Auto merge of #120576 - nnethercote:merge-Diagnostic-DiagnosticBuilder, r=davidtwco

Overhaul `Diagnostic` and `DiagnosticBuilder`

Implements the first part of https://github.com/rust-lang/compiler-team/issues/722, which moves functionality and use away from `Diagnostic`, onto `DiagnosticBuilder`.

Likely follow-ups:
- Move things around, because this PR was written to minimize diff size, so some things end up in sub-optimal places. E.g. `DiagnosticBuilder` has impls in both `diagnostic.rs` and `diagnostic_builder.rs`.
- Rename `Diagnostic` as `DiagInner` and `DiagnosticBuilder` as `Diag`.

r? `@davidtwco`

1 files changed, 7 insertions, 3 deletions

diff --git a/compiler/rustc_trait_selection/src/errors.rs b/compiler/rustc_trait_selection/src/errors.rs
index 407fff03e15..10911c0d002 100644
--- a/compiler/rustc_trait_selection/src/errors.rs
+++ b/compiler/rustc_trait_selection/src/errors.rs
@@ -1,7 +1,7 @@
 use crate::fluent_generated as fluent;
 use rustc_errors::{
-    codes::*, AddToDiagnostic, Applicability, DiagCtxt, Diagnostic, DiagnosticBuilder,
-    EmissionGuarantee, IntoDiagnostic, Level, SubdiagnosticMessageOp,
+    codes::*, AddToDiagnostic, Applicability, DiagCtxt, DiagnosticBuilder, EmissionGuarantee,
+    IntoDiagnostic, Level, SubdiagnosticMessageOp,
 };
 use rustc_macros::Diagnostic;
 use rustc_middle::ty::{self, ClosureKind, PolyTraitRef, Ty};
@@ -102,7 +102,11 @@ pub enum AdjustSignatureBorrow {
 }
 
 impl AddToDiagnostic for AdjustSignatureBorrow {
-    fn add_to_diagnostic_with<F: SubdiagnosticMessageOp>(self, diag: &mut Diagnostic, _: F) {
+    fn add_to_diagnostic_with<G: EmissionGuarantee, F: SubdiagnosticMessageOp<G>>(
+        self,
+        diag: &mut DiagnosticBuilder<'_, G>,
+        _f: F,
+    ) {
         match self {
             AdjustSignatureBorrow::Borrow { to_borrow } => {
                 diag.arg("len", to_borrow.len());