simplify & improve parse_ty_tuple_or_parens

7 files changed, 107 insertions, 62 deletions

diff --git a/src/librustc_parse/parser/ty.rs b/src/librustc_parse/parser/ty.rs
index 16adf5c05a4..08168cf7df9 100644
--- a/src/librustc_parse/parser/ty.rs
+++ b/src/librustc_parse/parser/ty.rs
@@ -142,7 +142,7 @@ impl<'a> Parser<'a> {
             } else {
                 let path = self.parse_path(PathStyle::Type)?;
                 let parse_plus = allow_plus == AllowPlus::Yes && self.check_plus();
-                self.parse_remaining_bounds(lifetime_defs, path, lo, parse_plus)?
+                self.parse_remaining_bounds_path(lifetime_defs, path, lo, parse_plus)?
             }
         } else if self.eat_keyword(kw::Impl) {
             self.parse_impl_ty(&mut impl_dyn_multi)?
@@ -203,21 +203,12 @@ impl<'a> Parser<'a> {
             match ty.kind {
                 // `(TY_BOUND_NOPAREN) + BOUND + ...`.
                 TyKind::Path(None, path) if maybe_bounds => {
-                    self.parse_remaining_bounds(Vec::new(), path, lo, true)
+                    self.parse_remaining_bounds_path(Vec::new(), path, lo, true)
                 }
-                TyKind::TraitObject(mut bounds, TraitObjectSyntax::None)
+                TyKind::TraitObject(bounds, TraitObjectSyntax::None)
                     if maybe_bounds && bounds.len() == 1 && !trailing_plus =>
                 {
-                    let path = match bounds.remove(0) {
-                        GenericBound::Trait(pt, ..) => pt.trait_ref.path,
-                        GenericBound::Outlives(..) => {
-                            return Err(self.struct_span_err(
-                                ty.span,
-                                "expected trait bound, not lifetime bound",
-                            ));
-                        }
-                    };
-                    self.parse_remaining_bounds(Vec::new(), path, lo, true)
+                    self.parse_remaining_bounds(bounds, true)
                 }
                 // `(TYPE)`
                 _ => Ok(TyKind::Paren(P(ty))),
@@ -227,18 +218,26 @@ impl<'a> Parser<'a> {
         }
     }
 
-    fn parse_remaining_bounds(
+    fn parse_remaining_bounds_path(
         &mut self,
         generic_params: Vec<GenericParam>,
         path: ast::Path,
         lo: Span,
         parse_plus: bool,
     ) -> PResult<'a, TyKind> {
-        assert_ne!(self.token, token::Question);
-
         let poly_trait_ref = PolyTraitRef::new(generic_params, path, lo.to(self.prev_token.span));
-        let mut bounds = vec![GenericBound::Trait(poly_trait_ref, TraitBoundModifier::None)];
-        if parse_plus {
+        let bounds = vec![GenericBound::Trait(poly_trait_ref, TraitBoundModifier::None)];
+        self.parse_remaining_bounds(bounds, parse_plus)
+    }
+
+    /// Parse the remainder of a bare trait object type given an already parsed list.
+    fn parse_remaining_bounds(
+        &mut self,
+        mut bounds: GenericBounds,
+        plus: bool,
+    ) -> PResult<'a, TyKind> {
+        assert_ne!(self.token, token::Question);
+        if plus {
             self.eat_plus(); // `+`, or `+=` gets split and `+` is discarded
             bounds.append(&mut self.parse_generic_bounds(Some(self.prev_token.span))?);
         }
@@ -358,7 +357,7 @@ impl<'a> Parser<'a> {
             }))
         } else if allow_plus == AllowPlus::Yes && self.check_plus() {
             // `Trait1 + Trait2 + 'a`
-            self.parse_remaining_bounds(Vec::new(), path, lo, true)
+            self.parse_remaining_bounds_path(Vec::new(), path, lo, true)
         } else {
             // Just a type path.
             Ok(TyKind::Path(None, path))
diff --git a/src/test/ui/parser/issue-68890-2.rs b/src/test/ui/parser/issue-68890-2.rs
index 4bf56f0b0c2..ae022460468 100644
--- a/src/test/ui/parser/issue-68890-2.rs
+++ b/src/test/ui/parser/issue-68890-2.rs
@@ -1,3 +1,6 @@
-type X = (?'a) +;
+fn main() {}
+
+type X<'a> = (?'a) +;
 //~^ ERROR `?` may only modify trait bounds, not lifetime bounds
-//~| ERROR expected trait bound, not lifetime bound
+//~| ERROR at least one trait is required for an object type
+//~| WARN trait objects without an explicit `dyn` are deprecated
diff --git a/src/test/ui/parser/issue-68890-2.stderr b/src/test/ui/parser/issue-68890-2.stderr
index d6196eb1506..d475c79cb27 100644
--- a/src/test/ui/parser/issue-68890-2.stderr
+++ b/src/test/ui/parser/issue-68890-2.stderr
@@ -1,14 +1,22 @@
 error: `?` may only modify trait bounds, not lifetime bounds
-  --> $DIR/issue-68890-2.rs:1:11
+  --> $DIR/issue-68890-2.rs:3:15
    |
-LL | type X = (?'a) +;
-   |           ^
+LL | type X<'a> = (?'a) +;
+   |               ^
 
-error: expected trait bound, not lifetime bound
-  --> $DIR/issue-68890-2.rs:1:11
+warning: trait objects without an explicit `dyn` are deprecated
+  --> $DIR/issue-68890-2.rs:3:14
    |
-LL | type X = (?'a) +;
-   |           ^^^
+LL | type X<'a> = (?'a) +;
+   |              ^^^^^^^ help: use `dyn`: `dyn (?'a) +`
+   |
+   = note: `#[warn(bare_trait_objects)]` on by default
+
+error[E0224]: at least one trait is required for an object type
+  --> $DIR/issue-68890-2.rs:3:14
+   |
+LL | type X<'a> = (?'a) +;
+   |              ^^^^^^^
 
 error: aborting due to 2 previous errors
 
diff --git a/src/test/ui/parser/issue-68890.rs b/src/test/ui/parser/issue-68890.rs
index a7c5a5e1300..bab4ed7f800 100644
--- a/src/test/ui/parser/issue-68890.rs
+++ b/src/test/ui/parser/issue-68890.rs
@@ -1,4 +1,4 @@
 enum e{A((?'a a+?+l))}
 //~^ ERROR `?` may only modify trait bounds, not lifetime bounds
 //~| ERROR expected one of `)`, `+`, or `,`
-//~| ERROR expected trait bound, not lifetime bound
+//~| ERROR expected item, found `)`
diff --git a/src/test/ui/parser/issue-68890.stderr b/src/test/ui/parser/issue-68890.stderr
index 9bb8761b67b..2a3bf6b41f0 100644
--- a/src/test/ui/parser/issue-68890.stderr
+++ b/src/test/ui/parser/issue-68890.stderr
@@ -10,11 +10,11 @@ error: expected one of `)`, `+`, or `,`, found `a`
 LL | enum e{A((?'a a+?+l))}
    |               ^ expected one of `)`, `+`, or `,`
 
-error: expected trait bound, not lifetime bound
-  --> $DIR/issue-68890.rs:1:11
+error: expected item, found `)`
+  --> $DIR/issue-68890.rs:1:21
    |
 LL | enum e{A((?'a a+?+l))}
-   |           ^^^
+   |                     ^ expected item
 
 error: aborting due to 3 previous errors
 
diff --git a/src/test/ui/parser/trait-object-trait-parens.rs b/src/test/ui/parser/trait-object-trait-parens.rs
index a113de14b6f..9fbc938c4dc 100644
--- a/src/test/ui/parser/trait-object-trait-parens.rs
+++ b/src/test/ui/parser/trait-object-trait-parens.rs
@@ -1,15 +1,20 @@
 trait Trait<'a> {}
 
+trait Obj {}
+
 fn f<T: (Copy) + (?Sized) + (for<'a> Trait<'a>)>() {}
 
 fn main() {
-    let _: Box<(Copy) + (?Sized) + (for<'a> Trait<'a>)>;
+    let _: Box<(Obj) + (?Sized) + (for<'a> Trait<'a>)>;
+    //~^ ERROR `?Trait` is not permitted in trait object types
+    //~| ERROR only auto traits can be used as additional traits
+    //~| WARN trait objects without an explicit `dyn` are deprecated
+    let _: Box<(?Sized) + (for<'a> Trait<'a>) + (Obj)>;
     //~^ ERROR `?Trait` is not permitted in trait object types
+    //~| ERROR only auto traits can be used as additional traits
     //~| WARN trait objects without an explicit `dyn` are deprecated
-    let _: Box<(?Sized) + (for<'a> Trait<'a>) + (Copy)>;
-    //~^ WARN trait objects without an explicit `dyn` are deprecated
-    let _: Box<(for<'a> Trait<'a>) + (Copy) + (?Sized)>;
-    //~^ ERROR use of undeclared lifetime name `'a`
-    //~| ERROR `?Trait` is not permitted in trait object types
+    let _: Box<(for<'a> Trait<'a>) + (Obj) + (?Sized)>;
+    //~^ ERROR `?Trait` is not permitted in trait object types
+    //~| ERROR only auto traits can be used as additional traits
     //~| WARN trait objects without an explicit `dyn` are deprecated
 }
diff --git a/src/test/ui/parser/trait-object-trait-parens.stderr b/src/test/ui/parser/trait-object-trait-parens.stderr
index 4b9f49423cb..7022a66ca1a 100644
--- a/src/test/ui/parser/trait-object-trait-parens.stderr
+++ b/src/test/ui/parser/trait-object-trait-parens.stderr
@@ -1,44 +1,74 @@
 error: `?Trait` is not permitted in trait object types
-  --> $DIR/trait-object-trait-parens.rs:6:25
+  --> $DIR/trait-object-trait-parens.rs:8:24
    |
-LL |     let _: Box<(Copy) + (?Sized) + (for<'a> Trait<'a>)>;
-   |                         ^^^^^^^^
+LL |     let _: Box<(Obj) + (?Sized) + (for<'a> Trait<'a>)>;
+   |                        ^^^^^^^^
 
 error: `?Trait` is not permitted in trait object types
-  --> $DIR/trait-object-trait-parens.rs:11:47
+  --> $DIR/trait-object-trait-parens.rs:12:17
    |
-LL |     let _: Box<(for<'a> Trait<'a>) + (Copy) + (?Sized)>;
-   |                                               ^^^^^^^^
+LL |     let _: Box<(?Sized) + (for<'a> Trait<'a>) + (Obj)>;
+   |                 ^^^^^^
+
+error: `?Trait` is not permitted in trait object types
+  --> $DIR/trait-object-trait-parens.rs:16:46
+   |
+LL |     let _: Box<(for<'a> Trait<'a>) + (Obj) + (?Sized)>;
+   |                                              ^^^^^^^^
 
 warning: trait objects without an explicit `dyn` are deprecated
-  --> $DIR/trait-object-trait-parens.rs:6:16
+  --> $DIR/trait-object-trait-parens.rs:8:16
    |
-LL |     let _: Box<(Copy) + (?Sized) + (for<'a> Trait<'a>)>;
-   |                ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: use `dyn`: `dyn (Copy) + (?Sized) + (for<'a> Trait<'a>)`
+LL |     let _: Box<(Obj) + (?Sized) + (for<'a> Trait<'a>)>;
+   |                ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: use `dyn`: `dyn (Obj) + (?Sized) + (for<'a> Trait<'a>)`
    |
    = note: `#[warn(bare_trait_objects)]` on by default
 
 warning: trait objects without an explicit `dyn` are deprecated
-  --> $DIR/trait-object-trait-parens.rs:9:16
+  --> $DIR/trait-object-trait-parens.rs:12:16
    |
-LL |     let _: Box<(?Sized) + (for<'a> Trait<'a>) + (Copy)>;
-   |                ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: use `dyn`: `dyn (?Sized) + (for<'a> Trait<'a>) + (Copy)`
+LL |     let _: Box<(?Sized) + (for<'a> Trait<'a>) + (Obj)>;
+   |                ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: use `dyn`: `dyn (?Sized) + (for<'a> Trait<'a>) + (Obj)`
 
 warning: trait objects without an explicit `dyn` are deprecated
-  --> $DIR/trait-object-trait-parens.rs:11:16
+  --> $DIR/trait-object-trait-parens.rs:16:16
+   |
+LL |     let _: Box<(for<'a> Trait<'a>) + (Obj) + (?Sized)>;
+   |                ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: use `dyn`: `dyn (for<'a> Trait<'a>) + (Obj) + (?Sized)`
+
+error[E0225]: only auto traits can be used as additional traits in a trait object
+  --> $DIR/trait-object-trait-parens.rs:8:35
+   |
+LL |     let _: Box<(Obj) + (?Sized) + (for<'a> Trait<'a>)>;
+   |                -----              ^^^^^^^^^^^^^^^^^^^
+   |                |                  |
+   |                |                  additional non-auto trait
+   |                |                  trait alias used in trait object type (additional use)
+   |                first non-auto trait
+   |                trait alias used in trait object type (first use)
+
+error[E0225]: only auto traits can be used as additional traits in a trait object
+  --> $DIR/trait-object-trait-parens.rs:12:49
    |
-LL |     let _: Box<(for<'a> Trait<'a>) + (Copy) + (?Sized)>;
-   |                ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: use `dyn`: `dyn (for<'a> Trait<'a>) + (Copy) + (?Sized)`
+LL |     let _: Box<(?Sized) + (for<'a> Trait<'a>) + (Obj)>;
+   |                           -------------------   ^^^^^
+   |                           |                     |
+   |                           |                     additional non-auto trait
+   |                           |                     trait alias used in trait object type (additional use)
+   |                           first non-auto trait
+   |                           trait alias used in trait object type (first use)
 
-error[E0261]: use of undeclared lifetime name `'a`
-  --> $DIR/trait-object-trait-parens.rs:11:31
+error[E0225]: only auto traits can be used as additional traits in a trait object
+  --> $DIR/trait-object-trait-parens.rs:16:38
    |
-LL | fn main() {
-   |        - help: consider introducing lifetime `'a` here: `<'a>`
-...
-LL |     let _: Box<(for<'a> Trait<'a>) + (Copy) + (?Sized)>;
-   |                               ^^ undeclared lifetime
+LL |     let _: Box<(for<'a> Trait<'a>) + (Obj) + (?Sized)>;
+   |                 -----------------    ^^^^^
+   |                 |                    |
+   |                 |                    additional non-auto trait
+   |                 |                    trait alias used in trait object type (additional use)
+   |                 first non-auto trait
+   |                 trait alias used in trait object type (first use)
 
-error: aborting due to 3 previous errors
+error: aborting due to 6 previous errors
 
-For more information about this error, try `rustc --explain E0261`.
+For more information about this error, try `rustc --explain E0225`.