
`evaluate_goal` avoid unnecessary step based on rust-lang/rust#142617. This does not mess with the debug logging for the trait solver and is a very nice cleanup for rust-lang/rust#142735. E.g. for ```rust #[derive(Clone)] struct Wrapper<T>(T); #[derive(Clone)] struct Nested; // using a separate type to avoid the fast paths fn is_clone<T: Clone>() {} fn main() { is_clone::<Wrapper<Nested>>(); } ``` We get the following proof tree with `RUSTC_LOG=rustc_type_ir::search_graph=debug,rustc_next_trait_solver=debug` ``` rustc_next_trait_solver::solve::eval_ctxt::evaluate_root_goal goal=Goal { param_env: ParamEnv { caller_bounds: [] }, predicate: Binder { value: TraitPredicate(<Wrapper<Nested> as std::clone::Clone>, polarity:Positive), bound_vars: [] } }, generate_proof_tree=No, span=src/main.rs:7:5: 7:34 (#0), stalled_on=None rustc_type_ir::search_graph::evaluate_goal input=CanonicalQueryInput { canonical: Canonical { value: QueryInput { goal: Goal { param_env: ParamEnv { caller_bounds: [] }, predicate: Binder { value: TraitPredicate(<Wrapper<Nested> as std::clone::Clone>, polarity:Positive), bound_vars: [] } }, predefined_opaques_in_body: PredefinedOpaques(PredefinedOpaquesData { opaque_types: [] }) }, max_universe: U0, variables: [] }, typing_mode: Analysis { defining_opaque_types_and_generators: [] } }, step_kind_from_parent=Unknown rustc_next_trait_solver::solve::eval_ctxt::probe::enter source=Impl(DefId(0:10 ~ main[21d2]::{impl#0})) rustc_next_trait_solver::solve::eval_ctxt::add_goal source=ImplWhereBound, goal=Goal { param_env: ParamEnv { caller_bounds: [] }, predicate: Binder { value: TraitPredicate(<_ as std::marker::Sized>, polarity:Positive), bound_vars: [] } } rustc_next_trait_solver::solve::eval_ctxt::add_goal source=ImplWhereBound, goal=Goal { param_env: ParamEnv { caller_bounds: [] }, predicate: Binder { value: TraitPredicate(<_ as std::clone::Clone>, polarity:Positive), bound_vars: [] } } rustc_type_ir::search_graph::evaluate_goal input=CanonicalQueryInput { canonical: Canonical { value: QueryInput { goal: Goal { param_env: ParamEnv { caller_bounds: [] }, predicate: Binder { value: TraitPredicate(<Nested as std::clone::Clone>, polarity:Positive), bound_vars: [] } }, predefined_opaques_in_body: PredefinedOpaques(PredefinedOpaquesData { opaque_types: [] }) }, max_universe: U0, variables: [] }, typing_mode: Analysis { defining_opaque_types_and_generators: [] } }, step_kind_from_parent=Unknown 0ms DEBUG rustc_type_ir::search_graph global cache hit, required_depth=0 0ms DEBUG rustc_type_ir::search_graph return=Ok(Canonical { value: Response { certainty: Yes, var_values: CanonicalVarValues { var_values: [] }, external_constraints: ExternalConstraints(ExternalConstraintsData { region_constraints: [], opaque_types: [], normalization_nested_goals: NestedNormalizationGoals([]) }) }, max_universe: U0, variables: [] }) rustc_next_trait_solver::solve::eval_ctxt::probe::enter source=BuiltinImpl(Misc) rustc_next_trait_solver::solve::trait_goals::merge_trait_candidates candidates=[Candidate { source: Impl(DefId(0:10 ~ main[21d2]::{impl#0})), result: Canonical { value: Response { certainty: Yes, var_values: CanonicalVarValues { var_values: [] }, external_constraints: ExternalConstraints(ExternalConstraintsData { region_constraints: [], opaque_types: [], normalization_nested_goals: NestedNormalizationGoals([]) }) }, max_universe: U0, variables: [] } }] 0ms DEBUG rustc_next_trait_solver::solve::trait_goals return=Ok((Canonical { value: Response { certainty: Yes, var_values: CanonicalVarValues { var_values: [] }, external_constraints: ExternalConstraints(ExternalConstraintsData { region_constraints: [], opaque_types: [], normalization_nested_goals: NestedNormalizationGoals([]) }) }, max_universe: U0, variables: [] }, Some(Misc))) 0ms DEBUG rustc_type_ir::search_graph insert global cache, evaluation_result=EvaluationResult { encountered_overflow: false, required_depth: 1, heads: CycleHeads { heads: {} }, nested_goals: NestedGoals { nested_goals: {} }, result: Ok(Canonical { value: Response { certainty: Yes, var_values: CanonicalVarValues { var_values: [] }, external_constraints: ExternalConstraints(ExternalConstraintsData { region_constraints: [], opaque_types: [], normalization_nested_goals: NestedNormalizationGoals([]) }) }, max_universe: U0, variables: [] }) } 0ms DEBUG rustc_type_ir::search_graph return=Ok(Canonical { value: Response { certainty: Yes, var_values: CanonicalVarValues { var_values: [] }, external_constraints: ExternalConstraints(ExternalConstraintsData { region_constraints: [], opaque_types: [], normalization_nested_goals: NestedNormalizationGoals([]) }) }, max_universe: U0, variables: [] }) ```
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