Don't give method suggestions when method probe fails due to bad impl of Deref

compiler/rustc_hir_typeck/src/method/mod.rs

@@ -18,8 +18,8 @@
     self, GenericArgs, GenericArgsRef, GenericParamDefKind, Ty, TypeVisitableExt,
 };
 use rustc_middle::{bug, span_bug};
-use rustc_span::Span;
 use rustc_span::symbol::Ident;
+use rustc_span::{ErrorGuaranteed, Span};
 use rustc_trait_selection::traits::query::evaluate_obligation::InferCtxtExt;
 use rustc_trait_selection::traits::{self, NormalizeExt};
 use tracing::{debug, instrument};
@@ -66,6 +66,9 @@ pub(crate) enum MethodError<'tcx> {
 
     // Found a match, but the return type is wrong
     BadReturnType,
+
+    // Error has already been emitted, no need to emit another one.
+    ErrorReported(ErrorGuaranteed),
 }
 
 // Contains a list of static methods that may apply, a list of unsatisfied trait predicates which
@@ -120,6 +123,7 @@ pub fn method_exists_for_diagnostic(
             Err(PrivateMatch(..)) => false,
             Err(IllegalSizedBound { .. }) => true,
             Err(BadReturnType) => false,
+            Err(ErrorReported(_)) => false,
         }
     }
 

compiler/rustc_hir_typeck/src/method/probe.rs

@@ -446,13 +446,7 @@ pub(crate) fn probe_op<OP, R>(
                     _ => bug!("unexpected bad final type in method autoderef"),
                 };
                 self.demand_eqtype(span, ty, Ty::new_error(self.tcx, guar));
-                return Err(MethodError::NoMatch(NoMatchData {
-                    static_candidates: Vec::new(),
-                    unsatisfied_predicates: Vec::new(),
-                    out_of_scope_traits: Vec::new(),
-                    similar_candidate: None,
-                    mode,
-                }));
+                return Err(MethodError::ErrorReported(guar));
             }
         }
 

compiler/rustc_hir_typeck/src/method/suggest.rs

@@ -386,6 +386,8 @@ trait `{}` provides `{item_name}` is implemented but not reachable",
                 return err.emit();
             }
 
+            MethodError::ErrorReported(guar) => guar,
+
             MethodError::BadReturnType => bug!("no return type expectations but got BadReturnType"),
         }
     }

tests/ui/methods/dont-suggest-import-on-deref-err.rs

@@ -0,0 +1,13 @@
+use std::clone::Clone;
+use std::ops::Deref;
+
+#[derive(Clone)]
+pub struct Foo {}
+
+impl Deref for Foo {}
+//~^ ERROR not all trait items implemented
+
+pub fn main() {
+    let f = Foo {};
+    let _ = f.clone();
+}

tests/ui/methods/dont-suggest-import-on-deref-err.stderr

@@ -0,0 +1,12 @@
+error[E0046]: not all trait items implemented, missing: `Target`, `deref`
+  --> $DIR/dont-suggest-import-on-deref-err.rs:7:1
+   |
+LL | impl Deref for Foo {}
+   | ^^^^^^^^^^^^^^^^^^ missing `Target`, `deref` in implementation
+   |
+   = help: implement the missing item: `type Target = /* Type */;`
+   = help: implement the missing item: `fn deref(&self) -> &<Self as Deref>::Target { todo!() }`
+
+error: aborting due to 1 previous error
+
+For more information about this error, try `rustc --explain E0046`.