0e388f2192
`is_force_warn` is only possible for diagnostics with `Level::Warning`, but it is currently stored in `Diagnostic::code`, which every diagnostic has. This commit: - removes the boolean `DiagnosticId::Lint::is_force_warn` field; - adds a `ForceWarning` variant to `Level`. Benefits: - The common `Level::Warning` case now has no arguments, replacing lots of `Warning(None)` occurrences. - `rustc_session::lint::Level` and `rustc_errors::Level` are more similar, both having `ForceWarning` and `Warning`.
The codegen crate contains the code to convert from MIR into LLVM IR,
and then from LLVM IR into machine code. In general it contains code
that runs towards the end of the compilation process.
For more information about how codegen works, see the rustc dev guide.