diff options
| -rw-r--r-- | tvix/eval/src/compiler/mod.rs | 111 |
1 files changed, 89 insertions, 22 deletions
diff --git a/tvix/eval/src/compiler/mod.rs b/tvix/eval/src/compiler/mod.rs index eefcbfcd65a0..6f48e8f3d5ba 100644 --- a/tvix/eval/src/compiler/mod.rs +++ b/tvix/eval/src/compiler/mod.rs @@ -103,6 +103,20 @@ enum Upvalue { Dynamic(SmolStr), } +/// Represents the current position of a local as resolved in a scope. +enum LocalPosition { + /// Local is not known in this scope. + Unknown, + + /// Local is known and defined at the given stack index. + Known(StackIdx), + + /// Local is known, but is being accessed recursively within its + /// own initialisation. Depending on context, this is either an + /// error or forcing a closure/thunk. + Recursive(StackIdx), +} + /// Represents a scope known during compilation, which can be resolved /// directly to stack indices. /// @@ -157,15 +171,39 @@ impl Scope { } /// Resolve the stack index of a statically known local. - fn resolve_local(&mut self, name: &str) -> Option<StackIdx> { + fn resolve_local(&mut self, name: &str) -> LocalPosition { for (idx, local) in self.locals.iter_mut().enumerate().rev() { if !local.phantom && local.name == name { local.used = true; - return Some(StackIdx(idx)); + + match local.depth { + // This local is still being initialised, meaning + // that we know its final runtime stack position, + // but it is not yet on the stack. + Depth::Unitialised => return LocalPosition::Recursive(StackIdx(idx)), + + // This local is known, but we need to account for + // uninitialised variables in this "initialiser + // stack". + Depth::At(_) => return LocalPosition::Known(self.resolve_uninit(idx)), + } } } - None + LocalPosition::Unknown + } + + /// Return the "initialiser stack slot" of a value, that is the + /// stack slot of a value which might only exist during the + /// initialisation of another. This requires accounting for the + /// stack offsets of any unitialised variables. + fn resolve_uninit(&mut self, locals_idx: usize) -> StackIdx { + StackIdx( + self.locals[..locals_idx] + .iter() + .filter(|local| matches!(local.depth, Depth::At(_))) + .count(), + ) } } @@ -556,14 +594,21 @@ impl Compiler { .scope_mut() .resolve_local(ident.ident_token().unwrap().text()) { - Some(idx) => self.chunk().push_op(OpCode::OpGetLocal(idx)), - None => { + LocalPosition::Unknown => { self.emit_error( ident.syntax().clone(), ErrorKind::UnknownStaticVariable, ); continue; } + + LocalPosition::Known(idx) => { + self.chunk().push_op(OpCode::OpGetLocal(idx)) + } + + LocalPosition::Recursive(_) => { + todo!("TODO: should be unreachable in inherits, check") + } }; } } @@ -731,11 +776,11 @@ impl Compiler { // If the identifier resolves statically, it // has precedence over dynamic bindings, and // the inherit is useless. - if self - .scope_mut() - .resolve_local(ident.ident_token().unwrap().text()) - .is_some() - { + if matches!( + self.scope_mut() + .resolve_local(ident.ident_token().unwrap().text()), + LocalPosition::Known(_) + ) { self.emit_warning(ident.syntax().clone(), WarningKind::UselessInherit); continue; } @@ -745,6 +790,7 @@ impl Compiler { ident.syntax().clone(), ident.ident_token().unwrap().text(), ); + self.mark_initialised(ident.ident_token().unwrap().text()); } } @@ -757,6 +803,7 @@ impl Compiler { ident.syntax().clone(), ident.ident_token().unwrap().text(), ); + self.mark_initialised(ident.ident_token().unwrap().text()); } } } @@ -787,10 +834,9 @@ impl Compiler { } self.compile(entry.value().unwrap()); - self.declare_local( - entry.attrpath().unwrap().syntax().clone(), - path.pop().unwrap(), - ); + let name = path.pop().unwrap(); + self.declare_local(entry.attrpath().unwrap().syntax().clone(), &name); + self.mark_initialised(&name); } // Deal with the body, then clean up the locals afterwards. @@ -811,8 +857,7 @@ impl Compiler { } match self.scope_mut().resolve_local(ident.text()) { - Some(idx) => self.chunk().push_op(OpCode::OpGetLocal(idx)), - None => { + LocalPosition::Unknown => { // Are we possibly dealing with an upvalue? if let Some(idx) = self.resolve_upvalue(self.contexts.len() - 1, ident.text()) { self.chunk().push_op(OpCode::OpGetUpvalue(idx)); @@ -829,6 +874,10 @@ impl Compiler { self.emit_constant(Value::String(ident.text().into())); self.chunk().push_op(OpCode::OpResolveWith) } + + LocalPosition::Recursive(_) => todo!("self-recursive upvalue"), + + LocalPosition::Known(idx) => self.chunk().push_op(OpCode::OpGetLocal(idx)), }; } @@ -840,8 +889,8 @@ impl Compiler { // resolve that directly (thus avoiding duplication on the // stack). self.compile(node.namespace().unwrap()); - self.declare_phantom(); + self.scope_mut().with_stack.push(With {}); let with_idx = self.scope().locals.len() - 1; @@ -871,7 +920,8 @@ impl Compiler { .text() .to_string(); - self.declare_local(param.syntax().clone(), name); + self.declare_local(param.syntax().clone(), &name); + self.mark_initialised(&name); } } @@ -1043,7 +1093,7 @@ impl Compiler { self.scope_mut().locals.push(Local { name, - depth: Depth::At(depth), + depth: Depth::Unitialised, node: Some(node), phantom: false, used: false, @@ -1064,6 +1114,19 @@ impl Compiler { }); } + /// Mark local as initialised after compiling its expression. + fn mark_initialised(&mut self, name: &str) { + let depth = self.scope().scope_depth; + for local in self.scope_mut().locals.iter_mut().rev() { + if matches!(local.depth, Depth::Unitialised) && local.name == name { + local.depth = Depth::At(depth); + return; + } + } + + panic!("critical compiler error: unbalanced locals stack"); + } + fn resolve_upvalue(&mut self, ctx_idx: usize, name: &str) -> Option<UpvalueIdx> { if ctx_idx == 0 { // There can not be any upvalue at the outermost context. @@ -1071,9 +1134,13 @@ impl Compiler { } // Determine whether the upvalue is a local in the enclosing context. - if let Some(idx) = self.contexts[ctx_idx - 1].scope.resolve_local(name) { - return Some(self.add_upvalue(ctx_idx, Upvalue::Stack(idx))); - } + match self.contexts[ctx_idx - 1].scope.resolve_local(name) { + LocalPosition::Known(idx) => { + return Some(self.add_upvalue(ctx_idx, Upvalue::Stack(idx))) + } + LocalPosition::Recursive(_) => todo!("self-recursive upvalue"), + LocalPosition::Unknown => { /* continue below */ } + }; // Determine whether the upvalue is a dynamic variable in the // enclosing context. |