implement the rest of feature(more_qualified_paths)

this handles:
```rust
let (<E>::ES { a } | <E>::ET(a)) = <E>::ES { a: 0 };
```

Author: WaffleLapkin

crates/hir-ty/src/infer.rs

@@ -1580,6 +1580,7 @@ impl<'db> InferenceContext<'db> {
             Some(path) => path,
             None => return (self.err_ty(), None),
         };
+
         let mut ctx = TyLoweringContext::new(
             self.db,
             &self.resolver,
@@ -1589,6 +1590,25 @@ impl<'db> InferenceContext<'db> {
             self.generic_def,
             LifetimeElisionKind::Infer,
         );
+
+        if let Some(type_anchor) = path.type_anchor() {
+            let segments = path.segments();
+            if segments.len() != 1 {
+                return (self.err_ty(), None);
+            }
+            let ty = ctx.lower_ty(type_anchor);
+            if let Some((AdtId::EnumId(id), _)) = ty.as_adt() {
+                let enum_data = self.db.enum_variants(id);
+                if let Some(variant) = enum_data.variant(segments.first().unwrap().name) {
+                    // FIXME: Report error if there are generics on the variant.
+                    return (ty, Some(variant.into()));
+                }
+            } else {
+                // FIXME: Report an error.
+                return (self.err_ty(), None);
+            }
+        }
+
         let mut path_ctx = ctx.at_path(path, node);
         let (resolution, unresolved) = if value_ns {
             let Some(res) = path_ctx.resolve_path_in_value_ns(HygieneId::ROOT) else {