Show and render error lifetime args as '_

crates/hir-ty/src/display.rs

@@ -1523,18 +1523,6 @@ fn hir_fmt_generic_arguments(
         None => (parameters, &[][..]),
     };
     for generic_arg in lifetimes.iter().chain(ty_or_const) {
-        // FIXME: Remove this
-        // most of our lifetimes will be errors as we lack elision and inference
-        // so don't render them for now
-        if !cfg!(test)
-            && matches!(
-                generic_arg.lifetime(Interner),
-                Some(l) if ***l.interned() == LifetimeData::Error
-            )
-        {
-            continue;
-        }
-
         if !mem::take(&mut first) {
             write!(f, ", ")?;
         }
@@ -1872,7 +1860,13 @@ impl HirDisplay for LifetimeData {
             LifetimeData::BoundVar(idx) => idx.hir_fmt(f),
             LifetimeData::InferenceVar(_) => write!(f, "_"),
             LifetimeData::Static => write!(f, "'static"),
-            LifetimeData::Error => write!(f, "'?"),
+            LifetimeData::Error => {
+                if cfg!(test) {
+                    write!(f, "'?")
+                } else {
+                    write!(f, "'_")
+                }
+            }
             LifetimeData::Erased => write!(f, "'<erased>"),
             LifetimeData::Phantom(void, _) => match *void {},
         }

crates/ide-assists/src/handlers/extract_function.rs

@@ -5649,7 +5649,7 @@ fn func<T: Debug>(i: Struct<'_, T>) {
     fun_name(i);
 }
 
-fn $0fun_name(i: Struct<T>) {
+fn $0fun_name(i: Struct<'_, T>) {
     foo(i);
 }
 "#,

crates/ide-completion/src/tests/predicate.rs

@@ -19,7 +19,7 @@ struct Foo<'lt, T, const C: usize> where $0 {}
             en Enum      Enum
             ma makro!(…) macro_rules! makro
             md module
-            st Foo<…>    Foo<{unknown}, _>
+            st Foo<…>    Foo<'_, {unknown}, _>
             st Record    Record
             st Tuple     Tuple
             st Unit      Unit
@@ -92,7 +92,7 @@ struct Foo<'lt, T, const C: usize> where for<'a> $0 {}
             en Enum      Enum
             ma makro!(…) macro_rules! makro
             md module
-            st Foo<…>    Foo<{unknown}, _>
+            st Foo<…>    Foo<'_, {unknown}, _>
             st Record    Record
             st Tuple     Tuple
             st Unit      Unit

crates/ide-completion/src/tests/type_pos.rs

@@ -20,8 +20,8 @@ struct Foo<'lt, T, const C: usize> {
             en Enum      Enum
             ma makro!(…) macro_rules! makro
             md module
-            sp Self      Foo<{unknown}, _>
-            st Foo<…>    Foo<{unknown}, _>
+            sp Self      Foo<'_, {unknown}, _>
+            st Foo<…>    Foo<'_, {unknown}, _>
             st Record    Record
             st Tuple     Tuple
             st Unit      Unit
@@ -45,8 +45,8 @@ struct Foo<'lt, T, const C: usize>(f$0);
             en Enum       Enum
             ma makro!(…)  macro_rules! makro
             md module
-            sp Self       Foo<{unknown}, _>
-            st Foo<…>     Foo<{unknown}, _>
+            sp Self       Foo<'_, {unknown}, _>
+            st Foo<…>     Foo<'_, {unknown}, _>
             st Record     Record
             st Tuple      Tuple
             st Unit       Unit

crates/ide/src/inlay_hints/bind_pat.rs

@@ -342,7 +342,7 @@ fn f<'a>() {
     let x = S::<'static>;
       //^ S<'static>
     let y = S::<'_>;
-      //^ S
+      //^ S<'_>
     let z = S::<'a>;
       //^ S<'a>