Y.3 LuneScript Development (Scopes and Symbols)

Continuation of LuneScript development.

Since the overview of each process in the flow has already been explained, this time we will go into a little internal explanation.

scope

LuneScript is a common lexical scope.

Also, there are the following types of scopes:

built-in scope
global scope
In-module scope

Built-in scopes manage built-in type symbols such as int and str , and built-in function symbols such as print() and string.format() .

The global scope manages lua 's global symbol compatible symbols.

Basically, all symbols of modules created by the user are managed within the module scope.

Scope structure

The scope has a tree structure, and each scope holds the following elements.

parent scope
list of symbols belonging to scope

For example, in Test.lns below,

// @lnsFront: skip
// Test.lns
fn func( val1:int ) {
  let val2 = val1 + 10;
}
func( 1 );

A scope consists of two things:

@Test scope
func scope

@Test scope is the scope that manages the module of Test.lns. A .lns file always has its own scope.

Note that LuneScript modules are managed by relative paths from the current directory.

A module with relative path dir/Test.lns has @Test scope inside @dir scope.

Classes in LuneScript

The scope is managed by the Ast.Scope class.

symbol

A scope manages the symbols belonging to that scope.

For example, for the following sources:

// @lnsFront: skip
// Test.lns
fn func( val1:int ) {
  let val2 = val1 + 10;
}
func( 1 );

User-defined func function symbols are registered in this @Test.

The val1 and val2 variable symbols are registered in the func scope.

The scope and symbols at this time become the following tree.

digraph G {
rankdir=RL;

builtin[label="<builtin>"];
global[label="<global>"];
dir[label="@dir"];
dir_sym[shape="box"];
Test[label="@Test"];
Test_sym[shape="box"];
func_sym[shape="box"];
func;
val1_sym[shape="box"];
val2_sym[shape="box"];

global->builtin
dir_sym->global
dir->dir_sym
Test_sym->dir
Test->Test_sym
func->func_sym
func_sym->Test
val1_sym->func
val2_sym->func
}

../lunescript_scope.png

Here, the ellipse is the scope and the square is the symbol.

Composition of symbols

A symbol consists of the following attributes:

access restrictions
name
type
mutable/immutable

For example, for the code below:

// @lnsFront: skip
// Test.lns
fn func( val1:int ) {
  let val2 = val1 + 10;
}
func( 1 );

Each symbol is:

access restrictions	name	type	mut/imut
local	func	fn (int)	imut
local	val1	int	imut
local	val2	int	imut

Classes in LuneScript

The scope is managed by the Ast.SymbolInfo class.