Function is_body_identity_function 

pub(crate) fn is_body_identity_function(
    cx: &LateContext<'_>,
    func: &Body<'_>,
) -> bool

Checks if a function’s body represents the identity function. Looks for bodies of the form:

• |x| x
• |x| return x
• |x| { return x }
• |x| { return x; }
• |(x, y)| (x, y)
• |[x, y]| [x, y]
• |Foo(bar, baz)| Foo(bar, baz)
• |Foo { bar, baz }| Foo { bar, baz }

Consider calling is_expr_untyped_identity_function or is_expr_identity_function instead.