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2022-10-26 r/5201 docs(tvix/eval): StackIdx, LocalIdx UpvalueIdxAdam Joseph1-2/+6
This adds a comment noting that StackIdx is an offset relative to the base of the current CallFrame, whereas UpvalueIdx is an absolute index into the upvalues array. It also removes the confusing mention of StackIdx in the descriptive comment for LocalIdx. They index into totally different structures; one exists at runtime and the other exists at compile time. Change-Id: Ib932b1b0679734c15001e8c5c95a08293fa016b4 Signed-off-by: Adam Joseph <adam@westernsemico.com> Reviewed-on: https://cl.tvl.fyi/c/depot/+/7017 Reviewed-by: grfn <grfn@gws.fyi> Reviewed-by: tazjin <tazjin@tvl.su> Tested-by: BuildkiteCI
2022-10-19 r/5159 feat(tvix/eval): deduplicate overlap between Closure and ThunkAdam Joseph1-12/+14
This commit deduplicates the Thunk-like functionality from Closure and unifies it with Thunk. Specifically, we now have one and only one way of breaking reference cycles in the Value-graph: Thunk. No other variant contains a RefCell. This should make it easier to reason about the behavior of the VM. InnerClosure and UpvaluesCarrier are no longer necessary. This refactoring allowed an improvement in code generation: `Rc<RefCell<>>`s are now created only for closures which do not have self-references or deferred upvalues, instead of for all closures. OpClosure has been split into two separate opcodes: - OpClosure creates non-recursive closures with no deferred upvalues. The VM will not create an `Rc<RefCell<>>` when executing this instruction. - OpThunkClosure is used for closures with self-references or deferred upvalues. The VM will create a Thunk when executing this opcode, but the Thunk will start out already in the `ThunkRepr::Evaluated` state, rather than in the `ThunkRepr::Suspeneded` state. To avoid confusion, OpThunk has been renamed OpThunkSuspended. Thanks to @sterni for suggesting that all this could be done without adding an additional variant to ThunkRepr. This does however mean that there will be mutating accesses to `ThunkRepr::Evaluated`, which was not previously the case. The field `is_finalised:bool` has been added to `Closure` to ensure that these mutating accesses are performed only on finalised Closures. Both the check and the field are present only if `#[cfg(debug_assertions)]`. Change-Id: I04131501029772f30e28da8281d864427685097f Signed-off-by: Adam Joseph <adam@westernsemico.com> Reviewed-on: https://cl.tvl.fyi/c/depot/+/7019 Tested-by: BuildkiteCI Reviewed-by: tazjin <tazjin@tvl.su>
2022-10-17 r/5154 feat(tvix/eval): Validate closed formalsGriffin Smith1-0/+6
Validate "closed formals" (formal parameters without an ellipsis) via a new ValidateClosedFormals op, which checks the arguments (in an attr set at the top of the stack) against the formal parameters on the Lambda in the current frame, and returns a new UnexpectedArgument error (including the span of the formals themselves!!) if any arguments aren't allowed Change-Id: Idcc47a59167a83be1832a6229f137d84e426c56c Reviewed-on: https://cl.tvl.fyi/c/depot/+/7002 Reviewed-by: tazjin <tazjin@tvl.su> Tested-by: BuildkiteCI
2022-10-17 r/5151 docs(tvix/eval) comments for various fieldsAdam Joseph1-5/+12
Change-Id: I8dcddf2b419761e475e71215c199eef2f7dc61dc Reviewed-on: https://cl.tvl.fyi/c/depot/+/7028 Autosubmit: Adam Joseph <adam@westernsemico.com> Tested-by: BuildkiteCI Reviewed-by: tazjin <tazjin@tvl.su>
2022-10-16 r/5147 fix(tvix/eval): resolve home relative paths at runtimesterni1-0/+3
Home relative paths depend on the environment to be resolved. We have elected to do everything that depends on the environment, e.g. resolving SPATH expressions using NIX_PATH, at runtime, so tvix evaluation would continue to behave correctly even if we separated the compilation and execution phases more, e.g. via serializing bytecode. Then the value of HOME, NIX_PATH etc. could reasonably change in the time until execution, yielding wrong results if the resolution results were cached in the bytecode. We also take the opportunity to fix the broken path concatenation previously found in the compiler, fixing b/205. Another thing we could consider is emitting a warning for home relative path literals, as they are by nature relatively fragile. One sideeffect of this change is that home path resolution errors become catchable which is not the case in C++ Nix. This will need to be fixed up in a subsequent change. Change-Id: I30bd69b575667c49170a9fdea23a020565d0f9ec Reviewed-on: https://cl.tvl.fyi/c/depot/+/7024 Autosubmit: sterni <sternenseemann@systemli.org> Reviewed-by: Adam Joseph <adam@westernsemico.com> Tested-by: BuildkiteCI
2022-10-14 r/5128 refactor(tvix/eval): remove OpResolveWithOrUpvalueAdam Joseph1-1/+0
The case branch in vm.rs for OpResolveWithOrUpvalue is unreachable/deadcode. I believe this opcode is unnecessary, since it should always be statically detectable (at parse-time) whether a reference is to an upvalue (i.e. enclosing binding); otherwise, and only then, is with-resolution applicable. Perhaps I've misunderstood how with-resolution works. If so, please explain it to me and -1/-2 this CL. Signed-off-by: Adam Joseph <adam@westernsemico.com> Change-Id: I4a90b9eb6cb3396df92a6a943d42ecc301871ba0 Reviewed-on: https://cl.tvl.fyi/c/depot/+/7009 Tested-by: BuildkiteCI Reviewed-by: tazjin <tazjin@tvl.su>
2022-10-12 r/5113 refactor(tvix/eval) s/NixPath/NixSearchPath/Adam Joseph1-2/+2
Since NixString is the Rust type for nix strings, people might mistake NixPath for the Rust type of nix paths, which it is not. Let's call it NixSearchPath instead. Signed-off-by: Adam Joseph <adam@westernsemico.com> Change-Id: Ib2ea155c4b27cb90d6180a04ea7b951d86607373 Reviewed-on: https://cl.tvl.fyi/c/depot/+/6927 Reviewed-by: kanepyork <rikingcoding@gmail.com> Tested-by: BuildkiteCI Reviewed-by: tazjin <tazjin@tvl.su>
2022-10-10 r/5087 feat(tvix/eval): Initial resolution of `<...>` pathsGriffin Smith1-0/+6
This commit implements (lazy) resolution of `<...>` paths via either the NIX_PATH environment variable, or the -I command-line flag - both handled via EvalOptions. As a result, EvalOptions can no longer derive Copy, meaning we have to clone it at each line of the repl - this is probably not a huge deal as repl performance is not exactly an inner loop and we're not cloning very much. Internally, this works by creating a thunk which pushes a constant containing the string inside the brackets to the stack, then a new opcode to resolve that path via the `NixPath`. To get that opcode to work, we now have to pass in the NixPath when constructing the VM. This (intentionally) leaves out proper implementation of path resolution via `findFile` (cppnix just calls whatever identifier called findFile is in scope!!!) as that's widely considered a bit of a misfeature, but if we do decide to implement that down the road it likely wouldn't be more than a few extra ops within the thunk introduced here. Change-Id: Ibc979b7e425b65cbe88599940520239a4a10cee2 Reviewed-on: https://cl.tvl.fyi/c/depot/+/6918 Autosubmit: grfn <grfn@gws.fyi> Reviewed-by: tazjin <tazjin@tvl.su> Tested-by: BuildkiteCI
2022-10-10 r/5082 refactor(tvix/eval): Compile OpAssert using conditional jumpsGriffin Smith1-2/+2
In order to behave nicely with tryEval, asserts need to leave the instruction pointer in a reasonable place even if they fail - whereas with the previous implementation catching a failed assert would still end up running the op for the *body* of the assert. With this change, we compile asserts much more like an `if` expression with conditional jumps rather than having an OpAssert op. Change-Id: I1b266c3be90185c84000da6b1995ac3e6fd5471b Reviewed-on: https://cl.tvl.fyi/c/depot/+/6925 Reviewed-by: tazjin <tazjin@tvl.su> Tested-by: BuildkiteCI
2022-09-29 r/4990 chore(tvix/eval): remove existing nested key implementationVincent Ambo1-1/+0
This implementation, which only ever worked for non-recursive attribute sets, is no longer needed and thus removed here. We have a new implementation of these nested keys coming up instead. Change-Id: I0c2875154026a4f5f6e0aa038e465f54444bf721 Reviewed-on: https://cl.tvl.fyi/c/depot/+/6783 Reviewed-by: sterni <sternenseemann@systemli.org> Tested-by: BuildkiteCI
2022-09-18 r/4912 docs(tvix/eval): Document OpAttrsGriffin Smith1-0/+4
Document the OpAttrs op, paying special attention to the (perhaps confusing) behavior of taking the number of *pairs*, not the number of *values*, which will be popped off the stack into the resulting attr set. Change-Id: I64df0290308ecae7a5c7e14ead37091d32701507 Reviewed-on: https://cl.tvl.fyi/c/depot/+/6654 Autosubmit: grfn <grfn@gws.fyi> Tested-by: BuildkiteCI Reviewed-by: sterni <sternenseemann@systemli.org> Reviewed-by: tazjin <tazjin@tvl.su>
2022-09-18 r/4901 test(tvix/eval): Add proof-of-concept test for ChunkGriffin Smith1-4/+4
This is pretty boring at the moment, but mostly serves as a foot in the door in the direction of writing more tests Change-Id: Id88eb4ec7e53ebb2d5b5c254c8f45ff750238811 Reviewed-on: https://cl.tvl.fyi/c/depot/+/6637 Autosubmit: grfn <grfn@gws.fyi> Tested-by: BuildkiteCI Reviewed-by: tazjin <tazjin@tvl.su>
2022-09-17 r/4890 refactor(tvix/eval): rename OpAttrsIsSet -> OpHasAttrVincent Ambo1-1/+1
This matches the name of the AST node from which it was compiled. Suggested by sterni in cl/6231 Change-Id: Ia51525158d2f47467c01fce2282005b1a8417a47 Reviewed-on: https://cl.tvl.fyi/c/depot/+/6623 Tested-by: BuildkiteCI Reviewed-by: sterni <sternenseemann@systemli.org> Reviewed-by: grfn <grfn@gws.fyi>
2022-09-15 r/4860 fix(tvix/eval): coerce string interpolation parts to stringsterni1-0/+3
With this puzzle piece of string compilation in place, `compile_str` becomes less redundant, as every part now needs to be compiled the same. The thunking logic becomes a bit trickier, since we need to thunk even in the case of `count == 1` if the single part is interpolating. Splitting the inner (shared) code in a separate function turned out to be easier for making rustc content. Change-Id: I6a554ca599926ae5907d7acffce349c9616f568f Reviewed-on: https://cl.tvl.fyi/c/depot/+/6582 Reviewed-by: tazjin <tazjin@tvl.su> Tested-by: BuildkiteCI
2022-09-13 r/4838 refactor(tvix/eval): use CodeIdx wrapper for instruction pointerVincent Ambo1-0/+16
As suggested by sterni in cl/6453. Change-Id: I3cf80d97c11fd7d085ab510f6be4b5f937c791ec Reviewed-on: https://cl.tvl.fyi/c/depot/+/6562 Reviewed-by: sterni <sternenseemann@systemli.org> Tested-by: BuildkiteCI
2022-09-11 r/4801 refactor(tvix/eval): capture entire with_stack in upvaluesVincent Ambo1-2/+1
This completely rewrites the handling of "dynamic upvalues" to, instead of resolving them at thunk/closure instantiation time (which forces some values too early), capture the entire with stack of parent contexts if it exists. There are a couple of things in here that could be written more efficiently, but I'm first working through this to get to a bug related to with + recursion and the code complexity of some of the optimisations is distracting. Change-Id: Ia538e06c9146e3bf8decb9adf02dd726d2c651cf Reviewed-on: https://cl.tvl.fyi/c/depot/+/6486 Tested-by: BuildkiteCI Reviewed-by: sterni <sternenseemann@systemli.org>
2022-09-10 r/4786 fix(tvix/eval): fix doc comment syntax where applicableVincent Ambo1-5/+5
As pointed out by grfn on cl/6091 Change-Id: I28308577b7cf99dffb4a4fd3cc8783eb9ab4d0d6 Reviewed-on: https://cl.tvl.fyi/c/depot/+/6460 Tested-by: BuildkiteCI Reviewed-by: sterni <sternenseemann@systemli.org>
2022-09-10 r/4783 feat(tvix/eval): implement OpTailCallVincent Ambo1-0/+1
If the last operation within a chunk is a function call, the call can be executed in the same call frame without increasing the depth of the call stack. To enable this, a new OpTailCall instruction (similar to OpCall) is introduced, but not yet emitted by the compiler. Change-Id: I9ffbd7da6d2d6a8ec7a724646435dc6ee89712f2 Reviewed-on: https://cl.tvl.fyi/c/depot/+/6457 Tested-by: BuildkiteCI Reviewed-by: sterni <sternenseemann@systemli.org>
2022-09-08 r/4756 fix(tvix/eval): compare *stack* slots when deciding whether to deferVincent Ambo1-1/+1
When deciding whether an upvalue needs to have a deferred resolution step, the *stack* indexes should be compared - not the locals indexes. The results are almost always the same, but there are tricky situations where this can cause errors. It's difficult to reproduce these errors in isolation, as they depend on other scope behaviour, so this is one in a series of commits to address the combination of issues which will gain some tests at the end. Change-Id: Iaa400b8d9500af58f493ab10e4f95022f3b5dd21 Reviewed-on: https://cl.tvl.fyi/c/depot/+/6423 Reviewed-by: sterni <sternenseemann@systemli.org> Tested-by: BuildkiteCI
2022-09-07 r/4706 fix(tvix/eval): address current clippy lintsVincent Ambo1-2/+2
Note that I've allowed `needless_lifetimes` for the attribute set iterator, as I find the type easier to understand with these annotations present. Change-Id: I33abb17837ee4813076cdb9a87f54bac4a37044e Reviewed-on: https://cl.tvl.fyi/c/depot/+/6373 Reviewed-by: sterni <sternenseemann@systemli.org> Tested-by: BuildkiteCI
2022-09-07 r/4688 feat(tvix/eval): implement OpForce in VMVincent Ambo1-0/+1
This operation forces the evaluation of a thunk. There is some potential here for making an implementation that avoids some copies, but the thunk machinery is tricky to get right so the first priority is to make sure it is correct by keeping the implementation simple. Change-Id: Ib381455b02f42ded717faff63f55afed4c8fb7e3 Reviewed-on: https://cl.tvl.fyi/c/depot/+/6352 Tested-by: BuildkiteCI Reviewed-by: sterni <sternenseemann@systemli.org>
2022-09-06 r/4674 feat(tvix/eval): Add Compiler::thunk method for emitting thunksVincent Ambo1-0/+3
The logic in this method is *very* similar to `compile_lambda`. It is intended to be called around any expression that should be thunked (such as function applications, attribute set values, etc.). Change-Id: Idfbb2daa9f4b735095378fb9c39a2fd07c8cff91 Reviewed-on: https://cl.tvl.fyi/c/depot/+/6344 Tested-by: BuildkiteCI Reviewed-by: sterni <sternenseemann@systemli.org>
2022-09-06 r/4667 feat(tvix/eval): implement OpFinalise instructionVincent Ambo1-1/+4
This instruction finalises the initialisation of deferred upvalues in closures (and soon, thunks). The compiler does not yet emit this instruction, some more accounting is needed for that. Change-Id: Ic4181b26e19779e206f51e17388559400da5f93a Reviewed-on: https://cl.tvl.fyi/c/depot/+/6337 Tested-by: BuildkiteCI Reviewed-by: sterni <sternenseemann@systemli.org>
2022-09-06 r/4665 feat(tvix/eval): detect deferred upvalue capturingVincent Ambo1-0/+1
Uses the threaded through slot offset to determine whether initialisation of a captured local upvalue must be defered to a later point where all values of a scope are available. This adds a new data representation to the opcode for this situation, but the equivalent runtime handling is not yet implemented. This is in part because there is more compiler machinery needed to find the resolution point. Change-Id: Ifd0c393f76abfe6e2d91483faf0f58947ab1dedc Reviewed-on: https://cl.tvl.fyi/c/depot/+/6329 Reviewed-by: sterni <sternenseemann@systemli.org> Tested-by: BuildkiteCI
2022-09-06 r/4658 fix(tvix/eval): correctly thread through dynamic upvaluesVincent Ambo1-0/+2
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>
2022-09-04 r/4635 feat(tvix/eval): implement upvalue resolution in `with` scopesVincent Ambo1-0/+1
These need to be handled specially by the runtime if the compiler determines that a given local must be resolved via `with`. Note that this implementation has a bug: It currently allows `with` inside of nested lambdas to shadow statically known identifiers. This will be cleaned up in the next commit. Change-Id: If196b99cbd1a0f2dbb4a40a0e88cdb09a009c6b9 Reviewed-on: https://cl.tvl.fyi/c/depot/+/6299 Tested-by: BuildkiteCI Reviewed-by: sterni <sternenseemann@systemli.org>
2022-09-03 r/4625 feat(tvix/eval): compile creation of closure objectsVincent Ambo1-1/+11
Fully implements the instructions for compiling closure objects (without runtime handling yet). Closure (and thunk) objects are created at runtime by capturing all known upvalues. To represent this, the instructions for creating them need to have a variable number of arguments. Due to that, this commit introduces new variants in OpCode that are not actually operations, but data. If the VM is implemented correctly, the instruction pointer should never point at these. Due to this, the VM will panic if it sees a data operand during an execution run. Change-Id: Ic56b49b3a42736dc437751e76df0e89c8d0619c6 Reviewed-on: https://cl.tvl.fyi/c/depot/+/6291 Tested-by: BuildkiteCI Reviewed-by: grfn <grfn@gws.fyi>
2022-09-03 r/4623 feat(tvix/eval): implement compilation of upvalue accessVincent Ambo1-1/+7
This adds a new upvalue tracking structure in the compiler to resolve upvalues and track their positions within a function when compiling a closure. The compiler will emit runtime upvalue access instructions after this commit, but the creation of the runtime closure object etc. is not yet wired up. Change-Id: Ib0c2c25f686bfd45f797c528753068858e3a770d Reviewed-on: https://cl.tvl.fyi/c/depot/+/6289 Tested-by: BuildkiteCI Reviewed-by: grfn <grfn@gws.fyi>
2022-09-03 r/4622 refactor(tvix/eval): add opcode::Count type for less ambiguityVincent Ambo1-5/+11
Change-Id: Ibde0b2baa1128a74c1364ee9a6330b62db3da699 Reviewed-on: https://cl.tvl.fyi/c/depot/+/6288 Autosubmit: tazjin <tazjin@tvl.su> Tested-by: BuildkiteCI Reviewed-by: sterni <sternenseemann@systemli.org>
2022-09-03 r/4621 refactor(tvix/eval): add opcode::StackIdx type for less ambiguityVincent Ambo1-2/+7
Change-Id: I9b9de1f681972c205d4d20bc5731d2ce79858edb Reviewed-on: https://cl.tvl.fyi/c/depot/+/6287 Tested-by: BuildkiteCI Reviewed-by: sterni <sternenseemann@systemli.org>
2022-09-03 r/4620 docs(tvix/eval): add docstrings for usize wrappers in opcodeVincent Ambo1-0/+3
Change-Id: I11b9324233c0aa48bd2fbac15a484962f925e72e Reviewed-on: https://cl.tvl.fyi/c/depot/+/6283 Tested-by: BuildkiteCI Reviewed-by: sterni <sternenseemann@systemli.org>
2022-09-03 r/4619 refactor(tvix/eval): add opcode::JumpOffset type for less ambiguityVincent Ambo1-4/+10
This adds a transparent wrapper around `usize` used for jump offsets in the opcodes. This is a step towards getting rid of ambiguous plain `usize` usage in the opcode. Change-Id: I21e35e67d94b32d68251908b96c7f62b6f56a8bb Reviewed-on: https://cl.tvl.fyi/c/depot/+/6282 Tested-by: BuildkiteCI Reviewed-by: sterni <sternenseemann@systemli.org>
2022-09-03 r/4613 refactor(tvix/eval): rename Value::NotFound & OpAttrOrNotFoundVincent Ambo1-1/+1
grfn suggested clearer naming for these in cl/6166. Change-Id: I83164bf1d1902ebd42272e9d5d63819a0f6a72c5 Reviewed-on: https://cl.tvl.fyi/c/depot/+/6277 Reviewed-by: grfn <grfn@gws.fyi> Tested-by: BuildkiteCI
2022-09-03 r/4608 fix(tvix/eval): address all current clippy lintsVincent Ambo1-0/+1
Change-Id: I758fc4f3b9078de7ca6228a75a4351c3e085c4cf Reviewed-on: https://cl.tvl.fyi/c/depot/+/6272 Reviewed-by: grfn <grfn@gws.fyi> Tested-by: BuildkiteCI
2022-09-02 r/4583 feat(tvix/eval): implement opcode for function calls in VMVincent Ambo1-0/+3
Nix functions always have a single argument and we do not yet make efforts to optimise this in Tvix for known multi-argument functions being directly applied. For this reason, the call instruction is fairly simple and just calls out to construct a new call frame. Note that the logic for terminating the run loop has moved to the top of the dispatch; this is because the loop run needs to be skipped if the call frame for the current lambda has just been dropped. Change-Id: I259bc07e19c1e55cd0a65207fa8105b23052b967 Reviewed-on: https://cl.tvl.fyi/c/depot/+/6249 Reviewed-by: sterni <sternenseemann@systemli.org> Reviewed-by: grfn <grfn@gws.fyi> Tested-by: BuildkiteCI
2022-09-01 r/4566 feat(tvix/eval): implement `assert` operatorVincent Ambo1-0/+3
This implements `assert`, which evaluates an expression and aborts evaluation if the value is not `true`. At this point we should introduce eval-failed-* tests; probably asserting against some representation of the error enum? Change-Id: If54c8f616d89b829c1860a4835dde60a2cd70d7a Reviewed-on: https://cl.tvl.fyi/c/depot/+/6230 Reviewed-by: grfn <grfn@gws.fyi> Reviewed-by: sterni <sternenseemann@systemli.org> Tested-by: BuildkiteCI
2022-08-31 r/4556 feat(tvix/eval): Implement OpResolveWith instructionVincent Ambo1-0/+1
Change-Id: I4d2a69f28a6b6199b3ff48ef81135e7da9fe1c3b Reviewed-on: https://cl.tvl.fyi/c/depot/+/6222 Tested-by: BuildkiteCI Reviewed-by: sterni <sternenseemann@systemli.org> Reviewed-by: grfn <grfn@gws.fyi>
2022-08-31 r/4553 feat(tvix/eval): implement OpPopWithVincent Ambo1-0/+1
Change-Id: I752d9428a73f893741746e9d5b79e8d8d570bb81 Reviewed-on: https://cl.tvl.fyi/c/depot/+/6219 Tested-by: BuildkiteCI Reviewed-by: sterni <sternenseemann@systemli.org> Reviewed-by: grfn <grfn@gws.fyi>
2022-08-31 r/4551 feat(tvix/eval): compile `with` expressionVincent Ambo1-0/+3
Adds an additional structure to the compiler's scope to track the runtime "with stack", i.e. the stack of values through which identifiers should be dynamically resolved within a with-scope. When encountering a `with` expression, the value from which the bindings should be resolved is pushed onto the stack and tracked by the compiler in the "with stack", as well as with a "phantom value" which indicates that the stack contains an additional slot which is not available to users via identifiers. Runtime handling of this is not yet implemented. Change-Id: I5e96fb55b6378e8e2a59c20c8518caa6df83da1c Reviewed-on: https://cl.tvl.fyi/c/depot/+/6217 Tested-by: BuildkiteCI Reviewed-by: sterni <sternenseemann@systemli.org>
2022-08-28 r/4524 feat(tvix/eval): add local identifier accessVincent Ambo1-0/+3
This makes basic `let ... in ...` statements work correctly. It does not yet account for the call frames pushed into the VM during function application. Change-Id: I67155171daf1a43011b96716dd9d1ab04b27db33 Reviewed-on: https://cl.tvl.fyi/c/depot/+/6190 Tested-by: BuildkiteCI Reviewed-by: grfn <grfn@gws.fyi>
2022-08-28 r/4522 feat(tvix/eval): compile simple `let ... in ...` expressionsVincent Ambo1-0/+3
These expressions now leave the binding values on the stack, and clean up the scope after the body of the expression. While variable access is not yet implemented (as the identifier node remains unhandled), this already gives us the correct stack behaviour. Change-Id: I138c20ace9c64502c94b2c0f99a6077cd912c00d Reviewed-on: https://cl.tvl.fyi/c/depot/+/6188 Tested-by: BuildkiteCI Reviewed-by: grfn <grfn@gws.fyi>
2022-08-26 r/4510 chore(tvix/eval): add variant_size_differences warning for OpCodeVincent Ambo1-0/+1
This makes it possible to quickly detect code errors that might blow up the size of the OpCode type. Change-Id: I7662dd0aa30c4762c0f9e4fa346418c9ca8b9994 Reviewed-on: https://cl.tvl.fyi/c/depot/+/6177 Tested-by: BuildkiteCI Reviewed-by: grfn <grfn@gws.fyi>
2022-08-26 r/4499 feat(tvix/vm): add opcodes for new Value::NotFound sentinelVincent Ambo1-0/+2
This sentinel value is going to be used for certain nested accesses into attribute sets. There is a new instruction similar to `OpAttrsSelect` which leaves the sentinel on the stack if a key is not found, instead of raising an error. Additionally, a new jump instruction makes its jump operation conditional on finding such a sentinel value. Change-Id: I2642f0a0bcc85bbe0ead68ea09a7dd794dbedeac Reviewed-on: https://cl.tvl.fyi/c/depot/+/6166 Tested-by: BuildkiteCI Reviewed-by: sterni <sternenseemann@systemli.org>
2022-08-26 r/4495 feat(tvix/eval): implement `?` operator (single-level only)Vincent Ambo1-0/+1
This makes it possible to check things like `{} ? a` with a single level of nesting. Change-Id: I567c36fcfd2f9e2f60071acd3ebfe56dea59b26f Reviewed-on: https://cl.tvl.fyi/c/depot/+/6161 Tested-by: BuildkiteCI Reviewed-by: grfn <grfn@gws.fyi> Reviewed-by: sterni <sternenseemann@systemli.org>
2022-08-26 r/4492 feat(tvix/eval): implement attribute set access operatorVincent Ambo1-0/+1
Fairly straightforward, handling the optimised representations manually and otherwise delegating to BTreeMap. Note that parsing of raw identifiers is not yet implemented. Encountering an identifier node usually means that there is locals access going on, so we need a special case for compiling a node in such a way that an identifier's literal value ends up on the stack. Change-Id: I13fbab7ac657b17ef3f4c5859fe737c321890c8a Reviewed-on: https://cl.tvl.fyi/c/depot/+/6158 Tested-by: BuildkiteCI Reviewed-by: sterni <sternenseemann@systemli.org> Reviewed-by: grfn <grfn@gws.fyi>
2022-08-26 r/4491 fix(tvix/eval): add operation to assert boolean typeVincent Ambo1-0/+3
This operation is required because both sides of the logical operators are strictly evaluated by Nix, even if the resulting value is not used further. For example, in our implementation of `&&`, if the left-hand side is `true`, then the result of the expression is simply the right-hand side value. This value must be asserted to be a boolean for the semantics of the language to work correctly. Change-Id: I34f5364f2a444753fa1d8b0a1a2b2d9cdf7c6700 Reviewed-on: https://cl.tvl.fyi/c/depot/+/6157 Tested-by: BuildkiteCI Reviewed-by: sterni <sternenseemann@systemli.org> Reviewed-by: grfn <grfn@gws.fyi>
2022-08-25 r/4486 feat(tvix/compiler): implement `||` operatorVincent Ambo1-0/+1
Same dance as `&&` but logically inverted. Change-Id: I213e200e3836527e9abe510f354ee7cd1f70d041 Reviewed-on: https://cl.tvl.fyi/c/depot/+/6151 Tested-by: BuildkiteCI Reviewed-by: grfn <grfn@gws.fyi> Reviewed-by: sterni <sternenseemann@systemli.org>
2022-08-25 r/4483 feat(tvix/eval): implement if/else expressionsVincent Ambo1-1/+8
These expressions use simple jumps to skip the correct expression conditionally in the bytecode by advancing the instruction pointer. Note that these expressions are already covered by a test behind the `nix_tests` feature flag, but adding more is probably sensible. Change-Id: Ibe0eba95d216321c883d3b6b5816e2ab6fe7eef1 Reviewed-on: https://cl.tvl.fyi/c/depot/+/6148 Tested-by: BuildkiteCI Reviewed-by: grfn <grfn@gws.fyi> Reviewed-by: sterni <sternenseemann@systemli.org>
2022-08-25 r/4479 feat(tvix/eval): implement list concatenationVincent Ambo1-0/+1
Change-Id: Icdf715d116371a9f139bdf95266410bf967bef25 Reviewed-on: https://cl.tvl.fyi/c/depot/+/6144 Reviewed-by: sterni <sternenseemann@systemli.org> Tested-by: BuildkiteCI
2022-08-25 r/4478 feat(tvix/eval): implement binary comparison operatorsVincent Ambo1-0/+4
This is accomplished by simply delegating to the Rust implementations of (Partial)Ord and (Partial)Eq, which are implemented for Value and underlying wrapper types to behave like they do in Nix. To ease the implementation overhead, a new comparison operator macro has been added to the VM module. Incomparable types will raise a new error variant when a comparison is attempted, containing both supplied types. This mimics the information carried in the error thrown by C++ Nix. Change-Id: Ia19634d69119d40722f3ca672387bc3a80096998 Reviewed-on: https://cl.tvl.fyi/c/depot/+/6143 Reviewed-by: sterni <sternenseemann@systemli.org> Tested-by: BuildkiteCI