diff options
Diffstat (limited to 'tvix/eval/src/compiler')
| -rw-r--r-- | tvix/eval/src/compiler/mod.rs | 13 | ||||
| -rw-r--r-- | tvix/eval/src/compiler/scope.rs | 129 |
2 files changed, 108 insertions, 34 deletions
diff --git a/tvix/eval/src/compiler/mod.rs b/tvix/eval/src/compiler/mod.rs index 87383c0ca967..b8d8fb11a247 100644 --- a/tvix/eval/src/compiler/mod.rs +++ b/tvix/eval/src/compiler/mod.rs @@ -1120,16 +1120,17 @@ impl Compiler<'_> { self.scope_mut().poison(global_ident, depth); } - for other in self.scope().locals.iter().rev() { - if other.has_name(&name) && other.depth == depth { - self.emit_error(node, ErrorKind::VariableAlreadyDefined(other.span)); + let span = self.span_for(node); + let (idx, shadowed) = self.scope_mut().declare_local(name, span); - break; + if let Some(shadow_idx) = shadowed { + let other = &self.scope()[shadow_idx]; + if other.depth == depth { + self.emit_error(node, ErrorKind::VariableAlreadyDefined(other.span)); } } - let span = self.span_for(node); - self.scope_mut().declare_local(name, span) + idx } /// Determine whether the current lambda context has any ancestors diff --git a/tvix/eval/src/compiler/scope.rs b/tvix/eval/src/compiler/scope.rs index d3c9f8300780..1a89ad6a0649 100644 --- a/tvix/eval/src/compiler/scope.rs +++ b/tvix/eval/src/compiler/scope.rs @@ -58,16 +58,6 @@ pub struct Local { } impl Local { - /// Does the name of this local match the given string? - pub fn has_name(&self, other: &str) -> bool { - match &self.name { - LocalName::Ident(name) => name == other, - - // Phantoms are *never* accessible by a name. - LocalName::Phantom => false, - } - } - /// Retrieve the name of the given local (if available). pub fn name(&self) -> Option<SmolStr> { match &self.name { @@ -121,13 +111,61 @@ pub struct Upvalue { #[derive(Clone, Copy, Debug, PartialEq, Eq, PartialOrd)] pub struct LocalIdx(usize); +/// Helper struct for indexing over `Scope::locals` by name. +#[derive(Debug)] +enum ByName { + Single(LocalIdx), + Shadowed(Vec<LocalIdx>), +} + +impl ByName { + /// Add an additional index for this name. + fn add_idx(&mut self, new: LocalIdx) { + match self { + ByName::Shadowed(indices) => indices.push(new), + ByName::Single(idx) => { + *self = ByName::Shadowed(vec![*idx, new]); + } + } + } + + /// Remove the most recent index for this name, unless it is a + /// single. Returns `true` if an entry was removed. + fn remove_idx(&mut self) -> bool { + match self { + ByName::Single(_) => false, + ByName::Shadowed(indices) => match indices[..] { + [fst, _snd] => { + *self = ByName::Single(fst); + true + } + _ => { + indices.pop(); + true + } + }, + } + } + + /// Return the most recent index. + pub fn index(&self) -> LocalIdx { + match self { + ByName::Single(idx) => *idx, + ByName::Shadowed(vec) => *vec.last().unwrap(), + } + } +} + /// Represents a scope known during compilation, which can be resolved /// directly to stack indices. #[derive(Debug, Default)] pub struct Scope { - pub locals: Vec<Local>, + locals: Vec<Local>, pub upvalues: Vec<Upvalue>, + /// Secondary by-name index over locals. + by_name: HashMap<String, ByName>, + /// How many scopes "deep" are these locals? scope_depth: usize, @@ -207,19 +245,23 @@ impl Scope { /// 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() { - if local.has_name(name) { - local.used = true; - - // This local is still being initialised, meaning that - // we know its final runtime stack position, but it is - // not yet on the stack. - if !local.initialised { - return LocalPosition::Recursive(LocalIdx(idx)); - } - - return LocalPosition::Known(LocalIdx(idx)); + if let Some(by_name) = self.by_name.get(name) { + let idx = by_name.index(); + let local = self + .locals + .get_mut(idx.0) + .expect("invalid compiler state: indexed local missing"); + + local.used = true; + + // This local is still being initialised, meaning that + // we know its final runtime stack position, but it is + // not yet on the stack. + if !local.initialised { + return LocalPosition::Recursive(idx); } + + return LocalPosition::Known(idx); } LocalPosition::Unknown @@ -243,11 +285,18 @@ impl Scope { LocalIdx(idx) } - /// Declare an uninitialised local variable. - pub fn declare_local(&mut self, name: String, span: codemap::Span) -> LocalIdx { - let idx = self.locals.len(); + /// Declare an uninitialised, named local variable. + /// + /// Returns the `LocalIdx` of the new local, and optionally the + /// index of a previous local shadowed by this one. + pub fn declare_local( + &mut self, + name: String, + span: codemap::Span, + ) -> (LocalIdx, Option<LocalIdx>) { + let idx = LocalIdx(self.locals.len()); self.locals.push(Local { - name: LocalName::Ident(name), + name: LocalName::Ident(name.clone()), span, depth: self.scope_depth, initialised: false, @@ -256,7 +305,19 @@ impl Scope { used: false, }); - LocalIdx(idx) + let mut shadowed = None; + match self.by_name.entry(name) { + hash_map::Entry::Occupied(mut entry) => { + let existing = entry.get_mut(); + shadowed = Some(existing.index()); + existing.add_idx(idx); + } + hash_map::Entry::Vacant(entry) => { + entry.insert(ByName::Single(idx)); + } + } + + (idx, shadowed) } /// Mark local as initialised after compiling its expression. @@ -328,6 +389,18 @@ impl Scope { if !local.used && !local.is_ignored() { unused_spans.push(local.span); } + + // remove the by-name index if this was a named local + if let LocalName::Ident(name) = local.name { + if let hash_map::Entry::Occupied(mut entry) = self.by_name.entry(name) { + // If no removal occured through `remove_idx` + // (i.e. there was no shadowing going on), + // nuke the whole entry. + if !entry.get_mut().remove_idx() { + entry.remove(); + } + } + } } } |