diff options
Diffstat (limited to 'tvix/eval/src/compiler.rs')
| -rw-r--r-- | tvix/eval/src/compiler.rs | 186 |
1 files changed, 125 insertions, 61 deletions
diff --git a/tvix/eval/src/compiler.rs b/tvix/eval/src/compiler.rs index 4043f268bf..1bbd791876 100644 --- a/tvix/eval/src/compiler.rs +++ b/tvix/eval/src/compiler.rs @@ -16,7 +16,9 @@ use path_clean::PathClean; use rnix::ast::{self, AstToken, HasEntry}; use rowan::ast::AstNode; +use std::collections::{hash_map, HashMap}; use std::path::{Path, PathBuf}; +use std::rc::Rc; use crate::chunk::Chunk; use crate::errors::{Error, ErrorKind, EvalResult}; @@ -78,15 +80,40 @@ struct Scope { // `with`. with_stack: Vec<With>, - // Certain symbols are considered to be "poisoning" the scope when - // defined. This is because users are allowed to override symbols - // like 'true' or 'null'. + // Users are allowed to override globally defined symbols like + // `true`, `false` or `null` in scopes. We call this "scope + // poisoning", as it requires runtime resolution of those tokens. // // To support this efficiently, the depth at which a poisoning // occured is tracked here. - poisoned_true: usize, - poisoned_false: usize, - poisoned_null: usize, + poisoned_tokens: HashMap<&'static str, usize>, +} + +impl Scope { + /// Mark a globally defined token as poisoned. + fn poison(&mut self, name: &'static str, depth: usize) { + match self.poisoned_tokens.entry(name) { + hash_map::Entry::Occupied(_) => { + /* do nothing, as the token is already poisoned at a + * lower scope depth */ + } + hash_map::Entry::Vacant(entry) => { + entry.insert(depth); + } + } + } + + /// Check whether a given token is poisoned. + fn is_poisoned(&self, name: &str) -> bool { + self.poisoned_tokens.contains_key(name) + } + + /// "Unpoison" tokens that were poisoned at a given depth. Used + /// when scopes are closed. + fn unpoison(&mut self, depth: usize) { + self.poisoned_tokens + .retain(|_, poisoned_at| *poisoned_at != depth); + } } /// Represents the lambda currently being compiled. @@ -104,11 +131,21 @@ impl LambdaCtx { } } +type GlobalsMap = HashMap<&'static str, Rc<dyn Fn(&mut Compiler)>>; + struct Compiler { contexts: Vec<LambdaCtx>, warnings: Vec<EvalWarning>, errors: Vec<Error>, root_dir: PathBuf, + + /// Carries all known global tokens; the full set of which is + /// created when the compiler is invoked. + /// + /// Each global has an associated token, which when encountered as + /// an identifier is resolved against the scope poisoning logic, + /// and a function that should emit code for the token. + globals: GlobalsMap, } // Helper functions for emitting code and metadata to the internal @@ -124,7 +161,7 @@ impl Compiler { } fn chunk(&mut self) -> &mut Chunk { - std::rc::Rc::<Chunk>::get_mut(self.context_mut().lambda.chunk()) + Rc::<Chunk>::get_mut(self.context_mut().lambda.chunk()) .expect("compiler flaw: long-lived chunk reference") } @@ -677,41 +714,29 @@ impl Compiler { } fn compile_ident(&mut self, node: ast::Ident) { - match node.ident_token().unwrap().text() { - // TODO(tazjin): Nix technically allows code like - // - // let null = 1; in null - // => 1 - // - // which we do *not* want to check at runtime. Once - // scoping is introduced, the compiler should carry some - // optimised information about any "weird" stuff that's - // happened to the scope (such as overrides of these - // literals, or builtins). - "true" if self.scope().poisoned_true == 0 => self.chunk().push_op(OpCode::OpTrue), - "false" if self.scope().poisoned_false == 0 => self.chunk().push_op(OpCode::OpFalse), - "null" if self.scope().poisoned_null == 0 => self.chunk().push_op(OpCode::OpNull), - - name => { - // Note: `with` and some other special scoping - // features are not yet implemented. - match self.resolve_local(name) { - Some(idx) => self.chunk().push_op(OpCode::OpGetLocal(idx)), - None => { - if self.scope().with_stack.is_empty() { - self.emit_error( - node.syntax().clone(), - ErrorKind::UnknownStaticVariable, - ); - return; - } - - // Variable needs to be dynamically resolved - // at runtime. - self.emit_constant(Value::String(name.into())); - self.chunk().push_op(OpCode::OpResolveWith) - } + let ident = node.ident_token().unwrap(); + + // If the identifier is a global, and it is not poisoned, emit + // the global directly. + if let Some(global) = self.globals.get(ident.text()) { + if !self.scope().is_poisoned(ident.text()) { + global.clone()(self); + return; + } + } + + match self.resolve_local(ident.text()) { + Some(idx) => self.chunk().push_op(OpCode::OpGetLocal(idx)), + None => { + if self.scope().with_stack.is_empty() { + self.emit_error(node.syntax().clone(), ErrorKind::UnknownStaticVariable); + return; } + + // Variable needs to be dynamically resolved + // at runtime. + self.emit_constant(Value::String(ident.text().into())); + self.chunk().push_op(OpCode::OpResolveWith) } }; } @@ -815,15 +840,8 @@ impl Compiler { // If this scope poisoned any builtins or special identifiers, // they need to be reset. - if self.scope().poisoned_true == self.scope().scope_depth { - self.scope_mut().poisoned_true = 0; - } - if self.scope().poisoned_false == self.scope().scope_depth { - self.scope_mut().poisoned_false = 0; - } - if self.scope().poisoned_null == self.scope().scope_depth { - self.scope_mut().poisoned_null = 0; - } + let depth = self.scope().scope_depth; + self.scope_mut().unpoison(depth); self.scope_mut().scope_depth -= 1; @@ -871,23 +889,24 @@ impl Compiler { /// compiled by pushing it to the locals. This is used to /// determine the stack offset of variables. fn declare_local<S: Into<String>>(&mut self, node: rnix::SyntaxNode, name: S) { - // Set up scope poisoning if required. let name = name.into(); - let mut scope = self.scope_mut(); - match name.as_str() { - "true" if scope.poisoned_true == 0 => scope.poisoned_true = scope.scope_depth, - - "false" if scope.poisoned_false == 0 => scope.poisoned_false = scope.scope_depth, - - "null" if scope.poisoned_null == 0 => scope.poisoned_null = scope.scope_depth, + let depth = self.scope().scope_depth; - _ => {} + // Do this little dance to get ahold of the *static* key and + // use it for poisoning if required. + let key: Option<&'static str> = match self.globals.get_key_value(name.as_str()) { + Some((key, _)) => Some(*key), + None => None, }; - scope.locals.push(Local { + if let Some(global_ident) = key { + self.scope_mut().poison(global_ident, depth); + } + + self.scope_mut().locals.push(Local { + depth, name: name.into(), node: Some(node), - depth: scope.scope_depth, phantom: false, used: false, }); @@ -969,6 +988,47 @@ fn normalise_ident_path<I: Iterator<Item = ast::Attr>>(path: I) -> EvalResult<Ve path.map(attr_to_string).collect() } +/// Prepare the full set of globals from additional globals supplied +/// by the caller of the compiler, as well as the built-in globals +/// that are always part of the language. +/// +/// Note that all builtin functions are *not* considered part of the +/// language in this sense and MUST be supplied as additional global +/// values, including the `builtins` set itself. +fn prepare_globals(additional: HashMap<&'static str, Value>) -> GlobalsMap { + let mut globals: GlobalsMap = HashMap::new(); + + globals.insert( + "true", + Rc::new(|compiler| { + compiler.chunk().push_op(OpCode::OpTrue); + }), + ); + + globals.insert( + "false", + Rc::new(|compiler| { + compiler.chunk().push_op(OpCode::OpFalse); + }), + ); + + globals.insert( + "null", + Rc::new(|compiler| { + compiler.chunk().push_op(OpCode::OpNull); + }), + ); + + for (ident, value) in additional.into_iter() { + globals.insert( + ident, + Rc::new(move |compiler| compiler.emit_constant(value.clone())), + ); + } + + globals +} + pub fn compile(expr: ast::Expr, location: Option<PathBuf>) -> EvalResult<CompilationResult> { let mut root_dir = match location { Some(dir) => Ok(dir), @@ -984,8 +1044,12 @@ pub fn compile(expr: ast::Expr, location: Option<PathBuf>) -> EvalResult<Compila root_dir.pop(); } + // TODO: accept globals as an external parameter + let globals = prepare_globals(HashMap::new()); + let mut c = Compiler { root_dir, + globals, contexts: vec![LambdaCtx::new()], warnings: vec![], errors: vec![], |