//! This module implements a compiler for compiling the rnix AST
//! representation to Tvix bytecode.
//!
//! A note on `unwrap()`: This module contains a lot of calls to
//! `unwrap()` or `expect(...)` on data structures returned by `rnix`.
//! The reason for this is that rnix uses the same data structures to
//! represent broken and correct ASTs, so all typed AST variants have
//! the ability to represent an incorrect node.
//!
//! However, at the time that the AST is passed to the compiler we
//! have verified that `rnix` considers the code to be correct, so all
//! variants are fulfilled. In cases where the invariant is guaranteed
//! by the code in this module, `debug_assert!` has been used to catch
//! mistakes early during development.
use path_clean::PathClean;
use rnix::ast::{self, AstToken, HasEntry};
use rowan::ast::AstNode;
use smol_str::SmolStr;
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};
use crate::opcode::{CodeIdx, Count, JumpOffset, OpCode, StackIdx, UpvalueIdx};
use crate::value::{Closure, Lambda, Value};
use crate::warnings::{EvalWarning, WarningKind};
/// Represents the result of compiling a piece of Nix code. If
/// compilation was successful, the resulting bytecode can be passed
/// to the VM.
pub struct CompilationOutput {
pub lambda: Lambda,
pub warnings: Vec<EvalWarning>,
pub errors: Vec<Error>,
}
/// Represents the initialisation status of a variable, tracking
/// whether it is only known or also already defined.
enum Depth {
/// Variable is defined and located at the given depth.
At(usize),
/// Variable is known but not yet defined.
Unitialised,
}
impl Depth {
/// Does this variable live above the other given depth?
fn above(&self, theirs: usize) -> bool {
match self {
Depth::Unitialised => false,
Depth::At(ours) => *ours > theirs,
}
}
/// Does this variable live below the other given depth?
fn below(&self, theirs: usize) -> bool {
match self {
Depth::Unitialised => false,
Depth::At(ours) => *ours < theirs,
}
}
}
/// Represents a single local already known to the compiler.
struct Local {
// Definition name, which can be different kinds of tokens (plain
// string or identifier). Nix does not allow dynamic names inside
// of `let`-expressions.
name: String,
// Syntax node at which this local was declared.
node: Option<rnix::SyntaxNode>,
// Scope depth of this local.
depth: Depth,
// Phantom locals are not actually accessible by users (e.g.
// intermediate values used for `with`).
phantom: bool,
// Is this local known to have been used at all?
used: bool,
}
/// Represents a stack offset containing keys which are currently
/// in-scope through a with expression.
#[derive(Debug)]
struct With {}
#[derive(Debug, PartialEq)]
enum Upvalue {
/// This upvalue captures a local from the stack.
Stack(StackIdx),
/// This upvalue captures an enclosing upvalue.
Upvalue(UpvalueIdx),
/// This upvalue captures a dynamically resolved value (i.e.
/// `with`).
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.
///
/// TODO(tazjin): `with`-stack
/// TODO(tazjin): flag "specials" (e.g. note depth if builtins are
/// overridden)
#[derive(Default)]
struct Scope {
locals: Vec<Local>,
upvalues: Vec<Upvalue>,
// How many scopes "deep" are these locals?
scope_depth: usize,
// Stack indices of attribute sets currently in scope through
// `with`.
with_stack: Vec<With>,
// 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_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);
}
/// Resolve the stack index of a statically known local.
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;
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)),
}
}
}
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(),
)
}
}
/// Represents the lambda currently being compiled.
struct LambdaCtx {
lambda: Lambda,
scope: Scope,
}
impl LambdaCtx {
fn new() -> Self {
LambdaCtx {
lambda: Lambda::new_anonymous(),
scope: Default::default(),
}
}
}
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
// structures of the compiler.
impl Compiler {
fn context(&self) -> &LambdaCtx {
&self.contexts[self.contexts.len() - 1]
}
fn context_mut(&mut self) -> &mut LambdaCtx {
let idx = self.contexts.len() - 1;
&mut self.contexts[idx]
}
fn chunk(&mut self) -> &mut Chunk {
Rc::<Chunk>::get_mut(self.context_mut().lambda.chunk())
.expect("compiler flaw: long-lived chunk reference")
}
fn scope(&self) -> &Scope {
&self.context().scope
}
fn scope_mut(&mut self) -> &mut Scope {
&mut self.context_mut().scope
}
fn emit_constant(&mut self, value: Value) {
let idx = self.chunk().push_constant(value);
self.chunk().push_op(OpCode::OpConstant(idx));
}
}
// Actual code-emitting AST traversal methods.
impl Compiler {
fn compile(&mut self, expr: ast::Expr) {
match expr {
ast::Expr::Literal(literal) => self.compile_literal(literal),
ast::Expr::Path(path) => self.compile_path(path),
ast::Expr::Str(s) => self.compile_str(s),
ast::Expr::UnaryOp(op) => self.compile_unary_op(op),
ast::Expr::BinOp(op) => self.compile_binop(op),
ast::Expr::HasAttr(has_attr) => self.compile_has_attr(has_attr),
ast::Expr::List(list) => self.compile_list(list),
ast::Expr::AttrSet(attrs) => self.compile_attr_set(attrs),
ast::Expr::Select(select) => self.compile_select(select),
ast::Expr::Assert(assert) => self.compile_assert(assert),
ast::Expr::IfElse(if_else) => self.compile_if_else(if_else),
ast::Expr::LetIn(let_in) => self.compile_let_in(let_in),
ast::Expr::Ident(ident) => self.compile_ident(ident),
ast::Expr::With(with) => self.compile_with(with),
ast::Expr::Lambda(lambda) => self.compile_lambda(lambda),
ast::Expr::Apply(apply) => self.compile_apply(apply),
// Parenthesized expressions are simply unwrapped, leaving
// their value on the stack.
ast::Expr::Paren(paren) => self.compile(paren.expr().unwrap()),
ast::Expr::LegacyLet(_) => todo!("legacy let"),
ast::Expr::Root(_) => unreachable!("there cannot be more than one root"),
ast::Expr::Error(_) => unreachable!("compile is only called on validated trees"),
}
}
fn compile_literal(&mut self, node: ast::Literal) {
match node.kind() {
ast::LiteralKind::Float(f) => {
self.emit_constant(Value::Float(f.value().unwrap()));
}
ast::LiteralKind::Integer(i) => {
self.emit_constant(Value::Integer(i.value().unwrap()));
}
ast::LiteralKind::Uri(u) => {
self.emit_warning(node.syntax().clone(), WarningKind::DeprecatedLiteralURL);
self.emit_constant(Value::String(u.syntax().text().into()));
}
}
}
fn compile_path(&mut self, node: ast::Path) {
// TODO(tazjin): placeholder implementation while waiting for
// https://github.com/nix-community/rnix-parser/pull/96
let raw_path = node.to_string();
let path = if raw_path.starts_with('/') {
Path::new(&raw_path).to_owned()
} else if raw_path.starts_with('~') {
let mut buf = match dirs::home_dir() {
Some(buf) => buf,
None => {
self.emit_error(
node.syntax().clone(),
ErrorKind::PathResolution("failed to determine home directory".into()),
);
return;
}
};
buf.push(&raw_path);
buf
} else if raw_path.starts_with('.') {
let mut buf = self.root_dir.clone();
buf.push(&raw_path);
buf
} else {
// TODO: decide what to do with findFile
todo!("other path types (e.g. <...> lookups) not yet implemented")
};
// TODO: Use https://github.com/rust-lang/rfcs/issues/2208
// once it is available
let value = Value::Path(path.clean());
self.emit_constant(value);
}
fn compile_str(&mut self, node: ast::Str) {
let mut count = 0;
// The string parts are produced in literal order, however
// they need to be reversed on the stack in order to
// efficiently create the real string in case of
// interpolation.
for part in node.normalized_parts().into_iter().rev() {
count += 1;
match part {
// Interpolated expressions are compiled as normal and
// dealt with by the VM before being assembled into
// the final string.
ast::InterpolPart::Interpolation(node) => self.compile(node.expr().unwrap()),
ast::InterpolPart::Literal(lit) => {
self.emit_constant(Value::String(lit.into()));
}
}
}
if count != 1 {
self.chunk().push_op(OpCode::OpInterpolate(Count(count)));
}
}
fn compile_unary_op(&mut self, op: ast::UnaryOp) {
self.compile(op.expr().unwrap());
let opcode = match op.operator().unwrap() {
ast::UnaryOpKind::Invert => OpCode::OpInvert,
ast::UnaryOpKind::Negate => OpCode::OpNegate,
};
self.chunk().push_op(opcode);
}
fn compile_binop(&mut self, op: ast::BinOp) {
use ast::BinOpKind;
// Short-circuiting and other strange operators, which are
// under the same node type as NODE_BIN_OP, but need to be
// handled separately (i.e. before compiling the expressions
// used for standard binary operators).
match op.operator().unwrap() {
BinOpKind::And => return self.compile_and(op),
BinOpKind::Or => return self.compile_or(op),
BinOpKind::Implication => return self.compile_implication(op),
_ => {}
};
// For all other operators, the two values need to be left on
// the stack in the correct order before pushing the
// instruction for the operation itself.
self.compile(op.lhs().unwrap());
self.compile(op.rhs().unwrap());
match op.operator().unwrap() {
BinOpKind::Add => self.chunk().push_op(OpCode::OpAdd),
BinOpKind::Sub => self.chunk().push_op(OpCode::OpSub),
BinOpKind::Mul => self.chunk().push_op(OpCode::OpMul),
BinOpKind::Div => self.chunk().push_op(OpCode::OpDiv),
BinOpKind::Update => self.chunk().push_op(OpCode::OpAttrsUpdate),
BinOpKind::Equal => self.chunk().push_op(OpCode::OpEqual),
BinOpKind::Less => self.chunk().push_op(OpCode::OpLess),
BinOpKind::LessOrEq => self.chunk().push_op(OpCode::OpLessOrEq),
BinOpKind::More => self.chunk().push_op(OpCode::OpMore),
BinOpKind::MoreOrEq => self.chunk().push_op(OpCode::OpMoreOrEq),
BinOpKind::Concat => self.chunk().push_op(OpCode::OpConcat),
BinOpKind::NotEqual => {
self.chunk().push_op(OpCode::OpEqual);
self.chunk().push_op(OpCode::OpInvert)
}
// Handled by separate branch above.
BinOpKind::And | BinOpKind::Implication | BinOpKind::Or => {
unreachable!()
}
};
}
fn compile_and(&mut self, node: ast::BinOp) {
debug_assert!(
matches!(node.operator(), Some(ast::BinOpKind::And)),
"compile_and called with wrong operator kind: {:?}",
node.operator(),
);
// Leave left-hand side value on the stack.
self.compile(node.lhs().unwrap());
// If this value is false, jump over the right-hand side - the
// whole expression is false.
let end_idx = self.chunk().push_op(OpCode::OpJumpIfFalse(JumpOffset(0)));
// Otherwise, remove the previous value and leave the
// right-hand side on the stack. Its result is now the value
// of the whole expression.
self.chunk().push_op(OpCode::OpPop);
self.compile(node.rhs().unwrap());
self.patch_jump(end_idx);
self.chunk().push_op(OpCode::OpAssertBool);
}
fn compile_or(&mut self, node: ast::BinOp) {
debug_assert!(
matches!(node.operator(), Some(ast::BinOpKind::Or)),
"compile_or called with wrong operator kind: {:?}",
node.operator(),
);
// Leave left-hand side value on the stack
self.compile(node.lhs().unwrap());
// Opposite of above: If this value is **true**, we can
// short-circuit the right-hand side.
let end_idx = self.chunk().push_op(OpCode::OpJumpIfTrue(JumpOffset(0)));
self.chunk().push_op(OpCode::OpPop);
self.compile(node.rhs().unwrap());
self.patch_jump(end_idx);
self.chunk().push_op(OpCode::OpAssertBool);
}
fn compile_implication(&mut self, node: ast::BinOp) {
debug_assert!(
matches!(node.operator(), Some(ast::BinOpKind::Implication)),
"compile_implication called with wrong operator kind: {:?}",
node.operator(),
);
// Leave left-hand side value on the stack and invert it.
self.compile(node.lhs().unwrap());
self.chunk().push_op(OpCode::OpInvert);
// Exactly as `||` (because `a -> b` = `!a || b`).
let end_idx = self.chunk().push_op(OpCode::OpJumpIfTrue(JumpOffset(0)));
self.chunk().push_op(OpCode::OpPop);
self.compile(node.rhs().unwrap());
self.patch_jump(end_idx);
self.chunk().push_op(OpCode::OpAssertBool);
}
fn compile_has_attr(&mut self, node: ast::HasAttr) {
// Put the attribute set on the stack.
self.compile(node.expr().unwrap());
// Push all path fragments with an operation for fetching the
// next nested element, for all fragments except the last one.
for (count, fragment) in node.attrpath().unwrap().attrs().enumerate() {
if count > 0 {
self.chunk().push_op(OpCode::OpAttrsTrySelect);
}
self.compile_attr(fragment);
}
// After the last fragment, emit the actual instruction that
// leaves a boolean on the stack.
self.chunk().push_op(OpCode::OpAttrsIsSet);
}
fn compile_attr(&mut self, node: ast::Attr) {
match node {
ast::Attr::Dynamic(dynamic) => self.compile(dynamic.expr().unwrap()),
ast::Attr::Str(s) => self.compile_str(s),
ast::Attr::Ident(ident) => self.emit_literal_ident(&ident),
}
}
// Compile list literals into equivalent bytecode. List
// construction is fairly simple, consisting of pushing code for
// each literal element and an instruction with the element count.
//
// The VM, after evaluating the code for each element, simply
// constructs the list from the given number of elements.
fn compile_list(&mut self, node: ast::List) {
let mut count = 0;
for item in node.items() {
count += 1;
self.compile(item);
}
self.chunk().push_op(OpCode::OpList(Count(count)));
}
// Compile attribute set literals into equivalent bytecode.
//
// This is complicated by a number of features specific to Nix
// attribute sets, most importantly:
//
// 1. Keys can be dynamically constructed through interpolation.
// 2. Keys can refer to nested attribute sets.
// 3. Attribute sets can (optionally) be recursive.
fn compile_attr_set(&mut self, node: ast::AttrSet) {
if node.rec_token().is_some() {
todo!("recursive attribute sets are not yet implemented")
}
let mut count = 0;
// Inherits have to be evaluated before entering the scope of
// a potentially recursive attribute sets (i.e. we always
// inherit "from the outside").
for inherit in node.inherits() {
match inherit.from() {
Some(from) => {
for ident in inherit.idents() {
count += 1;
// First emit the identifier itself
self.emit_literal_ident(&ident);
// Then emit the node that we're inheriting
// from.
//
// TODO: Likely significant optimisation
// potential in having a multi-select
// instruction followed by a merge, rather
// than pushing/popping the same attrs
// potentially a lot of times.
self.compile(from.expr().unwrap());
self.emit_literal_ident(&ident);
self.chunk().push_op(OpCode::OpAttrsSelect);
}
}
None => {
for ident in inherit.idents() {
count += 1;
self.emit_literal_ident(&ident);
match self
.scope_mut()
.resolve_local(ident.ident_token().unwrap().text())
{
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")
}
};
}
}
}
}
for kv in node.attrpath_values() {
count += 1;
// Because attribute set literals can contain nested keys,
// there is potentially more than one key fragment. If
// this is the case, a special operation to construct a
// runtime value representing the attribute path is
// emitted.
let mut key_count = 0;
for fragment in kv.attrpath().unwrap().attrs() {
key_count += 1;
self.compile_attr(fragment);
}
// We're done with the key if there was only one fragment,
// otherwise we need to emit an instruction to construct
// the attribute path.
if key_count > 1 {
self.chunk().push_op(OpCode::OpAttrPath(Count(key_count)));
}
// The value is just compiled as normal so that its
// resulting value is on the stack when the attribute set
// is constructed at runtime.
self.compile(kv.value().unwrap());
}
self.chunk().push_op(OpCode::OpAttrs(Count(count)));
}
fn compile_select(&mut self, node: ast::Select) {
let set = node.expr().unwrap();
let path = node.attrpath().unwrap();
if node.or_token().is_some() {
self.compile_select_or(set, path, node.default_expr().unwrap());
return;
}
// Push the set onto the stack
self.compile(set);
// Compile each key fragment and emit access instructions.
//
// TODO: multi-select instruction to avoid re-pushing attrs on
// nested selects.
for fragment in path.attrs() {
self.compile_attr(fragment);
self.chunk().push_op(OpCode::OpAttrsSelect);
}
}
/// Compile an `or` expression into a chunk of conditional jumps.
///
/// If at any point during attribute set traversal a key is
/// missing, the `OpAttrOrNotFound` instruction will leave a
/// special sentinel value on the stack.
///
/// After each access, a conditional jump evaluates the top of the
/// stack and short-circuits to the default value if it sees the
/// sentinel.
///
/// Code like `{ a.b = 1; }.a.c or 42` yields this bytecode and
/// runtime stack:
///
/// ```notrust
/// Bytecode Runtime stack
/// โโโโโโโโโโโโโโโโโโโโโโโโโโโโโโ โโโโโโโโโโโโโโโโโโโโโโโโโโโ
/// โ ... โ โ ... โ
/// โ 5 OP_ATTRS(1) โ โ โ 5 [ { a.b = 1; } ] โ
/// โ 6 OP_CONSTANT("a") โ โ โ 6 [ { a.b = 1; } "a" ] โ
/// โ 7 OP_ATTR_OR_NOT_FOUND โ โ โ 7 [ { b = 1; } ] โ
/// โ 8 JUMP_IF_NOT_FOUND(13) โ โ โ 8 [ { b = 1; } ] โ
/// โ 9 OP_CONSTANT("C") โ โ โ 9 [ { b = 1; } "c" ] โ
/// โ 10 OP_ATTR_OR_NOT_FOUND โ โ โ 10 [ NOT_FOUND ] โ
/// โ 11 JUMP_IF_NOT_FOUND(13) โ โ โ 11 [ ] โ
/// โ 12 JUMP(14) โ โ .. jumped over โ
/// โ 13 CONSTANT(42) โ โ โ 12 [ 42 ] โ
/// โ 14 ... โ โ .. .... โ
/// โโโโโโโโโโโโโโโโโโโโโโโโโโโโโโ โโโโโโโโโโโโโโโโโโโโโโโโโโโ
/// ```
fn compile_select_or(&mut self, set: ast::Expr, path: ast::Attrpath, default: ast::Expr) {
self.compile(set);
let mut jumps = vec![];
for fragment in path.attrs() {
self.compile_attr(fragment);
self.chunk().push_op(OpCode::OpAttrsTrySelect);
jumps.push(
self.chunk()
.push_op(OpCode::OpJumpIfNotFound(JumpOffset(0))),
);
}
let final_jump = self.chunk().push_op(OpCode::OpJump(JumpOffset(0)));
for jump in jumps {
self.patch_jump(jump);
}
// Compile the default value expression and patch the final
// jump to point *beyond* it.
self.compile(default);
self.patch_jump(final_jump);
}
fn compile_assert(&mut self, node: ast::Assert) {
// Compile the assertion condition to leave its value on the stack.
self.compile(node.condition().unwrap());
self.chunk().push_op(OpCode::OpAssert);
// The runtime will abort evaluation at this point if the
// assertion failed, if not the body simply continues on like
// normal.
self.compile(node.body().unwrap());
}
// Compile conditional expressions using jumping instructions in the VM.
//
// โโโโโโโโโโโโโโโโโโโโโโ
// โ 0 [ conditional ] โ
// โ 1 JUMP_IF_FALSE โโผโโ
// โ 2 [ main body ] โ โ Jump to else body if
// โโผโ3โโ JUMP โ โ condition is false.
// Jump over else body โโ 4 [ else body ]โโผโโ
// if condition is true.โโผโ5โโ ... โ
// โโโโโโโโโโโโโโโโโโโโโโ
fn compile_if_else(&mut self, node: ast::IfElse) {
self.compile(node.condition().unwrap());
let then_idx = self.chunk().push_op(OpCode::OpJumpIfFalse(JumpOffset(0)));
self.chunk().push_op(OpCode::OpPop); // discard condition value
self.compile(node.body().unwrap());
let else_idx = self.chunk().push_op(OpCode::OpJump(JumpOffset(0)));
self.patch_jump(then_idx); // patch jump *to* else_body
self.chunk().push_op(OpCode::OpPop); // discard condition value
self.compile(node.else_body().unwrap());
self.patch_jump(else_idx); // patch jump *over* else body
}
// Compile an `inherit` node of a `let`-expression.
fn compile_let_inherit<I: Iterator<Item = ast::Inherit>>(&mut self, inherits: I) {
for inherit in inherits {
match inherit.from() {
// 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() => {
self.emit_warning(inherit.syntax().clone(), WarningKind::UselessInherit);
continue;
}
None => {
for ident in inherit.idents() {
// If the identifier resolves statically, it
// has precedence over dynamic bindings, and
// the inherit is useless.
if matches!(
self.scope_mut()
.resolve_local(ident.ident_token().unwrap().text()),
LocalPosition::Known(_)
) {
self.emit_warning(ident.syntax().clone(), WarningKind::UselessInherit);
continue;
}
self.compile_ident(ident.clone());
self.declare_local(
ident.syntax().clone(),
ident.ident_token().unwrap().text(),
);
self.mark_initialised(ident.ident_token().unwrap().text());
}
}
Some(from) => {
for ident in inherit.idents() {
self.compile(from.expr().unwrap());
self.emit_literal_ident(&ident);
self.chunk().push_op(OpCode::OpAttrsSelect);
self.declare_local(
ident.syntax().clone(),
ident.ident_token().unwrap().text(),
);
self.mark_initialised(ident.ident_token().unwrap().text());
}
}
}
}
}
// Compile a standard `let ...; in ...` statement.
//
// Unless in a non-standard scope, the encountered values are
// simply pushed on the stack and their indices noted in the
// entries vector.
fn compile_let_in(&mut self, node: ast::LetIn) {
self.begin_scope();
self.compile_let_inherit(node.inherits());
for entry in node.attrpath_values() {
let mut path = match normalise_ident_path(entry.attrpath().unwrap().attrs()) {
Ok(p) => p,
Err(err) => {
self.errors.push(err);
continue;
}
};
if path.len() != 1 {
todo!("nested bindings in let expressions :(")
}
self.compile(entry.value().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.
self.compile(node.body().unwrap());
self.end_scope();
}
fn compile_ident(&mut self, node: ast::Ident) {
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.scope_mut().resolve_local(ident.text()) {
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));
return;
}
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)
}
LocalPosition::Recursive(_) => todo!("self-recursive upvalue"),
LocalPosition::Known(idx) => self.chunk().push_op(OpCode::OpGetLocal(idx)),
};
}
// Compile `with` expressions by emitting instructions that
// pop/remove the indices of attribute sets that are implicitly in
// scope through `with` on the "with-stack".
fn compile_with(&mut self, node: ast::With) {
// TODO: Detect if the namespace is just an identifier, and
// 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;
self.chunk().push_op(OpCode::OpPushWith(StackIdx(with_idx)));
self.compile(node.body().unwrap());
self.chunk().push_op(OpCode::OpPopWith);
self.scope_mut().with_stack.pop();
}
fn compile_lambda(&mut self, node: ast::Lambda) {
// Open new lambda context in compiler, which has its own
// scope etc.
self.contexts.push(LambdaCtx::new());
self.begin_scope();
// Compile the function itself
match node.param().unwrap() {
ast::Param::Pattern(_) => todo!("formals function definitions"),
ast::Param::IdentParam(param) => {
let name = param
.ident()
.unwrap()
.ident_token()
.unwrap()
.text()
.to_string();
self.declare_local(param.syntax().clone(), &name);
self.mark_initialised(&name);
}
}
self.compile(node.body().unwrap());
self.end_scope();
// TODO: determine and insert enclosing name, if available.
// Pop the lambda context back off, and emit the finished
// lambda as a constant.
let compiled = self.contexts.pop().unwrap();
#[cfg(feature = "disassembler")]
{
crate::disassembler::disassemble_chunk(&compiled.lambda.chunk);
}
// If the function is not a closure, just emit it directly and
// move on.
if compiled.lambda.upvalue_count == 0 {
self.emit_constant(Value::Closure(Closure::new(compiled.lambda)));
return;
}
// If the function is a closure, we need to emit the variable
// number of operands that allow the runtime to close over the
// upvalues.
let closure_idx = self
.chunk()
.push_constant(Value::Closure(Closure::new(compiled.lambda)));
self.chunk().push_op(OpCode::OpClosure(closure_idx));
for upvalue in compiled.scope.upvalues {
match upvalue {
Upvalue::Stack(idx) => self.chunk().push_op(OpCode::DataLocalIdx(idx)),
Upvalue::Upvalue(idx) => self.chunk().push_op(OpCode::DataUpvalueIdx(idx)),
Upvalue::Dynamic(s) => {
let idx = self.chunk().push_constant(Value::String(s.into()));
self.chunk().push_op(OpCode::DataDynamicIdx(idx))
}
};
}
}
fn compile_apply(&mut self, node: ast::Apply) {
// To call a function, we leave its arguments on the stack,
// followed by the function expression itself, and then emit a
// call instruction. This way, the stack is perfectly laid out
// to enter the function call straight away.
self.compile(node.argument().unwrap());
self.compile(node.lambda().unwrap());
self.chunk().push_op(OpCode::OpCall);
}
/// Emit the literal string value of an identifier. Required for
/// several operations related to attribute sets, where
/// identifiers are used as string keys.
fn emit_literal_ident(&mut self, ident: &ast::Ident) {
self.emit_constant(Value::String(ident.ident_token().unwrap().text().into()));
}
/// Patch the jump instruction at the given index, setting its
/// jump offset from the placeholder to the current code position.
///
/// This is required because the actual target offset of jumps is
/// not known at the time when the jump operation itself is
/// emitted.
fn patch_jump(&mut self, idx: CodeIdx) {
let offset = JumpOffset(self.chunk().code.len() - 1 - idx.0);
match &mut self.chunk().code[idx.0] {
OpCode::OpJump(n)
| OpCode::OpJumpIfFalse(n)
| OpCode::OpJumpIfTrue(n)
| OpCode::OpJumpIfNotFound(n) => {
*n = offset;
}
op => panic!("attempted to patch unsupported op: {:?}", op),
}
}
fn begin_scope(&mut self) {
self.scope_mut().scope_depth += 1;
}
fn end_scope(&mut self) {
debug_assert!(self.scope().scope_depth != 0, "can not end top scope");
// If this scope poisoned any builtins or special identifiers,
// they need to be reset.
let depth = self.scope().scope_depth;
self.scope_mut().unpoison(depth);
self.scope_mut().scope_depth -= 1;
// When ending a scope, all corresponding locals need to be
// removed, but the value of the body needs to remain on the
// stack. This is implemented by a separate instruction.
let mut pops = 0;
// TL;DR - iterate from the back while things belonging to the
// ended scope still exist.
while !self.scope().locals.is_empty()
&& self.scope().locals[self.scope().locals.len() - 1]
.depth
.above(self.scope().scope_depth)
{
pops += 1;
// While removing the local, analyse whether it has been
// accessed while it existed and emit a warning to the
// user otherwise.
if let Some(Local {
node: Some(node),
used,
..
}) = self.scope_mut().locals.pop()
{
if !used {
self.emit_warning(node, WarningKind::UnusedBinding);
}
}
}
if pops > 0 {
self.chunk().push_op(OpCode::OpCloseScope(Count(pops)));
}
}
/// Declare a local variable known in the scope that is being
/// 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) {
let name = name.into();
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,
};
if let Some(global_ident) = key {
self.emit_warning(node.clone(), WarningKind::ShadowedGlobal(global_ident));
self.scope_mut().poison(global_ident, depth);
}
let mut shadowed = false;
for local in self.scope().locals.iter().rev() {
if local.depth.below(self.scope().scope_depth) {
// Shadowing identifiers from higher scopes is allowed.
break;
}
if local.name == name {
shadowed = true;
break;
}
}
if shadowed {
self.emit_error(
node.clone(),
ErrorKind::VariableAlreadyDefined(name.clone()),
);
}
self.scope_mut().locals.push(Local {
name,
depth: Depth::Unitialised,
node: Some(node),
phantom: false,
used: false,
});
}
/// Declare a local variable that occupies a stack slot and should
/// be accounted for, but is not directly accessible by users
/// (e.g. attribute sets used for `with`).
fn declare_phantom(&mut self) {
let depth = self.scope().scope_depth;
self.scope_mut().locals.push(Local {
depth: Depth::At(depth),
name: "".into(),
node: None,
phantom: true,
used: true,
});
}
/// 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.
return None;
}
// Determine whether the upvalue is a local in the enclosing context.
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.
if !self.contexts[ctx_idx - 1].scope.with_stack.is_empty() {
return Some(self.add_upvalue(ctx_idx, Upvalue::Dynamic(SmolStr::new(name))));
}
// If the upvalue comes from even further up, we need to
// recurse to make sure that the upvalues are created at each
// level.
if let Some(idx) = self.resolve_upvalue(ctx_idx - 1, name) {
return Some(self.add_upvalue(ctx_idx, Upvalue::Upvalue(idx)));
}
None
}
fn add_upvalue(&mut self, ctx_idx: usize, upvalue: Upvalue) -> UpvalueIdx {
// If there is already an upvalue closing over the specified
// index, retrieve that instead.
for (idx, existing) in self.contexts[ctx_idx].scope.upvalues.iter().enumerate() {
if *existing == upvalue {
return UpvalueIdx(idx);
}
}
self.contexts[ctx_idx].scope.upvalues.push(upvalue);
let idx = UpvalueIdx(self.contexts[ctx_idx].lambda.upvalue_count);
self.contexts[ctx_idx].lambda.upvalue_count += 1;
idx
}
fn emit_warning(&mut self, node: rnix::SyntaxNode, kind: WarningKind) {
self.warnings.push(EvalWarning { node, kind })
}
fn emit_error(&mut self, node: rnix::SyntaxNode, kind: ErrorKind) {
self.errors.push(Error {
node: Some(node),
kind,
})
}
}
/// Convert a non-dynamic string expression to a string if possible,
/// or raise an error.
fn expr_str_to_string(expr: ast::Str) -> EvalResult<String> {
if expr.normalized_parts().len() == 1 {
if let ast::InterpolPart::Literal(s) = expr.normalized_parts().pop().unwrap() {
return Ok(s);
}
}
return Err(Error {
node: Some(expr.syntax().clone()),
kind: ErrorKind::DynamicKeyInLet(expr.syntax().clone()),
});
}
/// Convert a single identifier path fragment to a string if possible,
/// or raise an error about the node being dynamic.
fn attr_to_string(node: ast::Attr) -> EvalResult<String> {
match node {
ast::Attr::Ident(ident) => Ok(ident.ident_token().unwrap().text().into()),
ast::Attr::Str(s) => expr_str_to_string(s),
// The dynamic node type is just a wrapper. C++ Nix does not
// care about the dynamic wrapper when determining whether the
// node itself is dynamic, it depends solely on the expression
// inside (i.e. `let ${"a"} = 1; in a` is valid).
ast::Attr::Dynamic(ref dynamic) => match dynamic.expr().unwrap() {
ast::Expr::Str(s) => expr_str_to_string(s),
_ => Err(ErrorKind::DynamicKeyInLet(node.syntax().clone()).into()),
},
}
}
// Normalises identifier fragments into a single string vector for
// `let`-expressions; fails if fragments requiring dynamic computation
// are encountered.
fn normalise_ident_path<I: Iterator<Item = ast::Attr>>(path: I) -> EvalResult<Vec<String>> {
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>,
globals: HashMap<&'static str, Value>,
) -> EvalResult<CompilationOutput> {
let mut root_dir = match location {
Some(dir) => Ok(dir),
None => std::env::current_dir().map_err(|e| {
ErrorKind::PathResolution(format!("could not determine current directory: {}", e))
}),
}?;
// If the path passed from the caller points to a file, the
// filename itself needs to be truncated as this must point to a
// directory.
if root_dir.is_file() {
root_dir.pop();
}
let mut c = Compiler {
root_dir,
globals: prepare_globals(globals),
contexts: vec![LambdaCtx::new()],
warnings: vec![],
errors: vec![],
};
c.compile(expr);
Ok(CompilationOutput {
lambda: c.contexts.pop().unwrap().lambda,
warnings: c.warnings,
errors: c.errors,
})
}
