Add tests and tweak error message for dyn

Author: Jules-Bertholet

compiler/rustc_hir_analysis/src/hir_ty_lowering/dyn_compatibility.rs

@@ -151,10 +151,7 @@ impl<'tcx> dyn HirTyLowerer<'tcx> + '_ {
                 self.dcx()
                     .struct_span_err(
                         span,
-                        format!(
-                            "conflicting associated type bounds for `{item}` when \
-                            expanding trait alias"
-                        ),
+                        format!("conflicting associated type bounds for `{item}`"),
                     )
                     .with_span_label(
                         old_proj_span,

tests/ui/associated-type-bounds/duplicate.rs

@@ -224,6 +224,16 @@ fn uncallable_rtn(_: impl Trait<foo(..): Trait<ASSOC = 3>, foo(..): Trait<ASSOC
 
 fn callable_rtn(_: impl Trait<foo(..): Send, foo(..): Send, foo(..): Eq>) {}
 
+type Works = dyn Iterator<Item = i32, Item = i32>;
+// ^~ ERROR conflicting associated type bounds
+
+trait Trait2 {
+    const ASSOC: u32;
+}
+
+type AlsoWorks = dyn Trait2<ASSOC = 3u32, ASSOC = 3u32>;
+// ^~ ERROR conflicting associated type bounds
+
 fn main() {
     callable(iter::empty::<i32>());
     callable_const(());

tests/ui/associated-type-bounds/duplicate_err.rs

@@ -70,6 +70,16 @@ fn uncallable_const(_: impl Trait<ASSOC = 3, ASSOC = 4>) {}
 
 fn uncallable_rtn(_: impl Trait<foo(..): Trait<ASSOC = 3>, foo(..): Trait<ASSOC = 4>>) {}
 
+type MustFail = dyn Iterator<Item = i32, Item = u32>;
+//~^ ERROR conflicting associated type bounds
+
+trait Trait2 {
+    const ASSOC: u32;
+}
+
+type MustFail2 = dyn Trait2<ASSOC = 3u32, ASSOC = 4u32>;
+//~^ ERROR conflicting associated type bounds
+
 fn main() {
     uncallable(iter::empty::<u32>()); //~ ERROR [E0271]
     uncallable(iter::empty::<i32>()); //~ ERROR [E0271]

tests/ui/associated-type-bounds/duplicate_err.stderr

@@ -97,8 +97,26 @@ LL | fn mismatch_2() -> impl Iterator<Item: Copy, Item: Send> {
 LL |     iter::empty::<String>()
    |     ----------------------- return type was inferred to be `std::iter::Empty<String>` here
 
+error: conflicting associated type bounds for `Item`
+  --> $DIR/duplicate_err.rs:73:17
+   |
+LL | type MustFail = dyn Iterator<Item = i32, Item = u32>;
+   |                 ^^^^^^^^^^^^^----------^^----------^
+   |                              |           |
+   |                              |           `Item` is specified to be `u32` here
+   |                              `Item` is specified to be `i32` here
+
+error: conflicting associated type bounds for `ASSOC`
+  --> $DIR/duplicate_err.rs:80:18
+   |
+LL | type MustFail2 = dyn Trait2<ASSOC = 3u32, ASSOC = 4u32>;
+   |                  ^^^^^^^^^^^------------^^------------^
+   |                             |             |
+   |                             |             `ASSOC` is specified to be `4` here
+   |                             `ASSOC` is specified to be `3` here
+
 error[E0271]: expected `Empty<u32>` to be an iterator that yields `i32`, but it yields `u32`
-  --> $DIR/duplicate_err.rs:74:16
+  --> $DIR/duplicate_err.rs:84:16
    |
 LL |     uncallable(iter::empty::<u32>());
    |     ---------- ^^^^^^^^^^^^^^^^^^^^ expected `i32`, found `u32`
@@ -112,7 +130,7 @@ LL | fn uncallable(_: impl Iterator<Item = i32, Item = u32>) {}
    |                                ^^^^^^^^^^ required by this bound in `uncallable`
 
 error[E0271]: expected `Empty<i32>` to be an iterator that yields `u32`, but it yields `i32`
-  --> $DIR/duplicate_err.rs:75:16
+  --> $DIR/duplicate_err.rs:85:16
    |
 LL |     uncallable(iter::empty::<i32>());
    |     ---------- ^^^^^^^^^^^^^^^^^^^^ expected `u32`, found `i32`
@@ -126,7 +144,7 @@ LL | fn uncallable(_: impl Iterator<Item = i32, Item = u32>) {}
    |                                            ^^^^^^^^^^ required by this bound in `uncallable`
 
 error[E0271]: type mismatch resolving `<() as Trait>::ASSOC == 4`
-  --> $DIR/duplicate_err.rs:76:22
+  --> $DIR/duplicate_err.rs:86:22
    |
 LL |     uncallable_const(());
    |     ---------------- ^^ expected `4`, found `3`
@@ -142,7 +160,7 @@ LL | fn uncallable_const(_: impl Trait<ASSOC = 3, ASSOC = 4>) {}
    |                                              ^^^^^^^^^ required by this bound in `uncallable_const`
 
 error[E0271]: type mismatch resolving `<u32 as Trait>::ASSOC == 3`
-  --> $DIR/duplicate_err.rs:77:22
+  --> $DIR/duplicate_err.rs:87:22
    |
 LL |     uncallable_const(4u32);
    |     ---------------- ^^^^ expected `3`, found `4`
@@ -158,7 +176,7 @@ LL | fn uncallable_const(_: impl Trait<ASSOC = 3, ASSOC = 4>) {}
    |                                   ^^^^^^^^^ required by this bound in `uncallable_const`
 
 error[E0271]: type mismatch resolving `<() as Trait>::ASSOC == 4`
-  --> $DIR/duplicate_err.rs:78:20
+  --> $DIR/duplicate_err.rs:88:20
    |
 LL |     uncallable_rtn(());
    |     -------------- ^^ expected `4`, found `3`
@@ -174,7 +192,7 @@ LL | fn uncallable_rtn(_: impl Trait<foo(..): Trait<ASSOC = 3>, foo(..): Trait<A
    |                                                                           ^^^^^^^^^ required by this bound in `uncallable_rtn`
 
 error[E0271]: type mismatch resolving `<u32 as Trait>::ASSOC == 3`
-  --> $DIR/duplicate_err.rs:79:20
+  --> $DIR/duplicate_err.rs:89:20
    |
 LL |     uncallable_rtn(17u32);
    |     -------------- ^^^^^ expected `3`, found `4`
@@ -189,7 +207,7 @@ note: required by a bound in `uncallable_rtn`
 LL | fn uncallable_rtn(_: impl Trait<foo(..): Trait<ASSOC = 3>, foo(..): Trait<ASSOC = 4>>) {}
    |                                                ^^^^^^^^^ required by this bound in `uncallable_rtn`
 
-error: aborting due to 17 previous errors
+error: aborting due to 19 previous errors
 
 Some errors have detailed explanations: E0271, E0277, E0282.
 For more information about an error, try `rustc --explain E0271`.

tests/ui/associated-types/associated-types-overridden-binding-2.stderr

@@ -1,4 +1,4 @@
-error: conflicting associated type bounds for `Item` when expanding trait alias
+error: conflicting associated type bounds for `Item`
   --> $DIR/associated-types-overridden-binding-2.rs:6:13
    |
 LL | trait I32Iterator = Iterator<Item = i32>;

tests/ui/associated-types/associated-types-overridden-binding.stderr

@@ -22,7 +22,7 @@ note: required by a bound in `I32Iterator`
 LL | trait I32Iterator = Iterator<Item = i32>;
    |                              ^^^^^^^^^^ required by this bound in `I32Iterator`
 
-error: conflicting associated type bounds for `Item` when expanding trait alias
+error: conflicting associated type bounds for `Item`
   --> $DIR/associated-types-overridden-binding.rs:10:13
    |
 LL | trait I32Iterator = Iterator<Item = i32>;