0649474206
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
86 lines
2.8 KiB
Rust
86 lines
2.8 KiB
Rust
//! This module encapsulates some logic for upvalue handling, which is
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//! relevant to both thunks (delayed computations for lazy-evaluation)
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//! as well as closures (lambdas that capture variables from the
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//! surrounding scope).
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//!
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//! The upvalues of a scope are whatever data are needed at runtime
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//! in order to resolve each free variable in the scope to a value.
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//! "Upvalue" is a term taken from Lua.
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use std::ops::Index;
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use crate::{opcode::UpvalueIdx, Value};
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/// Structure for carrying upvalues of an UpvalueCarrier. The
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/// implementation of this struct encapsulates the logic for
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/// capturing and accessing upvalues.
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///
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/// Nix's `with` cannot be used to shadow an enclosing binding --
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/// like Rust's `use xyz::*` construct, but unlike Javascript's
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/// `with (xyz)`. This means that Nix has two kinds of identifiers,
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/// which can be distinguished at compile time:
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///
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/// - Static identifiers, which are bound in some enclosing scope by
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/// `let`, `name:` or `{name}:`
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/// - Dynamic identifiers, which are not bound in any enclosing
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/// scope
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#[derive(Clone, Debug)]
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pub struct Upvalues {
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/// The upvalues of static identifiers. Each static identifier
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/// is assigned an integer identifier at compile time, which is
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/// an index into this Vec.
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static_upvalues: Vec<Value>,
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/// The upvalues of dynamic identifiers, if any exist. This
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/// consists of the value passed to each enclosing `with val;`,
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/// from outermost to innermost.
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with_stack: Option<Vec<Value>>,
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}
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impl Upvalues {
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pub fn with_capacity(count: usize) -> Self {
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Upvalues {
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static_upvalues: Vec::with_capacity(count),
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with_stack: None,
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}
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}
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/// Push an upvalue at the end of the upvalue list.
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pub fn push(&mut self, value: Value) {
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self.static_upvalues.push(value);
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}
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/// Set the captured with stack.
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pub fn set_with_stack(&mut self, with_stack: Vec<Value>) {
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self.with_stack = Some(with_stack);
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}
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pub fn with_stack(&self) -> Option<&Vec<Value>> {
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self.with_stack.as_ref()
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}
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pub fn with_stack_len(&self) -> usize {
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match &self.with_stack {
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None => 0,
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Some(stack) => stack.len(),
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}
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}
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/// Resolve deferred upvalues from the provided stack slice,
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/// mutating them in the internal upvalue slots.
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pub fn resolve_deferred_upvalues(&mut self, stack: &[Value]) {
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for upvalue in self.static_upvalues.iter_mut() {
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if let Value::DeferredUpvalue(update_from_idx) = upvalue {
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*upvalue = stack[update_from_idx.0].clone();
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}
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}
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}
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}
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impl Index<UpvalueIdx> for Upvalues {
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type Output = Value;
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fn index(&self, index: UpvalueIdx) -> &Self::Output {
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&self.static_upvalues[index.0]
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}
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}
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