use var_debug_info for arg_name

Author: chenyukang

compiler/rustc_borrowck/src/diagnostics/conflict_errors.rs

@@ -524,20 +524,21 @@ impl<'infcx, 'tcx> MirBorrowckCtxt<'_, '_, 'infcx, 'tcx> {
         body: &hir::Expr<'_>,
         span: Option<Span>,
         move_span: Span,
-        err: &mut Diag<'tcx>,
+        err: &mut Diag<'infcx>,
     ) {
-        let sm = self.infcx.tcx.sess.source_map();
-        let arg_code = if let Some(span) = span
-            && let Ok(code) = sm.span_to_snippet(span)
-        {
-            code
+        let Some(span) = span else {
+            return;
+        };
+        let var_info = self.body.var_debug_info.iter().find(|info| info.source_info.span == span);
+        let arg_name = if let Some(var_info) = var_info {
+            var_info.name.to_string()
         } else {
             return;
         };
         struct MatchArgFinder {
             expr_span: Span,
             match_arg_span: Option<Span>,
-            arg_code: String,
+            arg_name: String,
         }
         impl Visitor<'_> for MatchArgFinder {
             fn visit_expr(&mut self, e: &hir::Expr<'_>) {
@@ -547,7 +548,7 @@ impl<'infcx, 'tcx> MirBorrowckCtxt<'_, '_, 'infcx, 'tcx> {
                         _,
                         path @ Path { segments: [seg], .. },
                     )) = &expr.kind
-                    && seg.ident.name.as_str() == &self.arg_code
+                    && seg.ident.name.as_str() == &self.arg_name
                     && self.expr_span.source_callsite().contains(expr.span)
                 {
                     self.match_arg_span = Some(path.span);
@@ -556,7 +557,7 @@ impl<'infcx, 'tcx> MirBorrowckCtxt<'_, '_, 'infcx, 'tcx> {
             }
         }
 
-        let mut finder = MatchArgFinder { expr_span: move_span, match_arg_span: None, arg_code };
+        let mut finder = MatchArgFinder { expr_span: move_span, match_arg_span: None, arg_name };
         finder.visit_expr(body);
         if let Some(macro_arg_span) = finder.match_arg_span {
             err.span_suggestion_verbose(