Rollup merge of #101434 - JhonnyBillM:replace-session-for-handler-in-into-diagnostic, r=davidtwco

Update `SessionDiagnostic::into_diagnostic` to take `Handler` instead of `ParseSess`

Suggested by the team in [this Zulip Topic](https://rust-lang.zulipchat.com/#narrow/stream/336883-i18n/topic/.23100717.20SessionDiagnostic.20on.20Handler).

`Handler` already has almost all the capabilities of `ParseSess` when it comes to diagnostic emission, in this migration we only needed to add the ability to access `source_map` from the emitter in order to get a `Snippet` and the `start_point`. Not sure if adding these two methods [`span_to_snippet_from_emitter` and  `span_start_point_from_emitter`] is the best way to address this gap.

P.S. If this goes in the right direction, then we probably may want to move `SessionDiagnostic` to `rustc_errors` and rename it to `DiagnosticHandler` or something similar.

r? `@davidtwco`
r? `@compiler-errors`

1 files changed, 4 insertions, 4 deletions

diff --git a/compiler/rustc_trait_selection/src/errors.rs b/compiler/rustc_trait_selection/src/errors.rs
index 81977f25ca2..ab0afc54514 100644
--- a/compiler/rustc_trait_selection/src/errors.rs
+++ b/compiler/rustc_trait_selection/src/errors.rs
@@ -1,7 +1,7 @@
-use rustc_errors::{fluent, ErrorGuaranteed};
+use rustc_errors::{fluent, ErrorGuaranteed, Handler};
 use rustc_macros::SessionDiagnostic;
 use rustc_middle::ty::{PolyTraitRef, Ty, Unevaluated};
-use rustc_session::{parse::ParseSess, Limit, SessionDiagnostic};
+use rustc_session::{Limit, SessionDiagnostic};
 use rustc_span::{Span, Symbol};
 
 #[derive(SessionDiagnostic)]
@@ -69,9 +69,9 @@ pub struct NegativePositiveConflict<'a> {
 impl SessionDiagnostic<'_> for NegativePositiveConflict<'_> {
     fn into_diagnostic(
         self,
-        sess: &ParseSess,
+        handler: &Handler,
     ) -> rustc_errors::DiagnosticBuilder<'_, ErrorGuaranteed> {
-        let mut diag = sess.struct_err(fluent::trait_selection::negative_positive_conflict);
+        let mut diag = handler.struct_err(fluent::trait_selection::negative_positive_conflict);
         diag.set_arg("trait_desc", self.trait_desc);
         diag.set_arg(
             "self_desc",