fix index returned for the use of BoundVar

crates/hir-ty/src/lib.rs

@@ -611,6 +611,10 @@ pub fn static_lifetime() -> Lifetime {
     LifetimeData::Static.intern(Interner)
 }
 
+pub fn error_lifetime() -> Lifetime {
+    static_lifetime()
+}
+
 pub(crate) fn fold_free_vars<T: HasInterner<Interner = Interner> + TypeFoldable<Interner>>(
     t: T,
     for_ty: impl FnMut(BoundVar, DebruijnIndex) -> Ty,

crates/hir-ty/src/lower.rs

@@ -54,7 +54,7 @@ use crate::{
         unknown_const_as_generic,
     },
     db::HirDatabase,
-    make_binders,
+    error_lifetime, make_binders,
     mapping::{from_chalk_trait_id, lt_to_placeholder_idx, ToChalk},
     static_lifetime, to_assoc_type_id, to_chalk_trait_id, to_placeholder_idx,
     utils::{
@@ -1327,7 +1327,7 @@ impl<'a> TyLoweringContext<'a> {
                             self.resolver.generic_def().expect("generics in scope"),
                         );
                         let idx = match generics.lifetime_idx(id) {
-                            None => return static_lifetime(),
+                            None => return error_lifetime(),
                             Some(idx) => idx,
                         };
 
@@ -1336,7 +1336,7 @@ impl<'a> TyLoweringContext<'a> {
                 }
                 .intern(Interner),
             },
-            None => static_lifetime(),
+            None => error_lifetime(),
         }
     }
 }

crates/hir-ty/src/utils.rs

@@ -318,14 +318,14 @@ impl Generics {
         parent + child
     }
 
-    /// Returns numbers of generic parameters excluding those from parent.
+    /// Returns numbers of generic parameters and lifetimes excluding those from parent.
     pub(crate) fn len_self(&self) -> usize {
-        self.params.type_or_consts.len()
+        self.params.type_or_consts.len() + self.params.lifetimes.len()
     }
 
-    /// Returns number of generic lifetime excluding those from parent.
-    pub(crate) fn len_lt_self(&self) -> usize {
-        self.params.lifetimes.len()
+    /// Returns number of generic parameter excluding those from parent
+    fn len_params(&self) -> usize {
+        self.params.type_or_consts.len()
     }
 
     /// (parent total, self param, type param list, const param list, impl trait)
@@ -376,11 +376,11 @@ impl Generics {
                 .enumerate()
                 .find(|(_, (idx, _))| *idx == lifetime.local_id)?;
 
-            Some((idx, data))
+            Some((self.len_params() + idx, data))
         } else {
             self.parent_generics()
                 .and_then(|g| g.find_lifetime(lifetime))
-                .map(|(idx, data)| (self.len_lt_self() + idx, data))
+                .map(|(idx, data)| (self.len_self() + idx, data))
         }
     }