Merge #4445

4445: Correctly fill default type parameters r=flodiebold a=montekki

Fixes #3877 

So, basically even if the parameters are omitted from the `impl` block, check the parameters in `trait` if they have a default type, and if they do go from `hir` to `ast::TypeArg`. I've added a helper for that but I am not sure that it's a proper way to go from `hir` to `ast` here.

Co-authored-by: Fedor Sakharov <[email protected]>

1 files changed, 5 insertions, 0 deletions

diff --git a/crates/ra_hir_ty/src/lib.rs b/crates/ra_hir_ty/src/lib.rs
index e8f3482fe..ccc4348f4 100644
--- a/crates/ra_hir_ty/src/lib.rs
+++ b/crates/ra_hir_ty/src/lib.rs
@@ -427,6 +427,11 @@ impl Substs {
     }
 }
 
+/// Return an index of a parameter in the generic type parameter list by it's id.
+pub fn param_idx(db: &dyn HirDatabase, id: TypeParamId) -> Option<usize> {
+    generics(db.upcast(), id.parent).param_idx(id)
+}
+
 #[derive(Debug, Clone)]
 pub struct SubstsBuilder {
     vec: Vec<Ty>,