Change how `force-warn` lint diagnostics are recorded.

`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`.

1 files changed, 2 insertions, 7 deletions

diff --git a/compiler/rustc_codegen_ssa/src/back/write.rs b/compiler/rustc_codegen_ssa/src/back/write.rs
index 6c066e61a58..8e835039970 100644
--- a/compiler/rustc_codegen_ssa/src/back/write.rs
+++ b/compiler/rustc_codegen_ssa/src/back/write.rs
@@ -1847,14 +1847,9 @@ impl SharedEmitterMain {
                     dcx.emit_diagnostic(d);
                 }
                 Ok(SharedEmitterMessage::InlineAsmError(cookie, msg, level, source)) => {
-                    let err_level = match level {
-                        Level::Error => Level::Error,
-                        Level::Warning(_) => Level::Warning(None),
-                        Level::Note => Level::Note,
-                        _ => bug!("Invalid inline asm diagnostic level"),
-                    };
+                    assert!(matches!(level, Level::Error | Level::Warning | Level::Note));
                     let msg = msg.strip_prefix("error: ").unwrap_or(&msg).to_string();
-                    let mut err = DiagnosticBuilder::<()>::new(sess.dcx(), err_level, msg);
+                    let mut err = DiagnosticBuilder::<()>::new(sess.dcx(), level, msg);
 
                     // If the cookie is 0 then we don't have span information.
                     if cookie != 0 {