Deprioritize fulfillment errors that come from expansions.

Author: m-ou-se

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

@@ -453,9 +453,11 @@ impl<'tcx> TypeErrCtxtExt<'tcx> for TypeErrCtxt<'_, 'tcx> {
             }
         }
 
-        for (error, suppressed) in iter::zip(errors, is_suppressed) {
-            if !suppressed {
-                self.report_fulfillment_error(error, body_id);
+        for from_expansion in [false, true] {
+            for (error, suppressed) in iter::zip(errors, &is_suppressed) {
+                if !suppressed && error.obligation.cause.span.from_expansion() == from_expansion {
+                    self.report_fulfillment_error(error, body_id);
+                }
             }
         }
 

tests/ui/inference/cannot-infer-partial-try-return.stderr

@@ -1,8 +1,6 @@
 error[E0282]: type annotations needed
   --> $DIR/cannot-infer-partial-try-return.rs:20:9
    |
-LL |         infallible()?;
-   |         ------------- type must be known at this point
 LL |         Ok(())
    |         ^^ cannot infer type of the type parameter `E` declared on the enum `Result`
    |

tests/ui/inference/question-mark-type-infer.stderr

@@ -1,8 +1,13 @@
 error[E0282]: type annotations needed
-  --> $DIR/question-mark-type-infer.rs:10:30
+  --> $DIR/question-mark-type-infer.rs:10:21
    |
 LL |     l.iter().map(f).collect()?
-   |                              ^ cannot infer type
+   |                     ^^^^^^^ cannot infer type of the type parameter `B` declared on the associated function `collect`
+   |
+help: consider specifying the generic argument
+   |
+LL |     l.iter().map(f).collect::<Vec<_>>()?
+   |                            ++++++++++
 
 error: aborting due to previous error
 

tests/ui/issues/issue-69455.stderr

@@ -1,14 +1,16 @@
-error[E0282]: type annotations needed
-  --> $DIR/issue-69455.rs:29:20
+error[E0284]: type annotations needed
+  --> $DIR/issue-69455.rs:29:41
    |
 LL |     println!("{}", 23u64.test(xs.iter().sum()));
-   |                    ^^^^^^^^^^^^^^^^^^^^^^^^^^^ cannot infer type of the type parameter `T` declared on the associated function `new_display`
+   |                          ----           ^^^ cannot infer type of the type parameter `S` declared on the associated function `sum`
+   |                          |
+   |                          type must be known at this point
    |
-   = note: this error originates in the macro `$crate::format_args_nl` which comes from the expansion of the macro `println` (in Nightly builds, run with -Z macro-backtrace for more info)
+   = note: cannot satisfy `<u64 as Test<_>>::Output == _`
 help: consider specifying the generic argument
    |
-LL |     println!("{}", 23u64.test(xs.iter().sum())::<T>);
-   |                                               +++++
+LL |     println!("{}", 23u64.test(xs.iter().sum::<S>()));
+   |                                            +++++
 
 error[E0283]: type annotations needed
   --> $DIR/issue-69455.rs:29:41
@@ -33,5 +35,5 @@ LL |     println!("{}", 23u64.test(xs.iter().sum::<S>()));
 
 error: aborting due to 2 previous errors
 
-Some errors have detailed explanations: E0282, E0283.
-For more information about an error, try `rustc --explain E0282`.
+Some errors have detailed explanations: E0283, E0284.
+For more information about an error, try `rustc --explain E0283`.

tests/ui/type/type-check/cannot_infer_local_or_vec_in_tuples.stderr

@@ -2,7 +2,7 @@ error[E0282]: type annotations needed for `(Vec<T>,)`
   --> $DIR/cannot_infer_local_or_vec_in_tuples.rs:2:9
    |
 LL |     let (x, ) = (vec![], );
-   |         ^^^^^
+   |         ^^^^^   ---------- type must be known at this point
    |
 help: consider giving this pattern a type, where the type for type parameter `T` is specified
    |