Targeted fixes addressing erroneous suggestions

compiler/rustc_trait_selection/src/traits/error_reporting/suggestions.rs

@@ -671,11 +671,16 @@ impl<'a, 'tcx> InferCtxtExt<'tcx> for InferCtxt<'a, 'tcx> {
         trait_pred: ty::PolyTraitPredicate<'tcx>,
     ) -> bool {
         // It only make sense when suggesting dereferences for arguments
-        let ObligationCauseCode::FunctionArgumentObligation { arg_hir_id, .. } = obligation.cause.code() else {
+        let ObligationCauseCode::FunctionArgumentObligation { arg_hir_id, .. } = obligation.cause.code()
-            return false;
+            else { return false; };
-        };
+        let Some(typeck_results) = self.in_progress_typeck_results
-        let param_env = obligation.param_env;
+            else { return false; };
-        let body_id = obligation.cause.body_id;
+        let typeck_results = typeck_results.borrow();
+        let hir::Node::Expr(expr) = self.tcx.hir().get(*arg_hir_id)
+            else { return false; };
+        let Some(arg_ty) = typeck_results.expr_ty_adjusted_opt(expr)
+            else { return false; };
+
         let span = obligation.cause.span;
         let mut real_trait_pred = trait_pred;
         let mut code = obligation.cause.code();
@@ -687,9 +692,19 @@ impl<'a, 'tcx> InferCtxtExt<'tcx> for InferCtxt<'a, 'tcx> {
 
             // Skipping binder here, remapping below
             let real_ty = real_trait_pred.self_ty().skip_binder();
+            if self.can_eq(obligation.param_env, real_ty, arg_ty).is_err() {
+                continue;
+            }
 
             if let ty::Ref(region, base_ty, mutbl) = *real_ty.kind() {
-                let mut autoderef = Autoderef::new(self, param_env, body_id, span, base_ty, span);
+                let mut autoderef = Autoderef::new(
+                    self,
+                    obligation.param_env,
+                    obligation.cause.body_id,
+                    span,
+                    base_ty,
+                    span,
+                );
                 if let Some(steps) = autoderef.find_map(|(ty, steps)| {
                     // Re-add the `&`
                     let ty = self.tcx.mk_ref(region, TypeAndMut { ty, mutbl });
@@ -697,8 +712,10 @@ impl<'a, 'tcx> InferCtxtExt<'tcx> for InferCtxt<'a, 'tcx> {
                     // Remapping bound vars here
                     let real_trait_pred_and_ty =
                         real_trait_pred.map_bound(|inner_trait_pred| (inner_trait_pred, ty));
-                    let obligation = self
+                    let obligation = self.mk_trait_obligation_with_new_self_ty(
-                        .mk_trait_obligation_with_new_self_ty(param_env, real_trait_pred_and_ty);
+                        obligation.param_env,
+                        real_trait_pred_and_ty,
+                    );
                     Some(steps).filter(|_| self.predicate_may_hold(&obligation))
                 }) {
                     if steps > 0 {
@@ -727,7 +744,7 @@ impl<'a, 'tcx> InferCtxtExt<'tcx> for InferCtxt<'a, 'tcx> {
                     let real_trait_pred_and_base_ty =
                         real_trait_pred.map_bound(|inner_trait_pred| (inner_trait_pred, base_ty));
                     let obligation = self.mk_trait_obligation_with_new_self_ty(
-                        param_env,
+                        obligation.param_env,
                         real_trait_pred_and_base_ty,
                     );
                     if self.predicate_may_hold(&obligation) {
@@ -855,6 +872,7 @@ impl<'a, 'tcx> InferCtxtExt<'tcx> for InferCtxt<'a, 'tcx> {
             _ => return false,
         };
         if matches!(obligation.cause.code(), ObligationCauseCode::FunctionArgumentObligation { .. })
+            && obligation.cause.span.can_be_used_for_suggestions()
         {
             // When the obligation error has been ensured to have been caused by
             // an argument, the `obligation.cause.span` points at the expression

src/test/ui/binop/issue-77910-1.stderr

@@ -19,12 +19,8 @@ LL |     assert_eq!(foo, y);
    |     ^^^^^^^^^^^^^^^^^^ `for<'r> fn(&'r i32) -> &'r i32 {foo}` cannot be formatted using `{:?}` because it doesn't implement `Debug`
    |
    = help: the trait `Debug` is not implemented for `for<'r> fn(&'r i32) -> &'r i32 {foo}`
+   = help: use parentheses to call the function: `foo(s)`
    = note: this error originates in the macro `assert_eq` (in Nightly builds, run with -Z macro-backtrace for more info)
-help: use parentheses to call the function
-  --> $SRC_DIR/core/src/macros/mod.rs:LL:COL
-   |
-LL |                     $crate::panicking::assert_failed(kind, &*left_val(s), &*right_val, $crate::option::Option::None);
-   |                                                                      +++
 
 error: aborting due to 2 previous errors
 

src/test/ui/closures/closure-move-sync.stderr

@@ -22,10 +22,6 @@ note: required by a bound in `spawn`
    |
 LL |     F: Send + 'static,
    |        ^^^^ required by this bound in `spawn`
-help: consider dereferencing here
-   |
-LL |     let t = thread::spawn(*|| {
-   |                           +
 
 error[E0277]: `Sender<()>` cannot be shared between threads safely
   --> $DIR/closure-move-sync.rs:18:19
@@ -47,10 +43,6 @@ note: required by a bound in `spawn`
    |
 LL |     F: Send + 'static,
    |        ^^^^ required by this bound in `spawn`
-help: consider dereferencing here
-   |
-LL |     thread::spawn(*|| tx.send(()).unwrap());
-   |                   +
 
 error: aborting due to 2 previous errors
 

src/test/ui/generator/not-send-sync.stderr

@@ -23,10 +23,6 @@ note: required by a bound in `assert_send`
    |
 LL |     fn assert_send<T: Send>(_: T) {}
    |                       ^^^^ required by this bound in `assert_send`
-help: consider dereferencing here
-   |
-LL |     assert_send(*|| {
-   |                 +
 
 error: generator cannot be shared between threads safely
   --> $DIR/not-send-sync.rs:9:17

src/test/ui/generator/print/generator-print-verbose-2.stderr

@@ -23,10 +23,6 @@ note: required by a bound in `assert_send`
    |
 LL |     fn assert_send<T: Send>(_: T) {}
    |                       ^^^^ required by this bound in `assert_send`
-help: consider dereferencing here
-   |
-LL |     assert_send(*|| {
-   |                 +
 
 error: generator cannot be shared between threads safely
   --> $DIR/generator-print-verbose-2.rs:12:17

src/test/ui/interior-mutability/interior-mutability.stderr

@@ -19,10 +19,6 @@ note: required by a bound in `catch_unwind`
    |
 LL | pub fn catch_unwind<F: FnOnce() -> R + UnwindSafe, R>(f: F) -> Result<R> {
    |                                        ^^^^^^^^^^ required by this bound in `catch_unwind`
-help: consider dereferencing here
-   |
-LL |     catch_unwind(*|| { x.set(23); });
-   |                  +
 
 error: aborting due to previous error
 

src/test/ui/issues/issue-70724-add_type_neq_err_label-unwrap.stderr

@@ -34,12 +34,8 @@ LL |     assert_eq!(a, 0);
    |     ^^^^^^^^^^^^^^^^ `fn() -> i32 {a}` cannot be formatted using `{:?}` because it doesn't implement `Debug`
    |
    = help: the trait `Debug` is not implemented for `fn() -> i32 {a}`
+   = help: use parentheses to call the function: `a()`
    = note: this error originates in the macro `assert_eq` (in Nightly builds, run with -Z macro-backtrace for more info)
-help: use parentheses to call the function
-  --> $SRC_DIR/core/src/macros/mod.rs:LL:COL
-   |
-LL |                     $crate::panicking::assert_failed(kind, &*left_val(), &*right_val, $crate::option::Option::None);
-   |                                                                      ++
 
 error: aborting due to 3 previous errors