Use correct crate for trait env in render_const_scalar()

crates/hir-ty/src/display.rs

@@ -152,6 +152,13 @@ impl HirFormatter<'_> {
             }
         }
     }
+
+    pub fn krate(&self) -> CrateId {
+        match self.display_target {
+            DisplayTarget::Diagnostics { krate } | DisplayTarget::Test { krate } => krate,
+            DisplayTarget::SourceCode { module_id, .. } => module_id.krate(),
+        }
+    }
 }
 
 pub trait HirDisplay {
@@ -655,10 +662,7 @@ fn render_const_scalar(
     memory_map: &MemoryMap,
     ty: &Ty,
 ) -> Result<(), HirDisplayError> {
-    // FIXME: We need to get krate from the final callers of the hir display
-    // infrastructure and have it here as a field on `f`.
-    let trait_env =
-        TraitEnvironment::empty(*f.db.crate_graph().crates_in_topological_order().last().unwrap());
+    let trait_env = TraitEnvironment::empty(f.krate());
     let ty = normalize(f.db, trait_env.clone(), ty.clone());
     match ty.kind(Interner) {
         TyKind::Scalar(s) => match s {

crates/ide/src/hover/tests.rs

@@ -10950,8 +10950,12 @@ pub struct ManuallyDrop$0<T: ?Sized> {
 
 #[test]
 fn projection_const() {
+    // This uses two crates, which have *no* relation between them, to test another thing:
+    // `render_const_scalar()` used to just use the last crate for the trait env, which will
+    // fail in this scenario.
     check(
         r#"
+//- /foo.rs crate:foo
 pub trait PublicFlags {
     type Internal;
 }
@@ -10967,12 +10971,13 @@ pub struct InternalBitFlags;
 impl PublicFlags for NoteDialects {
     type Internal = InternalBitFlags;
 }
+//- /bar.rs crate:bar
     "#,
         expect![[r#"
             *CLAP*
 
             ```rust
-            ra_test_fixture::NoteDialects
+            foo::NoteDialects
             ```
 
             ```rust