@ -32,6 +32,15 @@ pub enum EnvironmentType {
Object ,
}
/// The scope of a given variable
#[ derive(Debug, Clone, Copy) ]
pub enum VariableScope {
/// The variable declaration is scoped to the current block (`let` and `const`)
Block ,
/// The variable declaration is scoped to the current function (`var`)
Function ,
}
#[ derive(Debug) ]
pub struct LexicalEnvironment {
environment_stack : VecDeque < Environment > ,
@ -90,6 +99,12 @@ impl LexicalEnvironment {
self . environment_stack . pop_back ( ) ;
}
pub fn environments ( & self ) -> impl Iterator < Item = Environment > {
std ::iter ::successors ( Some ( self . get_current_environment_ref ( ) . clone ( ) ) , | env | {
env . borrow ( ) . get_outer_environment ( )
} )
}
pub fn get_global_object ( & self ) -> Option < Value > {
self . environment_stack
. get ( 0 )
@ -98,25 +113,74 @@ impl LexicalEnvironment {
. get_global_object ( )
}
pub fn create_mutable_binding ( & mut self , name : String , deletion : bool ) {
self . get_current_environment ( )
. borrow_mut ( )
. create_mutable_binding ( name , deletion )
pub fn create_mutable_binding ( & mut self , name : String , deletion : bool , scope : VariableScope ) {
match scope {
VariableScope ::Block = > self
. get_current_environment ( )
. borrow_mut ( )
. create_mutable_binding ( name , deletion ) ,
VariableScope ::Function = > {
// Find the first function or global environment (from the top of the stack)
let env = self
. environments ( )
. find ( | env | match env . borrow ( ) . get_environment_type ( ) {
EnvironmentType ::Function | EnvironmentType ::Global = > true ,
_ = > false ,
} )
. expect ( "No function or global environment" ) ;
env . borrow_mut ( ) . create_mutable_binding ( name , deletion ) ;
}
}
}
pub fn create_immutable_binding ( & mut self , name : String , deletion : bool ) -> bool {
self . get_current_environment ( )
. borrow_mut ( )
. create_immutable_binding ( name , deletion )
pub fn create_immutable_binding (
& mut self ,
name : String ,
deletion : bool ,
scope : VariableScope ,
) -> bool {
match scope {
VariableScope ::Block = > self
. get_current_environment ( )
. borrow_mut ( )
. create_immutable_binding ( name , deletion ) ,
VariableScope ::Function = > {
// Find the first function or global environment (from the top of the stack)
let env = self
. environments ( )
. find ( | env | match env . borrow ( ) . get_environment_type ( ) {
EnvironmentType ::Function | EnvironmentType ::Global = > true ,
_ = > false ,
} )
. expect ( "No function or global environment" ) ;
#[ allow(clippy::let_and_return) ]
// FIXME need to assign result to a variable to avoid borrow checker error
// (borrowed value `env` does not live long enough)
let b = env . borrow_mut ( ) . create_immutable_binding ( name , deletion ) ;
b
}
}
}
pub fn set_mutable_binding ( & mut self , name : & str , value : Value , strict : bool ) {
let env = self . get_current_environment ( ) ;
// Find the first environment which has the given binding
let env = self
. environments ( )
. find ( | env | env . borrow ( ) . has_binding ( name ) )
. expect ( "Binding does not exists" ) ; // TODO graceful error handling
env . borrow_mut ( ) . set_mutable_binding ( name , value , strict ) ;
}
pub fn initialize_binding ( & mut self , name : & str , value : Value ) {
let env = self . get_current_environment ( ) ;
// Find the first environment which has the given binding
let env = self
. environments ( )
. find ( | env | env . borrow ( ) . has_binding ( name ) )
. expect ( "Binding does not exists" ) ; // TODO graceful error handling
env . borrow_mut ( ) . initialize_binding ( name , value ) ;
}
@ -138,37 +202,16 @@ impl LexicalEnvironment {
. expect ( "Could not get mutable reference to back object" )
}
pub fn get_binding_value ( & mut self , name : & str ) -> Value {
let env : Environment = self . get_current_environment ( ) . clone ( ) ;
let borrowed_env = env . borrow ( ) ;
let result = borrowed_env . has_binding ( name ) ;
if result {
return borrowed_env . get_binding_value ( name , false ) ;
}
// Check outer scope
if borrowed_env . get_outer_environment ( ) . is_some ( ) {
let mut outer : Option < Environment > = borrowed_env . get_outer_environment ( ) ;
while outer . is_some ( ) {
if outer
. as_ref ( )
. expect ( "Could not get outer as reference" )
. borrow ( )
. has_binding ( & name )
{
return outer
. expect ( "Outer was None" )
. borrow ( )
. get_binding_value ( name , false ) ;
}
outer = outer
. expect ( "Outer was None" )
. borrow ( )
. get_outer_environment ( ) ;
}
}
pub fn has_binding ( & self , name : & str ) -> bool {
self . environments ( )
. any ( | env | env . borrow ( ) . has_binding ( name ) )
}
Gc ::new ( ValueData ::Undefined )
pub fn get_binding_value ( & mut self , name : & str ) -> Value {
self . environments ( )
. find ( | env | env . borrow ( ) . has_binding ( name ) )
. map ( | env | env . borrow ( ) . get_binding_value ( name , false ) )
. unwrap_or_else ( | | Gc ::new ( ValueData ::Undefined ) )
}
}
@ -236,3 +279,70 @@ pub fn new_global_environment(global: Value, this_value: Value) -> Environment {
var_names : HashSet ::new ( ) ,
} ) ) )
}
#[ cfg(test) ]
mod tests {
use crate ::exec ;
#[ test ]
fn let_is_blockscoped ( ) {
let scenario = r #"
{
let bar = "bar" ;
}
bar = = undefined ;
" #;
assert_eq! ( & exec ( scenario ) , "true" ) ;
}
#[ test ]
fn const_is_blockscoped ( ) {
let scenario = r #"
{
const bar = "bar" ;
}
bar = = undefined ;
" #;
assert_eq! ( & exec ( scenario ) , "true" ) ;
}
#[ test ]
fn var_not_blockscoped ( ) {
let scenario = r #"
{
var bar = "bar" ;
}
bar = = "bar" ;
" #;
assert_eq! ( & exec ( scenario ) , "true" ) ;
}
#[ test ]
fn set_outer_var_in_blockscope ( ) {
let scenario = r #"
var bar ;
{
bar = "foo" ;
}
bar = = "foo" ;
" #;
assert_eq! ( & exec ( scenario ) , "true" ) ;
}
#[ test ]
fn set_outer_let_in_blockscope ( ) {
let scenario = r #"
let bar ;
{
bar = "foo" ;
}
bar = = "foo" ;
" #;
assert_eq! ( & exec ( scenario ) , "true" ) ;
}
}
Ole Martin Ruud
5 years ago
committed by
Jason Williams