Merge #8856

8856: Use Chalk for unification r=flodiebold a=flodiebold

 - use Chalk's unification, get rid of our own `unify`
 - rewrite coercion to not use unification internals and to be more analogous to rustc
 - fix various coercion bugs
 - rewrite handling of obligations, since the old hacky optimization where we noted when an inference variable changes wasn't possible anymore
 - stop trying to deeply resolve types all the time during inference, instead only do it shallowly where necessary

Co-authored-by: Florian Diebold <[email protected]>

1 files changed, 5 insertions, 0 deletions

diff --git a/crates/hir_ty/src/chalk_ext.rs b/crates/hir_ty/src/chalk_ext.rs
index 5232a7d80..df340a6ca 100644
--- a/crates/hir_ty/src/chalk_ext.rs
+++ b/crates/hir_ty/src/chalk_ext.rs
@@ -18,6 +18,7 @@ pub trait TyExt {
     fn is_unit(&self) -> bool;
     fn is_never(&self) -> bool;
     fn is_unknown(&self) -> bool;
+    fn is_ty_var(&self) -> bool;
 
     fn as_adt(&self) -> Option<(hir_def::AdtId, &Substitution)>;
     fn as_builtin(&self) -> Option<BuiltinType>;
@@ -55,6 +56,10 @@ impl TyExt for Ty {
         matches!(self.kind(&Interner), TyKind::Error)
     }
 
+    fn is_ty_var(&self) -> bool {
+        matches!(self.kind(&Interner), TyKind::InferenceVar(_, _))
+    }
+
     fn as_adt(&self) -> Option<(hir_def::AdtId, &Substitution)> {
         match self.kind(&Interner) {
             TyKind::Adt(AdtId(adt), parameters) => Some((*adt, parameters)),