diff options
Diffstat (limited to 'tvix/eval/src/compiler.rs')
| -rw-r--r-- | tvix/eval/src/compiler.rs | 1093 |
1 files changed, 0 insertions, 1093 deletions
diff --git a/tvix/eval/src/compiler.rs b/tvix/eval/src/compiler.rs deleted file mode 100644 index 5cb02a66b96a..000000000000 --- a/tvix/eval/src/compiler.rs +++ /dev/null @@ -1,1093 +0,0 @@ -//! 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 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, OpCode}; -use crate::value::{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 CompilationResult { - pub lambda: Lambda, - pub warnings: Vec<EvalWarning>, - pub errors: Vec<Error>, -} - -/// 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: usize, - - // 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 { - depth: usize, -} - -/// 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>, - - // 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); - } -} - -/// 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)); - } - } - - 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(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(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(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()); - let mut count = 0; - - // Push all path fragments with an operation for fetching the - // next nested element, for all fragments except the last one. - for fragment in node.attrpath().unwrap().attrs() { - if count > 0 { - self.chunk().push_op(OpCode::OpAttrOrNotFound); - } - count += 1; - 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)); - } - - // 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.resolve_local(ident.ident_token().unwrap().text()) { - Some(idx) => self.chunk().push_op(OpCode::OpGetLocal(idx)), - None => { - self.emit_error( - ident.syntax().clone(), - ErrorKind::UnknownStaticVariable, - ); - continue; - } - }; - } - } - } - } - - 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(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)); - } - - 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 - /// ┌────────────────────────────┐ ┌─────────────────────────┐ - /// │ ... │ │ ... │ - /// │ 5 OP_ATTRS(1) │ → │ 5 [ { a.b = 1; } ] │ - /// │ 6 OP_CONSTANT("a") │ → │ 6 [ { a.b = 1; } "a" ] │ - /// │ 7 OP_ATTR_OR_NOT_FOUND │ → │ 7 [ { b = 1; } ] │ - /// │ 8 JUMP_IF_NOT_FOUND(13) │ → │ 8 [ { b = 1; } ] │ - /// │ 9 OP_CONSTANT("C") │ → │ 9 [ { b = 1; } "c" ] │ - /// │ 10 OP_ATTR_OR_NOT_FOUND │ → │ 10 [ NOT_FOUND ] │ - /// │ 11 JUMP_IF_NOT_FOUND(13) │ → │ 11 [ ] │ - /// │ 12 JUMP(14) │ │ .. jumped over │ - /// │ 13 CONSTANT(42) │ → │ 12 [ 42 ] │ - /// │ 14 ... │ │ .. .... │ - /// └────────────────────────────┘ └─────────────────────────┘ - /// ``` - 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::OpAttrOrNotFound); - jumps.push(self.chunk().push_op(OpCode::OpJumpIfNotFound(0))); - } - - let final_jump = self.chunk().push_op(OpCode::OpJump(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. - // - // ┌────────────────────┐ - // │ 0 [ conditional ] │ - // │ 1 JUMP_IF_FALSE →┼─┐ - // │ 2 [ main body ] │ │ Jump to else body if - // ┌┼─3─← JUMP │ │ condition is false. - // Jump over else body ││ 4 [ else body ]←┼─┘ - // if condition is true.└┼─5─→ ... │ - // └────────────────────┘ - fn compile_if_else(&mut self, node: ast::IfElse) { - self.compile(node.condition().unwrap()); - - let then_idx = self.chunk().push_op(OpCode::OpJumpIfFalse(0)); - - self.chunk().push_op(OpCode::OpPop); // discard condition value - self.compile(node.body().unwrap()); - - let else_idx = self.chunk().push_op(OpCode::OpJump(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 self - .resolve_local(ident.ident_token().unwrap().text()) - .is_some() - { - 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(), - ); - } - } - - 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(), - ); - } - } - } - } - } - - // 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()); - self.declare_local( - entry.attrpath().unwrap().syntax().clone(), - path.pop().unwrap(), - ); - } - - // 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.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) - } - }; - } - - // 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(); - let depth = self.scope().scope_depth; - self.scope_mut().with_stack.push(With { depth }); - - let with_idx = self.scope().locals.len() - 1; - self.chunk().push_op(OpCode::OpPushWith(with_idx)); - - self.compile(node.body().unwrap()); - } - - 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.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); - } - - self.emit_constant(Value::Lambda(compiled.lambda)); - } - - 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())); - } - - fn patch_jump(&mut self, idx: CodeIdx) { - let offset = 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 > 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(pops)); - } - - while !self.scope().with_stack.is_empty() - && self.scope().with_stack[self.scope().with_stack.len() - 1].depth - > self.scope().scope_depth - { - self.chunk().push_op(OpCode::OpPopWith); - self.scope_mut().with_stack.pop(); - } - } - - /// 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); - } - - self.scope_mut().locals.push(Local { - depth, - name: name.into(), - node: Some(node), - phantom: false, - used: false, - }); - } - - fn declare_phantom(&mut self) { - let depth = self.scope().scope_depth; - self.scope_mut().locals.push(Local { - depth, - name: "".into(), - node: None, - phantom: true, - used: true, - }); - } - - fn resolve_local(&mut self, name: &str) -> Option<usize> { - let scope = self.scope_mut(); - - for (idx, local) in scope.locals.iter_mut().enumerate().rev() { - if !local.phantom && local.name == name { - local.used = true; - return Some(idx); - } - } - - None - } - - 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<CompilationResult> { - 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(CompilationResult { - lambda: c.contexts.pop().unwrap().lambda, - warnings: c.warnings, - errors: c.errors, - }) -} |