A macro for letting macros absolve themselves of guilt, blaming any and all errors on their callers.
For example, consider a macro that has as its contract that the input must be an expression of a specific type. If a caller breaks this contract, a part of the macro body is highlighted as the error cause, even though it obviously was the caller's fault.
error[E0308]: mismatched types
--> examples/blame.rs:3:7
|
3 | let () = $e;
| ^^ expected `A`, found `()`
...
9 | b!(A);
| -----
| | |
| | this expression has type `A`
| in this macro invocation
Now you can finally tell those callers whose fault it really is.
error[E0308]: mismatched types
--> examples/blameless.rs:11:2
|
11 | b!(A);
| ^^^-^
| | |
| | this expression has type `A`
| expected `A`, found `()`
Due to using the proc_macro_span feature, this crate requires nightly.