refactor(tvix/eval): track with stack size as a simple integer

The `With` struct no longer contained any internals after the cleanup
logic for the stack had been moved into Compiler::compile_with,
leaving the `Vec<With>` to essentially act as a counter for the number
of things on the with stack.

That's inefficient of course, so with this commit it actually becomes
an integer (with an encapsulated API within scope::Scope).

Change-Id: I67a00987fc8b46b30d369a96d41e83c8af5b1998
Reviewed-on: https://cl.tvl.fyi/c/depot/+/6311
Tested-by: BuildkiteCI
Reviewed-by: sterni <sternenseemann@systemli.org>
This commit is contained in:
Vincent Ambo 2022-08-27 19:55:02 +03:00 committed by tazjin
parent 2cd08d136e
commit 932a70d0c2
2 changed files with 24 additions and 13 deletions

View file

@ -29,7 +29,7 @@ use crate::opcode::{CodeIdx, Count, JumpOffset, OpCode, StackIdx, UpvalueIdx};
use crate::value::{Closure, Lambda, Value};
use crate::warnings::{EvalWarning, WarningKind};
use self::scope::{Depth, Local, LocalPosition, Scope, Upvalue, With};
use self::scope::{Depth, Local, LocalPosition, Scope, Upvalue};
/// Represents the result of compiling a piece of Nix code. If
/// compilation was successful, the resulting bytecode can be passed
@ -601,7 +601,7 @@ impl Compiler {
// Within a `let` binding, inheriting from the outer
// scope is a no-op *if* the identifier can be
// statically resolved.
None if self.scope().with_stack.is_empty() => {
None if !self.scope().has_with() => {
self.emit_warning(inherit.syntax().clone(), WarningKind::UselessInherit);
continue;
}
@ -699,7 +699,7 @@ impl Compiler {
return;
}
if self.scope().with_stack.is_empty() {
if !self.scope().has_with() {
self.emit_error(node.syntax().clone(), ErrorKind::UnknownStaticVariable);
return;
}
@ -727,7 +727,7 @@ impl Compiler {
self.compile(node.namespace().unwrap());
self.declare_phantom();
self.scope_mut().with_stack.push(With {});
self.scope_mut().push_with();
let with_idx = self
.scope()
@ -745,7 +745,7 @@ impl Compiler {
self.compile(node.body().unwrap());
self.chunk().push_op(OpCode::OpPopWith);
self.scope_mut().with_stack.pop();
self.scope_mut().pop_with();
self.end_scope();
}
@ -991,7 +991,7 @@ impl Compiler {
// Determine whether the upvalue is a dynamic variable in the
// enclosing context.
if !self.contexts[ctx_idx - 1].scope.with_stack.is_empty() {
if self.contexts[ctx_idx - 1].scope.has_with() {
return Some(self.add_upvalue(ctx_idx, Upvalue::Dynamic(SmolStr::new(name))));
}

View file

@ -65,10 +65,6 @@ pub struct Local {
pub used: bool,
}
/// Represents an entry on the runtime with-stack.
#[derive(Debug)]
pub struct With {}
/// Represents the current position of a local as resolved in a scope.
pub enum LocalPosition {
/// Local is not known in this scope.
@ -112,9 +108,8 @@ pub struct Scope {
// How many scopes "deep" are these locals?
pub scope_depth: usize,
// Stack indices of attribute sets currently in scope through
// `with`.
pub with_stack: Vec<With>,
// Current size of the `with`-stack at runtime.
with_stack_size: usize,
// Users are allowed to override globally defined symbols like
// `true`, `false` or `null` in scopes. We call this "scope
@ -151,6 +146,22 @@ impl Scope {
.retain(|_, poisoned_at| *poisoned_at != depth);
}
/// Increase the `with`-stack size of this scope.
pub fn push_with(&mut self) {
self.with_stack_size += 1;
}
/// Decrease the `with`-stack size of this scope.
pub fn pop_with(&mut self) {
self.with_stack_size -= 1;
}
/// Does this scope currently require dynamic runtime resolution
/// of identifiers that could not be found?
pub fn has_with(&self) -> bool {
self.with_stack_size > 0
}
/// Resolve the stack index of a statically known local.
pub fn resolve_local(&mut self, name: &str) -> LocalPosition {
for (idx, local) in self.locals.iter_mut().enumerate().rev() {