Trait objects without an explicit `dyn` are deprecated

[pradeeptewani]

I have the code for iotedge which using the following:

    fn from(err: &'a Error) -> Self {
        match Fail::find_root_cause(err).downcast_ref::<ErrorKind>() {
            Some(ErrorKind::NotFound(_)) => ModuleRuntimeErrorReason::NotFound,
            _ => ModuleRuntimeErrorReason::Other,
        }
    }
While compiling, I get the following:
error: trait objects without an explicit `dyn` are deprecated
|    --> edgelet-docker/src/error.rs:151:15
|     |
| 151 |         match Fail::find_root_cause(err).downcast_ref::<ErrorKind>() {
|     |               ^^^^ help: use `dyn`: `<dyn Fail>`
|     |

Being a newbie, unable to understand how do I fix it. Any input would be of great help

[Michael-F-Bryan]

Please format your code using backticks (```) so people can read it.

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[pradeeptewani]

Thanks Michael. Edited the post

[2e71828]

@pradeeptewani

| 151 | match Fail::find_root_cause(err).downcast_ref::() {
|     |       ^^^^ help: use `dyn` : `<dyn Fail>`

Did you try replacing Fail with dyn Fail as the compiler suggests:

match dyn Fail::find_root_cause(err).downcast_ref::() {

Or:

match <dyn Fail>::find_root_cause(err).downcast_ref::() {

( I'm not sure which form is necessary)

[scottmcm]

@2e71828

( I'm not sure which form is necessary)

The trait name can be be a full path, like dyn std::fmt::Debug, so the <>s are there because Fail::find_root_cause isn't the trait.

[pradeeptewani]

Thanks. This helps.

Works and resolves the issue.