lint: warn about identical conditions inside and outside of functions

There could be a warning if something is checked outside of a function, passed inside the function and then checked inside the function again.
This might spot redundant conditions but also logic errors if the conditions are conflicting.

fn fun(awesomestruct: SomeStruct) {
   if awesomestruct.bar { return } // check inside function
   [...]
}

fn main() {
    let struct: SomeStruct = something(); 

    if struct.bar { // same condition that is inside of function
         fun(struct);
    }

}

Start from the Rust example in the issue and determine how the proposed warning would identify matching conditions across the function boundary. The issue names no files, tests, or entry points; done would require an agreed scope and observable warnings for redundant or conflicting conditions.