remove unnecessary variant

compiler/rustc_middle/src/traits/mod.rs

@@ -980,12 +980,9 @@ pub enum CodegenObligationError {
     /// overflow bug, since I believe this is the only case
     /// where ambiguity can result.
     Ambiguity,
-    /// This can trigger when we probe for the source of a `'static` lifetime requirement
+    /// This can trigger when we have a global bound that is not actually satisfied
-    /// on a trait object: `impl Foo for dyn Trait {}` has an implicit `'static` bound.
+    /// due to trivial bounds.
-    /// This can also trigger when we have a global bound that is not actually satisfied,
-    /// but was included during typeck due to the trivial_bounds feature.
     Unimplemented,
-    FulfillmentError,
     /// The selected impl has unconstrained generic parameters. This will emit an error
     /// during impl WF checking.
     UnconstrainedParam(ErrorGuaranteed),

compiler/rustc_traits/src/codegen.rs

@@ -70,7 +70,7 @@ pub(crate) fn codegen_select_candidate<'tcx>(
                 infcx.err_ctxt().report_overflow_obligation_cycle(&cycle);
             }
         }
-        return Err(CodegenObligationError::FulfillmentError);
+        return Err(CodegenObligationError::Unimplemented);
     }
 
     let impl_source = infcx.resolve_vars_if_possible(impl_source);

compiler/rustc_ty_utils/src/instance.rs

@@ -107,11 +107,9 @@ fn resolve_associated_item<'tcx>(
     let input = typing_env.as_query_input(trait_ref);
     let vtbl = match tcx.codegen_select_candidate(input) {
         Ok(vtbl) => vtbl,
-        Err(
+        Err(CodegenObligationError::Ambiguity | CodegenObligationError::Unimplemented) => {
-            CodegenObligationError::Ambiguity
+            return Ok(None);
-            | CodegenObligationError::Unimplemented
+        }
-            | CodegenObligationError::FulfillmentError,
-        ) => return Ok(None),
         Err(CodegenObligationError::UnconstrainedParam(guar)) => return Err(guar),
     };