Rollup merge of rust-lang#147768 - chenyukang:yukang-refactor-report-method-error, r=nnethercote

Code refactoring on hir report_no_match_method_error

While working on rust-lang#147753, I found `report_no_match_method_error` now is too long for maintain, 1200 lines of code now:
https://github.com/rust-lang/rust/blob/57ef8d642d21965304bde849bab4f389b4353e27/compiler/rustc_hir_typeck/src/method/suggest.rs#L589-L1736

this PR try to refactor it.

I tried my best to group most related code into same places, but the logic here is still very complex, there are some variables across different functions, maybe we need more work to make it better understand.

Maybe we could add a tidy check to avoid long spaghetti code.

r? `@nnethercote`

Author: matthiaskrgr

compiler/rustc_hir_typeck/src/fn_ctxt/suggestions.rs

@@ -1953,7 +1953,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
                         }
                     }
                 }
-                self.suggest_derive(diag, &[(trait_ref.upcast(self.tcx), None, None)]);
+                self.suggest_derive(diag, &vec![(trait_ref.upcast(self.tcx), None, None)]);
             }
         }
     }

compiler/rustc_hir_typeck/src/method/mod.rs

@@ -26,6 +26,7 @@ use tracing::{debug, instrument};
 pub(crate) use self::MethodError::*;
 use self::probe::{IsSuggestion, ProbeScope};
 use crate::FnCtxt;
+use crate::method::probe::UnsatisfiedPredicates;
 
 #[derive(Clone, Copy, Debug)]
 pub(crate) struct MethodCallee<'tcx> {
@@ -71,8 +72,7 @@ pub(crate) enum MethodError<'tcx> {
 #[derive(Debug)]
 pub(crate) struct NoMatchData<'tcx> {
     pub static_candidates: Vec<CandidateSource>,
-    pub unsatisfied_predicates:
-        Vec<(ty::Predicate<'tcx>, Option<ty::Predicate<'tcx>>, Option<ObligationCause<'tcx>>)>,
+    pub unsatisfied_predicates: UnsatisfiedPredicates<'tcx>,
     pub out_of_scope_traits: Vec<DefId>,
     pub similar_candidate: Option<ty::AssocItem>,
     pub mode: probe::Mode,

compiler/rustc_hir_typeck/src/method/probe.rs

@@ -165,13 +165,12 @@ struct PickDiagHints<'a, 'tcx> {
 
     /// Collects near misses when trait bounds for type parameters are unsatisfied and is only used
     /// for error reporting
-    unsatisfied_predicates: &'a mut Vec<(
-        ty::Predicate<'tcx>,
-        Option<ty::Predicate<'tcx>>,
-        Option<ObligationCause<'tcx>>,
-    )>,
+    unsatisfied_predicates: &'a mut UnsatisfiedPredicates<'tcx>,
 }
 
+pub(crate) type UnsatisfiedPredicates<'tcx> =
+    Vec<(ty::Predicate<'tcx>, Option<ty::Predicate<'tcx>>, Option<ObligationCause<'tcx>>)>;
+
 /// Criteria to apply when searching for a given Pick. This is used during
 /// the search for potentially shadowed methods to ensure we don't search
 /// more candidates than strictly necessary.
@@ -1212,11 +1211,7 @@ impl<'a, 'tcx> ProbeContext<'a, 'tcx> {
 
     fn pick_core(
         &self,
-        unsatisfied_predicates: &mut Vec<(
-            ty::Predicate<'tcx>,
-            Option<ty::Predicate<'tcx>>,
-            Option<ObligationCause<'tcx>>,
-        )>,
+        unsatisfied_predicates: &mut UnsatisfiedPredicates<'tcx>,
     ) -> Option<PickResult<'tcx>> {
         // Pick stable methods only first, and consider unstable candidates if not found.
         self.pick_all_method(&mut PickDiagHints {
@@ -1889,11 +1884,7 @@ impl<'a, 'tcx> ProbeContext<'a, 'tcx> {
         self_ty: Ty<'tcx>,
         instantiate_self_ty_obligations: &[PredicateObligation<'tcx>],
         probe: &Candidate<'tcx>,
-        possibly_unsatisfied_predicates: &mut Vec<(
-            ty::Predicate<'tcx>,
-            Option<ty::Predicate<'tcx>>,
-            Option<ObligationCause<'tcx>>,
-        )>,
+        possibly_unsatisfied_predicates: &mut UnsatisfiedPredicates<'tcx>,
     ) -> ProbeResult {
         self.probe(|snapshot| {
             let outer_universe = self.universe();