Rollup merge of #136928 - lcnr:method-lookup-check-wf, r=compiler-errors

eagerly prove WF when resolving fully qualified paths

fixes rust-lang/trait-system-refactor-initiative#161.

This hopefully shouldn't impact perf. I do think we need to deal with at least part of the fallout here, opening for vibes.

r? ``@compiler-errors``

Author: workingjubilee

compiler/rustc_hir_typeck/src/fn_ctxt/_impl.rs

@@ -798,13 +798,16 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
                 bug!("`resolve_ty_and_res_fully_qualified_call` called on `LangItem`")
             }
         };
+
+        self.register_wf_obligation(
+            ty.raw.into(),
+            qself.span,
+            ObligationCauseCode::WellFormed(None),
+        );
+        self.select_obligations_where_possible(|_| {});
+
         if let Some(&cached_result) = self.typeck_results.borrow().type_dependent_defs().get(hir_id)
         {
-            self.register_wf_obligation(
-                ty.raw.into(),
-                qself.span,
-                ObligationCauseCode::WellFormed(None),
-            );
             // Return directly on cache hit. This is useful to avoid doubly reporting
             // errors with default match binding modes. See #44614.
             let def = cached_result.map_or(Res::Err, |(kind, def_id)| Res::Def(kind, def_id));
@@ -824,18 +827,6 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
 
                 let trait_missing_method =
                     matches!(error, method::MethodError::NoMatch(_)) && ty.normalized.is_trait();
-                // If we have a path like `MyTrait::missing_method`, then don't register
-                // a WF obligation for `dyn MyTrait` when method lookup fails. Otherwise,
-                // register a WF obligation so that we can detect any additional
-                // errors in the self type.
-                if !trait_missing_method {
-                    self.register_wf_obligation(
-                        ty.raw.into(),
-                        qself.span,
-                        ObligationCauseCode::WellFormed(None),
-                    );
-                }
-
                 if item_name.name != kw::Empty {
                     self.report_method_error(
                         hir_id,
@@ -849,14 +840,6 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
                 result
             });
 
-        if result.is_ok() {
-            self.register_wf_obligation(
-                ty.raw.into(),
-                qself.span,
-                ObligationCauseCode::WellFormed(None),
-            );
-        }
-
         // Write back the new resolution.
         self.write_resolution(hir_id, result);
         (

tests/ui/associated-consts/associated-const-in-trait.rs

@@ -8,6 +8,7 @@ impl dyn Trait {
     //~^ ERROR the trait `Trait` is not dyn compatible [E0038]
     const fn n() -> usize { Self::N }
     //~^ ERROR the trait `Trait` is not dyn compatible [E0038]
+    //~| ERROR the trait `Trait` is not dyn compatible
 }
 
 fn main() {}

tests/ui/associated-consts/associated-const-in-trait.stderr

@@ -30,6 +30,22 @@ LL |     const N: usize;
    |           ^ ...because it contains this associated `const`
    = help: consider moving `N` to another trait
 
-error: aborting due to 2 previous errors
+error[E0038]: the trait `Trait` is not dyn compatible
+  --> $DIR/associated-const-in-trait.rs:9:29
+   |
+LL |     const fn n() -> usize { Self::N }
+   |                             ^^^^^^^ `Trait` is not dyn compatible
+   |
+note: for a trait to be dyn compatible it needs to allow building a vtable
+      for more information, visit <https://doc.rust-lang.org/reference/items/traits.html#dyn-compatibility>
+  --> $DIR/associated-const-in-trait.rs:4:11
+   |
+LL | trait Trait {
+   |       ----- this trait is not dyn compatible...
+LL |     const N: usize;
+   |           ^ ...because it contains this associated `const`
+   = help: consider moving `N` to another trait
+
+error: aborting due to 3 previous errors
 
 For more information about this error, try `rustc --explain E0038`.

tests/ui/associated-consts/wrong-projection-self-ty-invalid-bivariant-arg2.stderr

@@ -1,15 +1,3 @@
-error[E0599]: no associated item named `C` found for struct `Fail<i32, u32>` in the current scope
-  --> $DIR/wrong-projection-self-ty-invalid-bivariant-arg2.rs:15:23
-   |
-LL | struct Fail<T: Proj<Assoc = U>, U>(T);
-   | ---------------------------------- associated item `C` not found for this struct
-...
-LL |     Fail::<i32, u32>::C
-   |                       ^ associated item not found in `Fail<i32, u32>`
-   |
-   = note: the associated item was found for
-           - `Fail<i32, i32>`
-
 error[E0271]: type mismatch resolving `<i32 as Proj>::Assoc == u32`
   --> $DIR/wrong-projection-self-ty-invalid-bivariant-arg2.rs:15:5
    |
@@ -27,6 +15,18 @@ note: required by a bound in `Fail`
 LL | struct Fail<T: Proj<Assoc = U>, U>(T);
    |                     ^^^^^^^^^ required by this bound in `Fail`
 
+error[E0599]: no associated item named `C` found for struct `Fail<i32, u32>` in the current scope
+  --> $DIR/wrong-projection-self-ty-invalid-bivariant-arg2.rs:15:23
+   |
+LL | struct Fail<T: Proj<Assoc = U>, U>(T);
+   | ---------------------------------- associated item `C` not found for this struct
+...
+LL |     Fail::<i32, u32>::C
+   |                       ^ associated item not found in `Fail<i32, u32>`
+   |
+   = note: the associated item was found for
+           - `Fail<i32, i32>`
+
 error: aborting due to 2 previous errors
 
 Some errors have detailed explanations: E0271, E0599.

tests/ui/associated-types/hr-associated-type-bound-object.rs

@@ -9,6 +9,7 @@ fn f<'a, T: X<'a> + ?Sized>(x: &<T as X<'a>>::U) {
     <<T as X<'_>>::U>::clone(x);
     //~^ ERROR the trait bound `for<'b> <T as X<'b>>::U: Clone` is not satisfied
     //~| ERROR the trait bound `for<'b> <T as X<'b>>::U: Clone` is not satisfied
+    //~| ERROR the trait bound `for<'b> <T as X<'b>>::U: Clone` is not satisfied
     //~| ERROR the trait bound `<T as X<'_>>::U: Clone` is not satisfied
 }
 

tests/ui/associated-types/hr-associated-type-bound-object.stderr

@@ -47,6 +47,25 @@ help: consider further restricting the associated type
 LL | fn f<'a, T: X<'a> + ?Sized>(x: &<T as X<'a>>::U) where <T as X<'_>>::U: Clone {
    |                                                  ++++++++++++++++++++++++++++
 
+error[E0277]: the trait bound `for<'b> <T as X<'b>>::U: Clone` is not satisfied
+  --> $DIR/hr-associated-type-bound-object.rs:9:5
+   |
+LL |     <<T as X<'_>>::U>::clone(x);
+   |     ^^^^^^^^^^^^^^^^^^^^^^^^ the trait `for<'b> Clone` is not implemented for `<T as X<'b>>::U`
+   |
+note: required by a bound in `X`
+  --> $DIR/hr-associated-type-bound-object.rs:3:33
+   |
+LL | trait X<'a>
+   |       - required by a bound in this trait
+LL | where
+LL |     for<'b> <Self as X<'b>>::U: Clone,
+   |                                 ^^^^^ required by this bound in `X`
+help: consider further restricting the associated type
+   |
+LL | fn f<'a, T: X<'a> + ?Sized>(x: &<T as X<'a>>::U) where for<'b> <T as X<'b>>::U: Clone {
+   |                                                  ++++++++++++++++++++++++++++++++++++
+
 error[E0277]: the trait bound `for<'b> <T as X<'b>>::U: Clone` is not satisfied
   --> $DIR/hr-associated-type-bound-object.rs:9:5
    |
@@ -66,6 +85,6 @@ help: consider further restricting the associated type
 LL | fn f<'a, T: X<'a> + ?Sized>(x: &<T as X<'a>>::U) where for<'b> <T as X<'b>>::U: Clone {
    |                                                  ++++++++++++++++++++++++++++++++++++
 
-error: aborting due to 4 previous errors
+error: aborting due to 5 previous errors
 
 For more information about this error, try `rustc --explain E0277`.

tests/ui/associated-types/hr-associated-type-bound-param-2.rs

@@ -10,6 +10,7 @@ where
         <T::W>::clone(x);
         //~^ the trait bound `str: Clone` is not satisfied
         //~| the trait bound `str: Clone` is not satisfied
+        //~| the trait bound `str: Clone` is not satisfied
     }
 }
 

tests/ui/associated-types/hr-associated-type-bound-param-2.stderr

@@ -15,7 +15,7 @@ LL |     for<'b> <T as Z<'b, u16>>::W: Clone,
    |                                   ^^^^^ required by this bound in `Z`
 
 error[E0277]: the trait bound `str: Clone` is not satisfied
-  --> $DIR/hr-associated-type-bound-param-2.rs:17:14
+  --> $DIR/hr-associated-type-bound-param-2.rs:18:14
    |
 LL |     type W = str;
    |              ^^^ the trait `Clone` is not implemented for `str`
@@ -63,6 +63,22 @@ LL | {
 LL |     type W: ?Sized;
    |          - required by a bound in this associated type
 
+error[E0277]: the trait bound `str: Clone` is not satisfied
+  --> $DIR/hr-associated-type-bound-param-2.rs:10:9
+   |
+LL |         <T::W>::clone(x);
+   |         ^^^^^^^^^^^^^ the trait `Clone` is not implemented for `str`
+   |
+   = help: the trait `Clone` is implemented for `String`
+note: required by a bound in `Z`
+  --> $DIR/hr-associated-type-bound-param-2.rs:6:35
+   |
+LL | trait Z<'a, T: ?Sized>
+   |       - required by a bound in this trait
+...
+LL |     for<'b> <T as Z<'b, u16>>::W: Clone,
+   |                                   ^^^^^ required by this bound in `Z`
+
 error[E0277]: the trait bound `str: Clone` is not satisfied
   --> $DIR/hr-associated-type-bound-param-2.rs:10:9
    |
@@ -80,7 +96,7 @@ LL |     for<'b> <T as Z<'b, u16>>::W: Clone,
    |                                   ^^^^^ required by this bound in `Z`
 
 error[E0277]: the trait bound `str: Clone` is not satisfied
-  --> $DIR/hr-associated-type-bound-param-2.rs:22:10
+  --> $DIR/hr-associated-type-bound-param-2.rs:23:10
    |
 LL |     1u16.h("abc");
    |          ^ the trait `Clone` is not implemented for `str`
@@ -95,6 +111,6 @@ LL |     for<'b> <T as Z<'b, u16>>::W: Clone,
 LL |     fn h(&self, x: &T::W) {
    |        - required by a bound in this associated function
 
-error: aborting due to 6 previous errors
+error: aborting due to 7 previous errors
 
 For more information about this error, try `rustc --explain E0277`.

tests/ui/const-generics/defaults/doesnt_infer.stderr

@@ -2,15 +2,13 @@ error[E0284]: type annotations needed for `Foo<_>`
   --> $DIR/doesnt_infer.rs:13:9
    |
 LL |     let foo = Foo::foo();
-   |         ^^^   ---------- type must be known at this point
+   |         ^^^   --- type must be known at this point
    |
-note: required by a const generic parameter in `Foo::<N>::foo`
-  --> $DIR/doesnt_infer.rs:5:6
+note: required by a const generic parameter in `Foo`
+  --> $DIR/doesnt_infer.rs:3:12
    |
-LL | impl<const N: u32> Foo<N> {
-   |      ^^^^^^^^^^^^ required by this const generic parameter in `Foo::<N>::foo`
-LL |     fn foo() -> Self {
-   |        --- required by a bound in this associated function
+LL | struct Foo<const N: u32 = 2>;
+   |            ^^^^^^^^^^^^^^^^ required by this const generic parameter in `Foo`
 help: consider giving `foo` an explicit type, where the value of const parameter `N` is specified
    |
 LL |     let foo: Foo<N> = Foo::foo();
@@ -20,13 +18,15 @@ error[E0284]: type annotations needed for `Foo<_>`
   --> $DIR/doesnt_infer.rs:13:9
    |
 LL |     let foo = Foo::foo();
-   |         ^^^   --- type must be known at this point
+   |         ^^^   ---------- type must be known at this point
    |
-note: required by a const generic parameter in `Foo`
-  --> $DIR/doesnt_infer.rs:3:12
+note: required by a const generic parameter in `Foo::<N>::foo`
+  --> $DIR/doesnt_infer.rs:5:6
    |
-LL | struct Foo<const N: u32 = 2>;
-   |            ^^^^^^^^^^^^^^^^ required by this const generic parameter in `Foo`
+LL | impl<const N: u32> Foo<N> {
+   |      ^^^^^^^^^^^^ required by this const generic parameter in `Foo::<N>::foo`
+LL |     fn foo() -> Self {
+   |        --- required by a bound in this associated function
 help: consider giving `foo` an explicit type, where the value of const parameter `N` is specified
    |
 LL |     let foo: Foo<N> = Foo::foo();

tests/ui/const-generics/generic_arg_infer/issue-91614.stderr

@@ -2,9 +2,9 @@ error[E0284]: type annotations needed for `Mask<_, _>`
   --> $DIR/issue-91614.rs:6:9
    |
 LL |     let y = Mask::<_, _>::splat(false);
-   |         ^   -------------------------- type must be known at this point
+   |         ^   ------------ type must be known at this point
    |
-note: required by a const generic parameter in `Mask::<T, N>::splat`
+note: required by a const generic parameter in `Mask`
   --> $SRC_DIR/core/src/../../portable-simd/crates/core_simd/src/masks.rs:LL:COL
 help: consider giving `y` an explicit type, where the value of const parameter `N` is specified
    |
@@ -15,9 +15,9 @@ error[E0284]: type annotations needed for `Mask<_, _>`
   --> $DIR/issue-91614.rs:6:9
    |
 LL |     let y = Mask::<_, _>::splat(false);
-   |         ^   ------------ type must be known at this point
+   |         ^   -------------------------- type must be known at this point
    |
-note: required by a const generic parameter in `Mask`
+note: required by a const generic parameter in `Mask::<T, N>::splat`
   --> $SRC_DIR/core/src/../../portable-simd/crates/core_simd/src/masks.rs:LL:COL
 help: consider giving `y` an explicit type, where the value of const parameter `N` is specified
    |