jmid / luata-quickcheck Goto Github PK

It appears that the __metatable field of a metatable is considered when resolving metamethods. (At least in Lua 5.1, 5.2 and 5.3) it is the case that __metatable is only consulted when calling the getmetatable built-in from Lua code. It is not consulted when resolving actual metamethods. It exists only as a protection mechanism for metatables, and not for overloading them from the point of view of Lua.

This discrepancy causes luata to produce incorrect output for code using the __metatable metamethod.

local complexMt = { __metatable = "Complex number metatable protected" }

local function Complex(real,imag)
   local n = {real = real, imag = imag}
   setmetatable(n, complexMt)
   return n
end

function complexMt.__add(x,y)
   return Complex(x.real + y.real, x.imag + y.imag)
end

function complexMt:__tostring()
   return self.real .. "+" .. self.imag .. "i" 
end

z = Complex(1,0) + Complex(0,2)
print(z)

Expected output

$ lua mytest.lua
1+2i

Hi!

I'm working on an editor plugin for Lua (atom-autocomplete-lua) and I would like to rewrite it using proper lattices. It would be really helpful to be able to use some of the code from this repo (especially the lexer and parser), but I can't do that because there is no license on this repo. Might you consider adding a LICENSE file? Maybe something permissive like the MIT license?

The analysis seems to be confident that c is going to have a number type instead of the actual nil type. The analysis correctly identifies that the second return value might have number type (based on my understanding of the question mark) ? { number: Top } however the analysis seems to give the wrong confidence to the type of b with ! { number: Top }

local function f(x)
        if x > 10 then
                return 1,2 
        else
                return 3
        end 
end

a,b=f(0)
c=type(b)
print(c)

Expected output:

$ lua mytest.lua
nil