Pretty-print own args of existential projections

compiler/rustc_middle/src/ty/print/pretty.rs

@@ -3119,7 +3119,10 @@ macro_rules! define_print_and_forward_display {
 
     ty::ExistentialProjection<'tcx> {
         let name = cx.tcx().associated_item(self.def_id).name;
-        p!(write("{} = ", name), print(self.term))
+        // The args don't contain the self ty (as it has been erased) but the corresp.
+        // generics do as the trait always has a self ty param. We need to offset.
+        let args = &self.args[cx.tcx().generics_of(self.def_id).parent_count - 1..];
+        p!(path_generic_args(|cx| write!(cx, "{name}"), args), " = ", print(self.term))
     }
 
     ty::ProjectionPredicate<'tcx> {

tests/ui/generic-associated-types/gat-in-trait-path.base.stderr

@@ -51,7 +51,7 @@ LL |     type A<'a> where Self: 'a;
    = help: the following types implement the trait, consider defining an enum where each variant holds one of these types, implementing `Foo` for this new enum and using it instead:
              Fooy
              Fooer<T>
-   = note: required for the cast from `Box<Fooer<{integer}>>` to `Box<(dyn Foo<A = &'a ()> + 'static)>`
+   = note: required for the cast from `Box<Fooer<{integer}>>` to `Box<(dyn Foo<A<'a> = &'a ()> + 'static)>`
 
 error: aborting due to 3 previous errors
 

tests/ui/generic-associated-types/issue-76535.base.stderr

@@ -47,7 +47,7 @@ LL |     type SubType<'a>: SubTrait where Self: 'a;
    = help: consider moving `SubType` to another trait
    = help: only type `SuperStruct` is seen to implement the trait in this crate, consider using it directly instead
    = note: `SuperTrait` can be implemented in other crates; if you want to support your users passing their own types here, you can't refer to a specific type
-   = note: required for the cast from `Box<SuperStruct>` to `Box<dyn SuperTrait<SubType = SubStruct<'_>>>`
+   = note: required for the cast from `Box<SuperStruct>` to `Box<dyn SuperTrait<SubType<'_> = SubStruct<'_>>>`
 
 error: aborting due to 3 previous errors
 

tests/ui/generic-associated-types/issue-79422.base.stderr

@@ -49,7 +49,7 @@ LL |     type VRefCont<'a>: RefCont<'a, V> where Self: 'a;
    = help: the following types implement the trait, consider defining an enum where each variant holds one of these types, implementing `MapLike` for this new enum and using it instead:
              std::collections::BTreeMap<K, V>
              Source
-   = note: required for the cast from `Box<BTreeMap<u8, u8>>` to `Box<dyn MapLike<u8, u8, VRefCont = (dyn RefCont<'_, u8> + 'static)>>`
+   = note: required for the cast from `Box<BTreeMap<u8, u8>>` to `Box<dyn MapLike<u8, u8, VRefCont<'_> = (dyn RefCont<'_, u8> + 'static)>>`
 
 error: aborting due to 3 previous errors
 

tests/ui/generic-associated-types/issue-79422.extended.stderr

@@ -28,7 +28,7 @@ LL |     type VRefCont<'a> = &'a V where Self: 'a;
    = note: expected trait object `(dyn RefCont<'_, u8> + 'static)`
                  found reference `&u8`
    = help: `&u8` implements `RefCont` so you could box the found value and coerce it to the trait object `Box<dyn RefCont>`, you will have to change the expected type as well
-   = note: required for the cast from `Box<BTreeMap<u8, u8>>` to `Box<dyn MapLike<u8, u8, VRefCont = (dyn RefCont<'_, u8> + 'static)>>`
+   = note: required for the cast from `Box<BTreeMap<u8, u8>>` to `Box<dyn MapLike<u8, u8, VRefCont<'_> = (dyn RefCont<'_, u8> + 'static)>>`
 
 error: aborting due to 2 previous errors
 

tests/ui/traits/object/pretty.rs

@@ -18,6 +18,10 @@ trait FixedHrtb: for<'a> SuperGeneric<'a, Assoc2 = &'a u8> {}
 trait AnyDifferentBinders: for<'a> SuperGeneric<'a, Assoc2 = &'a u8> + Super {}
 trait FixedDifferentBinders: for<'a> SuperGeneric<'a, Assoc2 = &'a u8> + Super<Assoc = u8> {}
 
+trait HasGat<Outer> {
+    type Assoc<Inner> where Self: Sized;
+}
+
 fn dyn_super(x: &dyn Super<Assoc = u8>) { x } //~ERROR mismatched types
 fn dyn_any(x: &dyn Any<Assoc = u8>) { x } //~ERROR mismatched types
 fn dyn_fixed(x: &dyn Fixed) { x } //~ERROR mismatched types
@@ -34,4 +38,7 @@ fn dyn_fixed_hrtb(x: &dyn FixedHrtb) { x } //~ERROR mismatched types
 fn dyn_any_different_binders(x: &dyn AnyDifferentBinders<Assoc = u8>) { x } //~ERROR mismatched types
 fn dyn_fixed_different_binders(x: &dyn FixedDifferentBinders) { x } //~ERROR mismatched types
 
+fn dyn_has_gat(x: &dyn HasGat<u8, Assoc<bool> = ()>) { x } //~ERROR mismatched types
+//~^ WARN unnecessary associated type bound
+
 fn main() {}

tests/ui/traits/object/pretty.stderr

@@ -1,5 +1,14 @@
+warning: unnecessary associated type bound for not object safe associated type
+  --> $DIR/pretty.rs:41:35
+   |
+LL | fn dyn_has_gat(x: &dyn HasGat<u8, Assoc<bool> = ()>) { x }
+   |                                   ^^^^^^^^^^^^^^^^ help: remove this bound
+   |
+   = note: this associated type has a `where Self: Sized` bound, and while the associated type can be specified, it cannot be used because trait objects are never `Sized`
+   = note: `#[warn(unused_associated_type_bounds)]` on by default
+
 error[E0308]: mismatched types
-  --> $DIR/pretty.rs:21:43
+  --> $DIR/pretty.rs:25:43
    |
 LL | fn dyn_super(x: &dyn Super<Assoc = u8>) { x }
    |                                        -  ^ expected `()`, found `&dyn Super<Assoc = u8>`
@@ -10,7 +19,7 @@ LL | fn dyn_super(x: &dyn Super<Assoc = u8>) { x }
               found reference `&dyn Super<Assoc = u8>`
 
 error[E0308]: mismatched types
-  --> $DIR/pretty.rs:22:39
+  --> $DIR/pretty.rs:26:39
    |
 LL | fn dyn_any(x: &dyn Any<Assoc = u8>) { x }
    |                                    -  ^ expected `()`, found `&dyn Any<Assoc = u8>`
@@ -21,7 +30,7 @@ LL | fn dyn_any(x: &dyn Any<Assoc = u8>) { x }
               found reference `&dyn Any<Assoc = u8>`
 
 error[E0308]: mismatched types
-  --> $DIR/pretty.rs:23:31
+  --> $DIR/pretty.rs:27:31
    |
 LL | fn dyn_fixed(x: &dyn Fixed) { x }
    |                            -  ^ expected `()`, found `&dyn Fixed`
@@ -32,7 +41,7 @@ LL | fn dyn_fixed(x: &dyn Fixed) { x }
               found reference `&dyn Fixed`
 
 error[E0308]: mismatched types
-  --> $DIR/pretty.rs:24:50
+  --> $DIR/pretty.rs:28:50
    |
 LL | fn dyn_fixed_multi(x: &dyn Fixed<Assoc = u16>) { x }
    |                                               -  ^ expected `()`, found `&dyn Fixed<Assoc = u16>`
@@ -43,7 +52,7 @@ LL | fn dyn_fixed_multi(x: &dyn Fixed<Assoc = u16>) { x }
               found reference `&dyn Fixed<Assoc = u16>`
 
 error[E0308]: mismatched types
-  --> $DIR/pretty.rs:25:38
+  --> $DIR/pretty.rs:29:38
    |
 LL | fn dyn_fixed_sub(x: &dyn FixedSub) { x }
    |                                   -  ^ expected `()`, found `&dyn FixedSub`
@@ -54,7 +63,7 @@ LL | fn dyn_fixed_sub(x: &dyn FixedSub) { x }
               found reference `&dyn FixedSub`
 
 error[E0308]: mismatched types
-  --> $DIR/pretty.rs:26:44
+  --> $DIR/pretty.rs:30:44
    |
 LL | fn dyn_fixed_static(x: &dyn FixedStatic) { x }
    |                                         -  ^ expected `()`, found `&dyn FixedStatic`
@@ -65,7 +74,7 @@ LL | fn dyn_fixed_static(x: &dyn FixedStatic) { x }
               found reference `&dyn FixedStatic`
 
 error[E0308]: mismatched types
-  --> $DIR/pretty.rs:28:75
+  --> $DIR/pretty.rs:32:75
    |
 LL | fn dyn_super_generic(x: &dyn for<'a> SuperGeneric<'a, Assoc2 = &'a u8>) { x }
    |                                                                        -  ^ expected `()`, found `&dyn SuperGeneric<'a, Assoc2 = &u8>`
@@ -76,7 +85,7 @@ LL | fn dyn_super_generic(x: &dyn for<'a> SuperGeneric<'a, Assoc2 = &'a u8>) { x
               found reference `&dyn for<'a> SuperGeneric<'a, Assoc2 = &'a u8>`
 
 error[E0308]: mismatched types
-  --> $DIR/pretty.rs:29:71
+  --> $DIR/pretty.rs:33:71
    |
 LL | fn dyn_any_generic(x: &dyn for<'a> AnyGeneric<'a, Assoc2 = &'a u8>) { x }
    |                                                                    -  ^ expected `()`, found `&dyn AnyGeneric<'a, Assoc2 = &u8>`
@@ -87,7 +96,7 @@ LL | fn dyn_any_generic(x: &dyn for<'a> AnyGeneric<'a, Assoc2 = &'a u8>) { x }
               found reference `&dyn for<'a> AnyGeneric<'a, Assoc2 = &'a u8>`
 
 error[E0308]: mismatched types
-  --> $DIR/pretty.rs:30:60
+  --> $DIR/pretty.rs:34:60
    |
 LL | fn dyn_fixed_generic1(x: &dyn for<'a> FixedGeneric1<'a>) { x }
    |                                                         -  ^ expected `()`, found `&dyn FixedGeneric1<'a>`
@@ -98,7 +107,7 @@ LL | fn dyn_fixed_generic1(x: &dyn for<'a> FixedGeneric1<'a>) { x }
               found reference `&dyn for<'a> FixedGeneric1<'a>`
 
 error[E0308]: mismatched types
-  --> $DIR/pretty.rs:31:60
+  --> $DIR/pretty.rs:35:60
    |
 LL | fn dyn_fixed_generic2(x: &dyn for<'a> FixedGeneric2<'a>) { x }
    |                                                         -  ^ expected `()`, found `&dyn FixedGeneric2<'a>`
@@ -109,7 +118,7 @@ LL | fn dyn_fixed_generic2(x: &dyn for<'a> FixedGeneric2<'a>) { x }
               found reference `&dyn for<'a> FixedGeneric2<'a>`
 
 error[E0308]: mismatched types
-  --> $DIR/pretty.rs:32:79
+  --> $DIR/pretty.rs:36:79
    |
 LL | fn dyn_fixed_generic_multi(x: &dyn for<'a> FixedGeneric1<'a, Assoc2 = &u8>) { x }
    |                                                                            -  ^ expected `()`, found `&dyn FixedGeneric1<'a, Assoc2 = ...>`
@@ -120,7 +129,7 @@ LL | fn dyn_fixed_generic_multi(x: &dyn for<'a> FixedGeneric1<'a, Assoc2 = &u8>)
               found reference `&dyn for<'a> FixedGeneric1<'a, Assoc2 = &u8>`
 
 error[E0308]: mismatched types
-  --> $DIR/pretty.rs:33:40
+  --> $DIR/pretty.rs:37:40
    |
 LL | fn dyn_fixed_hrtb(x: &dyn FixedHrtb) { x }
    |                                     -  ^ expected `()`, found `&dyn FixedHrtb`
@@ -131,7 +140,7 @@ LL | fn dyn_fixed_hrtb(x: &dyn FixedHrtb) { x }
               found reference `&dyn FixedHrtb`
 
 error[E0308]: mismatched types
-  --> $DIR/pretty.rs:34:73
+  --> $DIR/pretty.rs:38:73
    |
 LL | fn dyn_any_different_binders(x: &dyn AnyDifferentBinders<Assoc = u8>) { x }
    |                                                                      -  ^ expected `()`, found `&dyn AnyDifferentBinders<Assoc = ...>`
@@ -142,7 +151,7 @@ LL | fn dyn_any_different_binders(x: &dyn AnyDifferentBinders<Assoc = u8>) { x }
               found reference `&dyn AnyDifferentBinders<Assoc = u8>`
 
 error[E0308]: mismatched types
-  --> $DIR/pretty.rs:35:65
+  --> $DIR/pretty.rs:39:65
    |
 LL | fn dyn_fixed_different_binders(x: &dyn FixedDifferentBinders) { x }
    |                                                              -  ^ expected `()`, found `&dyn FixedDifferentBinders`
@@ -152,6 +161,17 @@ LL | fn dyn_fixed_different_binders(x: &dyn FixedDifferentBinders) { x }
    = note: expected unit type `()`
               found reference `&dyn FixedDifferentBinders`
 
-error: aborting due to 14 previous errors
+error[E0308]: mismatched types
+  --> $DIR/pretty.rs:41:56
+   |
+LL | fn dyn_has_gat(x: &dyn HasGat<u8, Assoc<bool> = ()>) { x }
+   |                                                     -  ^ expected `()`, found `&dyn HasGat<u8, Assoc<bool> = ()>`
+   |                                                     |
+   |                                                     help: try adding a return type: `-> &dyn HasGat<u8, Assoc<bool> = ()>`
+   |
+   = note: expected unit type `()`
+              found reference `&dyn HasGat<u8, Assoc<bool> = ()>`
+
+error: aborting due to 15 previous errors; 1 warning emitted
 
 For more information about this error, try `rustc --explain E0308`.