770 lines
25 KiB
Rust
770 lines
25 KiB
Rust
use crate::{
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parser::{Child, SyntaxTree, Tree, TreeKind, TreeRef},
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tokens::{Lines, Token, TokenKind},
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};
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use std::{cell::RefCell, collections::HashMap, fmt, rc::Rc};
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// TODO: An error should have:
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//
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// - a start
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// - an end
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// - a focus
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// - descriptive messages
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//
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// that will have to wait for now
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#[derive(Clone, PartialEq, Eq)]
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pub struct Error {
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pub start: (usize, usize),
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pub end: (usize, usize),
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pub message: String,
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}
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impl Error {
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pub fn new<T>(line: usize, column: usize, message: T) -> Self
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where
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T: ToString,
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{
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Error {
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start: (line, column),
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end: (line, column),
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message: message.to_string(),
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}
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}
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pub fn new_spanned<T>(start: (usize, usize), end: (usize, usize), message: T) -> Self
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where
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T: ToString,
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{
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Error {
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start,
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end,
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message: message.to_string(),
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}
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}
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}
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impl fmt::Debug for Error {
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fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
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write!(f, "{self}")
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}
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}
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impl fmt::Display for Error {
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fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
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write!(f, "{}:{}: {}", self.start.0, self.start.1, self.message)
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}
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}
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#[derive(Copy, Clone)]
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pub enum Type {
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// Signals a type error. If you receive this then you know that an error
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// has already been reported; if you produce this be sure to also note
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// the error in the errors collection.
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Error,
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// Signals that the expression has a control-flow side-effect and that no
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// value will ever result from this expression. Usually this means
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// everything's fine.
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Unreachable,
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Nothing,
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// TODO: Numeric literals should be implicitly convertable, unlike other
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// types. Maybe just "numeric literal" type?
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F64,
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String,
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Bool,
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}
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impl Type {
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pub fn is_error(&self) -> bool {
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match self {
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Type::Error => true,
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_ => false,
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}
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}
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pub fn compatible_with(&self, other: &Type) -> bool {
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// TODO: This is wrong; we because of numeric literals etc.
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match (self, other) {
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(Type::F64, Type::F64) => true,
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(Type::String, Type::String) => true,
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(Type::Bool, Type::Bool) => true,
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(Type::Unreachable, Type::Unreachable) => true,
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(Type::Nothing, Type::Nothing) => true,
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// Avoid introducing more errors
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(Type::Error, _) => true,
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(_, Type::Error) => true,
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(_, _) => false,
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}
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}
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}
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impl fmt::Debug for Type {
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fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
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write!(f, "{self}")
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}
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}
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impl fmt::Display for Type {
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fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
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use Type::*;
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match self {
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Error => write!(f, "<< INTERNAL ERROR >>"),
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Unreachable => write!(f, "<< UNREACHABLE >>"),
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Nothing => write!(f, "()"),
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F64 => write!(f, "f64"),
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String => write!(f, "string"),
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Bool => write!(f, "bool"),
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}
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}
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}
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pub struct Declaration {
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pub declaration_type: Type,
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}
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pub struct Environment {
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pub parent: Option<EnvironmentRef>,
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pub declarations: HashMap<Box<str>, Declaration>,
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}
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impl Environment {
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pub fn new(parent: Option<EnvironmentRef>) -> Self {
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Environment {
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parent,
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declarations: HashMap::new(),
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}
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}
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pub fn bind(&self, token: &Token) -> Option<&Declaration> {
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if let Some(decl) = self.declarations.get(token.as_str()) {
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return Some(decl);
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}
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let mut current = &self.parent;
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while let Some(env) = current {
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if let Some(decl) = env.declarations.get(token.as_str()) {
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return Some(decl);
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}
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current = &env.parent;
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}
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None
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}
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}
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#[derive(Clone)]
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pub struct EnvironmentRef(Rc<Environment>);
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impl EnvironmentRef {
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pub fn new(environment: Environment) -> Self {
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EnvironmentRef(Rc::new(environment))
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}
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}
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impl std::ops::Deref for EnvironmentRef {
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type Target = Environment;
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fn deref(&self) -> &Self::Target {
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&self.0
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}
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}
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fn set_logical_parents(
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parents: &mut Vec<Option<TreeRef>>,
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syntax_tree: &SyntaxTree,
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t: TreeRef,
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parent: Option<TreeRef>,
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) {
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parents[t.index()] = parent.clone();
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let tree = &syntax_tree[t];
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// eprintln!("SET PARENT {parent:?} => CHILD {tree:?} ({t:?})");
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match tree.kind {
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TreeKind::Block | TreeKind::File => {
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// In a block (or at the top level), each child actually points
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// to the previous child as the logical parent, so that variable
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// declarations that occur as part of statements in the block are
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// available to statements later in the block.
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let mut parent = Some(t);
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for child in &tree.children {
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match child {
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Child::Token(_) => (),
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Child::Tree(ct) => {
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set_logical_parents(parents, syntax_tree, *ct, parent);
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parent = Some(*ct);
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}
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}
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}
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}
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TreeKind::LetStatement => {
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// In a let statement, the logical parent of the children is
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// actually the logical parent of the let statement, so that the
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// variable doesn't have itself in scope. :P
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for child in &tree.children {
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match child {
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Child::Token(_) => (),
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Child::Tree(ct) => set_logical_parents(parents, syntax_tree, *ct, parent),
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}
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}
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}
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_ => {
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// By default, the parent for each child is current tree.
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for child in &tree.children {
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match child {
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Child::Token(_) => (),
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Child::Tree(ct) => set_logical_parents(parents, syntax_tree, *ct, Some(t)),
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}
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}
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}
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}
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}
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enum Incremental<T> {
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InProgress,
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Complete(T),
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}
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pub struct Semantics<'a> {
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// TODO: Do I really want my own copy here? Should we standardize on Arc
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// or Rc or some other nice sharing mechanism?
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syntax_tree: &'a SyntaxTree<'a>,
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lines: &'a Lines,
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// Instead of physical parents, this is the set of *logical* parents.
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// This is what is used for binding.
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logical_parents: Vec<Option<TreeRef>>,
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// TODO: State should be externalized instead of this refcell nonsense.
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errors: RefCell<Vec<Error>>,
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types: RefCell<HashMap<TreeRef, Incremental<Type>>>,
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environments: RefCell<HashMap<TreeRef, Incremental<EnvironmentRef>>>,
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empty_environment: EnvironmentRef,
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}
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impl<'a> Semantics<'a> {
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pub fn new(tree: &'a SyntaxTree<'a>, lines: &'a Lines) -> Self {
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let mut logical_parents = Vec::with_capacity(tree.len());
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logical_parents.resize(tree.len(), None);
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if let Some(root) = tree.root() {
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set_logical_parents(&mut logical_parents, tree, root, None);
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}
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let mut semantics = Semantics {
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syntax_tree: tree,
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lines,
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logical_parents,
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errors: RefCell::new(vec![]),
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types: RefCell::new(HashMap::new()),
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environments: RefCell::new(HashMap::new()),
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empty_environment: EnvironmentRef::new(Environment::new(None)),
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};
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// NOTE: We ensure all the known errors are reported before we move
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// on to answering any other questions. We're going to work as
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// hard as we can from a partial tree.
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if let Some(tr) = semantics.syntax_tree.root() {
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semantics.gather_errors(tr);
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}
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semantics
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}
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pub fn tree(&self) -> &SyntaxTree<'a> {
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&self.syntax_tree
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}
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pub fn snapshot_errors(&self) -> Vec<Error> {
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(*self.errors.borrow()).clone()
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}
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pub fn logical_parent(&self, tr: TreeRef) -> Option<TreeRef> {
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if tr.index() < self.logical_parents.len() {
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self.logical_parents[tr.index()]
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} else {
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None
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}
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}
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fn report_error<T>(&self, position: usize, error: T)
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where
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T: ToString,
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{
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let (line, col) = self.lines.position(position);
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self.errors
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.borrow_mut()
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.push(Error::new(line, col, error.to_string()));
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}
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fn report_error_span<T>(&self, start: usize, end: usize, error: T)
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where
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T: ToString,
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{
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let start = self.lines.position(start);
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let end = self.lines.position(end);
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self.errors
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.borrow_mut()
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.push(Error::new_spanned(start, end, error.to_string()));
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}
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fn report_error_tree<T>(&self, tree: &Tree<'a>, error: T)
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where
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T: ToString,
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{
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self.report_error_span(tree.start_pos, tree.end_pos, error)
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}
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fn report_error_tree_ref<T>(&self, tree: TreeRef, error: T)
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where
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T: ToString,
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{
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let tree = &self.syntax_tree[tree];
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self.report_error_span(tree.start_pos, tree.end_pos, error)
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}
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fn gather_errors(&mut self, tree: TreeRef) {
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let mut stack = vec![tree];
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while let Some(tr) = stack.pop() {
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let tree = &self.syntax_tree[tr];
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for child in &tree.children {
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match child {
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Child::Token(t) => {
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if t.kind == TokenKind::Error {
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self.report_error(t.start, t.as_str());
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}
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}
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Child::Tree(t) => stack.push(*t),
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}
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}
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}
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}
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pub fn environment_of(&self, t: TreeRef) -> EnvironmentRef {
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match self.environments.borrow().get(&t) {
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None => (),
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Some(Incremental::Complete(e)) => return e.clone(),
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Some(Incremental::InProgress) => {
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// TODO: Rewrite as complete with empty after reporting error.
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// eprintln!("environment_of circular => {t:?}");
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self.report_error_tree_ref(
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t,
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"INTERNAL COMPILER ERROR: Circular dependency detected: environment",
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);
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return self.empty_environment.clone();
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}
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}
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self.environments
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.borrow_mut()
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.insert(t, Incremental::InProgress);
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let tree = &self.syntax_tree[t];
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// eprintln!("environment_of => {tree:?}");
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let parent = match self.logical_parents[t.index()] {
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Some(t) => self.environment_of(t),
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None => self.empty_environment.clone(),
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};
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let result = match tree.kind {
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TreeKind::LetStatement => self.environment_of_let(parent, tree),
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TreeKind::FunctionDecl => self.environment_of_func(parent, tree),
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// TODO: MORE Things that introduce an environment!
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_ => parent,
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};
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self.environments
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.borrow_mut()
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.insert(t, Incremental::Complete(result.clone()));
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result
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}
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fn environment_of_let(&self, parent: EnvironmentRef, tree: &Tree) -> EnvironmentRef {
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let Some(name) = tree.nth_token(1) else {
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return parent; // Error is already reported?
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};
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let declaration_type = match tree.nth_tree(3) {
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Some(expr) => self
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.type_of(expr)
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.expect("the tree in the expression should yield a type"),
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// The syntax error should already have been reported, so we'll
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// stick with error type here. (But bind the name, because we see
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// it!)
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None => Type::Error,
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};
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let mut environment = Environment::new(Some(parent));
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environment
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.declarations
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.insert(name.as_str().into(), Declaration { declaration_type });
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EnvironmentRef::new(environment)
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}
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fn environment_of_func(&self, parent: EnvironmentRef, tree: &Tree) -> EnvironmentRef {
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let Some(param_list) = tree.nth_tree(2) else {
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return parent; // SE
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};
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let param_list = &self.syntax_tree[param_list];
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if param_list.kind != TreeKind::ParamList {
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return parent; // SE
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}
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let mut environment = Environment::new(Some(parent));
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for child in param_list.children.iter() {
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let Child::Tree(ct) = child else {
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continue;
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};
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let param = &self.syntax_tree[*ct];
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if param.kind != TreeKind::Parameter {
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continue;
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}
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let Some(param_name) = param.nth_token(0) else {
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continue;
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};
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let declaration_type = if let Some(type_expression) = param.nth_tree(2) {
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self.type_of(type_expression)
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.expect("the type expression should yield *some* type here")
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} else {
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Type::Error
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};
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environment
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.declarations
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.insert(param_name.as_str().into(), Declaration { declaration_type });
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}
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EnvironmentRef::new(environment)
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}
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pub fn type_of(&self, t: TreeRef) -> Option<Type> {
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match self.types.borrow().get(&t) {
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None => (),
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Some(Incremental::Complete(existing)) => return Some(existing.clone()),
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Some(Incremental::InProgress) => {
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// TODO: Rewrite as complete with error after reporting error.
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// eprintln!("type_of circular => {t:?}");
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self.report_error_tree_ref(
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t,
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"INTERNAL COMPILER ERROR: Circular dependency detected: type",
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);
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return Some(Type::Error);
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}
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}
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self.types.borrow_mut().insert(t, Incremental::InProgress);
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let tree = &self.syntax_tree[t];
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// eprintln!("type_of => {tree:?}");
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let result = match tree.kind {
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TreeKind::Error => Some(Type::Error),
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TreeKind::UnaryExpression => self.type_of_unary(tree),
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TreeKind::BinaryExpression => self.type_of_binary(tree),
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TreeKind::TypeExpression => self.type_of_type_expr(tree),
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TreeKind::Block => self.type_of_block(tree),
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TreeKind::LiteralExpression => self.type_of_literal(tree),
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TreeKind::GroupingExpression => self.type_of_grouping(tree),
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TreeKind::ConditionalExpression => self.type_of_conditional(tree),
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TreeKind::CallExpression => self.type_of_call(tree),
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TreeKind::Argument => self.type_of_argument(tree),
|
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TreeKind::LetStatement => Some(Type::Nothing),
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TreeKind::ReturnStatement => Some(Type::Unreachable),
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TreeKind::ExpressionStatement => self.type_of_expression_statement(tree),
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TreeKind::Identifier => self.type_of_identifier(tree),
|
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// TODO: Previously I had short-circuited here and not put anything
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// in the table if this node isn't the kind that I would
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// normally compute a type for. I should keep doing that to
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// detect nonsense without blowing out the hash table. If
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// we're going to be computing a type for every node it
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// should just be an array instead of a hash table.
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_ => None,
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};
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// NOTE: These return `None` if they encounter some problem.
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let result = result.unwrap_or(Type::Error);
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self.types
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.borrow_mut()
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.insert(t, Incremental::Complete(result.clone()));
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Some(result)
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}
|
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|
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fn type_of_unary(&self, tree: &Tree) -> Option<Type> {
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assert_eq!(tree.kind, TreeKind::UnaryExpression);
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let op = tree.nth_token(0)?;
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let expr = tree.nth_tree(1)?;
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let argument_type = self
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.type_of(expr)
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.expect("Our argument should be an expression");
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match (op.kind, argument_type) {
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(TokenKind::Plus, Type::F64) => Some(Type::F64),
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(TokenKind::Minus, Type::F64) => Some(Type::F64),
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(TokenKind::Bang, Type::Bool) => Some(Type::Bool),
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|
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// This is dumb and should be punished, probably.
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(_, Type::Unreachable) => {
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self.report_error(
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op.start,
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"cannot apply a unary operator to something that doesn't yield a value",
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);
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Some(Type::Error)
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}
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|
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// Propagate existing errors without additional complaint.
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(_, Type::Error) => Some(Type::Error),
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|
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(_, arg_type) => {
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self.report_error(
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op.start,
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format!(
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"cannot apply unary operator '{}' to value of type {}",
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op.as_str(),
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arg_type
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),
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);
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Some(Type::Error)
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}
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}
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}
|
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|
|
fn type_of_binary(&self, tree: &Tree) -> Option<Type> {
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assert_eq!(tree.kind, TreeKind::BinaryExpression);
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let lhs = self
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.type_of(tree.nth_tree(0)?)
|
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.expect("must be an expression");
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let op = tree.nth_token(1)?;
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|
let rhs = self
|
|
.type_of(tree.nth_tree(2)?)
|
|
.expect("must be an expression");
|
|
|
|
match (op.kind, lhs, rhs) {
|
|
(
|
|
TokenKind::Plus | TokenKind::Minus | TokenKind::Star | TokenKind::Slash,
|
|
Type::F64,
|
|
Type::F64,
|
|
) => Some(Type::F64),
|
|
|
|
(TokenKind::Plus, Type::String, Type::String) => Some(Type::String),
|
|
|
|
(TokenKind::And | TokenKind::Or, Type::Bool, Type::Bool) => Some(Type::Bool),
|
|
|
|
// This is dumb and should be punished, probably.
|
|
(_, _, Type::Unreachable) => {
|
|
self.report_error(
|
|
op.start,
|
|
format!("cannot apply '{op}' to an argument that doesn't yield a value (on the right)"),
|
|
);
|
|
Some(Type::Error)
|
|
}
|
|
(_, Type::Unreachable, _) => {
|
|
self.report_error(
|
|
op.start,
|
|
format!("cannot apply '{op}' to an argument that doesn't yield a value (on the left)"),
|
|
);
|
|
Some(Type::Error)
|
|
}
|
|
|
|
// Propagate existing errors without additional complaint.
|
|
(_, Type::Error, _) => Some(Type::Error),
|
|
(_, _, Type::Error) => Some(Type::Error),
|
|
|
|
// Missed the whole table, it must be an error.
|
|
(_, left_type, right_type) => {
|
|
self.report_error(
|
|
op.start,
|
|
format!("cannot apply binary operator '{op}' to expressions of type '{left_type}' (on the left) and '{right_type}' (on the right)"),
|
|
);
|
|
Some(Type::Error)
|
|
}
|
|
}
|
|
}
|
|
|
|
fn type_of_type_expr(&self, tree: &Tree) -> Option<Type> {
|
|
assert_eq!(tree.kind, TreeKind::TypeExpression);
|
|
|
|
// TODO: This will *clearly* need to get better.
|
|
let token = tree.nth_token(0)?;
|
|
match token.as_str() {
|
|
"f64" => Some(Type::F64),
|
|
"string" => Some(Type::String),
|
|
"bool" => Some(Type::Bool),
|
|
"()" => Some(Type::Nothing),
|
|
_ => Some(Type::Error),
|
|
}
|
|
}
|
|
|
|
fn type_of_block(&self, tree: &Tree) -> Option<Type> {
|
|
assert_eq!(tree.kind, TreeKind::Block);
|
|
|
|
if tree.children.len() < 2 {
|
|
return None;
|
|
}
|
|
|
|
if tree.children.len() == 2 {
|
|
// Empty blocks generate Nothing.
|
|
return Some(Type::Nothing);
|
|
}
|
|
|
|
// The type of the block is the type of the last expression.
|
|
// (But the last child is the closing brace probably?)
|
|
let last_is_brace = tree.nth_token(tree.children.len() - 1).is_some();
|
|
let last_index = tree.children.len() - if last_is_brace { 2 } else { 1 };
|
|
|
|
let mut is_unreachable = false;
|
|
for i in 1..last_index {
|
|
// TODO: if `is_unreachable` here then we actually have
|
|
// unreachable code here! We should warn about it I guess.
|
|
|
|
is_unreachable = self
|
|
.type_of(tree.nth_tree(i)?)
|
|
.map(|t| matches!(t, Type::Unreachable))
|
|
.unwrap_or(false)
|
|
|| is_unreachable;
|
|
}
|
|
|
|
// NOTE: If for some reason the last statement is unsuitable for a
|
|
// type then we consider the type of the block to be Nothing.
|
|
// (And explicitly not Error, which is what returning None
|
|
// would yield.)
|
|
let last_type = self
|
|
.type_of(tree.nth_tree(last_index)?)
|
|
.unwrap_or(Type::Nothing);
|
|
|
|
// If anything in this block generated an "Unreachable" then the
|
|
// whole type of the block is "unreachable" no matter what.
|
|
Some(if is_unreachable {
|
|
Type::Unreachable
|
|
} else {
|
|
last_type
|
|
})
|
|
}
|
|
|
|
fn type_of_literal(&self, tree: &Tree) -> Option<Type> {
|
|
assert_eq!(tree.kind, TreeKind::LiteralExpression);
|
|
|
|
let tok = tree.nth_token(0)?;
|
|
let pig = match tok.kind {
|
|
TokenKind::Number => Type::F64,
|
|
TokenKind::String => Type::String,
|
|
TokenKind::True | TokenKind::False => Type::Bool,
|
|
_ => panic!("the token {tok} doesn't have a type!"),
|
|
};
|
|
Some(pig)
|
|
}
|
|
|
|
fn type_of_grouping(&self, tree: &Tree) -> Option<Type> {
|
|
assert_eq!(tree.kind, TreeKind::GroupingExpression);
|
|
|
|
let expr = tree.nth_tree(1)?;
|
|
Some(
|
|
self.type_of(expr)
|
|
.expect("the thing in the parenthesis must have some type"),
|
|
)
|
|
}
|
|
|
|
fn type_of_conditional(&self, tree: &Tree) -> Option<Type> {
|
|
assert_eq!(tree.kind, TreeKind::ConditionalExpression);
|
|
|
|
let cond_tree = tree.nth_tree(1)?;
|
|
let cond_type = self.type_of(cond_tree).expect("must be expression");
|
|
let then_type = self.type_of(tree.nth_tree(2)?).expect("must be expression");
|
|
|
|
let has_else = tree
|
|
.nth_token(3)
|
|
.map(|t| t.kind == TokenKind::Else)
|
|
.unwrap_or(false);
|
|
let else_type = if has_else {
|
|
Some(self.type_of(tree.nth_tree(4)?).expect("must be expression"))
|
|
} else {
|
|
None
|
|
};
|
|
|
|
if !cond_type.compatible_with(&Type::Bool) {
|
|
if !cond_type.is_error() {
|
|
self.report_error_tree_ref(cond_tree, "conditions must yield a boolean");
|
|
}
|
|
Some(Type::Error)
|
|
} else {
|
|
match (then_type, else_type) {
|
|
(Type::Error, _) => Some(Type::Error),
|
|
(_, Some(Type::Error)) => Some(Type::Error),
|
|
|
|
(Type::Unreachable, None) => Some(Type::Unreachable),
|
|
(Type::Unreachable, Some(t)) => Some(t),
|
|
(t, Some(Type::Unreachable)) => Some(t),
|
|
|
|
(then_type, else_type) => {
|
|
let else_type = else_type.unwrap_or(Type::Nothing);
|
|
if !then_type.compatible_with(&else_type) {
|
|
self.report_error_tree(
|
|
tree,
|
|
format!("the type of the `then` branch ({then_type}) must match the type of the `else` branch ({else_type})"),
|
|
);
|
|
Some(Type::Error)
|
|
} else {
|
|
Some(then_type)
|
|
}
|
|
}
|
|
}
|
|
}
|
|
}
|
|
|
|
fn type_of_call(&self, tree: &Tree) -> Option<Type> {
|
|
assert_eq!(tree.kind, TreeKind::CallExpression);
|
|
Some(Type::Error)
|
|
}
|
|
|
|
fn type_of_argument(&self, tree: &Tree) -> Option<Type> {
|
|
assert_eq!(tree.kind, TreeKind::Argument);
|
|
Some(Type::Error)
|
|
}
|
|
|
|
fn type_of_expression_statement(&self, tree: &Tree) -> Option<Type> {
|
|
assert_eq!(tree.kind, TreeKind::ExpressionStatement);
|
|
let last_is_semicolon = tree
|
|
.nth_token(tree.children.len() - 1)
|
|
.map(|t| t.kind == TokenKind::Semicolon)
|
|
.unwrap_or(false);
|
|
|
|
let expression_type = self.type_of(tree.nth_tree(0)?).expect("must be expression");
|
|
Some(match expression_type {
|
|
Type::Unreachable => Type::Unreachable,
|
|
_ => {
|
|
// A semicolon at the end of an expression statement discards
|
|
// the value, leaving us with nothing. (Even if the
|
|
// expression otherwise generated a type error!)
|
|
if last_is_semicolon {
|
|
Type::Nothing
|
|
} else {
|
|
expression_type
|
|
}
|
|
}
|
|
})
|
|
}
|
|
|
|
fn type_of_identifier(&self, tree: &Tree) -> Option<Type> {
|
|
assert_eq!(tree.kind, TreeKind::Identifier);
|
|
|
|
let id = tree.nth_token(0)?;
|
|
if let Some(parent) = tree.parent {
|
|
let environment = self.environment_of(parent);
|
|
if let Some(declaration) = environment.bind(id) {
|
|
return Some(declaration.declaration_type);
|
|
}
|
|
}
|
|
|
|
self.report_error_tree(tree, format!("cannot find value {id} here"));
|
|
Some(Type::Error)
|
|
}
|
|
}
|