Drop environment when evaluating const without generic parameters

Author: tiif

compiler/rustc_trait_selection/src/traits/mod.rs

@@ -635,9 +635,18 @@ pub fn try_evaluate_const<'tcx>(
                         return Err(EvaluateConstErr::HasGenericsOrInfers);
                     }
 
-                    let typing_env = infcx
+                    let mut typing_env;
+
+                    typing_env = infcx
                         .typing_env(tcx.erase_and_anonymize_regions(param_env))
                         .with_post_analysis_normalized(tcx);
+
+                    // Since there is no generic parameter, we can just drop the environment
+                    // to prevent query cycle.
+                    if !uv.args.has_non_region_param() {
+                        typing_env = infcx.typing_env(ty::ParamEnv::empty());
+                    }
+
                     (uv.args, typing_env)
                 }
             };