diff options
Diffstat (limited to 'tvix/eval/src/compiler/mod.rs')
| -rw-r--r-- | tvix/eval/src/compiler/mod.rs | 96 |
1 files changed, 51 insertions, 45 deletions
diff --git a/tvix/eval/src/compiler/mod.rs b/tvix/eval/src/compiler/mod.rs index 2985c7e90e..34a15330c2 100644 --- a/tvix/eval/src/compiler/mod.rs +++ b/tvix/eval/src/compiler/mod.rs @@ -19,10 +19,9 @@ mod scope; use codemap::Span; use rnix::ast::{self, AstToken}; use smol_str::SmolStr; -use std::cell::RefCell; use std::collections::HashMap; use std::path::{Path, PathBuf}; -use std::rc::Rc; +use std::rc::{Rc, Weak}; use std::sync::Arc; use crate::chunk::Chunk; @@ -42,6 +41,10 @@ pub struct CompilationOutput { pub lambda: Rc<Lambda>, pub warnings: Vec<EvalWarning>, pub errors: Vec<Error>, + + // This field must outlive the rc::Weak reference which breaks + // the builtins -> import -> builtins reference cycle. + pub globals: Rc<GlobalsMap>, } /// Represents the lambda currently being compiled. @@ -69,11 +72,19 @@ impl LambdaCtx { } } -/// Alias for the map of globally available functions that should -/// implicitly be resolvable in the global scope. -type GlobalsMap = HashMap<&'static str, Rc<dyn Fn(&mut Compiler, Span)>>; +/// The map of globally available functions that should implicitly +/// be resolvable in the global scope. +pub type GlobalsMap = HashMap<&'static str, Rc<dyn Fn(&mut Compiler, Span)>>; + +/// Functions with this type are used to construct a +/// self-referential `builtins` object; it takes a weak reference to +/// its own result, similar to how nixpkgs' overlays work. +/// Rc::new_cyclic() is what "ties the knot". The heap allocation +/// (Box) and vtable (dyn) do not impair runtime or compile-time +/// performance; they exist only during compiler startup. +pub type GlobalsMapFunc = Box<dyn FnOnce(&Weak<GlobalsMap>) -> GlobalsMap>; -struct Compiler<'observer> { +pub struct Compiler<'observer> { contexts: Vec<LambdaCtx>, warnings: Vec<EvalWarning>, errors: Vec<Error>, @@ -85,7 +96,7 @@ struct Compiler<'observer> { /// 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, + globals: Rc<GlobalsMap>, /// File reference in the codemap contains all known source code /// and is used to track the spans from which instructions where @@ -108,7 +119,7 @@ impl<'observer> Compiler<'observer> { pub(crate) fn new( location: Option<PathBuf>, file: Arc<codemap::File>, - globals: Rc<RefCell<HashMap<&'static str, Value>>>, + globals: Rc<GlobalsMap>, observer: &'observer mut dyn CompilerObserver, ) -> EvalResult<Self> { let mut root_dir = match location { @@ -136,8 +147,6 @@ impl<'observer> Compiler<'observer> { root_dir.pop(); } - let globals = globals.borrow(); - #[cfg(not(target_arch = "wasm32"))] debug_assert!(root_dir.is_absolute()); @@ -145,7 +154,7 @@ impl<'observer> Compiler<'observer> { root_dir, file, observer, - globals: prepare_globals(&globals), + globals, contexts: vec![LambdaCtx::new()], warnings: vec![], errors: vec![], @@ -186,7 +195,7 @@ impl Compiler<'_> { /// Emit a single constant to the current bytecode chunk and track /// the source span from which it was compiled. - fn emit_constant<T: ToSpan>(&mut self, value: Value, node: &T) { + pub(super) fn emit_constant<T: ToSpan>(&mut self, value: Value, node: &T) { let idx = self.chunk().push_constant(value); self.push_op(OpCode::OpConstant(idx), node); } @@ -1174,54 +1183,50 @@ fn optimise_tail_call(chunk: &mut Chunk) { /// 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. +/// that are always part of the language. This also "ties the knot" +/// required in order for import to have a reference cycle back to +/// the globals. /// /// 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, span| { - compiler.push_op(OpCode::OpTrue, &span); - }), - ); - - globals.insert( - "false", - Rc::new(|compiler, span| { - compiler.push_op(OpCode::OpFalse, &span); - }), - ); - - globals.insert( - "null", - Rc::new(|compiler, span| { - compiler.push_op(OpCode::OpNull, &span); - }), - ); - - for (ident, value) in additional.iter() { - let value: Value = value.clone(); +pub fn prepare_globals(additional: GlobalsMapFunc) -> Rc<GlobalsMap> { + Rc::new_cyclic(Box::new(|weak: &Weak<GlobalsMap>| { + let mut globals = additional(weak); + globals.insert( - ident, - Rc::new(move |compiler, span| compiler.emit_constant(value.clone(), &span)), + "true", + Rc::new(|compiler, span| { + compiler.push_op(OpCode::OpTrue, &span); + }), + ); + + globals.insert( + "false", + Rc::new(|compiler, span| { + compiler.push_op(OpCode::OpFalse, &span); + }), + ); + + globals.insert( + "null", + Rc::new(|compiler, span| { + compiler.push_op(OpCode::OpNull, &span); + }), ); - } - globals + globals + })) } pub fn compile( expr: &ast::Expr, location: Option<PathBuf>, file: Arc<codemap::File>, - globals: Rc<RefCell<HashMap<&'static str, Value>>>, + globals: Rc<GlobalsMap>, observer: &mut dyn CompilerObserver, ) -> EvalResult<CompilationOutput> { - let mut c = Compiler::new(location, file, globals, observer)?; + let mut c = Compiler::new(location, file, globals.clone(), observer)?; let root_span = c.span_for(expr); let root_slot = c.scope_mut().declare_phantom(root_span, false); @@ -1240,5 +1245,6 @@ pub fn compile( lambda, warnings: c.warnings, errors: c.errors, + globals: globals, }) } |