Show source of ambiguity in a few more places

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

@@ -2020,7 +2020,7 @@ impl<'a, 'tcx> InferCtxtPrivExt<'a, 'tcx> for InferCtxt<'a, 'tcx> {
                     subst,
                     impl_candidates,
                     ErrorCode::E0283,
-                    false,
+                    true,
                 );
 
                 let obligation = Obligation::new(
@@ -2132,7 +2132,7 @@ impl<'a, 'tcx> InferCtxtPrivExt<'a, 'tcx> for InferCtxt<'a, 'tcx> {
                     a.into(),
                     vec![],
                     ErrorCode::E0282,
-                    false,
+                    true,
                 )
             }
             ty::PredicateKind::Projection(data) => {
@@ -2149,7 +2149,7 @@ impl<'a, 'tcx> InferCtxtPrivExt<'a, 'tcx> for InferCtxt<'a, 'tcx> {
                         self_ty.into(),
                         vec![],
                         ErrorCode::E0284,
-                        false,
+                        true,
                     );
                     err.note(&format!("cannot satisfy `{}`", predicate));
                     err

src/test/ui/const-generics/generic_arg_infer/issue-91614.stderr

@@ -2,7 +2,7 @@ error[E0283]: type annotations needed for `Mask<_, LANES>`
   --> $DIR/issue-91614.rs:6:9
    |
 LL |     let y = Mask::<_, _>::splat(false);
-   |         ^
+   |         ^   ------------------- type must be known at this point
    |
    = note: cannot satisfy `_: MaskElement`
 note: required by a bound in `Mask::<T, LANES>::splat`

src/test/ui/inference/cannot-infer-partial-try-return.stderr

@@ -3,6 +3,9 @@ error[E0282]: type annotations needed for `Result<(), QualifiedError<_>>`
    |
 LL |     let x = || -> Result<_, QualifiedError<_>> {
    |             ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+LL |
+LL |         infallible()?;
+   |         ------------- type must be known at this point
    |
 help: try giving this closure an explicit return type
    |

src/test/ui/inference/erase-type-params-in-label.stderr

@@ -2,7 +2,7 @@ error[E0283]: type annotations needed for `Foo<i32, &str, W, Z>`
   --> $DIR/erase-type-params-in-label.rs:2:9
    |
 LL |     let foo = foo(1, "");
-   |         ^^^
+   |         ^^^   --- type must be known at this point
    |
    = note: cannot satisfy `_: Default`
 note: required by a bound in `foo`
@@ -23,7 +23,7 @@ error[E0283]: type annotations needed for `Bar<i32, &str, Z>`
   --> $DIR/erase-type-params-in-label.rs:5:9
    |
 LL |     let bar = bar(1, "");
-   |         ^^^
+   |         ^^^   --- type must be known at this point
    |
    = note: cannot satisfy `_: Default`
 note: required by a bound in `bar`

src/test/ui/inference/issue-72616.stderr

@@ -2,7 +2,9 @@ error[E0283]: type annotations needed
   --> $DIR/issue-72616.rs:20:37
    |
 LL |         if String::from("a") == "a".try_into().unwrap() {}
-   |                                     ^^^^^^^^
+   |                              --     ^^^^^^^^
+   |                              |
+   |                              type must be known at this point
    |
    = note: multiple `impl`s satisfying `String: PartialEq<_>` found in the `alloc` crate:
            - impl PartialEq for String;

src/test/ui/inference/issue-72690.stderr

@@ -55,7 +55,7 @@ error[E0283]: type annotations needed for `&T`
   --> $DIR/issue-72690.rs:17:9
    |
 LL |     let _ = "x".as_ref();
-   |         ^
+   |         ^       ------ type must be known at this point
    |
    = note: multiple `impl`s satisfying `str: AsRef<_>` found in the following crates: `core`, `std`:
            - impl AsRef<OsStr> for str;

src/test/ui/inference/issue-86162-1.stderr

@@ -2,7 +2,9 @@ error[E0283]: type annotations needed
   --> $DIR/issue-86162-1.rs:7:9
    |
 LL |     foo(gen()); //<- Do not suggest `foo::<impl Clone>()`!
-   |         ^^^ cannot infer type of the type parameter `T` declared on the function `gen`
+   |     --- ^^^ cannot infer type of the type parameter `T` declared on the function `gen`
+   |     |
+   |     type must be known at this point
    |
    = note: cannot satisfy `_: Clone`
 note: required by a bound in `foo`

src/test/ui/inference/issue-86162-2.stderr

@@ -2,7 +2,9 @@ error[E0283]: type annotations needed
   --> $DIR/issue-86162-2.rs:12:14
    |
 LL |     Foo::bar(gen()); //<- Do not suggest `Foo::bar::<impl Clone>()`!
-   |              ^^^ cannot infer type of the type parameter `T` declared on the function `gen`
+   |     -------- ^^^ cannot infer type of the type parameter `T` declared on the function `gen`
+   |     |
+   |     type must be known at this point
    |
    = note: cannot satisfy `_: Clone`
 note: required by a bound in `Foo::bar`

src/test/ui/issues/issue-69455.stderr

@@ -14,7 +14,9 @@ error[E0283]: type annotations needed
   --> $DIR/issue-69455.rs:29:41
    |
 LL |     println!("{}", 23u64.test(xs.iter().sum()));
-   |                                         ^^^ cannot infer type of the type parameter `S` declared on the associated function `sum`
+   |                          ----           ^^^ cannot infer type of the type parameter `S` declared on the associated function `sum`
+   |                          |
+   |                          type must be known at this point
    |
 note: multiple `impl`s satisfying `u64: Test<_>` found
   --> $DIR/issue-69455.rs:11:1

src/test/ui/issues/issue-7813.stderr

@@ -2,7 +2,7 @@ error[E0282]: type annotations needed for `&[_; 0]`
   --> $DIR/issue-7813.rs:2:9
    |
 LL |     let v = &[];
-   |         ^
+   |         ^   --- type must be known at this point
    |
 help: consider giving `v` an explicit type, where the placeholders `_` are specified
    |

src/test/ui/suggestions/suggest-closure-return-type-1.stderr

@@ -2,7 +2,7 @@ error[E0282]: type annotations needed for `[_; 0]`
   --> $DIR/suggest-closure-return-type-1.rs:4:18
    |
 LL |     unbound_drop(|| -> _ { [] });
-   |                  ^^^^^^^
+   |                  ^^^^^^^   -- type must be known at this point
    |
 help: try giving this closure an explicit return type
    |

src/test/ui/suggestions/suggest-closure-return-type-2.stderr

@@ -2,7 +2,7 @@ error[E0282]: type annotations needed for `[_; 0]`
   --> $DIR/suggest-closure-return-type-2.rs:4:18
    |
 LL |     unbound_drop(|| { [] })
-   |                  ^^
+   |                  ^^   -- type must be known at this point
    |
 help: try giving this closure an explicit return type
    |

src/test/ui/suggestions/suggest-closure-return-type-3.stderr

@@ -2,7 +2,7 @@ error[E0282]: type annotations needed for `[_; 0]`
   --> $DIR/suggest-closure-return-type-3.rs:4:18
    |
 LL |     unbound_drop(|| []);
-   |                  ^^
+   |                  ^^ -- type must be known at this point
    |
 help: try giving this closure an explicit return type
    |

src/test/ui/traits/issue-77982.stderr

@@ -26,7 +26,9 @@ error[E0283]: type annotations needed
   --> $DIR/issue-77982.rs:8:10
    |
 LL |     opts.get(opt.as_ref());
-   |          ^^^ cannot infer type of the type parameter `Q` declared on the associated function `get`
+   |          ^^^     ------ type must be known at this point
+   |          |
+   |          cannot infer type of the type parameter `Q` declared on the associated function `get`
    |
    = note: multiple `impl`s satisfying `String: AsRef<_>` found in the following crates: `alloc`, `std`:
            - impl AsRef<OsStr> for String;
@@ -42,7 +44,9 @@ error[E0283]: type annotations needed
   --> $DIR/issue-77982.rs:13:59
    |
 LL |     let ips: Vec<_> = (0..100_000).map(|_| u32::from(0u32.into())).collect();
-   |                                                           ^^^^
+   |                                            ---------      ^^^^
+   |                                            |
+   |                                            type must be known at this point
    |
    = note: multiple `impl`s satisfying `u32: From<_>` found in the following crates: `core`, `std`:
            - impl From<Ipv4Addr> for u32;
@@ -59,7 +63,7 @@ error[E0283]: type annotations needed for `Box<T>`
   --> $DIR/issue-77982.rs:36:9
    |
 LL |     let _ = ().foo();
-   |         ^
+   |         ^      --- type must be known at this point
    |
 note: multiple `impl`s satisfying `(): Foo<'_, _>` found
   --> $DIR/issue-77982.rs:29:1
@@ -77,7 +81,7 @@ error[E0283]: type annotations needed for `Box<T>`
   --> $DIR/issue-77982.rs:40:9
    |
 LL |     let _ = (&()).bar();
-   |         ^
+   |         ^         --- type must be known at this point
    |
 note: multiple `impl`s satisfying `&(): Bar<'_, _>` found
   --> $DIR/issue-77982.rs:32:1

src/test/ui/type/type-check/cannot_infer_local_or_array.stderr

@@ -2,7 +2,7 @@ error[E0282]: type annotations needed for `[_; 0]`
   --> $DIR/cannot_infer_local_or_array.rs:2:9
    |
 LL |     let x = [];
-   |         ^
+   |         ^   -- type must be known at this point
    |
 help: consider giving `x` an explicit type, where the placeholders `_` are specified
    |