detect unstable rustc options and suggest the correct syntax #5546
Labels
A-diagnostics
Area: Error and warning messages generated by Cargo itself.
C-feature-request
Category: proposal for a feature. Before PR, ping rust-lang/cargo if this is not `Feature accepted`
There are cases when a user is suggested to use an unstable
rustc
option (and the suggestion forexternal-macro-backtrace
is even in therustc
output). However, if a user tries to add this option to hiscargo
command line, the error message just says that this flag is unknown.It would be a good idea to output something like
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