Rollup merge of #151036 - issue-151026, r=mati865

Better handle when trying to iterate on a `Range` of a type that isn't `Step`

Mention when a trait bound corresponds to an unstable trait.

Mention `Range` when `Step` bound is unment, and explain that only some std types impl `Iterator` for `Range`.

CC #151026

Author: JonathanBrouwer

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

@@ -681,7 +681,7 @@ impl<'a, 'tcx> TypeErrCtxt<'a, 'tcx> {
                     // Ambiguous predicates should never error
                     | ty::PredicateKind::Ambiguous
                     // We never return Err when proving UnstableFeature goal.
-                    | ty::PredicateKind::Clause(ty::ClauseKind::UnstableFeature{ .. })
+                    | ty::PredicateKind::Clause(ty::ClauseKind::UnstableFeature { .. })
                     | ty::PredicateKind::NormalizesTo { .. }
                     | ty::PredicateKind::AliasRelate { .. }
                     | ty::PredicateKind::Clause(ty::ClauseKind::ConstArgHasType { .. }) => {

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

@@ -5550,7 +5550,14 @@ pub(super) fn get_explanation_based_on_obligation<'tcx>(
         };
         if let ty::PredicatePolarity::Positive = trait_predicate.polarity() {
             format!(
-                "{pre_message}the trait `{}` is not implemented for{desc} `{}`",
+                "{pre_message}the {}trait `{}` is not implemented for{desc} `{}`",
+                if tcx.lookup_stability(trait_predicate.def_id()).map(|s| s.level.is_stable())
+                    == Some(false)
+                {
+                    "nightly-only, unstable "
+                } else {
+                    ""
+                },
                 trait_predicate.print_modifiers_and_trait_path(),
                 tcx.short_string(trait_predicate.self_ty().skip_binder(), long_ty_path),
             )

library/core/src/iter/range.rs

@@ -21,6 +21,13 @@ unsafe_impl_trusted_step![AsciiChar char i8 i16 i32 i64 i128 isize u8 u16 u32 u6
 /// The *successor* operation moves towards values that compare greater.
 /// The *predecessor* operation moves towards values that compare lesser.
 #[rustc_diagnostic_item = "range_step"]
+#[rustc_on_unimplemented(
+    message = "`std::ops::Range<{Self}>` is not an iterator",
+    label = "`Range<{Self}>` is not an iterator",
+    note = "`Range` only implements `Iterator` for select types in the standard library, \
+            particularly integers; to see the full list of types, see the documentation for the \
+            unstable `Step` trait"
+)]
 #[unstable(feature = "step_trait", issue = "42168")]
 pub trait Step: Clone + PartialOrd + Sized {
     /// Returns the bounds on the number of *successor* steps required to get from `start` to `end`

tests/run-make/missing-unstable-trait-bound/missing-bound.stderr

@@ -1,9 +1,10 @@
-error[E0277]: the trait bound `T: Step` is not satisfied
+error[E0277]: `std::ops::Range<T>` is not an iterator
  --> missing-bound.rs:2:14
   |
 2 |     for _ in t {}
-  |              ^ the trait `Step` is not implemented for `T`
+  |              ^ `Range<T>` is not an iterator
   |
+  = note: `Range` only implements `Iterator` for select types in the standard library, particularly integers; to see the full list of types, see the documentation for the unstable `Step` trait
   = note: required for `std::ops::Range<T>` to implement `Iterator`
   = note: required for `std::ops::Range<T>` to implement `IntoIterator`
 

tests/ui-fulldeps/rustc-dev-remap.only-remap.stderr

@@ -4,7 +4,7 @@ error[E0277]: the trait bound `NotAValidResultType: VisitorResult` is not satisf
 LL |     type Result = NotAValidResultType;
    |                   ^^^^^^^^^^^^^^^^^^^ unsatisfied trait bound
    |
-help: the trait `VisitorResult` is not implemented for `NotAValidResultType`
+help: the nightly-only, unstable trait `VisitorResult` is not implemented for `NotAValidResultType`
   --> $DIR/rustc-dev-remap.rs:LL:COL
    |
 LL | struct NotAValidResultType;

tests/ui-fulldeps/rustc-dev-remap.remap-unremap.stderr

@@ -4,7 +4,7 @@ error[E0277]: the trait bound `NotAValidResultType: VisitorResult` is not satisf
 LL |     type Result = NotAValidResultType;
    |                   ^^^^^^^^^^^^^^^^^^^ unsatisfied trait bound
    |
-help: the trait `VisitorResult` is not implemented for `NotAValidResultType`
+help: the nightly-only, unstable trait `VisitorResult` is not implemented for `NotAValidResultType`
   --> $DIR/rustc-dev-remap.rs:LL:COL
    |
 LL | struct NotAValidResultType;

tests/ui-fulldeps/session-diagnostic/diagnostic-derive-doc-comment-field.stderr

@@ -7,7 +7,7 @@ LL | #[derive(Diagnostic)]
 LL |     arg: NotIntoDiagArg,
    |          ^^^^^^^^^^^^^^ unsatisfied trait bound
    |
-help: the trait `IntoDiagArg` is not implemented for `NotIntoDiagArg`
+help: the nightly-only, unstable trait `IntoDiagArg` is not implemented for `NotIntoDiagArg`
   --> $DIR/diagnostic-derive-doc-comment-field.rs:28:1
    |
 LL | struct NotIntoDiagArg;
@@ -29,7 +29,7 @@ LL | #[derive(Subdiagnostic)]
 LL |     arg: NotIntoDiagArg,
    |          ^^^^^^^^^^^^^^ unsatisfied trait bound
    |
-help: the trait `IntoDiagArg` is not implemented for `NotIntoDiagArg`
+help: the nightly-only, unstable trait `IntoDiagArg` is not implemented for `NotIntoDiagArg`
   --> $DIR/diagnostic-derive-doc-comment-field.rs:28:1
    |
 LL | struct NotIntoDiagArg;

tests/ui-fulldeps/session-diagnostic/diagnostic-derive.stderr

@@ -657,7 +657,7 @@ LL | #[derive(Diagnostic)]
 LL |     other: Hello,
    |            ^^^^^ unsatisfied trait bound
    |
-help: the trait `IntoDiagArg` is not implemented for `Hello`
+help: the nightly-only, unstable trait `IntoDiagArg` is not implemented for `Hello`
   --> $DIR/diagnostic-derive.rs:40:1
    |
 LL | struct Hello {}

tests/ui/abi/issues/issue-22565-rust-call.stderr

@@ -2,7 +2,7 @@ error[E0277]: functions with the "rust-call" ABI must take a single non-self tup
   --> $DIR/issue-22565-rust-call.rs:3:1
    |
 LL | extern "rust-call" fn b(_i: i32) {}
-   | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ the trait `std::marker::Tuple` is not implemented for `i32`
+   | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ the nightly-only, unstable trait `std::marker::Tuple` is not implemented for `i32`
 
 error: functions with the "rust-call" ABI must take a single non-self tuple argument
   --> $DIR/issue-22565-rust-call.rs:17:5
@@ -32,7 +32,7 @@ error[E0277]: functions with the "rust-call" ABI must take a single non-self tup
   --> $DIR/issue-22565-rust-call.rs:27:7
    |
 LL |     b(10);
-   |       ^^ the trait `std::marker::Tuple` is not implemented for `i32`
+   |       ^^ the nightly-only, unstable trait `std::marker::Tuple` is not implemented for `i32`
 
 error: functions with the "rust-call" ABI must take a single non-self tuple argument
   --> $DIR/issue-22565-rust-call.rs:29:5

tests/ui/async-await/coroutine-not-future.stderr

@@ -2,7 +2,7 @@ error[E0277]: the trait bound `impl Future<Output = ()>: Coroutine<_>` is not sa
   --> $DIR/coroutine-not-future.rs:36:21
    |
 LL |     takes_coroutine(async_fn());
-   |     --------------- ^^^^^^^^^^ the trait `Coroutine<_>` is not implemented for `impl Future<Output = ()>`
+   |     --------------- ^^^^^^^^^^ the nightly-only, unstable trait `Coroutine<_>` is not implemented for `impl Future<Output = ()>`
    |     |
    |     required by a bound introduced by this call
    |
@@ -16,7 +16,7 @@ error[E0277]: the trait bound `impl Future<Output = ()>: Coroutine<_>` is not sa
   --> $DIR/coroutine-not-future.rs:38:21
    |
 LL |     takes_coroutine(returns_async_block());
-   |     --------------- ^^^^^^^^^^^^^^^^^^^^^ the trait `Coroutine<_>` is not implemented for `impl Future<Output = ()>`
+   |     --------------- ^^^^^^^^^^^^^^^^^^^^^ the nightly-only, unstable trait `Coroutine<_>` is not implemented for `impl Future<Output = ()>`
    |     |
    |     required by a bound introduced by this call
    |
@@ -30,7 +30,7 @@ error[E0277]: the trait bound `{async block@$DIR/coroutine-not-future.rs:40:21:
   --> $DIR/coroutine-not-future.rs:40:21
    |
 LL |     takes_coroutine(async {});
-   |     --------------- ^^^^^^^^ the trait `Coroutine<_>` is not implemented for `{async block@$DIR/coroutine-not-future.rs:40:21: 40:26}`
+   |     --------------- ^^^^^^^^ the nightly-only, unstable trait `Coroutine<_>` is not implemented for `{async block@$DIR/coroutine-not-future.rs:40:21: 40:26}`
    |     |
    |     required by a bound introduced by this call
    |