Nested tuple values are exponential in parsing time

[stringhandler]

Project version

0.7.2

Project

compiler

What happened?

Increasing the depth of nesting increases compile time.

Minimal reproduction steps

fn main() {
    let x: ((((((((((((((((((u32,),),),),),),),),),),),),),),),),),) = ((((((((((((((((((0,),),),),),),),),),),),),),),),),),);
}

Above is depth 18 and takes 8 seconds. Depth 20 takes 35s