Replace persistent variable system

Previous system linked the variable name with the saved value, meaning the variable could not be renamed or moved outside the global scope.

Instead we propose to store all persistent values in a global table, identifying each by a key. To still allow nice manipulation with identifiers, the alias syntax replace the persistent syntax for symbols - an aliases symbol will act as if a function call was used in place of the identifier when it appear.

parser/expression/primary/function_definition.lua

@@ -167,11 +167,11 @@ return primary {
 		local mod_const, mod_exported, rem = source:consume(str:match("^(%:(:?)([&@]?)%$)(.-)$"))
 
 		-- get modifiers
-		local constant, exported, persistent
+		local constant, exported, alias
 		if mod_const == ":" then constant = true end
 		if mod_exported == "@" then exported = true
-		elseif mod_exported == "&" then persistent = true end
-		local modifiers = { constant = constant, exported = exported, persistent = persistent }
+		elseif mod_exported == "&" then alias = true end
+		local modifiers = { constant = constant, exported = exported, alias = alias }
 
 		-- search for a valid signature
 		local symbol, parameters

parser/expression/primary/symbol.lua

@@ -16,11 +16,11 @@ return primary {
 
 	parse = function(self, source, str)
 		local mod_const, mod_export, rem = source:consume(str:match("^(%:(:?)([&@]?))(.-)$"))
-		local constant, persistent, type_check_exp, exported
+		local constant, alias, type_check_exp, exported
 
 		-- get modifier
 		if mod_const == ":" then constant = true end
-		if mod_export == "&" then persistent = true
+		if mod_export == "&" then alias = true
 		elseif mod_export == "@" then exported = true end
 
 		-- name
@@ -35,6 +35,6 @@ return primary {
 			type_check_exp = exp.arguments.positional[2]
 		end
 
-		return ident:to_symbol{ constant = constant, persistent = persistent, exported = exported, type_check = type_check_exp }:set_source(source), rem
+		return ident:to_symbol{ constant = constant, alias = alias, exported = exported, type_check = type_check_exp }:set_source(source), rem
 	end
 }

parser/expression/secondary/infix/assignment_call.lua

@@ -18,7 +18,7 @@ return infix {
 	end,
 
 	build_ast = function(self, left, right)
-		left.arguments:add_assignment(right)
-		return Call:new(left.func, left.arguments) -- recreate Call since we modified left.arguments
+		local args = left.arguments:with_assignment(right)
+		return Call:new(left.func, args)
 	end,
 }