Re: A practical code analysis question

[Fabien <fleutot+lua@...>]

So you want to find AST nodes which are:

• under either a 'Forin' or 'Fornum' node;
• are operators, with operator name 'concat';

I guess that printing the offending line number is good enough. There's a declarative tree exploration library in metalua's head, which we discussed at the last workshop, called metalua.treequery. No proper doc yet, only a blog post. Your problem is addressed as follows (tested with the latest version in the luaeclipse branch):

$ cat find_concats_in_loops.lua

require 'metalua.compiler'

local ast = mlc.luastring_to_ast[[

x = this..is..allowed

for i=1,10 do

    print(nasty..cat)

end

for _ in generator() do

    if not directly_under_for then

        print(nasty..anyway)

    end

end

for i=1, math.huge do

    print "no concat, no problem"

end 

]]

-- predicate to find concat operators: --

local is_op_concat = |x| x.tag=='Op' and x[1]=='concat'

local T = require 'metalua.treequery'

-- Here's the actual query: --

T(ast)

    :under ('Forin', 'Fornum') 

    :filter (is_op_concat)  

    :foreach (function (node)

        local line = node.lineinfo.first.line

        printf ("Offending node on line %i", line)

    end)

$ metalua find_concats_in_loops.lua

Offending node on line 3

Offending node on line 7

$ _