Preserve ErrorGuaranteed in ParamName

Author: oli-obk

compiler/rustc_ast_lowering/src/lib.rs

@@ -2147,10 +2147,10 @@ impl<'a, 'hir> LoweringContext<'a, 'hir> {
             GenericParamKind::Lifetime => {
                 // AST resolution emitted an error on those parameters, so we lower them using
                 // `ParamName::Error`.
-                let param_name = if let Some(LifetimeRes::Error(_guar)) =
+                let param_name = if let Some(LifetimeRes::Error(guar)) =
                     self.resolver.get_lifetime_res(param.id)
                 {
-                    ParamName::Error
+                    ParamName::Error(guar)
                 } else {
                     let ident = self.lower_ident(param.ident);
                     ParamName::Plain(ident)

compiler/rustc_hir/src/hir.rs

@@ -63,14 +63,16 @@ pub enum ParamName {
     /// Indicates an illegal name was given and an error has been
     /// reported (so we should squelch other derived errors). Occurs
     /// when, e.g., `'_` is used in the wrong place.
-    Error,
+    Error(ErrorGuaranteed),
 }
 
 impl ParamName {
     pub fn ident(&self) -> Ident {
         match *self {
             ParamName::Plain(ident) => ident,
-            ParamName::Fresh | ParamName::Error => Ident::with_dummy_span(kw::UnderscoreLifetime),
+            ParamName::Fresh | ParamName::Error(_) => {
+                Ident::with_dummy_span(kw::UnderscoreLifetime)
+            }
         }
     }
 }

compiler/rustc_hir/src/intravisit.rs

@@ -904,7 +904,7 @@ pub fn walk_generic_param<'v, V: Visitor<'v>>(
     try_visit!(visitor.visit_id(param.hir_id));
     match param.name {
         ParamName::Plain(ident) => try_visit!(visitor.visit_ident(ident)),
-        ParamName::Error | ParamName::Fresh => {}
+        ParamName::Error(_) | ParamName::Fresh => {}
     }
     match param.kind {
         GenericParamKind::Lifetime { .. } => {}

compiler/rustc_hir_analysis/src/check/wfcheck.rs

@@ -1895,7 +1895,7 @@ fn check_variances_for_type_defn<'tcx>(
         }
 
         match hir_param.name {
-            hir::ParamName::Error => {}
+            hir::ParamName::Error(_guar) => {}
             _ => {
                 let has_explicit_bounds = explicitly_bounded_params.contains(&parameter);
                 report_bivariance(tcx, hir_param, has_explicit_bounds, item.kind);