Rework obligation handling

We can't do the easy hack that we did before anymore, where we kept
track of whether any inference variables changed since the last time we
rechecked obligations. Instead, we store the obligations in
canonicalized form; that way we can easily check the inference variables
to see whether they have changed since the goal was canonicalized.

1 files changed, 5 insertions, 2 deletions

diff --git a/crates/hir_ty/src/infer/coerce.rs b/crates/hir_ty/src/infer/coerce.rs
index 4d80b4a08..911343cb9 100644
--- a/crates/hir_ty/src/infer/coerce.rs
+++ b/crates/hir_ty/src/infer/coerce.rs
@@ -402,12 +402,15 @@ impl<'a> InferenceContext<'a> {
         // solve `CoerceUnsized` and `Unsize` goals at this point and leaves the
         // rest for later. Also, there's some logic about sized type variables.
         // Need to find out in what cases this is necessary
-        let solution = self.db.trait_solve(krate, canonicalized.value.clone()).ok_or(TypeError)?;
+        let solution = self
+            .db
+            .trait_solve(krate, canonicalized.value.clone().cast(&Interner))
+            .ok_or(TypeError)?;
 
         match solution {
             Solution::Unique(v) => {
                 canonicalized.apply_solution(
-                    self,
+                    &mut self.table,
                     Canonical {
                         binders: v.binders,
                         // FIXME handle constraints