Add help for E0514

[ticki]

Part of #30520

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[ticki]

Fixes #30363

[ticki]

r? @arielb1

[arielb1]

This is a little unclear. Maybe "consider recompiling it with this compiler"?

[ticki]

Well, it requires the user to explicitly removing the binaries, since they're compiled with an older compiler.

[arielb1]

"the binaries" in this case sounds like the intended binary output of this compiler.

[GuillaumeGomez]

@arielb1: Why not "consider recompiling it with your current rustc version"?

[bors]

☔ The latest upstream changes (presumably #31065) made this pull request unmergeable. Please resolve the merge conflicts.

[steveklabnik]

👍 to @GuillaumeGomez 's suggestion

[arielb1]

r=me to that modulo a rebase

[ticki]

Sure thing.

[ticki]

Rebased.

[ticki]

goddammit lints.

[ticki]

Rebased again.

[arielb1]

<syntax macros>:2:14: 2:70 error: no method named `span_help` found for type `&'a rustc::session::Session` in the current scope
<syntax macros>:2 { ( $ err ) . span_help ( $ span , & format ! ( $ ( $ message ) * ) ) ; } )

[ticki]

The internal API must have changed. Have span_help! been renamed? If so, what is it named now.

[alexcrichton]

Closing due to inactivity, but feel free to resubmit with the build errors fixed!