Rollup merge of #115629 - compiler-errors:sugg-deref-unsize, r=oli-obk

Don't suggest dereferencing to unsized type

Rudimentary check that the self type is Sized. I don't really like any of this diagnostics code -- it's really messy and also really prone to false positives and negatives, but oh well.

Fixes #115569

23 files changed, 61 insertions, 14 deletions

diff --git a/compiler/rustc_middle/src/ty/print/pretty.rs b/compiler/rustc_middle/src/ty/print/pretty.rs
index 7191ed7a0f6..12254ed1a4d 100644
--- a/compiler/rustc_middle/src/ty/print/pretty.rs
+++ b/compiler/rustc_middle/src/ty/print/pretty.rs
@@ -1250,21 +1250,18 @@ pub trait PrettyPrinter<'tcx>:
                         .generics_of(principal.def_id)
                         .own_args_no_defaults(cx.tcx(), principal.args);
 
-                    let mut projections = predicates.projection_bounds();
-
-                    let mut args = args.iter().cloned();
-                    let arg0 = args.next();
-                    let projection0 = projections.next();
-                    if arg0.is_some() || projection0.is_some() {
-                        let args = arg0.into_iter().chain(args);
-                        let projections = projection0.into_iter().chain(projections);
+                    let mut projections: Vec<_> = predicates.projection_bounds().collect();
+                    projections.sort_by_cached_key(|proj| {
+                        cx.tcx().item_name(proj.item_def_id()).to_string()
+                    });
 
+                    if !args.is_empty() || !projections.is_empty() {
                         p!(generic_delimiters(|mut cx| {
-                            cx = cx.comma_sep(args)?;
-                            if arg0.is_some() && projection0.is_some() {
+                            cx = cx.comma_sep(args.iter().copied())?;
+                            if !args.is_empty() && !projections.is_empty() {
                                 write!(cx, ", ")?;
                             }
-                            cx.comma_sep(projections)
+                            cx.comma_sep(projections.iter().copied())
                         }));
                     }
                 }
diff --git a/compiler/rustc_trait_selection/src/traits/error_reporting/suggestions.rs b/compiler/rustc_trait_selection/src/traits/error_reporting/suggestions.rs
index 611ec6b00ef..32fb10ce4a6 100644
--- a/compiler/rustc_trait_selection/src/traits/error_reporting/suggestions.rs
+++ b/compiler/rustc_trait_selection/src/traits/error_reporting/suggestions.rs
@@ -838,7 +838,20 @@ impl<'tcx> TypeErrCtxtExt<'tcx> for TypeErrCtxt<'_, 'tcx> {
                         obligation.param_env,
                         real_trait_pred_and_base_ty,
                     );
-                    if self.predicate_may_hold(&obligation) {
+                    let sized_obligation = Obligation::new(
+                        self.tcx,
+                        obligation.cause.clone(),
+                        obligation.param_env,
+                        ty::TraitRef::from_lang_item(
+                            self.tcx,
+                            hir::LangItem::Sized,
+                            obligation.cause.span,
+                            [base_ty],
+                        ),
+                    );
+                    if self.predicate_may_hold(&obligation)
+                        && self.predicate_must_hold_modulo_regions(&sized_obligation)
+                    {
                         let call_node = self.tcx.hir().get(*call_hir_id);
                         let msg = "consider dereferencing here";
                         let is_receiver = matches!(
diff --git a/tests/ui/traits/object/enforce-supertrait-projection.rs b/tests/ui/traits/object/enforce-supertrait-projection.rs
index 2c9b41eea2a..0ea944ec2df 100644
--- a/tests/ui/traits/object/enforce-supertrait-projection.rs
+++ b/tests/ui/traits/object/enforce-supertrait-projection.rs
@@ -7,7 +7,7 @@ trait Trait: SuperTrait<A = <Self as SuperTrait>::B> {}
 
 fn transmute<A, B>(x: A) -> B {
     foo::<A, B, dyn Trait<A = A, B = B>>(x)
-    //~^ ERROR type mismatch resolving `<dyn Trait<B = B, A = A> as SuperTrait>::A == B`
+    //~^ ERROR type mismatch resolving `<dyn Trait<A = A, B = B> as SuperTrait>::A == B`
 }
 
 fn foo<A, B, T: ?Sized>(x: T::A) -> B
diff --git a/tests/ui/traits/object/enforce-supertrait-projection.stderr b/tests/ui/traits/object/enforce-supertrait-projection.stderr
index 848b4e69a4b..2fb94d34896 100644
--- a/tests/ui/traits/object/enforce-supertrait-projection.stderr
+++ b/tests/ui/traits/object/enforce-supertrait-projection.stderr
@@ -1,4 +1,4 @@
-error[E0271]: type mismatch resolving `<dyn Trait<B = B, A = A> as SuperTrait>::A == B`
+error[E0271]: type mismatch resolving `<dyn Trait<A = A, B = B> as SuperTrait>::A == B`
   --> $DIR/enforce-supertrait-projection.rs:9:17
    |
 LL | fn transmute<A, B>(x: A) -> B {
diff --git a/tests/ui/traits/suggest-dereferences/dont-suggest-unsize-deref.rs b/tests/ui/traits/suggest-dereferences/dont-suggest-unsize-deref.rs
new file mode 100644
index 00000000000..c6f9e345618
--- /dev/null
+++ b/tests/ui/traits/suggest-dereferences/dont-suggest-unsize-deref.rs
@@ -0,0 +1,15 @@
+fn use_iterator<I>(itr: I)
+where
+    I: IntoIterator<Item = i32>,
+{
+}
+
+fn pass_iterator<I>(i: &dyn IntoIterator<Item = i32, IntoIter = I>)
+where
+    I: Iterator<Item = i32>,
+{
+    use_iterator(i);
+    //~^ ERROR `&dyn IntoIterator<IntoIter = I, Item = i32>` is not an iterator
+}
+
+fn main() {}
diff --git a/tests/ui/traits/suggest-dereferences/dont-suggest-unsize-deref.stderr b/tests/ui/traits/suggest-dereferences/dont-suggest-unsize-deref.stderr
new file mode 100644
index 00000000000..bd0e7ca2c02
--- /dev/null
+++ b/tests/ui/traits/suggest-dereferences/dont-suggest-unsize-deref.stderr
@@ -0,0 +1,22 @@
+error[E0277]: `&dyn IntoIterator<IntoIter = I, Item = i32>` is not an iterator
+  --> $DIR/dont-suggest-unsize-deref.rs:11:18
+   |
+LL |     use_iterator(i);
+   |     ------------ ^ `&dyn IntoIterator<IntoIter = I, Item = i32>` is not an iterator
+   |     |
+   |     required by a bound introduced by this call
+   |
+   = help: the trait `Iterator` is not implemented for `&dyn IntoIterator<IntoIter = I, Item = i32>`
+   = note: required for `&dyn IntoIterator<IntoIter = I, Item = i32>` to implement `IntoIterator`
+note: required by a bound in `use_iterator`
+  --> $DIR/dont-suggest-unsize-deref.rs:3:8
+   |
+LL | fn use_iterator<I>(itr: I)
+   |    ------------ required by a bound in this function
+LL | where
+LL |     I: IntoIterator<Item = i32>,
+   |        ^^^^^^^^^^^^^^^^^^^^^^^^ required by this bound in `use_iterator`
+
+error: aborting due to previous error
+
+For more information about this error, try `rustc --explain E0277`.
diff --git a/tests/ui/traits/suggest-deferences/issue-39029.fixed b/tests/ui/traits/suggest-dereferences/issue-39029.fixed
index a1abf668b8b..a1abf668b8b 100644
--- a/tests/ui/traits/suggest-deferences/issue-39029.fixed
+++ b/tests/ui/traits/suggest-dereferences/issue-39029.fixed
diff --git a/tests/ui/traits/suggest-deferences/issue-39029.rs b/tests/ui/traits/suggest-dereferences/issue-39029.rs
index 90d097105ed..90d097105ed 100644
--- a/tests/ui/traits/suggest-deferences/issue-39029.rs
+++ b/tests/ui/traits/suggest-dereferences/issue-39029.rs
diff --git a/tests/ui/traits/suggest-deferences/issue-39029.stderr b/tests/ui/traits/suggest-dereferences/issue-39029.stderr
index 49105de3d69..49105de3d69 100644
--- a/tests/ui/traits/suggest-deferences/issue-39029.stderr
+++ b/tests/ui/traits/suggest-dereferences/issue-39029.stderr
diff --git a/tests/ui/traits/suggest-deferences/issue-62530.fixed b/tests/ui/traits/suggest-dereferences/issue-62530.fixed
index 406caaa007f..406caaa007f 100644
--- a/tests/ui/traits/suggest-deferences/issue-62530.fixed
+++ b/tests/ui/traits/suggest-dereferences/issue-62530.fixed
diff --git a/tests/ui/traits/suggest-deferences/issue-62530.rs b/tests/ui/traits/suggest-dereferences/issue-62530.rs
index 53846be7306..53846be7306 100644
--- a/tests/ui/traits/suggest-deferences/issue-62530.rs
+++ b/tests/ui/traits/suggest-dereferences/issue-62530.rs
diff --git a/tests/ui/traits/suggest-deferences/issue-62530.stderr b/tests/ui/traits/suggest-dereferences/issue-62530.stderr
index e47ae0b65af..e47ae0b65af 100644
--- a/tests/ui/traits/suggest-deferences/issue-62530.stderr
+++ b/tests/ui/traits/suggest-dereferences/issue-62530.stderr
diff --git a/tests/ui/traits/suggest-deferences/multiple-0.fixed b/tests/ui/traits/suggest-dereferences/multiple-0.fixed
index b7160b75c60..b7160b75c60 100644
--- a/tests/ui/traits/suggest-deferences/multiple-0.fixed
+++ b/tests/ui/traits/suggest-dereferences/multiple-0.fixed
diff --git a/tests/ui/traits/suggest-deferences/multiple-0.rs b/tests/ui/traits/suggest-dereferences/multiple-0.rs
index 9ac55177ffa..9ac55177ffa 100644
--- a/tests/ui/traits/suggest-deferences/multiple-0.rs
+++ b/tests/ui/traits/suggest-dereferences/multiple-0.rs
diff --git a/tests/ui/traits/suggest-deferences/multiple-0.stderr b/tests/ui/traits/suggest-dereferences/multiple-0.stderr
index 6a4d4b8d521..6a4d4b8d521 100644
--- a/tests/ui/traits/suggest-deferences/multiple-0.stderr
+++ b/tests/ui/traits/suggest-dereferences/multiple-0.stderr
diff --git a/tests/ui/traits/suggest-deferences/multiple-1.rs b/tests/ui/traits/suggest-dereferences/multiple-1.rs
index 91c6c7924a4..91c6c7924a4 100644
--- a/tests/ui/traits/suggest-deferences/multiple-1.rs
+++ b/tests/ui/traits/suggest-dereferences/multiple-1.rs
diff --git a/tests/ui/traits/suggest-deferences/multiple-1.stderr b/tests/ui/traits/suggest-dereferences/multiple-1.stderr
index 6e12321c233..6e12321c233 100644
--- a/tests/ui/traits/suggest-deferences/multiple-1.stderr
+++ b/tests/ui/traits/suggest-dereferences/multiple-1.stderr
diff --git a/tests/ui/traits/suggest-deferences/root-obligation.fixed b/tests/ui/traits/suggest-dereferences/root-obligation.fixed
index 7a8433f9057..7a8433f9057 100644
--- a/tests/ui/traits/suggest-deferences/root-obligation.fixed
+++ b/tests/ui/traits/suggest-dereferences/root-obligation.fixed
diff --git a/tests/ui/traits/suggest-deferences/root-obligation.rs b/tests/ui/traits/suggest-dereferences/root-obligation.rs
index 51bac2107e3..51bac2107e3 100644
--- a/tests/ui/traits/suggest-deferences/root-obligation.rs
+++ b/tests/ui/traits/suggest-dereferences/root-obligation.rs
diff --git a/tests/ui/traits/suggest-deferences/root-obligation.stderr b/tests/ui/traits/suggest-dereferences/root-obligation.stderr
index 1363fb8c47a..1363fb8c47a 100644
--- a/tests/ui/traits/suggest-deferences/root-obligation.stderr
+++ b/tests/ui/traits/suggest-dereferences/root-obligation.stderr
diff --git a/tests/ui/traits/suggest-deferences/suggest-dereferencing-receiver-argument.fixed b/tests/ui/traits/suggest-dereferences/suggest-dereferencing-receiver-argument.fixed
index ea3d1bf853a..ea3d1bf853a 100644
--- a/tests/ui/traits/suggest-deferences/suggest-dereferencing-receiver-argument.fixed
+++ b/tests/ui/traits/suggest-dereferences/suggest-dereferencing-receiver-argument.fixed
diff --git a/tests/ui/traits/suggest-deferences/suggest-dereferencing-receiver-argument.rs b/tests/ui/traits/suggest-dereferences/suggest-dereferencing-receiver-argument.rs
index 9eda68027b2..9eda68027b2 100644
--- a/tests/ui/traits/suggest-deferences/suggest-dereferencing-receiver-argument.rs
+++ b/tests/ui/traits/suggest-dereferences/suggest-dereferencing-receiver-argument.rs
diff --git a/tests/ui/traits/suggest-deferences/suggest-dereferencing-receiver-argument.stderr b/tests/ui/traits/suggest-dereferences/suggest-dereferencing-receiver-argument.stderr
index ede31a2c7bc..ede31a2c7bc 100644
--- a/tests/ui/traits/suggest-deferences/suggest-dereferencing-receiver-argument.stderr
+++ b/tests/ui/traits/suggest-dereferences/suggest-dereferencing-receiver-argument.stderr