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This vector type has served us well for now, but it contains internal refcounts
which are incompatible with upcoming changes related to garbage collection.
The performance impact of this change within all benchmarks I ran was within the
margin of error:
[nix-shell:/tmp/perf]$ hyperfine "./before -E '(import <nixpkgs> {}).firefox.outPath' --log-level ERROR --no-warnings"
Benchmark 1: ./u64 -E '(import <nixpkgs> {}).firefox.outPath' --log-level ERROR --no-warnings
Time (mean ± σ): 7.528 s ± 0.272 s [User: 6.578 s, System: 0.631 s]
Range (min … max): 7.160 s … 8.012 s 10 runs
nix-shell:/tmp/perf]$ hyperfine "./std-vec -E '(import <nixpkgs> {}).firefox.outPath' --log-level ERROR --no-warnings"
Benchmark 1: ./std-vec -E '(import <nixpkgs> {}).firefox.outPath' --log-level ERROR --no-warnings
Time (mean ± σ): 7.515 s ± 0.178 s [User: 6.508 s, System: 0.652 s]
Range (min … max): 7.276 s … 7.861 s 10 runs
Change-Id: Ib95f871956e336a1e5771f6293583854b1efb276
Reviewed-on: https://cl.tvl.fyi/c/depot/+/12197
Reviewed-by: aspen <root@gws.fyi>
Tested-by: BuildkiteCI
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In order to correctly propagate errors in the comparator passed to
builtins.sort, we need to do all the sorting in a context where we can
short-circuit return `Value`s (because catchables are Values on the `Ok`
side of the Result , not `Err`s). Unfortunately this means we have
to *inline* the List `sort_by` implementation into the builtin_sort
function - fortunately this is the only place that was called so this is
relatively low cost. This does that, and adds the requisite `try_value!`
invocation to allow us to propagate comparator errors here.
As before, this doesn't include tests, primarily since those are coming
in the next commit.
Change-Id: I8453c3aa2cd82299eae89828e2a2bb118da4cd48
Reviewed-on: https://cl.tvl.fyi/c/depot/+/10754
Tested-by: BuildkiteCI
Reviewed-by: raitobezarius <tvl@lahfa.xyz>
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Relates to b/321.
Change-Id: I37284f89b186e469eb432e2bbedb37aa125a6ad4
Reviewed-on: https://cl.tvl.fyi/c/depot/+/9961
Tested-by: BuildkiteCI
Reviewed-by: flokli <flokli@flokli.de>
Autosubmit: tazjin <tazjin@tvl.su>
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This drops the usage of serde::Serialize, as the trait can not be used
to implement the correct semantics (function colouring!).
Instead, a manual JSON serialisation function is written which
correctly handles toString, outPath and other similar weirdnesses.
Unexpectedly, the eval-okay-tojson test from the C++ Nix test suite
now passes, too.
This fixes an issue where serialising data structures containing
derivations to JSON would fail.
Change-Id: I5c39e3d8356ee93a07eda481410f88610f6dd9f8
Reviewed-on: https://cl.tvl.fyi/c/depot/+/8209
Reviewed-by: raitobezarius <tvl@lahfa.xyz>
Tested-by: BuildkiteCI
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The size of a `Vector<Value>` is 64 *bytes*, which is quite large, and
it bloated the entire Value type to this size.
This change adds an indirection for the inner vector through Rc.
Initially I tried to use a Box, but this breaks pointer equality
guarantees for the Vector when it is small enough to be inlined.
This reduces the size of Value from 64 to 32 bytes.
Change-Id: Ic3211e861b1966c78b2c3d536ba291fea92647fd
Reviewed-on: https://cl.tvl.fyi/c/depot/+/8150
Reviewed-by: raitobezarius <tvl@lahfa.xyz>
Tested-by: BuildkiteCI
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Warning: This is probably the biggest refactor in tvix-eval history,
so far.
This replaces all instances of trampolines and recursion during
evaluation of the VM loop with generators. A generator is an
asynchronous function that can be suspended to yield a message (in our
case, vm::generators::GeneratorRequest) and receive a
response (vm::generators::GeneratorResponsee).
The `genawaiter` crate provides an interpreter for generators that can
drive their execution and lets us move control flow between the VM and
suspended generators.
To do this, massive changes have occured basically everywhere in the
code. On a high-level:
1. The VM is now organised around a frame stack. A frame is either a
call frame (execution of Tvix bytecode) or a generator frame (a
running or suspended generator).
The VM has an outer loop that pops a frame off the frame stack, and
then enters an inner loop either driving the execution of the
bytecode or the execution of a generator.
Both types of frames have several branches that can result in the
frame re-enqueuing itself, and enqueuing some other work (in the
form of a different frame) on top of itself. The VM will eventually
resume the frame when everything "above" it has been suspended.
In this way, the VM's new frame stack takes over much of the work
that was previously achieved by recursion.
2. All methods previously taking a VM have been refactored into async
functions that instead emit/receive generator messages for
communication with the VM.
Notably, this includes *all* builtins.
This has had some other effects:
- Some test have been removed or commented out, either because they
tested code that was mostly already dead (nix_eq) or because they
now require generator scaffolding which we do not have in place for
tests (yet).
- Because generator functions are technically async (though no async
IO is involved), we lose the ability to use much of the Rust
standard library e.g. in builtins. This has led to many algorithms
being unrolled into iterative versions instead of iterator
combinations, and things like sorting had to be implemented from scratch.
- Many call sites that previously saw a `Result<..., ErrorKind>`
bubble up now only see the result value, as the error handling is
encapsulated within the generator loop.
This reduces number of places inside of builtin implementations
where error context can be attached to calls that can fail.
Currently what we gain in this tradeoff is significantly more
detailed span information (which we still need to bubble up, this
commit does not change the error display).
We'll need to do some analysis later of how useful the errors turn
out to be and potentially introduce some methods for attaching
context to a generator frame again.
This change is very difficult to do in stages, as it is very much an
"all or nothing" change that affects huge parts of the codebase. I've
tried to isolate changes that can be isolated into the parent CLs of
this one, but this change is still quite difficult to wrap one's mind
and I'm available to discuss it and explain things to any reviewer.
Fixes: b/238, b/237, b/251 and potentially others.
Change-Id: I39244163ff5bbecd169fe7b274df19262b515699
Reviewed-on: https://cl.tvl.fyi/c/depot/+/8104
Reviewed-by: raitobezarius <tvl@lahfa.xyz>
Reviewed-by: Adam Joseph <adam@westernsemico.com>
Tested-by: BuildkiteCI
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In order to implement an asynchronous builtins.sort (required for
moving builtins to generators), we need an `async` sorting algorithm
as our comparators involve invoking a Nix function.
This commit implements a fairly simple, optimised bubble sort as the
sorting algorithm used in our `async fn sort_by`.
There don't seem to be any crates providing async versions of things
like this, and they might actually be pretty hard to implement
generically due to some constraints about how `async` works.
Note that this algorithm is less efficient than the hybrid
"timsort/mergesort/insert sort" used in the Rust standard library. I
tried to write a merge sort implementation, but ran into isuses with
the sort becoming unstable because our comparators can not yield
equality. This is the simplest implementation which I know to be
correct.
Note that as of this commit this is *not* covered by the Tvix test
suite, but it will be as soon as the rest of the generator code lands.
Change-Id: Ia9a604f7dd941d6acc9212c902e0e637ed75bebc
Reviewed-on: https://cl.tvl.fyi/c/depot/+/8239
Reviewed-by: Adam Joseph <adam@westernsemico.com>
Tested-by: BuildkiteCI
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Instead of going through Vec/BTreeMap for generating our internal
types, use the proptest strategies from imbl.
The one thing I couldn't figure out in the previous implementation is
where the ranges/sizes of generated collections came from. The
strategies in proptest use different types (Range, with an unknown
default value, and SizeRange with 0..100). I've opted to specify
0..100 directly, but we can probably make it configurable.
Change-Id: I749bc4c703fe424099240cab822b1642e5216361
Reviewed-on: https://cl.tvl.fyi/c/depot/+/7791
Autosubmit: tazjin <tazjin@tvl.su>
Tested-by: BuildkiteCI
Reviewed-by: flokli <flokli@flokli.de>
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This CL addresses clippy warning len_without_is_empty
which expects `.is_empty()` method to be present when
implementing `.len()` method for an item.
Change-Id: I8878db630b9ef5853649a906b764a33299bb5dc8
Signed-off-by: Aaqa Ishtyaq <aaqaishtyaq@gmail.com>
Reviewed-on: https://cl.tvl.fyi/c/depot/+/7806
Reviewed-by: flokli <flokli@flokli.de>
Tested-by: BuildkiteCI
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Implements `Serialize` for `tvix_eval::Value`. Special care is taken
with serialisation of attribute sets, and forcing of thunks.
The tests should cover both cases well.
Change-Id: I9bb135bacf6f87bc6bd0bd88cef0a42308e6c335
Reviewed-on: https://cl.tvl.fyi/c/depot/+/7803
Reviewed-by: flokli <flokli@flokli.de>
Tested-by: BuildkiteCI
Autosubmit: tazjin <tazjin@tvl.su>
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Co-Authored-By: Vincent Ambo <tazjin@tvl.su>
Change-Id: Ib6f7d1f4f4faac36b44f5f75cccc57bf912cf606
Reviewed-on: https://cl.tvl.fyi/c/depot/+/7626
Reviewed-by: tazjin <tazjin@tvl.su>
Tested-by: BuildkiteCI
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This uses the `im::OrdMap` for `NixAttrs` to enable sharing of memory
between different iterations of a map.
This slightly speeds up eval, but not significantly. Future work might
include benchmarking whether using a `HashMap` and only ordering in
cases where order is actually required would help.
This switches to a fork of `im` that fixes some bugs with its OrdMap
implementation.
Change-Id: I2f6a5ff471b6d508c1e8a98b13f889f49c0d9537
Reviewed-on: https://cl.tvl.fyi/c/depot/+/7676
Reviewed-by: sterni <sternenseemann@systemli.org>
Tested-by: BuildkiteCI
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The conversion from im::Vector -> Vec is cheaper for NixList
construction (of course), so where possible we should make use of
that.
This updates most builtins dealing with lists to use Vector directly,
and marks the function constructing NixList from Vec as deprecated so
that we get appropriate warnings in places where it's still in use.
These places are currently inside of JSON serialisation logic which is
in flux right now, so lets leave them as-is until it's stabilised.
Change-Id: I037f12a2800f2576db4d9526bd935efd079163f0
Reviewed-on: https://cl.tvl.fyi/c/depot/+/7671
Reviewed-by: sterni <sternenseemann@systemli.org>
Tested-by: BuildkiteCI
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This is a persistent, structurally sharing data structure which is
more efficient in some of our use-cases. I have verified the
efficiency improvement using `hyperfine` repeatedly over expressions
on nixpkgs.
Lists are not the most performance-critical structure in Nix (that
would be attribute sets), but we can already see a small (~5-10%)
improvement.
Note that there are a handful of cases where we still go via `Vec`
that need to be fixed, most notable for `builtins.sort` which can not
currently be implemented directly using `im::Vector` because of a
restrictive type bound.
Change-Id: I237cc50cbd7629a046e5a5e4601fbb40355e551d
Reviewed-on: https://cl.tvl.fyi/c/depot/+/7670
Tested-by: BuildkiteCI
Reviewed-by: sterni <sternenseemann@systemli.org>
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Change-Id: I2ab53453ed7370b520bb929ef7285e4f23eec65b
Reviewed-on: https://cl.tvl.fyi/c/depot/+/7453
Reviewed-by: tazjin <tazjin@tvl.su>
Tested-by: BuildkiteCI
Autosubmit: Adam Joseph <adam@westernsemico.com>
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When we start unrecursivifying (sp?) things, Rust's borrow checker
is going to be a headache; its magic only works when you use the CPU
stack as your call stack.
Fixing the borrow checker issues usually involves adding lots of
`clone()`s. Right now `NixList` is the only variant of `Value` that
isn't cheap to clone() -- all the others are either a wrapper around
Rc or else are of bounded size.
Note that this requires dropping the `DerefMut for NixList` instance
and using `Vec<Value>` instead in those situations.
Change-Id: I5a47df66855342aa2064f8f3cb7934ff422d26bd
Signed-off-by: Adam Joseph <adam@westernsemico.com>
Reviewed-on: https://cl.tvl.fyi/c/depot/+/7359
Reviewed-by: tazjin <tazjin@tvl.su>
Tested-by: BuildkiteCI
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It isn't possible to implement PartialEq properly for Value, because
any sensible implementation needs to force() thunks, which cannot be
done without a `&mut VM`.
The existing derive(PartialEq) has false negatives, which caused the
bug which cl/7142 fixed. Fortunately that bug was easy to find, but
a silent false negative deep within the bowels of nixpkgs could be a
real nightmare to hunt down.
Let's just remove the PartialEq impl for Value, and the other
derive(PartialEq)'s that depend on it.
Signed-off-by: Adam Joseph <adam@westernsemico.com>
Change-Id: Iacd3726fefc7fc1edadcd7e9b586e04cf8466775
Reviewed-on: https://cl.tvl.fyi/c/depot/+/7144
Reviewed-by: kanepyork <rikingcoding@gmail.com>
Reviewed-by: tazjin <tazjin@tvl.su>
Tested-by: BuildkiteCI
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This is a bit tricky because the comparator can throw errors, so we
need to propagate them out if they exist and try to avoid sorting
forever by returning a reasonable ordering in this case (as
short-circuiting is not available).
Co-Authored-By: Vincent Ambo <tazjin@tvl.su>
Change-Id: Icae1d30f43ec1ae64b2ba51e73ee467605686792
Reviewed-on: https://cl.tvl.fyi/c/depot/+/7072
Tested-by: BuildkiteCI
Reviewed-by: sterni <sternenseemann@systemli.org>
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Lists are compared lexicographically in C++ nix as of [0], and our
updated nix test suites depend on this. This implements comparison of
list values in `Value::nix_cmp` using a very similar algorithm to what
C++ does - similarly to there, this requires passing in the VM so we can
force thunks in the list elements as we go.
[0]: https://github.com/NixOS/nix/commit/09471d2680292af48b2788108de56a8da755d661#
Change-Id: I5d8bb07f90647a1fec83f775243e21af856afbb1
Reviewed-on: https://cl.tvl.fyi/c/depot/+/7070
Autosubmit: grfn <grfn@gws.fyi>
Reviewed-by: sterni <sternenseemann@systemli.org>
Tested-by: BuildkiteCI
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This adds a function NixList::force_elements() which forces each
element of the list shallowly. This behavior is needed for
`builtins.replaceStrings`, and probably a few other builtins as
well.
Signed-off-by: Adam Joseph <adam@westernsemico.com>
Change-Id: I3f0681acbbfe50e781b5f07b6a441647f5e6f8da
Reviewed-on: https://cl.tvl.fyi/c/depot/+/7094
Tested-by: BuildkiteCI
Reviewed-by: tazjin <tazjin@tvl.su>
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Change-Id: I3e0aa017a7100cbeb86d2e5747471b36affcc102
Reviewed-on: https://cl.tvl.fyi/c/depot/+/7038
Autosubmit: grfn <grfn@gws.fyi>
Reviewed-by: tazjin <tazjin@tvl.su>
Tested-by: BuildkiteCI
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Using the same method as in Thunk::deep_force, detect cycles when
printing values by maintaining a set of already seen thunks.
With this, display of infinite values matches that of Nix:
> nix-instantiate --eval --strict -E 'let as = { x = 123; y = as; }; in as'
{ x = 123; y = { x = 123; y = <CYCLE>; }; }
> tvix-eval -E 'let as = { x = 123; y = as; }; in as'
=> { x = 123; y = { x = 123; y = <CYCLE>; }; } :: set
Change-Id: I007b918d5131d82c28884e46e46ff365ef691aa8
Reviewed-on: https://cl.tvl.fyi/c/depot/+/7056
Tested-by: BuildkiteCI
Reviewed-by: grfn <grfn@gws.fyi>
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This is done via a new `deepForce` function on Value. Since values can
be cyclical (for example, see the test-case), we need to do some extra
work to avoid RefCell borrow errors if we ever hit a graph cycle:
While deep-forcing values, we keep a set of thunks that we have
already seen and avoid doing any work on the same thunk twice. The set
is encapsulated in a separate type to stop potentially invalid
pointers from leaking out.
Finally, since deep_force is conceptually similar to
`VM::force_for_output` (but more suited to usage in eval since it
doesn't clone the values) this removes the latter, replacing it with
the former.
Co-Authored-By: Vincent Ambo <tazjin@tvl.su>
Change-Id: Iefddefcf09fae3b6a4d161a5873febcff54b9157
Reviewed-on: https://cl.tvl.fyi/c/depot/+/7000
Tested-by: BuildkiteCI
Reviewed-by: grfn <grfn@gws.fyi>
Reviewed-by: tazjin <tazjin@tvl.su>
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In `a++b`, the previous implementation would move `b` (i.e. memcpy
its elements) twice. Let's do that only once.
We sure do call NixList.clone() a whole lot. At some point in the
future we probably want to do a SmolStr-type split for NixList into
a two-variant enum where one side is an Rc<Vec<Value>> for lists
longer than a certain length.
Signed-off-by: Adam Joseph <adam@westernsemico.com>
Change-Id: I32154d18785a1f663454a8b9d4afd3e78bffdf9c
Reviewed-on: https://cl.tvl.fyi/c/depot/+/7040
Tested-by: BuildkiteCI
Reviewed-by: tazjin <tazjin@tvl.su>
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This is the same code as before, just moved into a trait impl to gain
access to stuff that needs IntoIterator
Change-Id: Iff9375cd05593dd2681fa85ccc7f4554bf944a02
Reviewed-on: https://cl.tvl.fyi/c/depot/+/6842
Autosubmit: tazjin <tazjin@tvl.su>
Reviewed-by: sterni <sternenseemann@systemli.org>
Tested-by: BuildkiteCI
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Pass in, but ignore, a mutable reference to the VM to the `nix_eq`
functions, in preparation for using that VM to force thunks during
comparison.
Change-Id: I565435d8dfb33768f930fdb5a6b0fb1365d7e161
Reviewed-on: https://cl.tvl.fyi/c/depot/+/6651
Autosubmit: grfn <grfn@gws.fyi>
Tested-by: BuildkiteCI
Reviewed-by: tazjin <tazjin@tvl.su>
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Using rust's PartialEq trait to implement Nix equality semantics is
reasonably fraught with peril, both because the actual laws are
different than what nix expects, and (more importantly) because certain
things actually require extra context to compare for equality (for
example, thunks need to be forced). This converts the manual PartialEq
impl for Value (and all its descendants) to a *derived* PartialEq
impl (which requires a lot of extra PartialEq derives on miscellanious
other types within the codebase), and converts the previous
nix-semantics equality comparison into a new `nix_eq` method. This
returns an EvalResult, even though it can't currently return an error,
to allow it to fail when eg forcing thunks (which it will do soon).
Since the PartialEq impls for Value and NixAttrs are now quite boring,
this converts the generated proptests for those into handwritten ones
that cover `nix_eq` instead
Change-Id: If3da7171f88c22eda5b7a60030d8b00c3b76f672
Reviewed-on: https://cl.tvl.fyi/c/depot/+/6650
Autosubmit: grfn <grfn@gws.fyi>
Tested-by: BuildkiteCI
Reviewed-by: tazjin <tazjin@tvl.su>
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Impl Arbitrary for Value (and NixAttrs and NixList) in the same way we
did for NixString. Value currently only generates non-"internal"
values (no thunks, AttrNotFound, etc.) and can't generate
functions (builtins or closures), because those'd require full
generation of tvix bytecode, which is a bit more work than I'd like to
do now - there's a `todo!` left in the code for a place where we could
allow opting-in to internal values and functions later.
Change-Id: I07a59e2b1d89cfaa912d4ecebd642caf4ddb040a
Reviewed-on: https://cl.tvl.fyi/c/depot/+/6627
Autosubmit: grfn <grfn@gws.fyi>
Tested-by: BuildkiteCI
Reviewed-by: tazjin <tazjin@tvl.su>
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TL;DR:
- support `builtins.head`
- define `ErrorKind::IndexOutOfBounds` and canonical error code
- support basic unit tests
Change-Id: I859107ffb4e220cba1be8c2ac41d1913dcca37ff
Reviewed-on: https://cl.tvl.fyi/c/depot/+/6544
Reviewed-by: wpcarro <wpcarro@gmail.com>
Autosubmit: wpcarro <wpcarro@gmail.com>
Reviewed-by: sterni <sternenseemann@systemli.org>
Reviewed-by: tazjin <tazjin@tvl.su>
Tested-by: BuildkiteCI
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Get the length of a list
Change-Id: I41d91e96d833269541a1b3c23b7cc879f96d1e5a
Reviewed-on: https://cl.tvl.fyi/c/depot/+/6407
Tested-by: BuildkiteCI
Reviewed-by: sterni <sternenseemann@systemli.org>
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This does not require a custom iterator type (for now?)
Change-Id: I5beb194bd8629571bd4040c69c977c27149807fa
Reviewed-on: https://cl.tvl.fyi/c/depot/+/6371
Reviewed-by: sterni <sternenseemann@systemli.org>
Tested-by: BuildkiteCI
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Change-Id: Idf92ac82438fbfcf7b2f6e058830e4744637d8c6
Reviewed-on: https://cl.tvl.fyi/c/depot/+/6262
Tested-by: BuildkiteCI
Reviewed-by: sterni <sternenseemann@systemli.org>
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Change-Id: I35741856f34b86a538f226a8eaf8806edede60ec
Reviewed-on: https://cl.tvl.fyi/c/depot/+/6207
Reviewed-by: grfn <grfn@gws.fyi>
Tested-by: BuildkiteCI
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For representation wrappers that are used to control the visibility of
type internals, this ensures that the wrapper does not increase the
size of the type.
In practice, the optimiser likely does this anyways but it is good to
guarantee it.
Change-Id: Ic6df7d668fe6006dfbd5b6cfcfc2088afa95b810
Reviewed-on: https://cl.tvl.fyi/c/depot/+/6178
Tested-by: BuildkiteCI
Reviewed-by: grfn <grfn@gws.fyi>
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Ensuring that the implementation is not leaking out of the module lets
us keep things open for optimisations (e.g. empty list or pairs
through tuples).
Change-Id: I18fd9b7740f28c55736471e16c6b4095a05dd6d0
Reviewed-on: https://cl.tvl.fyi/c/depot/+/6145
Tested-by: BuildkiteCI
Reviewed-by: sterni <sternenseemann@systemli.org>
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Change-Id: Icdf715d116371a9f139bdf95266410bf967bef25
Reviewed-on: https://cl.tvl.fyi/c/depot/+/6144
Reviewed-by: sterni <sternenseemann@systemli.org>
Tested-by: BuildkiteCI
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Change-Id: I991d235cf52fbd42eb839b384f9c55ee64fa86c4
Reviewed-on: https://cl.tvl.fyi/c/depot/+/6100
Tested-by: BuildkiteCI
Reviewed-by: grfn <grfn@gws.fyi>
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There might be more logic in the future to encapsulate different
backing implementations of lists as well.
Change-Id: Ib7064fab48bf88b0c8913b0ecfa2108177c7c9fd
Reviewed-on: https://cl.tvl.fyi/c/depot/+/6093
Tested-by: BuildkiteCI
Reviewed-by: grfn <grfn@gws.fyi>
Autosubmit: tazjin <tazjin@tvl.su>
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