Add a type system

Add a check_types method that can check lua types for correctness.

spec/typeing.lua

@@ -0,0 +1,21 @@
+--Make sure the type checking works
+
+describe("smr type checking",function()
+	it("should load without errors",function()
+		local types = require("types")
+	end)
+	it("should not error when an argument is a number",function()
+		local types = require("types")
+		local n = 5
+		assert(types.number(n))
+	end)
+	it("should error when an argument is a table",function()
+		local types = require("types")
+		local t = {}
+		assert.has.errors(function()
+			types.number(t)
+		end)
+	end)
+end)
+
+

src/lua/types.lua

@@ -0,0 +1,47 @@
+--[[
+Type checking, vaguely inspired by Python3's typing module.
+]]
+
+local types = {}
+
+function types.positive(arg)
+	local is_number, err = types.number(arg)
+	if not is_number then
+		return false, err
+	end
+	if arg < 0 then
+		return false, string.format("was not positive")
+	end
+	return true
+end
+
+--Basic lua types
+local builtin_types = {
+	"nil","boolean","number","string","table","function","coroutine","userdata"
+}
+for _,type_ in pairs(builtin_types) do
+	types[type_] = function(arg)
+		local argtype = type(arg)
+		if not argtype == type_ then
+			return false, string.format("was not a %s, was a %s",type_,argtype)
+		end
+	end
+end
+
+function types.matches_pattern(pattern)
+	return function(arg)
+		local is_string, err = types.string(arg)
+		if not is_string then
+			return false, err
+		end
+		if not string.match(arg, pattern) then
+			return false, string.format(
+				"Expected %q to match pattern %q, but it did not.",
+				arg,
+				pattern
+			)
+		end
+	end
+end
+
+return types

src/lua/util.lua

@@ -222,6 +222,36 @@ function util.parse_tags(str)
 	return tags
 end
 
+if config.debugging then
+	function util.checktypes(...)
+		local args = {...}
+		if #args == 1 then
+			args = table.unpack(args)
+		end
+		assert(
+			#args % 3 == 0,
+			"Arguments to checktypes() must be triplets of " ..
+			"<variable>, <lua type>, <type check function> "
+		)
+		for i = 1,#args,3 do
+			local var, ltype, veri_f = args[i+0], args[i+1], args[i+2]
+			assert(
+				type(var) == ltype,
+				string.format(
+					"Expected argument %d (%q) to be type %s, but was %s",
+					i/3
+				)
+			)
+			if veri_f then
+				assert(veri_f(var))
+			end
+		end
+	end
+else
+	function util.checktypes(...)
+	end
+end
+
 local function decodeentity(capture)
 	return string.char(tonumber(capture,16)) --Decode base 16 and conver to character
 end