Auto merge of #101619 - Xiretza:rustc_parse-session-diagnostics, r=davidtwco

Migrate more of rustc_parse to SessionDiagnostic

Still far from complete, but I thought I'd add a checkpoint here because rebasing was starting to get annoying.

compiler/rustc_errors/src/diagnostic.rs

@@ -3,6 +3,8 @@ use crate::{
     CodeSuggestion, DiagnosticMessage, EmissionGuarantee, Level, LintDiagnosticBuilder, MultiSpan,
     SubdiagnosticMessage, Substitution, SubstitutionPart, SuggestionStyle,
 };
+use rustc_ast as ast;
+use rustc_ast_pretty::pprust;
 use rustc_data_structures::fx::FxHashMap;
 use rustc_error_messages::FluentValue;
 use rustc_hir as hir;
@@ -175,6 +177,24 @@ impl IntoDiagnosticArg for hir::ConstContext {
     }
 }
 
+impl IntoDiagnosticArg for ast::Path {
+    fn into_diagnostic_arg(self) -> DiagnosticArgValue<'static> {
+        DiagnosticArgValue::Str(Cow::Owned(pprust::path_to_string(&self)))
+    }
+}
+
+impl IntoDiagnosticArg for ast::token::Token {
+    fn into_diagnostic_arg(self) -> DiagnosticArgValue<'static> {
+        DiagnosticArgValue::Str(pprust::token_to_string(&self))
+    }
+}
+
+impl IntoDiagnosticArg for ast::token::TokenKind {
+    fn into_diagnostic_arg(self) -> DiagnosticArgValue<'static> {
+        DiagnosticArgValue::Str(pprust::token_kind_to_string(&self))
+    }
+}
+
 /// Trait implemented by error types. This should not be implemented manually. Instead, use
 /// `#[derive(Subdiagnostic)]` -- see [rustc_macros::Subdiagnostic].
 #[cfg_attr(bootstrap, rustc_diagnostic_item = "AddSubdiagnostic")]