1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
|
// Resolves variable access to their specific instances in the
// environment chain.
//
// https://craftinginterpreters.com/resolving-and-binding.html
use std::collections::HashMap;
use std::rc::Rc;
use crate::errors::{Error, ErrorKind};
use crate::parser::{self, Expr, Statement};
use crate::scanner::Token;
#[derive(Default)]
struct Resolver<'a> {
scopes: Vec<HashMap<&'a str, bool>>,
}
impl<'a> Resolver<'a> {
// AST traversal
fn resolve(&mut self, program: &'a mut parser::Block) -> Result<(), Error> {
self.begin_scope();
for stmt in program {
self.resolve_stmt(stmt)?;
}
self.end_scope();
Ok(())
}
fn resolve_stmt(&mut self, stmt: &'a mut Statement) -> Result<(), Error> {
match stmt {
Statement::Expr(expr) => self.resolve_expr(expr),
Statement::Print(expr) => self.resolve_expr(expr),
Statement::Var(var) => self.resolve_var(var),
Statement::Return(ret) => self.resolve_expr(&mut ret.value),
Statement::Block(block) => self.resolve(block),
Statement::If(if_stmt) => {
self.resolve_expr(&mut if_stmt.condition)?;
self.resolve_stmt(&mut if_stmt.then_branch)?;
if let Some(branch) = if_stmt.else_branch.as_mut() {
self.resolve_stmt(branch)?;
}
Ok(())
}
Statement::While(while_stmt) => {
self.resolve_expr(&mut while_stmt.condition)?;
self.resolve_stmt(&mut while_stmt.body)
}
Statement::Function(func) => match Rc::get_mut(func) {
Some(func) => self.resolve_function(func),
// The resolver does not clone references, so unless
// the interpreter is called before the resolver this
// case should never happen.
None => {
return Err(Error {
line: 0,
kind: ErrorKind::InternalError(
"multiple function references before interpretation".into(),
),
})
}
},
}
}
fn resolve_var(&mut self, var: &'a mut parser::Var) -> Result<(), Error> {
self.declare(&var.name);
if let Some(init) = &mut var.initialiser {
self.resolve_expr(init)?;
}
self.define(&var.name);
Ok(())
}
fn resolve_function(&mut self, func: &'a mut parser::Function) -> Result<(), Error> {
self.declare(&func.name);
self.define(&func.name);
self.begin_scope();
for param in &func.params {
self.declare(param);
self.define(param);
}
for stmt in &mut func.body {
self.resolve_stmt(stmt)?;
}
self.end_scope();
Ok(())
}
fn resolve_expr(&mut self, expr: &'a mut Expr) -> Result<(), Error> {
match expr {
Expr::Variable(var) => self.resolve_variable(var),
Expr::Assign(assign) => self.resolve_assign(assign),
Expr::Grouping(grouping) => self.resolve_expr(&mut grouping.0),
Expr::Call(call) => self.resolve_call(call),
Expr::Literal(_) => Ok(()),
Expr::Unary(unary) => self.resolve_expr(&mut unary.right),
Expr::Logical(log) => {
self.resolve_expr(&mut log.left)?;
self.resolve_expr(&mut log.right)
}
Expr::Binary(binary) => {
self.resolve_expr(&mut binary.left)?;
self.resolve_expr(&mut binary.right)
}
}
}
fn resolve_variable(&mut self, var: &'a mut parser::Variable) -> Result<(), Error> {
if let Some(scope) = self.scopes.last_mut() {
if let Some(false) = scope.get(var.name.lexeme.as_str()) {
return Err(Error {
line: var.name.line,
kind: ErrorKind::StaticError(
"can't read local variable in its own initialiser".into(),
),
});
}
}
var.depth = self.resolve_local(&var.name);
Ok(())
}
fn resolve_assign(&mut self, assign: &'a mut parser::Assign) -> Result<(), Error> {
self.resolve_expr(&mut assign.value)?;
assign.depth = self.resolve_local(&assign.name);
Ok(())
}
fn resolve_local(&mut self, name: &'a Token) -> Option<usize> {
for (c, scope) in self.scopes.iter().rev().enumerate() {
if scope.contains_key(name.lexeme.as_str()) {
return Some(c);
}
}
None
}
fn resolve_call(&mut self, call: &'a mut parser::Call) -> Result<(), Error> {
self.resolve_expr(&mut call.callee)?;
for arg in call.args.iter_mut() {
self.resolve_expr(arg)?;
}
Ok(())
}
// Internal helpers
fn declare(&mut self, name: &'a Token) {
if let Some(scope) = self.scopes.last_mut() {
scope.insert(&name.lexeme, false);
}
}
fn define(&mut self, name: &'a Token) {
if let Some(scope) = self.scopes.last_mut() {
scope.insert(&name.lexeme, true);
}
}
fn begin_scope(&mut self) {
self.scopes.push(Default::default());
}
fn end_scope(&mut self) {
self.scopes.pop();
}
}
pub fn resolve(mut block: parser::Block) -> Result<parser::Block, Error> {
let mut resolver: Resolver = Default::default();
resolver.resolve(&mut block)?;
Ok(block)
}
|
