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Diffstat (limited to 'tvix/eval/src/value/function.rs')
-rw-r--r-- | tvix/eval/src/value/function.rs | 112 |
1 files changed, 112 insertions, 0 deletions
diff --git a/tvix/eval/src/value/function.rs b/tvix/eval/src/value/function.rs new file mode 100644 index 000000000000..7592e3d64164 --- /dev/null +++ b/tvix/eval/src/value/function.rs @@ -0,0 +1,112 @@ +//! This module implements the runtime representation of functions. +use std::{collections::BTreeMap, hash::Hash, rc::Rc}; + +use codemap::Span; +use smol_str::SmolStr; + +use crate::{chunk::Chunk, upvalues::Upvalues}; + +use super::NixString; + +#[derive(Clone, Debug, PartialEq)] +pub(crate) struct Formals { + /// Map from argument name, to whether that argument is required + pub(crate) arguments: BTreeMap<NixString, bool>, + + /// Do the formals of this function accept extra arguments + pub(crate) ellipsis: bool, + + /// The span of the formals themselves, to use to emit errors + pub(crate) span: Span, + + /// Optionally tracks a name for all function arguments (args@ style). + /// Used by toXML. + pub(crate) name: Option<String>, +} + +impl Formals { + /// Returns true if the given arg is a valid argument to these formals. + /// + /// This is true if it is either listed in the list of arguments, or the formals have an + /// ellipsis + pub(crate) fn contains<Q>(&self, arg: &Q) -> bool + where + Q: ?Sized + Hash + Ord + Eq, + NixString: std::borrow::Borrow<Q>, + { + self.ellipsis || self.arguments.contains_key(arg) + } +} + +/// The opcodes for a thunk or closure, plus the number of +/// non-executable opcodes which are allowed after an OpThunkClosure or +/// OpThunkSuspended referencing it. At runtime `Lambda` is usually wrapped +/// in `Rc` to avoid copying the `Chunk` it holds (which can be +/// quite large). +/// +/// In order to correctly reproduce cppnix's "pointer equality" +/// semantics it is important that we never clone a Lambda -- +/// use `Rc<Lambda>::clone()` instead. This struct deliberately +/// does not `derive(Clone)` in order to prevent this from being +/// done accidentally. +/// +#[derive(/* do not add Clone here */ Debug, Default)] +pub struct Lambda { + pub(crate) chunk: Chunk, + + /// Name of the function (equivalent to the name of the + /// identifier (e.g. a value in a let-expression or an attribute + /// set entry) it is located in). + pub(crate) name: Option<SmolStr>, + + /// Number of upvalues which the code in this Lambda closes + /// over, and which need to be initialised at + /// runtime. Information about the variables is emitted using + /// data-carrying opcodes (see [`crate::opcode::OpCode::DataStackIdx`]). + pub(crate) upvalue_count: usize, + pub(crate) formals: Option<Formals>, +} + +impl Lambda { + pub fn chunk(&mut self) -> &mut Chunk { + &mut self.chunk + } +} + +/// +/// In order to correctly reproduce cppnix's "pointer equality" +/// semantics it is important that we never clone a Lambda -- +/// use `Rc<Lambda>::clone()` instead. This struct deliberately +/// does not `derive(Clone)` in order to prevent this from being +/// done accidentally. +/// +#[derive(/* do not add Clone here */ Debug)] +pub struct Closure { + pub lambda: Rc<Lambda>, + pub upvalues: Rc<Upvalues>, +} + +impl Closure { + pub fn new(lambda: Rc<Lambda>) -> Self { + Self::new_with_upvalues( + Rc::new(Upvalues::with_capacity(lambda.upvalue_count)), + lambda, + ) + } + + pub fn new_with_upvalues(upvalues: Rc<Upvalues>, lambda: Rc<Lambda>) -> Self { + Closure { upvalues, lambda } + } + + pub fn chunk(&self) -> &Chunk { + &self.lambda.chunk + } + + pub fn lambda(&self) -> Rc<Lambda> { + self.lambda.clone() + } + + pub fn upvalues(&self) -> Rc<Upvalues> { + self.upvalues.clone() + } +} |