Auto merge of #63180 - varkor:trait-alias-impl-trait, r=Centril

Change opaque type syntax from `existential type` to type alias `impl Trait`

This implements a new feature gate `type_alias_impl_trait` (this is slightly different from the originally proposed feature name, but matches what has been used in discussion since), deprecating the old `existential_types` feature.

The syntax for opaque types has been changed. In addition, the "existential" terminology has been replaced with "opaque", as per previous discussion and the RFC.

This makes partial progress towards implementing https://github.com/rust-lang/rust/issues/63063.

r? @Centril

8 files changed, 16 insertions, 22 deletions

diff --git a/src/test/ui/parser/default.stderr b/src/test/ui/parser/default.stderr
index ded088acfc4..e199045134e 100644
--- a/src/test/ui/parser/default.stderr
+++ b/src/test/ui/parser/default.stderr
@@ -1,8 +1,8 @@
-error: expected one of `async`, `const`, `existential`, `extern`, `fn`, `type`, or `unsafe`, found `pub`
+error: expected one of `async`, `const`, `extern`, `fn`, `type`, or `unsafe`, found `pub`
   --> $DIR/default.rs:22:13
    |
 LL |     default pub fn foo<T: Default>() -> T { T::default() }
-   |             ^^^ expected one of 7 possible tokens here
+   |             ^^^ expected one of `async`, `const`, `extern`, `fn`, `type`, or `unsafe` here
 
 error[E0449]: unnecessary visibility qualifier
   --> $DIR/default.rs:16:5
diff --git a/src/test/ui/parser/issue-20711-2.rs b/src/test/ui/parser/issue-20711-2.rs
index 49b8de03c37..0063a334182 100644
--- a/src/test/ui/parser/issue-20711-2.rs
+++ b/src/test/ui/parser/issue-20711-2.rs
@@ -1,11 +1,9 @@
-// ignore-tidy-linelength
-
 struct Foo;
 
 impl Foo {
     fn foo() {}
 
     #[stable(feature = "rust1", since = "1.0.0")]
-} //~ ERROR expected one of `async`, `const`, `crate`, `default`, `existential`, `extern`, `fn`, `pub`, `type`, or
+} //~ ERROR expected one of `async`, `const`, `crate`, `default`, `extern`, `fn`, `pub`, `type`, or
 
 fn main() {}
diff --git a/src/test/ui/parser/issue-20711-2.stderr b/src/test/ui/parser/issue-20711-2.stderr
index f67dfa09aca..56749c107d1 100644
--- a/src/test/ui/parser/issue-20711-2.stderr
+++ b/src/test/ui/parser/issue-20711-2.stderr
@@ -1,8 +1,8 @@
-error: expected one of `async`, `const`, `crate`, `default`, `existential`, `extern`, `fn`, `pub`, `type`, or `unsafe`, found `}`
-  --> $DIR/issue-20711-2.rs:9:1
+error: expected one of `async`, `const`, `crate`, `default`, `extern`, `fn`, `pub`, `type`, or `unsafe`, found `}`
+  --> $DIR/issue-20711-2.rs:7:1
    |
 LL |     #[stable(feature = "rust1", since = "1.0.0")]
-   |                                                  - expected one of 10 possible tokens here
+   |                                                  - expected one of 9 possible tokens here
 LL | }
    | ^ unexpected token
 
diff --git a/src/test/ui/parser/issue-20711.rs b/src/test/ui/parser/issue-20711.rs
index 8d8401da61a..dc216167b8a 100644
--- a/src/test/ui/parser/issue-20711.rs
+++ b/src/test/ui/parser/issue-20711.rs
@@ -1,9 +1,7 @@
-// ignore-tidy-linelength
-
 struct Foo;
 
 impl Foo {
     #[stable(feature = "rust1", since = "1.0.0")]
-} //~ ERROR expected one of `async`, `const`, `crate`, `default`, `existential`, `extern`, `fn`, `pub`, `type`, or
+} //~ ERROR expected one of `async`, `const`, `crate`, `default`, `extern`, `fn`, `pub`, `type`, or
 
 fn main() {}
diff --git a/src/test/ui/parser/issue-20711.stderr b/src/test/ui/parser/issue-20711.stderr
index 26b819fa298..f7b99a91b51 100644
--- a/src/test/ui/parser/issue-20711.stderr
+++ b/src/test/ui/parser/issue-20711.stderr
@@ -1,8 +1,8 @@
-error: expected one of `async`, `const`, `crate`, `default`, `existential`, `extern`, `fn`, `pub`, `type`, or `unsafe`, found `}`
-  --> $DIR/issue-20711.rs:7:1
+error: expected one of `async`, `const`, `crate`, `default`, `extern`, `fn`, `pub`, `type`, or `unsafe`, found `}`
+  --> $DIR/issue-20711.rs:5:1
    |
 LL |     #[stable(feature = "rust1", since = "1.0.0")]
-   |                                                  - expected one of 10 possible tokens here
+   |                                                  - expected one of 9 possible tokens here
 LL | }
    | ^ unexpected token
 
diff --git a/src/test/ui/parser/issue-41155.stderr b/src/test/ui/parser/issue-41155.stderr
index 719845e6999..624d1a3d11e 100644
--- a/src/test/ui/parser/issue-41155.stderr
+++ b/src/test/ui/parser/issue-41155.stderr
@@ -1,8 +1,8 @@
-error: expected one of `(`, `async`, `const`, `default`, `existential`, `extern`, `fn`, `type`, or `unsafe`, found `}`
+error: expected one of `(`, `async`, `const`, `default`, `extern`, `fn`, `type`, or `unsafe`, found `}`
   --> $DIR/issue-41155.rs:5:1
    |
 LL |     pub
-   |        - expected one of 9 possible tokens here
+   |        - expected one of 8 possible tokens here
 LL | }
    | ^ unexpected token
 
diff --git a/src/test/ui/parser/removed-syntax-static-fn.rs b/src/test/ui/parser/removed-syntax-static-fn.rs
index df3964196b8..0caddb9855d 100644
--- a/src/test/ui/parser/removed-syntax-static-fn.rs
+++ b/src/test/ui/parser/removed-syntax-static-fn.rs
@@ -1,10 +1,8 @@
-// ignore-tidy-linelength
-
 struct S;
 
 impl S {
     static fn f() {}
+    //~^ ERROR expected one of `async`, `const`, `crate`, `default`, `extern`, `fn`, `pub`, `type`,
 }
-//~^^ ERROR expected one of `async`, `const`, `crate`, `default`, `existential`, `extern`, `fn`, `pub`, `type`,
 
 fn main() {}
diff --git a/src/test/ui/parser/removed-syntax-static-fn.stderr b/src/test/ui/parser/removed-syntax-static-fn.stderr
index 84e0432c48c..21cb71df657 100644
--- a/src/test/ui/parser/removed-syntax-static-fn.stderr
+++ b/src/test/ui/parser/removed-syntax-static-fn.stderr
@@ -1,8 +1,8 @@
-error: expected one of `async`, `const`, `crate`, `default`, `existential`, `extern`, `fn`, `pub`, `type`, `unsafe`, or `}`, found `static`
-  --> $DIR/removed-syntax-static-fn.rs:6:5
+error: expected one of `async`, `const`, `crate`, `default`, `extern`, `fn`, `pub`, `type`, `unsafe`, or `}`, found `static`
+  --> $DIR/removed-syntax-static-fn.rs:4:5
    |
 LL | impl S {
-   |         - expected one of 11 possible tokens here
+   |         - expected one of 10 possible tokens here
 LL |     static fn f() {}
    |     ^^^^^^ unexpected token