Do not fail method_autoderef_steps on infer types. Let method resolution handle it

Author: oli-obk

compiler/rustc_hir_typeck/src/method/probe.rs

@@ -556,6 +556,7 @@ fn method_autoderef_steps<'tcx>(
 
     let final_ty = autoderef.final_ty(true);
     let opt_bad_ty = match final_ty.kind() {
+        ty::Infer(ty::TyVar(_)) if !reached_raw_pointer => None,
         ty::Infer(ty::TyVar(_)) | ty::Error(_) => Some(MethodAutoderefBadTy {
             reached_raw_pointer,
             ty: infcx.make_query_response_ignoring_pending_obligations(inference_vars, final_ty),

tests/crashes/121613-2.rs

@@ -1,8 +1,14 @@
-//@ known-bug: #121613
+//! This test used to ICE #121613
+//! Using a generic parameter where there are none expected
+//! caused an ICE, hiding the important later errors.
+
+#![feature(more_qualified_paths)]
+
 fn main() {
     let _ = <Foo as A>::Assoc { br: 2 };
 
     let <E>::V(..) = E::V(|a, b| a.cmp(b));
+    //~^ ERROR: multiple applicable items in scope
 }
 
 struct StructStruct {

tests/crashes/121613.rs renamed to tests/ui/associated-types/param_mismatch_on_associatedtype_constructor.rs

@@ -0,0 +1,22 @@
+error[E0034]: multiple applicable items in scope
+  --> $DIR/param_mismatch_on_associatedtype_constructor.rs:10:36
+   |
+LL |     let <E>::V(..) = E::V(|a, b| a.cmp(b));
+   |                                    ^^^ multiple `cmp` found
+   |
+note: candidate #1 is defined in the trait `Iterator`
+  --> $SRC_DIR/core/src/iter/traits/iterator.rs:LL:COL
+note: candidate #2 is defined in the trait `Ord`
+  --> $SRC_DIR/core/src/cmp.rs:LL:COL
+help: disambiguate the method for candidate #1
+   |
+LL |     let <E>::V(..) = E::V(|a, b| Iterator::cmp(a, b));
+   |                                  ~~~~~~~~~~~~~~~~~~~
+help: disambiguate the method for candidate #2
+   |
+LL |     let <E>::V(..) = E::V(|a, b| Ord::cmp(&a, b));
+   |                                  ~~~~~~~~~~~~~~~
+
+error: aborting due to 1 previous error
+
+For more information about this error, try `rustc --explain E0034`.

tests/ui/associated-types/param_mismatch_on_associatedtype_constructor.stderr

@@ -29,12 +29,12 @@ impl<F> Deref for Value<Rc<F>> {
 
 fn main() {
     let var_fn = Value::wrap();
-    //~^ ERROR type annotations needed for `Value<Rc<_>>`
 
     // The combination of `Value: Wrap` obligation plus the autoderef steps
     // (caused by the `Deref` impl above) actually means that the self type
     // of the method fn below is constrained to be `Value<Rc<dyn Fn(?0, ?1) -> ?2>>`.
     // However, that's only known to us on the error path -- we still need
     // to emit an ambiguity error, though.
     let _ = var_fn.clone();
+    //~^ ERROR: the size for values of type `dyn Fn(_, _) -> _` cannot be known
 }

tests/ui/autoref-autoderef/deref-ambiguity-becomes-nonambiguous.rs

@@ -1,17 +1,18 @@
-error[E0282]: type annotations needed for `Value<Rc<_>>`
-  --> $DIR/deref-ambiguity-becomes-nonambiguous.rs:31:9
+error[E0277]: the size for values of type `dyn Fn(_, _) -> _` cannot be known at compilation time
+  --> $DIR/deref-ambiguity-becomes-nonambiguous.rs:38:13
    |
-LL |     let var_fn = Value::wrap();
-   |         ^^^^^^
-...
 LL |     let _ = var_fn.clone();
-   |                    ----- type must be known at this point
+   |             ^^^^^^^^^^^^^^ doesn't have a size known at compile-time
    |
-help: consider giving `var_fn` an explicit type, where the placeholders `_` are specified
+   = help: the trait `Sized` is not implemented for `dyn Fn(_, _) -> _`, which is required by `Value<Rc<_>>: Deref`
+note: required for `Value<Rc<dyn Fn(_, _) -> _>>` to implement `Deref`
+  --> $DIR/deref-ambiguity-becomes-nonambiguous.rs:22:9
    |
-LL |     let var_fn: Value<Rc<_>> = Value::wrap();
-   |               ++++++++++++++
+LL | impl<F> Deref for Value<Rc<F>> {
+   |      -  ^^^^^     ^^^^^^^^^^^^
+   |      |
+   |      unsatisfied trait bound introduced here
 
 error: aborting due to 1 previous error
 
-For more information about this error, try `rustc --explain E0282`.
+For more information about this error, try `rustc --explain E0277`.

tests/ui/autoref-autoderef/deref-ambiguity-becomes-nonambiguous.stderr

@@ -5,7 +5,7 @@ LL |     needs_foo(|x| {
    |                ^
 ...
 LL |         x.to_string();
-   |           --------- type must be known at this point
+   |         ------------- type must be known at this point
    |
 help: consider giving this closure parameter an explicit type
    |

tests/ui/closures/deduce-signature/obligation-with-leaking-placeholders.next.stderr

@@ -5,7 +5,7 @@ LL |         let mut iter = foo(n - 1, m);
    |             ^^^^^^^^
 LL |
 LL |         assert_eq!(iter.get(), 1);
-   |                         --- type must be known at this point
+   |                    ---------- type must be known at this point
    |
 help: consider giving `iter` an explicit type
    |

tests/ui/impl-trait/call_method_ambiguous.next.stderr

@@ -5,7 +5,7 @@ LL |         let x = my_foo();
    |             ^
 LL |
 LL |         x.my_debug();
-   |           -------- type must be known at this point
+   |         ------------ type must be known at this point
    |
 help: consider giving `x` an explicit type
    |

tests/ui/impl-trait/call_method_on_inherent_impl.next.stderr

@@ -4,7 +4,7 @@ error[E0282]: type annotations needed for `&_`
 LL |         let x = &my_foo();
    |             ^
 LL |         x.my_debug();
-   |           -------- type must be known at this point
+   |         ------------ type must be known at this point
    |
 help: consider giving `x` an explicit type, where the placeholders `_` are specified
    |