Move check to end of function to filter out methods with better context errors

Author: iSwapna

compiler/rustc_hir_typeck/src/method/suggest.rs

@@ -470,36 +470,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
             );
         }
 
-        // Check if any of the candidates match
-        if let Mode::MethodCall = mode && let SelfSource::MethodCall(mut rcvr_expr) = source {
-        while let hir::ExprKind::MethodCall(_path_segment, parent_expr, _args, method_span) =
-        rcvr_expr.kind
-            {
-                if let hir::ExprKind::MethodCall(.. ) = parent_expr.kind {
-                } else {
-                    break;
-                }
-                let prev_ty = self.resolve_vars_if_possible(
-                    self.typeck_results
-                        .borrow()
-                        .expr_ty_adjusted_opt(parent_expr)
-                        .unwrap_or(Ty::new_misc_error(self.tcx)),);
-
-                for _matched_method in self.probe_for_name_many(
-                    Mode::MethodCall,
-                    item_name,
-                    None,
-                    IsSuggestion(true),
-                    prev_ty,
-                    rcvr_expr.hir_id,
-                    ProbeScope::TraitsInScope,) {
-                        err.span_label(method_span, format!("{item_kind} `{item_name}` is available on `{prev_ty}`"));
-                    }
-                    rcvr_expr = parent_expr;
-
-            }
-         }
-
+        let mut internal_mutation_in_method = false;
         if let SelfSource::MethodCall(rcvr_expr) = source {
             self.suggest_fn_call(&mut err, rcvr_expr, rcvr_ty, |output_ty| {
                 let call_expr =
@@ -513,7 +484,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
                 );
                 probe.is_ok()
             });
-
+            internal_mutation_in_method = true;
             self.note_internal_mutation_in_method(
                 &mut err,
                 rcvr_expr,
@@ -1271,6 +1242,33 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
             }
         }
 
+        // Only if an appropriate error source is not found, check method chain for possible candiates
+        let error_source_not_found = unsatisfied_predicates.is_empty() && !internal_mutation_in_method;
+        if error_source_not_found && let Mode::MethodCall = mode && let SelfSource::MethodCall(mut rcvr_expr) = source {
+        while let hir::ExprKind::MethodCall(_path_segment, parent_expr, _args, method_span) =
+        rcvr_expr.kind
+            {
+                print!("rcvr_expr {:?}", rcvr_expr);
+                let prev_ty = self.resolve_vars_if_possible(
+                    self.typeck_results
+                        .borrow()
+                        .expr_ty_adjusted_opt(parent_expr)
+                        .unwrap_or(Ty::new_misc_error(self.tcx)),);
+
+                for _matched_method in self.probe_for_name_many(
+                    Mode::MethodCall,
+                    item_name,
+                    None,
+                    IsSuggestion(true),
+                    prev_ty,
+                    rcvr_expr.hir_id,
+                    ProbeScope::AllTraits,) {
+                        err.span_label(method_span, format!("{item_kind} `{item_name}` is available on `{prev_ty}`"));
+                    }
+                    rcvr_expr = parent_expr;
+
+            }
+        }
         self.note_derefed_ty_has_method(&mut err, source, rcvr_ty, item_name, expected);
         return Some(err);
     }

tests/ui/mismatched_types/issue-36053-2.stderr

@@ -19,11 +19,10 @@ error[E0599]: the method `count` exists for struct `Filter<Fuse<Once<&str>>, {cl
   --> $DIR/issue-36053-2.rs:7:55
    |
 LL |     once::<&str>("str").fuse().filter(|a: &str| true).count();
-   |                                ---------------------- ^^^^^ method cannot be called due to unsatisfied trait bounds
-   |                                |      |
-   |                                |      doesn't satisfy `<_ as FnOnce<(&&str,)>>::Output = bool`
-   |                                |      doesn't satisfy `_: FnMut<(&&str,)>`
-   |                                method `count` is available on `Fuse<std::iter::Once<&str>>`
+   |                                       ---------       ^^^^^ method cannot be called due to unsatisfied trait bounds
+   |                                       |
+   |                                       doesn't satisfy `<_ as FnOnce<(&&str,)>>::Output = bool`
+   |                                       doesn't satisfy `_: FnMut<(&&str,)>`
   --> $SRC_DIR/core/src/iter/adapters/filter.rs:LL:COL
    |
    = note: doesn't satisfy `_: Iterator`

tests/ui/structs/method-chain-expression-failure.stderr

@@ -5,9 +5,7 @@ LL | struct D;
    | -------- method `foo` not found for this struct
 ...
 LL |     A.b().c().d().foo();
-   |           ---     ^^^ method not found in `D`
-   |           |
-   |           method `foo` is available on `&B`
+   |                   ^^^ method not found in `D`
 
 error: aborting due to previous error
 

tests/ui/suggestions/chain-method-call-mutation-in-place.stderr

@@ -18,9 +18,7 @@ error[E0599]: no method named `sort` found for unit type `()` in the current sco
   --> $DIR/chain-method-call-mutation-in-place.rs:3:72
    |
 LL |     vec![1, 2, 3].into_iter().collect::<Vec<i32>>().sort_by_key(|i| i).sort();
-   |                                                     ------------------ ^^^^ method not found in `()`
-   |                                                     |
-   |                                                     method `sort` is available on `&mut [i32]`
+   |                                                                        ^^^^ method not found in `()`
    |
 note: method `sort_by_key` modifies its receiver in-place, it is not meant to be used in method chains.
   --> $DIR/chain-method-call-mutation-in-place.rs:3:53

tests/ui/typeck/issue-31173.stderr

@@ -31,7 +31,6 @@ LL | |             found_e = true;
 LL | |             false
 LL | |         })
 LL | |         .cloned()
-   | |          -------- method `collect` is available on `TakeWhile<&mut std::vec::IntoIter<u8>, [closure@$DIR/issue-31173.rs:7:21: 7:25]>`
 LL | |         .collect();
    | |         -^^^^^^^ method cannot be called due to unsatisfied trait bounds
    | |_________|