1 files changed, 23 insertions, 2 deletions

diff --git a/crates/hir_ty/src/display.rs b/crates/hir_ty/src/display.rs
index e77481906..0e827a29e 100644
--- a/crates/hir_ty/src/display.rs
+++ b/crates/hir_ty/src/display.rs
@@ -4,7 +4,7 @@ use std::fmt;
 
 use crate::{
     db::HirDatabase, utils::generics, ApplicationTy, CallableDefId, FnSig, GenericPredicate,
-    Obligation, OpaqueTyId, ProjectionTy, Substs, TraitRef, Ty, TypeCtor,
+    Lifetime, Obligation, OpaqueTyId, ProjectionTy, Substs, TraitRef, Ty, TypeCtor,
 };
 use hir_def::{
     find_path, generics::TypeParamProvenance, item_scope::ItemInNs, AdtId, AssocContainerId,
@@ -178,6 +178,7 @@ impl DisplayTarget {
 #[derive(Debug)]
 pub enum DisplaySourceCodeError {
     PathNotFound,
+    UnknownType,
 }
 
 pub enum HirDisplayError {
@@ -558,7 +559,14 @@ impl HirDisplay for Ty {
                     }
                 };
             }
-            Ty::Unknown => write!(f, "{{unknown}}")?,
+            Ty::Unknown => {
+                if f.display_target.is_source_code() {
+                    return Err(HirDisplayError::DisplaySourceCodeError(
+                        DisplaySourceCodeError::UnknownType,
+                    ));
+                }
+                write!(f, "{{unknown}}")?;
+            }
             Ty::Infer(..) => write!(f, "_")?,
         }
         Ok(())
@@ -710,6 +718,19 @@ impl HirDisplay for GenericPredicate {
     }
 }
 
+impl HirDisplay for Lifetime {
+    fn hir_fmt(&self, f: &mut HirFormatter) -> Result<(), HirDisplayError> {
+        match self {
+            Lifetime::Parameter(id) => {
+                let generics = generics(f.db.upcast(), id.parent);
+                let param_data = &generics.params.lifetimes[id.local_id];
+                write!(f, "{}", &param_data.name)
+            }
+            Lifetime::Static => write!(f, "'static"),
+        }
+    }
+}
+
 impl HirDisplay for Obligation {
     fn hir_fmt(&self, f: &mut HirFormatter) -> Result<(), HirDisplayError> {
         match self {