ccfb971dc5
This puts together the puzzle pieces for threading dynamic upvalues (that is, upvalues resolved from the `with`-stack) all the way through. Reading the test case enclosed in this commit and walking through it is recommended to understand what problem is being tackled here. In short, because the compiler can not statically know *which* with-scope a dynamic argument is resolved from it needs to lay the groundwork for resolving from *all* possible scopes. There are multiple different approaches to doing this. The approach chosen in this commit is that if a dynamic upvalue is detected, the compiler will emit instructions to close over this dynamic value in *all* enclosing lambda contexts. It uses a new instruction for this that will leave around a sentinel value in case an identifier could not be resolved, and wire the location of this found value (or sentinel) up through the upvalues to the next level of nesting. In this tradeoff, tvix potentially closes over more upvalues than are needed (but in practice, how often do people create *really* deep `with`-stacks? and in *this* kind of code situation? maybe we should even warn for this!) but avoids keeping the entire attribute sets themselves around. Looking at the test case, each surrounding closure will close over *all* dynamic identifiers that are referenced later on visible to it, but only the last one for each identifier will actually end up being used. This also covers our bases for an additional edge-case this creates, in which an identifier potentially resolves to a dynamic upvalue *and* to a dynamic value within the function's own scope (again, would anyone really do this?) by introducing a resolution instruction for that particular case. There is likely some potential for cleaning up this code which is quite ugly in some parts, but as this implementation is now carefully calibrated to work I decided it is time to commit it and clean it up in subsequent commits. Change-Id: Ib701e3e6da39bd2c95938d1384036ff4f9fb3749 Reviewed-on: https://cl.tvl.fyi/c/depot/+/6322 Tested-by: BuildkiteCI Reviewed-by: sterni <sternenseemann@systemli.org> |
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| benches | ||
| docs | ||
| src | ||
| .gitignore | ||
| .skip-subtree | ||
| Cargo.lock | ||
| Cargo.toml | ||
| default.nix | ||
| README.md | ||
Tvix Evaluator
This project implements an interpreter for the Nix programming language.
The interpreter aims to be compatible with nixpkgs, on the
foundation of Nix 2.3.
Work on this project is extremely in-progress, and the state of the project in the public repository may not necessarily reflect the state of the private codebase, as we are slowly working on publishing it.
We expect this to have caught up in a handful of weeks (as of 2022-08-12).
Please contact TVL with any questions you might have.
Nix test suite
C++ Nix implements a language test suite in the form of Nix source code files, and their expected output. The coverage of this test suite is not complete, but we intend to be compatible with it.
We have ported the test suite to Tvix, but do not run it by default as we are not yet compatible with it.
You can run the test suite by enabling the nix_tests feature in
Cargo:
cargo test --features nix_tests
rnix-parser
Tvix is written in memory of jD91mZM2, the author of rnix-parser who sadly passed away.
Tvix makes heavy use of rnix-parser in its bytecode compiler. The parser is now maintained by Nix community members.