Deny `where` clauses on `auto` traits

12 files changed, 135 insertions, 47 deletions

diff --git a/compiler/rustc_ast_passes/src/ast_validation.rs b/compiler/rustc_ast_passes/src/ast_validation.rs
index 24108f779c8..0f5580db30f 100644
--- a/compiler/rustc_ast_passes/src/ast_validation.rs
+++ b/compiler/rustc_ast_passes/src/ast_validation.rs
@@ -683,31 +683,53 @@ impl<'a> AstValidator<'a> {
         }
     }
 
+    fn emit_e0568(&self, span: Span, ident_span: Span) {
+        struct_span_err!(
+            self.session,
+            span,
+            E0568,
+            "auto traits cannot have super traits or lifetime bounds"
+        )
+        .span_label(ident_span, "auto trait cannot have super traits or lifetime bounds")
+        .span_suggestion(
+            span,
+            "remove the super traits or lifetime bounds",
+            String::new(),
+            Applicability::MachineApplicable,
+        )
+        .emit();
+    }
+
     fn deny_super_traits(&self, bounds: &GenericBounds, ident_span: Span) {
-        if let [first @ last] | [first, .., last] = &bounds[..] {
-            let span = first.span().to(last.span());
-            struct_span_err!(self.session, span, E0568, "auto traits cannot have super traits")
-                .span_label(ident_span, "auto trait cannot have super traits")
-                .span_suggestion(
-                    span,
-                    "remove the super traits",
-                    String::new(),
-                    Applicability::MachineApplicable,
-                )
-                .emit();
+        if let [.., last] = &bounds[..] {
+            let span = ident_span.shrink_to_hi().to(last.span());
+            self.emit_e0568(span, ident_span);
+        }
+    }
+
+    fn deny_where_clause(&self, where_clause: &WhereClause, ident_span: Span) {
+        if !where_clause.predicates.is_empty() {
+            self.emit_e0568(where_clause.span, ident_span);
         }
     }
 
     fn deny_items(&self, trait_items: &[P<AssocItem>], ident_span: Span) {
         if !trait_items.is_empty() {
             let spans: Vec<_> = trait_items.iter().map(|i| i.ident.span).collect();
+            let total_span = trait_items.first().unwrap().span.to(trait_items.last().unwrap().span);
             struct_span_err!(
                 self.session,
                 spans,
                 E0380,
-                "auto traits cannot have methods or associated items"
+                "auto traits cannot have associated items"
+            )
+            .span_suggestion(
+                total_span,
+                "remove these associated items",
+                String::new(),
+                Applicability::MachineApplicable,
             )
-            .span_label(ident_span, "auto trait cannot have items")
+            .span_label(ident_span, "auto trait cannot have associated items")
             .emit();
         }
     }
@@ -1184,6 +1206,7 @@ impl<'a> Visitor<'a> for AstValidator<'a> {
                     // Auto traits cannot have generics, super traits nor contain items.
                     self.deny_generic_params(generics, item.ident.span);
                     self.deny_super_traits(bounds, item.ident.span);
+                    self.deny_where_clause(&generics.where_clause, item.ident.span);
                     self.deny_items(trait_items, item.ident.span);
                 }
                 self.no_questions_in_bounds(bounds, "supertraits", true);
diff --git a/src/test/ui/auto-traits/auto-trait-validation.fixed b/src/test/ui/auto-traits/auto-trait-validation.fixed
new file mode 100644
index 00000000000..da878ac6222
--- /dev/null
+++ b/src/test/ui/auto-traits/auto-trait-validation.fixed
@@ -0,0 +1,13 @@
+#![feature(auto_traits)]
+
+// run-rustfix
+
+auto trait Generic {}
+//~^ auto traits cannot have generic parameters [E0567]
+auto trait Bound {}
+//~^ auto traits cannot have super traits or lifetime bounds [E0568]
+auto trait LifetimeBound {}
+//~^ auto traits cannot have super traits or lifetime bounds [E0568]
+auto trait MyTrait {  }
+//~^ auto traits cannot have associated items [E0380]
+fn main() {}
diff --git a/src/test/ui/auto-traits/auto-trait-validation.rs b/src/test/ui/auto-traits/auto-trait-validation.rs
index a997b044c8f..d43055e270b 100644
--- a/src/test/ui/auto-traits/auto-trait-validation.rs
+++ b/src/test/ui/auto-traits/auto-trait-validation.rs
@@ -1,9 +1,13 @@
 #![feature(auto_traits)]
 
+// run-rustfix
+
 auto trait Generic<T> {}
 //~^ auto traits cannot have generic parameters [E0567]
 auto trait Bound : Copy {}
-//~^ auto traits cannot have super traits [E0568]
+//~^ auto traits cannot have super traits or lifetime bounds [E0568]
+auto trait LifetimeBound : 'static {}
+//~^ auto traits cannot have super traits or lifetime bounds [E0568]
 auto trait MyTrait { fn foo() {} }
-//~^ auto traits cannot have methods or associated items [E0380]
+//~^ auto traits cannot have associated items [E0380]
 fn main() {}
diff --git a/src/test/ui/auto-traits/auto-trait-validation.stderr b/src/test/ui/auto-traits/auto-trait-validation.stderr
index 4040e66c6af..2c380e5b09a 100644
--- a/src/test/ui/auto-traits/auto-trait-validation.stderr
+++ b/src/test/ui/auto-traits/auto-trait-validation.stderr
@@ -1,28 +1,37 @@
 error[E0567]: auto traits cannot have generic parameters
-  --> $DIR/auto-trait-validation.rs:3:19
+  --> $DIR/auto-trait-validation.rs:5:19
    |
 LL | auto trait Generic<T> {}
    |            -------^^^ help: remove the parameters
    |            |
    |            auto trait cannot have generic parameters
 
-error[E0568]: auto traits cannot have super traits
-  --> $DIR/auto-trait-validation.rs:5:20
+error[E0568]: auto traits cannot have super traits or lifetime bounds
+  --> $DIR/auto-trait-validation.rs:7:17
    |
 LL | auto trait Bound : Copy {}
-   |            -----   ^^^^ help: remove the super traits
+   |            -----^^^^^^^ help: remove the super traits or lifetime bounds
    |            |
-   |            auto trait cannot have super traits
+   |            auto trait cannot have super traits or lifetime bounds
 
-error[E0380]: auto traits cannot have methods or associated items
-  --> $DIR/auto-trait-validation.rs:7:25
+error[E0568]: auto traits cannot have super traits or lifetime bounds
+  --> $DIR/auto-trait-validation.rs:9:25
    |
-LL | auto trait MyTrait { fn foo() {} }
-   |            -------      ^^^
+LL | auto trait LifetimeBound : 'static {}
+   |            -------------^^^^^^^^^^ help: remove the super traits or lifetime bounds
    |            |
-   |            auto trait cannot have items
+   |            auto trait cannot have super traits or lifetime bounds
+
+error[E0380]: auto traits cannot have associated items
+  --> $DIR/auto-trait-validation.rs:11:25
+   |
+LL | auto trait MyTrait { fn foo() {} }
+   |            -------   ---^^^-----
+   |            |         |
+   |            |         help: remove these associated items
+   |            auto trait cannot have associated items
 
-error: aborting due to 3 previous errors
+error: aborting due to 4 previous errors
 
 Some errors have detailed explanations: E0380, E0567, E0568.
 For more information about an error, try `rustc --explain E0380`.
diff --git a/src/test/ui/auto-traits/issue-23080-2.stderr b/src/test/ui/auto-traits/issue-23080-2.stderr
index efeceafdd2a..267a712f62f 100644
--- a/src/test/ui/auto-traits/issue-23080-2.stderr
+++ b/src/test/ui/auto-traits/issue-23080-2.stderr
@@ -1,10 +1,10 @@
-error[E0380]: auto traits cannot have methods or associated items
+error[E0380]: auto traits cannot have associated items
   --> $DIR/issue-23080-2.rs:5:10
    |
 LL | unsafe auto trait Trait {
-   |                   ----- auto trait cannot have items
+   |                   ----- auto trait cannot have associated items
 LL |     type Output;
-   |          ^^^^^^
+   |     -----^^^^^^- help: remove these associated items
 
 error: aborting due to previous error
 
diff --git a/src/test/ui/auto-traits/issue-23080.stderr b/src/test/ui/auto-traits/issue-23080.stderr
index 73ecb1c362e..c1b16b2f403 100644
--- a/src/test/ui/auto-traits/issue-23080.stderr
+++ b/src/test/ui/auto-traits/issue-23080.stderr
@@ -1,10 +1,13 @@
-error[E0380]: auto traits cannot have methods or associated items
+error[E0380]: auto traits cannot have associated items
   --> $DIR/issue-23080.rs:5:8
    |
-LL | unsafe auto trait Trait {
-   |                   ----- auto trait cannot have items
-LL |     fn method(&self) {
-   |        ^^^^^^
+LL |   unsafe auto trait Trait {
+   |                     ----- auto trait cannot have associated items
+LL |       fn method(&self) {
+   |  _____-  ^^^^^^
+LL | |         println!("Hello");
+LL | |     }
+   | |_____- help: remove these associated items
 
 error: aborting due to previous error
 
diff --git a/src/test/ui/auto-traits/issue-84075.rs b/src/test/ui/auto-traits/issue-84075.rs
new file mode 100644
index 00000000000..a6afe24ea4c
--- /dev/null
+++ b/src/test/ui/auto-traits/issue-84075.rs
@@ -0,0 +1,16 @@
+// Regression test for issue #84075.
+
+#![feature(auto_traits)]
+
+auto trait Magic where Self: Copy {} //~ ERROR E0568
+impl<T: Magic> Magic for T {}
+
+fn copy<T: Magic>(x: T) -> (T, T) { (x, x) }
+
+#[derive(Debug)]
+struct NoClone;
+
+fn main() {
+    let (a, b) = copy(NoClone);
+    println!("{:?} {:?}", a, b);
+}
diff --git a/src/test/ui/auto-traits/issue-84075.stderr b/src/test/ui/auto-traits/issue-84075.stderr
new file mode 100644
index 00000000000..02dca598ec2
--- /dev/null
+++ b/src/test/ui/auto-traits/issue-84075.stderr
@@ -0,0 +1,11 @@
+error[E0568]: auto traits cannot have super traits or lifetime bounds
+  --> $DIR/issue-84075.rs:5:18
+   |
+LL | auto trait Magic where Self: Copy {}
+   |            ----- ^^^^^^^^^^^^^^^^ help: remove the super traits or lifetime bounds
+   |            |
+   |            auto trait cannot have super traits or lifetime bounds
+
+error: aborting due to previous error
+
+For more information about this error, try `rustc --explain E0568`.
diff --git a/src/test/ui/auto-traits/typeck-auto-trait-no-supertraits-2.rs b/src/test/ui/auto-traits/typeck-auto-trait-no-supertraits-2.rs
index 6cceaf821f6..98359ef51b7 100644
--- a/src/test/ui/auto-traits/typeck-auto-trait-no-supertraits-2.rs
+++ b/src/test/ui/auto-traits/typeck-auto-trait-no-supertraits-2.rs
@@ -2,6 +2,7 @@
 #![feature(negative_impls)]
 
 auto trait Magic : Sized where Option<Self> : Magic {} //~ ERROR E0568
+//~^ ERROR E0568
 impl<T:Magic> Magic for T {}
 
 fn copy<T: Magic>(x: T) -> (T, T) { (x, x) }
diff --git a/src/test/ui/auto-traits/typeck-auto-trait-no-supertraits-2.stderr b/src/test/ui/auto-traits/typeck-auto-trait-no-supertraits-2.stderr
index 63b3300f6db..4827916fa5c 100644
--- a/src/test/ui/auto-traits/typeck-auto-trait-no-supertraits-2.stderr
+++ b/src/test/ui/auto-traits/typeck-auto-trait-no-supertraits-2.stderr
@@ -1,11 +1,19 @@
-error[E0568]: auto traits cannot have super traits
-  --> $DIR/typeck-auto-trait-no-supertraits-2.rs:4:20
+error[E0568]: auto traits cannot have super traits or lifetime bounds
+  --> $DIR/typeck-auto-trait-no-supertraits-2.rs:4:17
    |
 LL | auto trait Magic : Sized where Option<Self> : Magic {}
-   |            -----   ^^^^^ help: remove the super traits
+   |            -----^^^^^^^^ help: remove the super traits or lifetime bounds
    |            |
-   |            auto trait cannot have super traits
+   |            auto trait cannot have super traits or lifetime bounds
 
-error: aborting due to previous error
+error[E0568]: auto traits cannot have super traits or lifetime bounds
+  --> $DIR/typeck-auto-trait-no-supertraits-2.rs:4:26
+   |
+LL | auto trait Magic : Sized where Option<Self> : Magic {}
+   |            -----         ^^^^^^^^^^^^^^^^^^^^^^^^^^ help: remove the super traits or lifetime bounds
+   |            |
+   |            auto trait cannot have super traits or lifetime bounds
+
+error: aborting due to 2 previous errors
 
 For more information about this error, try `rustc --explain E0568`.
diff --git a/src/test/ui/auto-traits/typeck-auto-trait-no-supertraits.stderr b/src/test/ui/auto-traits/typeck-auto-trait-no-supertraits.stderr
index 796638fc54d..d7716f4b61f 100644
--- a/src/test/ui/auto-traits/typeck-auto-trait-no-supertraits.stderr
+++ b/src/test/ui/auto-traits/typeck-auto-trait-no-supertraits.stderr
@@ -1,10 +1,10 @@
-error[E0568]: auto traits cannot have super traits
-  --> $DIR/typeck-auto-trait-no-supertraits.rs:28:19
+error[E0568]: auto traits cannot have super traits or lifetime bounds
+  --> $DIR/typeck-auto-trait-no-supertraits.rs:28:17
    |
 LL | auto trait Magic: Copy {}
-   |            -----  ^^^^ help: remove the super traits
+   |            -----^^^^^^ help: remove the super traits or lifetime bounds
    |            |
-   |            auto trait cannot have super traits
+   |            auto trait cannot have super traits or lifetime bounds
 
 error: aborting due to previous error
 
diff --git a/src/test/ui/traits/inductive-overflow/supertrait-auto-trait.stderr b/src/test/ui/traits/inductive-overflow/supertrait-auto-trait.stderr
index 7895e50eef5..8405d7ddc7a 100644
--- a/src/test/ui/traits/inductive-overflow/supertrait-auto-trait.stderr
+++ b/src/test/ui/traits/inductive-overflow/supertrait-auto-trait.stderr
@@ -1,10 +1,10 @@
-error[E0568]: auto traits cannot have super traits
-  --> $DIR/supertrait-auto-trait.rs:8:19
+error[E0568]: auto traits cannot have super traits or lifetime bounds
+  --> $DIR/supertrait-auto-trait.rs:8:17
    |
 LL | auto trait Magic: Copy {}
-   |            -----  ^^^^ help: remove the super traits
+   |            -----^^^^^^ help: remove the super traits or lifetime bounds
    |            |
-   |            auto trait cannot have super traits
+   |            auto trait cannot have super traits or lifetime bounds
 
 error[E0277]: the trait bound `NoClone: Copy` is not satisfied
   --> $DIR/supertrait-auto-trait.rs:16:23