Its main remaining purpose is to handle namespacing of type
names. It will be eliminated entirely in a future commit to remove
another undue responsibility from `Decl`.
It is worth noting that in future, the `Zcu.SrcLoc` type should probably
be eliminated entirely in favour of storing `Zcu.LazySrcLoc` values.
This is because `Zcu.SrcLoc` is not valid across incremental updates,
and we want to be able to reuse error messages from previous updates
even if the source file in question changed. The error reporting logic
should instead simply resolve the location from the `LazySrcLoc` on the
fly.
This reverts commit a7de02e05216db9a04e438703ddf1b6b12f3fbef.
This did not implement the accepted proposal, and I did not sign off
on the changes. I would like a chance to review this, please.
Previously the error had a note suggesting to use `try`, `catch`, or
`if`, even for error sets where none of those work.
Instead, in case of an error set the way you can handle the error
depends very much on the specific case. For example you might be in a
`catch` where you are discarding or ignoring the error set capture
value, in which case one way to handle the error might be to `return`
the error.
So, in that case, we do not attach that error note.
Additionally, this makes the error tell you what kind of an error it is:
is it an error set or an error union? This distinction is very relevant
in how to handle the error.
Maybe I'm just being pedantic here (most likely) but I don't like how we're
just telling the user here how to "suppress this error" by "assigning the value to '_'".
I think it's better if we use the word "discard" here which I think is
the official terminology and also tells the user what it actually means
to "assign the value to '_'".
Also, using the value would also be a way to "suppress the error".
It is just one of the two options: discard or use.
This commit reverts the handling of partially-undefined values in
bitcasting to transform these bits into an arbitrary numeric value,
like happens on `master` today.
As @andrewrk rightly points out, #19634 has unfortunate consequences
for the standard library, and likely requires more thought. To avoid
a major breaking change, it has been decided to revert this design
decision for now, and make a more informed decision further down the
line.
We've got a big one here! This commit reworks how we represent pointers
in the InternPool, and rewrites the logic for loading and storing from
them at comptime.
Firstly, the pointer representation. Previously, pointers were
represented in a highly structured manner: pointers to fields, array
elements, etc, were explicitly represented. This works well for simple
cases, but is quite difficult to handle in the cases of unusual
reinterpretations, pointer casts, offsets, etc. Therefore, pointers are
now represented in a more "flat" manner. For types without well-defined
layouts -- such as comptime-only types, automatic-layout aggregates, and
so on -- we still use this "hierarchical" structure. However, for types
with well-defined layouts, we use a byte offset associated with the
pointer. This allows the comptime pointer access logic to deal with
reinterpreted pointers far more gracefully, because the "base address"
of a pointer -- for instance a `field` -- is a single value which
pointer accesses cannot exceed since the parent has undefined layout.
This strategy is also more useful to most backends -- see the updated
logic in `codegen.zig` and `codegen/llvm.zig`. For backends which do
prefer a chain of field and elements accesses for lowering pointer
values, such as SPIR-V, there is a helpful function in `Value` which
creates a strategy to derive a pointer value using ideally only field
and element accesses. This is actually more correct than the previous
logic, since it correctly handles pointer casts which, after the dust
has settled, end up referring exactly to an aggregate field or array
element.
In terms of the pointer access code, it has been rewritten from the
ground up. The old logic had become rather a mess of special cases being
added whenever bugs were hit, and was still riddled with bugs. The new
logic was written to handle the "difficult" cases correctly, the most
notable of which is restructuring of a comptime-only array (for
instance, converting a `[3][2]comptime_int` to a `[2][3]comptime_int`.
Currently, the logic for loading and storing work somewhat differently,
but a future change will likely improve the loading logic to bring it
more in line with the store strategy. As far as I can tell, the rewrite
has fixed all bugs exposed by #19414.
As a part of this, the comptime bitcast logic has also been rewritten.
Previously, bitcasts simply worked by serializing the entire value into
an in-memory buffer, then deserializing it. This strategy has two key
weaknesses: pointers, and undefined values. Representations of these
values at comptime cannot be easily serialized/deserialized whilst
preserving data, which means many bitcasts would become runtime-known if
pointers were involved, or would turn `undefined` values into `0xAA`.
The new logic works by "flattening" the datastructure to be cast into a
sequence of bit-packed atomic values, and then "unflattening" it; using
serialization when necessary, but with special handling for `undefined`
values and for pointers which align in virtual memory. The resulting
code is definitely slower -- more on this later -- but it is correct.
The pointer access and bitcast logic required some helper functions and
types which are not generally useful elsewhere, so I opted to split them
into separate files `Sema/comptime_ptr_access.zig` and
`Sema/bitcast.zig`, with simple re-exports in `Sema.zig` for their small
public APIs.
Whilst working on this branch, I caught various unrelated bugs with
transitive Sema errors, and with the handling of `undefined` values.
These bugs have been fixed, and corresponding behavior test added.
In terms of performance, I do anticipate that this commit will regress
performance somewhat, because the new pointer access and bitcast logic
is necessarily more complex. I have not yet taken performance
measurements, but will do shortly, and post the results in this PR. If
the performance regression is severe, I will do work to to optimize the
new logic before merge.
Resolves: #19452Resolves: #19460
