Anselme v2.0.0-alpha rewrite

Woke up and felt like changing a couple things. It's actually been worked on for a while, little at a time...

The goal was to make the language and implementation much simpler. Well I don't know if it really ended up being simpler but it sure is more robust.

Main changes:
* proper first class functions and closures supports! proper scoping rules! no more namespace shenanigans!
* everything is an expression, no more statements! make the implementation both simpler and more complex, but it's much more consistent now! the syntax has massively changed as a result though.
* much more organized and easy to modify codebase: one file for each AST node, no more random fields or behavior set by some random node exceptionally, everything should now follow the same API defined in ast.abstract.Node

Every foundational feature should be implemented right now. The vast majority of things that were possible in v2 are possible now; some things aren't, but that's usually because v2 is a bit more sane.
The main missing things before a proper release are tests and documentation. There's a few other things that might be implemented later, see the ideas.md file.

parser/expression/contextual/function_parameter.lua

@@ -0,0 +1,40 @@
+local primary = require("parser.expression.primary.primary")
+local identifier = require("parser.expression.primary.identifier")
+local expression_to_ast = require("parser.expression.to_ast")
+
+local ast = require("ast")
+local FunctionParameter = ast.FunctionParameter
+
+local operator_priority = require("common").operator_priority
+local assignment_priority = operator_priority["_=_"]
+local type_check_priority = operator_priority["_::_"]
+
+return primary {
+	match = function(self, str)
+		return identifier:match(str)
+	end,
+	parse = function(self, source, str, limit_pattern, no_default_value)
+		local source_param = source:clone()
+
+		-- name
+		local ident, rem = identifier:parse(source, str)
+
+		-- type check
+		local type_check
+		if rem:match("^%s*::") then
+			local scheck = source:consume(rem:match("^(%s*::%s*)(.*)$"))
+			type_check, rem = expression_to_ast(source, scheck, limit_pattern, type_check_priority)
+		end
+
+		-- default value
+		local default
+		if not no_default_value then
+			if rem:match("^%s*=") then
+				local sdefault = source:consume(rem:match("^(%s*=%s*)(.*)$"))
+				default, rem = expression_to_ast(source, sdefault, limit_pattern, assignment_priority)
+			end
+		end
+
+		return FunctionParameter:new(ident, default, type_check):set_source(source_param), rem
+	end
+}

parser/expression/contextual/function_parameter_no_default.lua

@@ -0,0 +1,7 @@
+local function_parameter = require("parser.expression.contextual.function_parameter")
+
+return function_parameter {
+	parse = function(self, source, str, limit_pattern)
+		return function_parameter:parse(source, str, limit_pattern, true)
+	end
+}

parser/expression/contextual/parameter_tuple.lua

@@ -0,0 +1,49 @@
+local primary = require("parser.expression.primary.primary")
+local function_parameter = require("parser.expression.contextual.function_parameter")
+local function_parameter_no_default = require("parser.expression.contextual.function_parameter_no_default")
+
+local ast = require("ast")
+local ParameterTuple = ast.ParameterTuple
+
+return primary {
+	match = function(self, str)
+		return str:match("^%(")
+	end,
+	parse = function(self, source, str, limit_pattern)
+		local source_start = source:clone()
+		local parameters = ParameterTuple:new()
+		local rem = source:consume(str:match("^(%()(.*)$"))
+
+		-- i would LOVE to reuse the regular list parsing code for this, but unfortunately the list parsing code
+		-- itself depends on this and expect this to be available quite early, and it's ANNOYING
+		while not rem:match("^%s*%)") do
+			-- parameter
+			local func_param
+			func_param, rem = function_parameter:expect(source, rem, limit_pattern)
+
+			-- next! comma separator
+			if not rem:match("^%s*%)") then
+				if not rem:match("^%s*,") then
+					error(("unexpected %q at end of argument list"):format(rem), 0)
+				end
+				rem = source:consume(rem:match("^(%s*,)(.*)$"))
+			end
+
+			-- add
+			parameters:insert(func_param)
+		end
+		rem = rem:match("^%s*%)(.*)$")
+
+		-- assigment param
+		if rem:match("^%s*=") then
+			rem = source:consume(rem:match("^(%s*=%s*)(.*)$"))
+
+			local func_param
+			func_param, rem = function_parameter_no_default:expect(source, rem, limit_pattern)
+
+			parameters:insert_assignment(func_param)
+		end
+
+		return parameters:set_source(source_start), rem
+	end
+}